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Li Zeng, Wei Li, Ce-Shi Chen. Breast cancer animal models and applications. Zoological Research. doi: 10.24272/j.issn.2095-8137.2020.095
Citation: Li Zeng, Wei Li, Ce-Shi Chen. Breast cancer animal models and applications. Zoological Research. doi: 10.24272/j.issn.2095-8137.2020.095

Breast cancer animal models and applications

doi: 10.24272/j.issn.2095-8137.2020.095
Funds:  This study was supported in part by grants from the National Key R&D Program of China (2018YFC2000400), National Natural Science Foundation of China (81830087, U1602221, 31771516), and Project of Innovative Research Team of Yunnan Province (2019HC005)
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  • Corresponding author: E-mail: chenc@mail.kiz.ac.cn
  • Received Date: 2020-04-22
  • Accepted Date: 2020-06-19
  • Available Online: 2020-06-27
  • Breast cancer is the most common malignancy in women. Basic and translational breast cancer research relies heavily on experimental animal models. Ideally, such models for breast cancer should have commonality with human breast cancer in terms of tumor etiology, biological behavior, pathology, and response to therapeutics. This review introduces current progress in different breast cancer experimental animal models and analyzes their characteristics, advantages, disadvantages, and potential applications. Finally, we propose future research directions for breast cancer animal models.
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  • [1] Aceto N, Bardia A, Miyamoto DT, Donaldson MC, Wittner BS, Spencer JA, et al. 2014. Circulating tumor cell clusters are oligoclonal precursors of breast cancer metastasis. Cell, 158(5): 1110−1122. doi:  10.1016/j.cell.2014.07.013
    [2] Allred DC, Clark GM, Molina R, Tandon AK, Schnitt SJ, Gilchrist KW, et al. 1992. Overexpression of HER-2/neu and its relationship with other prognostic factors change during the progression of in situ to invasive breast cancer. Human Pathology, 23(9): 974−979. doi:  10.1016/0046-8177(92)90257-4
    [3] Almholt K, Lund LR, Rygaard J, Nielsen BS, Danø K, Rømer J, et al. 2005. Reduced metastasis of transgenic mammary cancer in urokinase-deficient mice. International Journal of Cancer, 113(4): 525−532. doi:  10.1002/ijc.20631
    [4] Amundadottir LT, Johnson MD, Merlino G, Smith GH, Dickson RB. 1995. Synergistic interaction of transforming growth factor α and c-myc in mouse mammary and salivary gland tumorigenesis. Cell Growth & Differentiation: the Molecular Biology Journal of the American Association for Cancer Research, 6(6): 737−748.
    [5] Anastasiadi Z, Lianos GD, Ignatiadou E, Harissis HV, Mitsis M. 2017. Breast cancer in young women: an overview. Updates in Surgery, 69(3): 313−317. doi:  10.1007/s13304-017-0424-1
    [6] Aslakson CJ, Miller FR. 1992. Selective events in the metastatic process defined by analysis of the sequential dissemination of subpopulations of a mouse mammary tumor. Cancer Research, 52(6): 1399−1405.
    [7] Bagheri-Yarmand R, Kourbali Y, Rath AM, Vassy R, Martin A, Jozefonvicz J, et al. 1999. Carboxymethyl benzylamide dextran blocks angiogenesis of MDA-MB435 breast carcinoma xenografted in fat pad and its lung metastases in nude mice. Cancer Research, 59(3): 507−510.
    [8] Barros ACSD, Muranaka ENK, Mori LJ, Pelizon CHT, Iriya K, Giocondo G, et al. 2004. Induction of experimental mammary carcinogenesis in rats with 7, 12-dimethylbenz(a)anthracene. Revista do Hospital das Clínicas, 59(5): 257−261. doi:  10.1590/S0041-87812004000500006
    [9] Baselga J, Norton L, Albanell J, Kim YM, Mendelsohn J. 1998. Recombinant humanized anti-HER2 antibody (HerceptinTM) enhances the antitumor activity of paclitaxel and doxorubicin against HER2/neu overexpressing human breast cancer xenografts. Cancer Research, 58(13): 2825−2831.
    [10] Borowsky AD. 2011. Choosing a mouse model: experimental biology in context--the utility and limitations of mouse models of breast cancer. Cold Spring Harbor Perspectives in Biology, 3(9): a009670.
    [11] Bos PD, Zhang XHF, Nadal C, Shu WP, Gomis RR, Nguyen DX, et al. 2009. Genes that mediate breast cancer metastasis to the brain. Nature, 459(7249): 1005−1009. doi:  10.1038/nature08021
    [12] Bouchard L, Lamarre L, Tremblay PJ, Jolicoeur P. 1989. Stochastic appearance of mammary tumors in transgenic mice carrying the MMTV/c-neu oncogene. Cell, 57(6): 931−936. doi:  10.1016/0092-8674(89)90331-0
    [13] Bray F, Ferlay J, Soerjomataram I, Siegel RL, Torre LA, Jemal A. 2018. Global cancer statistics 2018: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA: A Cancer Journal for Clinicians, 68(6): 394−424. doi:  10.3322/caac.21492
    [14] Brodie A, Lu Q, Liu Y, Long B, Wang JP, Yue W. 1998. Preclinical studies using the intratumoral aromatase model for postmenopausal breast cancer. Oncology(Williston Park, N.Y.), 12(3 Suppl 5): 36−40.
    [15] Broerse JJ, Hennen LA, van Zwieten MJ. 1985. Radiation carcinogenesis in experimental animals and its implications for radiation protection. International Journal of Radiation Biology and Related Studies in Physics, Chemistry and Medicine, 48(2): 167−187. doi:  10.1080/09553008514551171
    [16] Bu W, Xin L, Toneff M, Li L, Li Y. 2009. Lentivirus vectors for stably introducing genes into mammary epithelial cells in vivo. Journal of Mammary Gland Biology and Neoplasia, 14(4): 401−404. doi:  10.1007/s10911-009-9154-4
    [17] Burdall SE, Hanby AM, Lansdown MRJ, Speirs V. 2003. Breast cancer cell lines: friend or foe?. Breast Cancer Research, 5(2): 89−95. doi:  10.1186/bcr577
    [18] Cailleau R, Young R, Olivé M, Reeves WJ Jr. 1974. Breast tumor cell lines from pleural effusions. NCI: Journal of the National Cancer Institute, 53(3): 661−674. doi:  10.1093/jnci/53.3.661
    [19] Cardiff RD, Kenney N. 2011. A compendium of the mouse mammary tumor biologist: from the initial observations in the house mouse to the development of genetically engineered mice. Cold Spring Harbor Perspectives in Biology, 3(6): a003111.
    [20] Cerliani JP, Guillardoy T, Giulianelli S, Vaque JP, Gutkind JS, Vanzulli SI, et al. 2011. Interaction between FGFR-2, STAT5, and progesterone receptors in breast cancer. Cancer Research, 71(10): 3720−3731. doi:  10.1158/0008-5472.CAN-10-3074
    [21] Chakrabarti R, Kang YB. 2015. Transplantable mouse tumor models of breast cancer metastasis. In: Eferl R, Casanova E. Mouse Models of Cancer: Methods and Protocols. New York, NY: Humana Press, 367–380.
    [22] Chan MM, Lu X, Merchant FM, Iglehart JD, Miron PL. 2007. Serial transplantation of NMU-induced rat mammary tumors: a model of human breast cancer progression. International Journal of Cancer, 121(3): 474−485. doi:  10.1002/ijc.22684
    [23] Charafe-Jauffret E, Ginestier C, Iovino F, Wicinski J, Cervera N, Finetti P, et al. 2009. Breast cancer cell lines contain functional cancer stem cells with metastatic capacity and a distinct molecular signature. Cancer Research, 69(4): 1302−1313. doi:  10.1158/0008-5472.CAN-08-2741
    [24] Chen MJ, Ou C, Yang C, Yang WP, Qin QH, Jiang W, et al. 2019. A novel animal model of induced breast precancerous lesion in tree shrew. Biological and Pharmaceutical Bulletin, 42(4): 580−585. doi:  10.1248/bpb.b18-00688
    [25] Cho SY, Kang W, Han JY, Min S, Kang J, Lee A, et al. 2016. An integrative approach to precision cancer medicine using patient-derived Xenografts. Molecules and Cells, 39(2): 77−86. doi:  10.14348/molcells.2016.2350
    [26] Chow LWC, Cheung MNB, Loo WTY, Guan XY. 2003. A rat cell line derived from DMBA-induced mammary carcinoma. Life Sciences, 73(1): 27−40. doi:  10.1016/S0024-3205(03)00253-4
    [27] Clarke AR. 2000. Manipulating the germline: its impact on the study of carcinogenesis. Carcinogenesis, 21(3): 435−441. doi:  10.1093/carcin/21.3.435
    [28] Clarke R. 2009. The role of preclinical animal models in breast cancer drug development. Breast Cancer Research, 11(Suppl 3): S22.
    [29] Davies BR, Platt-Higgins AM, Schmidt G, Rudland PS. 1999. Development of hyperplasias, preneoplasias, and mammary tumors in MMTV-c-erbB-2 and MMTV-TGFα transgenic rats. The American Journal of Pathology, 155(1): 303−314. doi:  10.1016/S0002-9440(10)65124-3
    [30] DeRose YS, Wang GY, Lin YC, Bernard PS, Buys SS, Ebbert MTW, et al. 2011. Tumor grafts derived from women with breast cancer authentically reflect tumor pathology, growth, metastasis and disease outcomes. Nature Medicine, 17(11): 1514−1520. doi:  10.1038/nm.2454
    [31] Ding Q, Gan L. 2012. Conditional control of gene expression in the mouse retina. In: Wang SZ. Retinal Development: Methods and Protocols. Totowa, NJ: Humana Press, 3–15.
    [32] Dong J, Zhao W, Shi A, Toneff M, Lydon J, So D, et al. 2016. The PR status of the originating cell of ER/PR-negative mouse mammary tumors. Oncogene, 35(31): 4149−4154. doi:  10.1038/onc.2015.465
    [33] Dow LE. 2015. Modeling disease in vivowith CRISPR/Cas9. Trends in Molecular Medicine, 21(10): 609−621. doi:  10.1016/j.molmed.2015.07.006
    [34] Du ZJ, Li Y. 2007. RCAS-TVA in the mammary gland: an in vivo oncogene screen and a high fidelity model for breast transformation?. Cell Cycle, 6(7): 823−826. doi:  10.4161/cc.6.7.4074
    [35] Du ZJ, Podsypanina K, Huang SX, McGrath A, Toneff MJ, Bogoslovskaia E, et al. 2006. Introduction of oncogenes into mammary glands in vivowith an avian retroviral vector initiates and promotes carcinogenesis in mouse models. Proceedings of the National Academy of Sciences of the United States of America, 103(46): 17396−17401. doi:  10.1073/pnas.0608607103
    [36] Duan QW, Liu YF, Rockwell S. 2013. Fenbendazole as a potential anticancer drug. Anticancer Research, 33(2): 355−362.
    [37] Duarte AA, Gogola E, Sachs N, Barazas M, Annunziato S, de Ruiter JR, et al. 2018. BRCA-deficient mouse mammary tumor organoids to study cancer-drug resistance. Nature Methods, 15(2): 134−140. doi:  10.1038/nmeth.4535
    [38] Elliot OS, Elliot MW, Lisco H. 1966. Breast cancer in a tree shrew (Tupaia glis). Nature, 211(5053): 1105. doi:  10.1038/2111105a0
    [39] Engel LW, Young NA, Tralka TS, Lippman ME, O'Brien SJ, Joyce MJ. 1978. Establishment and characterization of three new continuous cell lines derived from human breast carcinomas. Cancer Research, 38(10): 3352−3364.
    [40] Erin N, Kale Ş, Tanrıöver G, Köksoy S, Duymuş Ö, Korcum AF. 2013. Differential characteristics of heart, liver, and brain metastatic subsets of murine breast carcinoma. Breast Cancer Research and Treatment, 139(3): 677−689. doi:  10.1007/s10549-013-2584-0
    [41] Ethier SP, Kokeny KE, Ridings JW, Dilts CA. 1996. erbB family receptor expression and growth regulation in a newly isolated human breast cancer cell line. Cancer Research, 56(4): 899−907.
    [42] Fabris VT. 2014. From chromosomal abnormalities to the identification of target genes in mouse models of breast cancer. Cancer Genetics, 207(6): 233−246. doi:  10.1016/j.cancergen.2014.06.025
    [43] Fan Y, Huang ZY, Cao CC, Chen CS, Chen YX, Fan DD, et al. 2013. Genome of the Chinese tree shrew. Nature Communications, 4(1): 1426. doi:  10.1038/ncomms2416
    [44] Fan Y, Ye MS, Zhang JY, Xu L, Yu DD, Gu TL, et al. 2019. Chromosomal level assembly and population sequencing of the Chinese tree shrew genome. Zoological Research, 40(6): 506−521. doi:  10.24272/j.issn.2095-8137.2019.063
    [45] Fantozzi A, Christofori G. 2006. Mouse models of breast cancer metastasis. Breast Cancer Research, 8(4): 212. doi:  10.1186/bcr1530
    [46] Fidler MM, Gupta S, Soerjomataram I, Ferlay J, Steliarova-Foucher E, Bray F. 2017. Cancer incidence and mortality among young adults aged 20–39 years worldwide in 2012: a population-based study. The Lancet Oncology, 18(12): 1579−1589. doi:  10.1016/S1470-2045(17)30677-0
    [47] Fisher GH, Orsulic S, Holland E, Hively WP, Li Y, Lewis BC, et al. 1999. Development of a flexible and specific gene delivery system for production of murine tumor models. Oncogene, 18(38): 5253−5260. doi:  10.1038/sj.onc.1203087
    [48] Flynn R, Grundmann A, Renz P, Hänseler W, James WS, Cowley SA, et al. 2015. CRISPR-mediated genotypic and phenotypic correction of a chronic granulomatous disease mutation in human iPS cells. Experimental Hematology, 43(10): 838−848. doi:  10.1016/j.exphem.2015.06.002
    [49] Fry DW, Harvey PJ, Keller PR, Elliott WL, Meade M, Trachet E, et al. 2004. Specific inhibition of cyclin-dependent kinase 4/6 by PD 0332991 and associated antitumor activity in human tumor xenografts. Molecular Cancer Therapeutics, 3(11): 1427−1438.
    [50] Füredi A, Szebényi K, Tóth S, Cserepes M, Hámori L, Nagy V, et al. 2017a. Pegylated liposomal formulation of doxorubicin overcomes drug resistance in a genetically engineered mouse model of breast cancer. Journal of Controlled Release, 261: 287−296. doi:  10.1016/j.jconrel.2017.07.010
    [51] Füredi A, Tóth S, Szebényi K, Pape VFS, Türk D, Kucsma N, et al. 2017b. Identification and validation of compounds selectively killing resistant cancer: delineating cell line-specific effects from p-glycoprotein-induced toxicity. Molecular Cancer Therapeutics, 16(1): 45−56. doi:  10.1158/1535-7163.MCT-16-0333-T
    [52] Ge GZ, Xia HJ, He BL, Zhang HL, Liu WJ, Shao M, et al. 2016. Generation and characterization of a breast carcinoma model by PyMT overexpression in mammary epithelial cells of tree shrew, an animal close to primates in evolution. International Journal of Cancer, 138(3): 642−651. doi:  10.1002/ijc.29814
    [53] Gheorghescu AK, Tywoniuk B, Duess J, Buchete NV, Thompson J. 2015. Exposure of chick embryos to cadmium changes the extra-embryonic vascular branching pattern and alters expression of VEGF-A and VEGF-R2. Toxicology and Applied Pharmacology, 289(1): 79−88. doi:  10.1016/j.taap.2015.09.004
    [54] Goddard ET, Fischer J, Schedin P. 2016. A portal vein injection model to study liver metastasis of breast cancer. Journal of Visualized Experiments, (118): 54903.
    [55] Gogola E, Duarte AA, de Ruiter JR, Wiegant WW, Schmid JA, de Bruijn R, et al. 2018. Selective loss of PARG restores PARylation and counteracts PARP inhibitor-mediated synthetic lethality. Cancer Cell, 33(6): 1078−1093. doi:  10.1016/j.ccell.2018.05.008
    [56] Green JE, Shibata MA, Yoshidome K, Liu ML, Jorcyk C, Anver MR, et al. 2000. The C3(1)/SV40 T-antigen transgenic mouse model of mammary cancer: ductal epithelial cell targeting with multistage progression to carcinoma. Oncogene, 19(8): 1020−1027. doi:  10.1038/sj.onc.1203280
    [57] Gullino PM, Pettigrew HM, Grantham FH. 1975. N-nitrosomethylurea as mammary gland carcinogen in rats. Journal of the National Cancer Institute, 54(2): 401−414.
    [58] Guy CT, Cardiff RD, Muller WJ. 1992a. Induction of mammary tumors by expression of polyomavirus middle T oncogene: a transgenic mouse model for metastatic disease. Molecular and Cellular Biology, 12(3): 954−961. doi:  10.1128/MCB.12.3.954
    [59] Guy CT, Webster MA, Schaller M, Parsons TJ, Cardiff RD, Muller WJ. 1992b. Expression of the neu protooncogene in the mammary epithelium of transgenic mice induces metastatic disease. Proceedings of the National Academy of Sciences of the United States of America, 89(22): 10578−10582. doi:  10.1073/pnas.89.22.10578
    [60] Halter SA, Dempsey P, Matsui Y, Stokes MK, Graves-Deal R, Hogan BL, et al. 1992. Distinctive patterns of hyperplasia in transgenic mice with mouse mammary tumor virus transforming growth factor-α. Characterization of mammary gland and skin proliferations. The American Journal of Pathology, 140(5): 1131−1146.
    [61] Hámori L, Kudlik G, Szebényi K, Kucsma N, Szeder B, Póti Á, et al. 2020. Establishment and characterization of a Brca1-/-, p53-/- mouse mammary tumor cell line. International Journal of Molecular Sciences, 21(4): 1185. doi:  10.3390/ijms21041185
    [62] Hanahan D, Wagner EF, Palmiter RD. 2007. The origins of oncomice: a history of the first transgenic mice genetically engineered to develop cancer. Genes & Development, 21(18): 2258−2270.
    [63] Harrell JC, Dye WW, Allred DC, Jedlicka P, Spoelstra NS, Sartorius CA, et al. 2006. Estrogen receptor positive breast cancer metastasis: altered hormonal sensitivity and tumor aggressiveness in lymphatic vessels and lymph nodes. Cancer Research, 66(18): 9308−9315. doi:  10.1158/0008-5472.CAN-06-1769
    [64] Heston WE, Vlahakis G. 1971. Mammary tumors, plaques, and hyperplastic alveolar nodules in various combinations of mouse inbred strains and the different lines of the mammary tumor virus. International Journal of Cancer, 7(1): 141−148. doi:  10.1002/ijc.2910070116
    [65] Hidalgo M, Amant F, Biankin AV, Budinská E, Byrne AT, Caldas C, et al. 2014. Patient-derived xenograft models: an emerging platform for translational cancer research. Cancer Discovery, 4(9): 998−1013. doi:  10.1158/2159-8290.CD-14-0001
    [66] Hoffman RM. 1999. Orthotopic metastatic mouse models for anticancer drug discovery and evaluation: a bridge to the clinic. Investigational New Drugs, 17(4): 343−359. doi:  10.1023/A:1006326203858
    [67] Holen I, Speirs V, Morrissey B, Blyth K. 2017. In vivo models in breast cancer research: progress, challenges and future directions. Disease Models & Mechanisms, 10(4): 359−371.
    [68] Holliday DL, Speirs V. 2011. Choosing the right cell line for breast cancer research. Breast Cancer Research, 13(4): 215. doi:  10.1186/bcr2889
    [69] Holzer RG, MacDougall C, Cortright G, Atwood K, Green JE, Jorcyk CL. 2003. Development and characterization of a progressive series of mammary adenocarcinoma cell lines derived from the C3(1)/SV40 Large T-antigen transgenic mouse model. Breast Cancer Research and Treatment, 77(1): 65−76. doi:  10.1023/A:1021175931177
    [70] Hundley JE, Koester SK, Troyer DA, Hilsenbeck SG, Subler MA, Windle JJ. 1997. Increased tumor proliferation and genomic instability without decreased apoptosis in MMTV-ras mice deficient in p53. Molecular and Cellular Biology, 17(2): 723−731. doi:  10.1128/MCB.17.2.723
    [71] Hutchinson JN, Muller MJ. 2000. Transgenic mouse models of human breast cancer. Oncogene, 19(53): 6130−6137. doi:  10.1038/sj.onc.1203970
    [72] Jagadeeshan S, Sagayaraj RV, Paneerselvan N, Ghouse SS, Malathi R. 2017. Toxicity and anti-angiogenicity evaluation of Pak1 inhibitor IPA-3 using zebrafish embryo model. Cell Biology and Toxicology, 33(1): 41−56. doi:  10.1007/s10565-016-9358-5
    [73] Jaspers JE, Kersbergen A, Boon U, Sol W, van Deemter L, Zander SA, et al. 2013. Loss of 53BP1 causes PARP inhibitor resistance in Brca1-mutated mouse mammary tumors. Cancer Discovery, 3(1): 68−81. doi:  10.1158/2159-8290.CD-12-0049
    [74] Jia L, Zhou Z, Liang H, Wu J, Shi P, Li F, et al. 2016. KLF5 promotes breast cancer proliferation, migration and invasion in part by upregulating the transcription of TNFAIP2. Oncogene, 35(16): 2040−2051. doi:  10.1038/onc.2015.263
    [75] Jiang M, Xu XY, Bi YL, Xu JY, Qin CY, Han MY. 2014. Systemic inflammation promotes lung metastasis via E-selectin upregulation in mouse breast cancer model. Cancer Biology & Therapy, 15(6): 789−796.
    [76] Johnstone CN, Smith YE, Cao Y, Burrows AD, Cross RSN, Ling XW, et al. 2015. Functional and molecular characterisation of EO771. LMB tumours, a new C57BL/6-mouse-derived model of spontaneously metastatic mammary cancer. Disease Models & Mechanisms, 8(3): 237−251.
    [77] Jonkers J, Derksen PWB. 2007. Modeling metastatic breast cancer in mice. Journal of Mammary Gland Biology and Neoplasia, 12(2–3): 191−203.
    [78] Kaya P, Lee SR, Lee YH, Kwon SW, Yang H, Lee HW, et al. 2019. Curcumae radix extract decreases mammary tumor-derived lung metastasis via suppression of C-C chemokine receptor type 7 Expression. Nutrients, 11(2): 410. doi:  10.3390/nu11020410
    [79] Keegan NM, Gleeson JP, Hennessy BT, Morris PG. 2018. PI3K inhibition to overcome endocrine resistance in breast cancer. Expert Opinion on Investigational Drugs, 27(1): 1−15. doi:  10.1080/13543784.2018.1417384
    [80] Kij A, Kus K, Smeda M, Zakrzewska A, Proniewski B, Matyjaszczyk K, et al. 2018. Differential effects of nitric oxide deficiency on primary tumour growth, pulmonary metastasis and prostacyclin/thromboxane A2 balance in orthotopic and intravenous murine models of 4T1 breast cancer. Journal of Physiology and Pharmacology, 69(6): 911−919.
    [81] Kim H, Kim M, Im SK, Fang S. 2018. Mouse Cre-LoxP system: general principles to determine tissue-specific roles of target genes. Laboratory Animal Research, 34(4): 147−159. doi:  10.5625/lar.2018.34.4.147
    [82] Kim IS, Baek SH. 2010. Mouse models for breast cancer metastasis. Biochemical and Biophysical Research Communications, 394(3): 443−447. doi:  10.1016/j.bbrc.2010.03.070
    [83] Kim LS, Huang S, Lu WX, Lev DC, Price JE. 2004. Vascular endothelial growth factor expression promotes the growth of breast cancer brain metastases in nude mice. Clinical & Experimental Metastasis, 21(2): 107−118.
    [84] Knudsen ES, Hutcheson J, Vail P, Witkiewicz AK. 2017. Biological specificity of CDK4/6 inhibitors: dose response relationship, in vivo signaling, and composite response signature. Oncotarget, 8(27): 43678−43691. doi:  10.18632/oncotarget.18435
    [85] Koboldt DC, Fulton RS, McLellan MD, Schmidt H, Kalicki-Veizer J, McMichael JF, et al. 2012. Comprehensive molecular portraits of human breast tumours. Nature, 490(7418): 61−70. doi:  10.1038/nature11412
    [86] Kuperwasser C, Dessain S, Bierbaum BE, Garnet D, Sperandio K, Gauvin GP, et al. 2005. A mouse model of human breast cancer metastasis to human bone. Cancer Research, 65(14): 6130−6138. doi:  10.1158/0008-5472.CAN-04-1408
    [87] Kusuma N, Denoyer D, Eble JA, Redvers RP, Parker BS, Pelzer R, et al. 2012. Integrin-dependent response to laminin-511 regulates breast tumor cell invasion and metastasis. International Journal of Cancer, 130(3): 555−566. doi:  10.1002/ijc.26018
    [88] Lacroix M, Leclercq G. 2004. Relevance of breast cancer cell lines as models for breast Tumours: an update. Breast Cancer Research and Treatment, 83(3): 249−289. doi:  10.1023/B:BREA.0000014042.54925.cc
    [89] Lanari C, Molinolo AA, Pasqualini CD. 1986. Induction of mammary adenocarcinomas by medroxyprogesterone acetate in BALB/c female mice. Cancer Letters, 33(2): 215−23. doi:  10.1016/0304-3835(86)90027-3
    [90] Lebert JM, Lester R, Powell E, Seal M, McCarthy J. 2018. Advances in the systemic treatment of triple-negative breast cancer. Current Oncology, 25(Suppl 1): S142−S150.
    [91] Lee JH, Kim B, Jin WJ, Kim JW, Kim HK, Ha H, et al. 2014. Trolox inhibits osteolytic bone metastasis of breast cancer through both PGE2-dependent and independent mechanisms. Biochemical Pharmacology, 91(1): 51−60. doi:  10.1016/j.bcp.2014.06.005
    [92] Lee K, Macaulay VM, Nicholls JE, Detre S, Ashworth A, Dowsett M. 1995. An in vivo model of intratumoural aromatase using aromatase-transfected MCF7 human breast cancer cells. International Journal of Cancer, 62(3): 297−302. doi:  10.1002/ijc.2910620311
    [93] Li B, Rosen JM, McMenamin-Balano J, Muller WJ, Perkins AS. 1997. neu/ERBB2 cooperates with p53172H during mammary tumorigenesis in transgenic mice. Molecular and Cellular Biology, 17(6): 3155−3163. doi:  10.1128/MCB.17.6.3155
    [94] Li ML, Hu JD, Heermeier K, Hennighausen L, Furth PA. 1996. Expression of a viral oncoprotein during mammary gland development alters cell fate and function: induction of p53-independent apoptosis is followed by impaired milk protein production in surviving cells. Cell Growth & Differentiation: the Molecular Biology Journal of the American Association for Cancer Research, 7(1): 3−11.
    [95] Li W, Teng F, Li TD, Zhou Q. 2013. Simultaneous generation and germline transmission of multiple gene mutations in rat using CRISPR-Cas systems. Nature Biotechnology, 31(8): 684−686. doi:  10.1038/nbt.2652
    [96] Li Y, Hively WP, Varmus HE. 2000. Use of MMTV-Wnt-1 transgenic mice for studying the genetic basis of breast cancer. Oncogene, 19(8): 1002−1009. doi:  10.1038/sj.onc.1203273
    [97] Liby K, Neltner B, Mohamet L, Menchen L, Ben-Jonathan N. 2003. Prolactin overexpression by MDA-MB-435 human breast cancer cells accelerates tumor growth. Breast Cancer Research and Treatment, 79(2): 241−252. doi:  10.1023/A:1023956223037
    [98] Lin EY, Jones JG, Li P, Zhu LY, Whitney KD, Muller WJ, et al. 2003. Progression to malignancy in the Polyoma middle T Oncoprotein mouse breast cancer model provides a reliable model for human diseases. The American Journal of Pathology, 163(5): 2113−2126. doi:  10.1016/S0002-9440(10)63568-7
    [99] Liu H, Kato Y, Erzinger SA, Kiriakova GM, Qian YZ, Palmieri D, et al. 2012. The role of MMP-1 in breast cancer growth and metastasis to the brain in a xenograft model. BMC Cancer, 12(1): 583. doi:  10.1186/1471-2407-12-583
    [100] Liu PX, Cheng HL, Santiago S, Raeder M, Zhang F, Isabella A, et al. 2011. Oncogenic PIK3CA-driven mammary tumors frequently recur via PI3K pathway-dependent and PI3K pathway-independent mechanisms. Nature Medicine, 17(9): 1116−1120. doi:  10.1038/nm.2402
    [101] Liu R, Shi PG, Zhou ZM, Zhang HL, Li W, Zhang H, et al. 2018. Krüpple-like factor 5 is essential for mammary gland development and tumorigenesis. The Journal of Pathology, 246(4): 497−507. doi:  10.1002/path.5153
    [102] Liu XL, Holstege H, van der Gulden H, Treur-Mulder M, Zevenhoven J, Velds A, et al. 2007. Somatic loss of BRCA1 and p53 in mice induces mammary tumors with features of human BRCA1-mutated basal-like breast cancer. Proceedings of the National Academy of Sciences of the United States of America, 104(29): 12111−12116. doi:  10.1073/pnas.0702969104
    [103] Lu X, Wang QQ, Hu GH, Van Poznak C, Fleisher M, Reiss M, et al. 2009. ADAMTS1 and MMP1 proteolytically engage EGF-like ligands in an osteolytic signaling cascade for bone metastasis. Genes & Development, 23(16): 1882−1894.
    [104] Luque-Cabal M, Garcia-Teijido P, Fernández-Pérez Y, Sánchez-Lorenzo L, Palacio-Vázquez I. 2016. Mechanisms behind the resistance to Trastuzumab in HER2-amplified breast cancer and strategies to overcome it. Clinical Medicine Insights: Oncology, 10(Suppl 1): 21−30.
    [105] Machida Y, Sudo Y, Uchiya N, Imai T. 2019. Increased susceptibility to mammary carcinogenesis and an opposite trend in endometrium in Trp53 heterozygous knockout female mice by backcrossing the BALB/c strain onto the background C3H strain. Journal of Toxicologic Pathology, 32(3): 197−203. doi:  10.1293/tox.2018-0057
    [106] Maroulakou IG, Anver M, Garrett L, Green JE. 1994. Prostate and mammary adenocarcinoma in transgenic mice carrying a rat C3(1) simian virus 40 large tumor antigen fusion gene. Proceedings of the National Academy of Sciences of the United States of America, 91(23): 11236−11240. doi:  10.1073/pnas.91.23.11236
    [107] Matsui Y, Halter SA, Holt JT, Hogan BLM, Coffey RJ. 1990. Development of mammary hyperplasia and neoplasia in MMTV-TGFα transgenic mice. Cell, 61(6): 1147−1155. doi:  10.1016/0092-8674(90)90077-R
    [108] McLellan MA, Rosenthal NA, Pinto AR. 2017. Cre-loxP-mediated recombination: general principles and experimental considerations. Current Protocols in Mouse Biology, 7(1): 1−12. doi:  10.1002/cpmo.22
    [109] Meraz IM, Majidi M, Meng F, Shao RP, Ha MJ, Neri S, et al. 2019. An improved patient-derived Xenograft humanized mouse model for evaluation of lung cancer immune responses. Cancer Immunology Research, 7(8): 1267−1279. doi:  10.1158/2326-6066.CIR-18-0874
    [110] Mercatali L, La Manna F, Groenewoud A, Casadei R, Recine F, Miserocchi G, et al. 2016. Development of a Patient-Derived Xenograft (PDX) of breast cancer bone metastasis in a Zebrafish model. International Journal of Molecular Sciences, 17(8): 1375. doi:  10.3390/ijms17081375
    [111] Minn AJ, Gupta GP, Siegel PM, Bos PD, Shu WP, Giri DD, et al. 2005. Genes that mediate breast cancer metastasis to lung. Nature, 436(7050): 518−524. doi:  10.1038/nature03799
    [112] Minn AJ, Kang YB, Serganova I, Gupta GP, Giri DD, Doubrovin M, et al. 2005. Distinct organ-specific metastatic potential of individual breast cancer cells and primary tumors. The Journal of Clinical Investigation, 115(1): 44−55. doi:  10.1172/JCI22320
    [113] Mishra S, Tamta AK, Sarikhani M, Desingu PA, Kizkekra SM, Pandit AS, et al. 2018. Subcutaneous Ehrlich Ascites Carcinoma mice model for studying cancer-induced cardiomyopathy. Scientific Reports, 8(1): 5599. doi:  10.1038/s41598-018-23669-9
    [114] Mollard S, Mousseau Y, Baaj Y, Richard L, Cook-Moreau J, Monteil J, et al. 2011. How can grafted breast cancer models be optimized?. Cancer Biology & Therapy, 12(10): 855−864.
    [115] Morris VL, Tuck AB, Wilson SM, Percy D, Chambers AF. 1993. Tumor progression and metastasis in murine D2 hyperplastic alveolar nodule mammary tumor cell lines. Clinical & Experimental Metastasis, 11(1): 103−112.
    [116] Mottolese M, Morelli L, Agrimi U, Benevolo M, Sciarretta F, Antonucci G, et al. 1994. Spontaneous canine mammary tumors. A model for monoclonal antibody diagnosis and treatment of human breast cancer. Laboratory Investigation; A Journal of Technical Methods and Pathology, 71(2): 182−187.
    [117] Mukherjee A, Soyal SM, Wheeler DA, Fernandez-Valdivia R, Nguyen J, DeMayo FJ, et al. 2006. Targeting iCre expression to murine progesterone receptor cell-lineages using bacterial artificial chromosome transgenesis. Genesis, 44(12): 601−610. doi:  10.1002/dvg.20257
    [118] Nagasawa H, Yanai R, Taniguchi H, Tokuzen R, Nakahara W. 1976. Two-way selection of a stock of Swiss albino mice for mammary tumorigenesis: establishment of two new strains (SHN and SLN). JNCI: Journal of the National Cancer Institute, 57(2): 425−430. doi:  10.1093/jnci/57.2.425
    [119] Nagy A. 2000. Cre recombinase: the universal reagent for genome tailoring. Genesis, 26(2): 99−109. doi:  10.1002/(SICI)1526-968X(200002)26:2<99::AID-GENE1>3.0.CO;2-B
    [120] Nakanishi H, Taylor RM, Chrest FJ, Masui T, Utsumi K, Tatematsu M, et al. 1995. Progression of hormone-dependent adenocarcinoma cells to hormone-independent spindle carcinoma cells in vitro in a clonal spontaneous rat mammary tumor cell line. Cancer Research, 55(2): 399−407.
    [121] Neal JT, Li XN, Zhu JJ, Giangarra V, Grzeskowiak CL, Ju JH, et al. 2018. Organoid modeling of the tumor immune microenvironment. Cell, 175(7): 1972−1988. doi:  10.1016/j.cell.2018.11.021
    [122] Neve RM, Chin K, Fridlyand J, Yeh J, Baehner FL, Fevr T, et al. 2006. A collection of breast cancer cell lines for the study of functionally distinct cancer subtypes. Cancer Cell, 10(6): 515−527. doi:  10.1016/j.ccr.2006.10.008
    [123] Nielsen LL, Discafani CM, Gurnani M, Tyler RD. 1991. Histopathology of salivary and mammary gland tumors in transgenic mice expressing a human Ha-ras oncogene. Cancer Research, 51(14): 3762−3767.
    [124] Nohmi T, Masumura K, Toyoda-Hokaiwado N. 2017. Transgenic rat models for mutagenesis and carcinogenesis. Genes and Environment, 39(1): 11. doi:  10.1186/s41021-016-0072-6
    [125] Nutter F, Holen I, Brown HK, Cross SS, Evans CA, Walker M, et al. 2014. Different molecular profiles are associated with breast cancer cell homing compared with colonisation of bone: evidence using a novel bone-seeking cell line. Endocrine-Related Cancer, 21(2): 327−341. doi:  10.1530/ERC-13-0158
    [126] Osborne CK, Hobbs K, Clark GM. 1985. Effect of estrogens and antiestrogens on growth of human breast cancer cells in athymic nude mice. Cancer Research, 45(2): 584−590.
    [127] Ottewell PD, Wang N, Brown HK, Reeves KJ, Fowles CA, Croucher PI, et al. 2014. Zoledronic acid has differential antitumor activity in the pre- and postmenopausal bone microenvironment in vivo. Clinical Cancer Research, 20(11): 2922−2932. doi:  10.1158/1078-0432.CCR-13-1246
    [128] Ozaslan M, Karagoz ID, Kilic IH, Guldur ME. 2011. Ehrlich ascites carcinoma. African Journal of Biotechnology, 10(13): 2375−2378.
    [129] Ozzello L, Sordat B, Merenda C, Carrel S, Hurlimann J, Mach JP. 1974. Transplantation of a human mammary carcinoma cell line (BT 20) into nude mice2. JNCI: Journal of the National Cancer Institute, 52(5): 1669−1672. doi:  10.1093/jnci/52.5.1669
    [130] Palmieri C, Patten DK, Januszewski A, Zucchini G, Howell SJ. 2013. Breast cancer: current and future endocrine therapies. Molecular and Cellular Endocrinology, 382(1): 695−723.
    [131] Park JW, Neve RM, Szollosi J, Benz CC. 2008. Unraveling the biologic and clinical complexities of HER2. Clinical Breast Cancer, 8(5): 392−401. doi:  10.3816/CBC.2008.n.047
    [132] Park MK, Lee CH, Lee H. 2018. Mouse models of breast cancer in preclinical research. Laboratory Animal Research, 34(4): 160−165. doi:  10.5625/lar.2018.34.4.160
    [133] Paschall AV, Liu KB. 2016. An orthotopic mouse model of spontaneous breast cancer metastasis. Journal of Visualized Experiments, (114): 54040.
    [134] Pattengale PK, Stewart TA, Leder A, Sinn E, Muller W, Tepler I, et al. 1989. Animal models of human disease. Pathology and molecular biology of spontaneous neoplasms occurring in transgenic mice carrying and expressing activated cellular oncogenes. The American Journal of Pathology, 135(1): 39−61.
    [135] Pei XF, Noble MS, Davoli MA, Rosfjord E, Tilli MT, Furth PA, et al. 2004. Explant-cell culture of primary mammary tumors from MMTV-c-Myc transgenic mice. In Vitro Cellular & Developmental Biology - Animal, 40(1–2): 14−21.
    [136] Peña L, Perez-Alenza MD, Rodriguez-Bertos A, Nieto A. 2003. Canine inflammatory mammary carcinoma: histopathology, immunohistochemistry and clinical implications of 21 cases. Breast Cancer Research and Treatment, 78(2): 141−148. doi:  10.1023/A:1022991802116
    [137] Pillai SG, Li SQ, Siddappa CM, Ellis MJ, Watson MA, Aft R. 2018. Identifying biomarkers of breast cancer micrometastatic disease in bone marrow using a patient-derived xenograft mouse model. Breast Cancer Research, 20(1): 2. doi:  10.1186/s13058-017-0927-1
    [138] Price JE. 1996. Metastasis from human breast cancer cell lines. Breast Cancer Research and Treatment, 39(1): 93−102. doi:  10.1007/BF01806081
    [139] Qin JY, Zhou ZM, Chen WL, Wang CY, Zhang HL, Ge GZ, et al. 2015. BAP1 promotes breast cancer cell proliferation and metastasis by deubiquitinating KLF5. Nature Communications, 6(1): 8471. doi:  10.1038/ncomms9471
    [140] Rao GN, Piegorsch WW, Haseman JK. 1987. Influence of body weight on the incidence of spontaneous tumors in rats and mice of long-term studies. The American Journal of Clinical Nutrition, 45(1): 252−260. doi:  10.1093/ajcn/45.1.252
    [141] Rashid OM, Takabe K. 2015. Animal models for exploring the pharmacokinetics of breast cancer therapies. Expert Opinion on Drug Metabolism & Toxicology, 11(2): 221−230.
    [142] Ren J, Liu SJ, Cui C, Ten Dijke P. 2017. Invasive behavior of human breast cancer cells in embryonic Zebrafish. Journal of Visualized Experiments, (122): 55459.
    [143] Rockwell SC, Kallman RF, Fajardo LF. 1972. Characteristics of a serially transplanted mouse mammary tumor and its tissue-culture-adapted derivative. Journal of the National Cancer Institute, 49(3): 735−749.
    [144] Romieu-Mourez R, Kim DW, Shin SM, Demicco EG, Landesman-Bollag E, Seldin DC, et al. 2003. Mouse mammary tumor virus c-rel transgenic mice develop mammary tumors. Molecular and Cellular Biology, 23(16): 5738−5754. doi:  10.1128/MCB.23.16.5738-5754.2003
    [145] Rose-Hellekant TA, Sandgren EP. 2000. Transforming growth factor alpha- and c-myc-induced mammary carcinogenesis in transgenic mice. Oncogene, 19(8): 1092−1096. doi:  10.1038/sj.onc.1203350
    [146] Rottenberg S, Jaspers JE, Kersbergen A, van der Burg E, Nygren AOH, Zander SAL, et al. 2008. High sensitivity of BRCA1-deficient mammary tumors to the PARP inhibitor AZD2281 alone and in combination with platinum drugs. Proceedings of the National Academy of Sciences of the United States of America, 105(44): 17079−17084. doi:  10.1073/pnas.0806092105
    [147] Rottenberg S, Nygren AOH, Pajic M, van Leeuwen FWB, van der Heijden I, van de Wetering K, et al. 2007. Selective induction of chemotherapy resistance of mammary tumors in a conditional mouse model for hereditary breast cancer. Proceedings of the National Academy of Sciences of the United States of America, 104(29): 12117−12122. doi:  10.1073/pnas.0702955104
    [148] Rusnak DW, Lackey K, Affleck K, Wood ER, Alligood KJ, Rhodes N, et al. 2001. The effects of the novel, reversible epidermal growth factor receptor/ErbB-2 tyrosine kinase inhibitor, GW2016, on the growth of human normal and tumor-derived cell lines in vitro and in vivo. Molecular Cancer Therapeutics, 1(2): 85−94.
    [149] Russo IH, Russo J. 1996. Mammary gland Neoplasia in long-term rodent studies. Environmental Health Perspectives, 104(9): 938−967. doi:  10.1289/ehp.96104938
    [150] Russo J, Gusterson BA, Rogers AE, Russo IH, Wellings SR, van Zwieten MJ. 1990. Comparative study of human and rat mammary tumorigenesis. Laboratory Investigation; A Journal of Technical Methods and Pathology, 62(3): 244−278.
    [151] Sahabi K, Rajendren SK, Foong JN, Selvarajah GT. 2018. Mammary gland tumours in the dog, a spontaneous tumour model of comparative value to human breast cancer. Pertanika Journal of Tropical Agricultural Science, 41(2): 541−574.
    [152] Sandgren EP, Schroeder JA, Qui TH, Palmiter RD, Brinster RL, Lee DC. 1995. Inhibition of mammary gland involution is associated with transforming growth factor α but not c-myc-induced Tumorigenesis in transgenic mice. Cancer Research, 55(17): 3915−3827.
    [153] Santarelli R, Tzeng YJ, Zimmermann C, Guhl E, Graessmann A. 1996. SV40 T-antigen induces breast cancer formation with a high efficiency in lactating and virgin WAP-SV-T transgenic animals but with a low efficiency in ovariectomized animals. Oncogene, 12(3): 495−505.
    [154] Shafee N, Smith CR, Wei SZ, Kim Y, Mills GB, Hortobagyi GN, et al. 2008. Cancer stem cells contribute to cisplatin resistance in Brca1/p53-mediated mouse mammary tumors. Cancer Research, 68(9): 3243−3250. doi:  10.1158/0008-5472.CAN-07-5480
    [155] Shao M, Xu TR, Chen CS. 2016. The big bang of genome editing technology: development and application of the CRISPR/Cas9 system in disease animal models. Zoological Research, 37(4): 191−204.
    [156] Shi HY, Zhang WG, Liang R, Abraham S, Kittrell FS, Medina D, et al. 2001. Blocking tumor growth, invasion, and metastasis by maspin in a syngeneic breast cancer model. Cancer Research, 61(18): 6945−6951.
    [157] Sinn E, Muller W, Pattengale P, Tepler I, Wallace R, Leder P. 1987. Coexpression of MMTV/v-Ha-ras and MMTV/c-myc genes in transgenic mice: synergistic action of oncogenes in vivo. Cell, 49(4): 465−475. doi:  10.1016/0092-8674(87)90449-1
    [158] Smith BF, Migone FK, Cox NR, Baker H. 2003. An in utero allotransplantation model of metastatic breast cancer in the cat. In Vivo, 17(1): 35−39.
    [159] Stambolic V, Tsao MS, Macpherson D, Suzuki A, Chapman WB, Mak TW. 2000. High incidence of breast and endometrial neoplasia resembling human Cowden syndrome in pten+/- mice. Cancer Research, 60(13): 3605−11.
    [160] Stamp G, Fantl V, Poulsom R, Jamieson S, Smith R, Peters G, et al. 1992. Nonuniform expression of a mouse mammary tumor virus-driven int-2/Fgf-3 transgene in pregnancy-responsive breast tumors. Cell Growth & Differentiation: the Molecular Biology Journal of the American Association for Cancer Research, 3(12): 929−938.
    [161] Stewart TA, Pattengale PK, Leder P. 1984. Spontaneous mammary adenocarcinomas in transgenic mice that carry and express MTV/myc fusion genes. Cell, 38(3): 627−637. doi:  10.1016/0092-8674(84)90257-5
    [162] Strong LC. 1936. The establishment of the “a” strain of inbred mice. Journal of Heredity, 27(1): 21−24. doi:  10.1093/oxfordjournals.jhered.a104133
    [163] Su XF, Colditz GA, Willett WC, Collins LC, Schnitt SJ, Connolly JL, et al. 2010. Genetic variation and circulating levels of IGF-I and IGFBP-3 in relation to risk of proliferative benign breast disease. International Journal of Cancer, 126(1): 180−190. doi:  10.1002/ijc.24674
    [164] Sun BC, Zhang SW, Zhang DF, Li Y, Zhao XL, Luo Y, et al. 2008. Identification of metastasis-related proteins and their clinical relevance to triple-negative human breast cancer. Clinical Cancer Research, 14(21): 7050−7059. doi:  10.1158/1078-0432.CCR-08-0520
    [165] Suva LJ, Washam C, Nicholas RW, Griffin RJ. 2011. Bone metastasis: mechanisms and therapeutic opportunities. Nature Reviews Endocrinology, 7(4): 208−218. doi:  10.1038/nrendo.2010.227
    [166] Swain SM, Baselga J, Kim SB, Ro J, Semiglazov V, Campone M, et al. 2015. Pertuzumab, Trastuzumab, and Docetaxel in HER2-positive metastatic breast cancer. The New England Journal of Medicine, 372(8): 724−734. doi:  10.1056/NEJMoa1413513
    [167] Szymanska H, Lechowska-Piskorowska J, Krysiak E, Strzalkowska A, Unrug-Bielawska K, Grygalewicz B, et al. 2014. Neoplastic and nonneoplastic lesions in aging mice of unique and common inbred strains contribution to modeling of human neoplastic diseases. Veterinary Pathology, 51(3): 663−679. doi:  10.1177/0300985813501334
    [168] Taneja P, Frazier DP, Kendig RD, Maglic D, Sugiyama T, Kai F, et al. 2009. MMTV mouse models and the diagnostic values of MMTV-like sequences in human breast cancer. Expert Review of Molecular Diagnostics, 9(5): 423−440. doi:  10.1586/erm.09.31
    [169] Thompson HJ, Meeker LD. 1983. Induction of mammary gland carcinomas by the subcutaneous injection of 1-methyl-1-nitrosourea. Cancer Research, 43(4): 1628−1629.
    [170] Thompson HJ, Singh M. 2000. Rat models of premalignant breast disease. Journal of Mammary Gland Biology and Neoplasia, 5(4): 409−420. doi:  10.1023/A:1009582012493
    [171] To C, Kim EH, Royce DB, Williams CR, Collins RM, Risingsong R, et al. 2014. The PARP inhibitors, veliparib and olaparib, are effective chemopreventive agents for delaying mammary tumor development in BRCA1-deficient mice. Cancer Prevention Research, 7(7): 698−707. doi:  10.1158/1940-6207.CAPR-14-0047
    [172] Törnell J, Rymo L, Isaksson OGP. 1991. Induction of mammary adenocarcinomas in metallothionein promoter-human growth hormone transgenic mice. International Journal of Cancer, 49(1): 114−117. doi:  10.1002/ijc.2910490121
    [173] Trempe GL. 1976. Human breast cancer in culture. In: St-Arneault G, Band P, Israël L. Breast Cancer: A Multidisciplinary Approach. Berlin: Springer, 33–41.
    [174] Tsukamoto AS, Grosschedl R, Guzman RC, Parslow T, Varmus HE. 1988. Expression of the int-1 gene in transgenic mice is associated with mammary gland hyperplasia and adenocarcinomas in male and female mice. Cell, 55(4): 619−625. doi:  10.1016/0092-8674(88)90220-6
    [175] Tulotta C, Groenewoud A, Ewa Snaar-Jagalska B, Ottewell P. 2019. Animal models of breast cancer bone metastasis. In: Idris AI. Bone Research Protocols. New York, NY: Springer, 309–330.
    [176] Vargo-Gogola T, Rosen JM. 2007. Modelling breast cancer: one size does not fit all. Nature Reviews Cancer, 7(9): 659−672. doi:  10.1038/nrc2193
    [177] Vora SR, Juric D, Kim N, Mino-Kenudson M, Huynh T, Costa C, et al. 2014. CDK 4/6 inhibitors sensitize PIK3CA mutant breast cancer to PI3K inhibitors. Cancer Cell, 26(1): 136−149. doi:  10.1016/j.ccr.2014.05.020
    [178] Wakeling AE, Dukes M, Bowler J. 1991. A potent specific pure antiestrogen with clinical potential. Cancer Research, 51(15): 3867−3873.
    [179] Wang CY, Nie Z, Zhou ZM, Zhang HL, Liu R, Wu J, et al. 2015. The interplay between TEAD4 and KLF5 promotes breast cancer partially through inhibiting the transcription of p27 Kip1. Oncotarget, 6(19): 17685−17697. doi:  10.18632/oncotarget.3779
    [180] Wang MN, Yao LC, Cheng MS, Cai DY, Martinek J, Pan CX, et al. 2018. Humanized mice in studying efficacy and mechanisms of PD-1-targeted cancer immunotherapy. The FASEB Journal, 32(3): 1537−1549. doi:  10.1096/fj.201700740R
    [181] Wang TC, Cardiff RD, Zukerberg L, Lees E, Arnold A, Schmidt EV. 1994. Mammary hyperplasia and carcinoma in MMTV-cyclin D1 transgenic mice. Nature, 369(6482): 669−671. doi:  10.1038/369669a0
    [182] Welsch CW. 1987. Rodent models to examine in vivo hormonal regulation of mammary gland Tumorigenesis. In: Medina D, Kidwell W, Heppner G, Anderson E. Cellular and Molecular Biology of Mammary Cancer. Boston: Springer, 163–179.
    [183] Wetterwald A, van der Pluijm G, Que I, Sijmons B, Buijs J, Karperien M, et al. 2002. Optical imaging of cancer metastasis to bone marrow: a mouse model of minimal residual disease. The American Journal of Pathology, 160(3): 1143−1153. doi:  10.1016/S0002-9440(10)64934-6
    [184] Wright LE, Ottewell PD, Rucci N, Peyruchaud O, Pagnotti GM, Chiechi A, et al. 2016. Murine models of breast cancer bone metastasis. BoneKEy Reports, 5: 804.
    [185] Xia HJ, Chen CS. 2011. Progress of non-human primate animal models of cancers. Zoological Research, 32(1): 70−80.
    [186] Xia HJ, He BL, Wang CY, Zhang HL, Ge GZ, Zhang YX, et al. 2014. PTEN/PIK3CA genes are frequently mutated in spontaneous and medroxyprogesterone acetate-accelerated 7, 12-dimethylbenz(a)anthracene-induced mammary tumours of tree shrews. European Journal of Cancer, 50(18): 3230−3242. doi:  10.1016/j.ejca.2014.10.012
    [187] Xia HJ, Wang CY, Zhang HL, He BL, Jiao JL, Chen CS. 2012. Characterization of spontaneous breast tumor in tree shrews (Tupaia belangeri chinenesis). Zoological Research, 33(1): 55−59.
    [188] Xiao J, Liu R, Chen CS. 2017. Tree shrew (Tupaia belangeri) as a novel laboratory disease animal model. Zoological Research, 38(3): 127−137. doi:  10.24272/j.issn.2095-8137.2017.033
    [189] Xu XL, Wagner KU, Larson D, Weaver Z, Li CL, Ried T, et al. 1999. Conditional mutation of Brca1 in mammary epithelial cells results in blunted ductal morphogenesis and tumour formation. Nature Genetics, 22(1): 37−43. doi:  10.1038/8743
    [190] Yang Y, Yang HH, Hu Y, Watson PH, Liu HT, Geiger TR, et al. 2017. Immunocompetent mouse allograft models for development of therapies to target breast cancer metastasis. Oncotarget, 8(19): 30621−30643. doi:  10.18632/oncotarget.15695
    [191] Yoneda T, Williams PJ, Hiraga T, Niewolna M, Nishimura R. 2001. A bone-seeking clone exhibits different biological properties from the MDA-MB-231 parental human breast cancer cells and a brain-seeking clone in vivo and in vitro. Journal of Bone and Mineral Research, 16(8): 1486−1495. doi:  10.1359/jbmr.2001.16.8.1486
    [192] Zander SAL, Sol W, Greenberger L, Zhang YX, van Tellingen O, Jonkers J, et al. 2012. EZN-2208 (PEG-SN38) overcomes ABCG2-mediated topotecan resistance in BRCA1-deficient mouse mammary tumors. PLoS One, 7(9): e45248. doi:  10.1371/journal.pone.0045248
    [193] Zheng LL, Zhou BG, Meng XM, Zhu WF, Zuo AR, Wang XM, et al. 2014. A model of spontaneous mouse mammary tumor for human estrogen receptor- and progesterone receptor-negative breast cancer. International Journal of Oncology, 45(6): 2241−2249. doi:  10.3892/ijo.2014.2657
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Breast cancer animal models and applications

doi: 10.24272/j.issn.2095-8137.2020.095
Funds:  This study was supported in part by grants from the National Key R&D Program of China (2018YFC2000400), National Natural Science Foundation of China (81830087, U1602221, 31771516), and Project of Innovative Research Team of Yunnan Province (2019HC005)

Abstract: Breast cancer is the most common malignancy in women. Basic and translational breast cancer research relies heavily on experimental animal models. Ideally, such models for breast cancer should have commonality with human breast cancer in terms of tumor etiology, biological behavior, pathology, and response to therapeutics. This review introduces current progress in different breast cancer experimental animal models and analyzes their characteristics, advantages, disadvantages, and potential applications. Finally, we propose future research directions for breast cancer animal models.

Li Zeng, Wei Li, Ce-Shi Chen. Breast cancer animal models and applications. Zoological Research. doi: 10.24272/j.issn.2095-8137.2020.095
Citation: Li Zeng, Wei Li, Ce-Shi Chen. Breast cancer animal models and applications. Zoological Research. doi: 10.24272/j.issn.2095-8137.2020.095
    • Breast cancer is the most common disease in women worldwide both in terms of morbidity and mortality (Fidler et al., 2017). By 2018, there was an estimated 18.1 million new cancer cases and 9.6 million cancer deaths globally, including ~2 million new breast cancer cases, accounting for 11.6% of all cancer cases, and ~626 000 breast cancer deaths, accounting for 6.6% of all deaths (Bray et al., 2018). Among breast cancer patient deaths, many have stemmed from a lack of cost-effective treatment (Anastasiadi et al., 2017). Animal models have played a vital role in the history and development of basic and translational breast cancer research in humans. This review introduces different experimental animal models of breast cancer, from the selection of animals to the establishment of different animal models, and analyzes their characteristics, advantages, disadvantages, and potential applications. Finally, we propose future research directions for breast cancer animal models.

    • Non-mammalian animals, such as Caenorhabditis elegans, Drosophila, zebrafish, and chickens, are frequently used to mimic breast cancer cell growth, migration, and metastasis. The benefits of utilizing these animals include rapid experimental cycles and low costs because of their short reproductive cycles. Chickens and zebrafish have been applied to study tumor angiogenesis (Gheorghescu et al., 2015; Jagadeeshan et al., 2017). For example, Mercatali et al. (2016) injected primary cultured bone metastases cells from breast cancer patients into zebrafish embryos to study their metastatic potential. Ren et al. (2017) transplanted fluorescent protein and chemically labeled human breast cancer cells into zebrafish embryos and visualized the spatiotemporal processes of cancer cell spread, invasion, and metastasis. However, the disadvantage of these animals is that they are very different from humans and appear to lack many homologous genes. Additionally, the physiological structures of most organs are very different between these animals and humans.

    • Compared with non-mammalian animals, mammals are more similar to humans. Rodents, especially mice and rats, are the most popular animals for breast cancer research. In addition, tree shrews are increasingly used due to their closer evolutionary relationship to primates than to rodents. However, the disadvantages of using mammals for breast cancer research include long experimental periods and high costs.

      Among mammalian animals, mice are the most popular (Jonkers & Derksen, 2007) due to their small size, low cost, short generation time, and mature gene editing technology. Mice are also similar to humans in terms of anatomy, physiology, and genetics. Additionally, there are many inbred strains of mice available. However, breast cancer mouse models also have several drawbacks. For example, mice can tolerate higher doses of drugs than humans, and thus the blood concentration that can be achieved in mice cannot be reached in human patients; as such, 90% of new anticancer drugs fail in human clinical trials even though they were effective in mouse models. Additionally, mouse breast cancer metastasis usually occurs in the lung, but not the lymph node, liver, bone, and brain (Kim & Baek, 2010), where human breast cancers usually metastasize.

      Other rodents (e.g., rats, hamsters, moles), dogs, cats, pigs, tree shrews, and non-human primates (NHPs) are also commonly used for breast cancer research. Smith et al. (2003) reported that intrauterine transplantation in cats is a reproducible experimental model for metastatic breast cancer. Spontaneous breast tumors are very common in female dogs, accounting for 50% of all tumors diagnosed. Sahabi et al. (2018) also found dogs to be a suitable large-animal model for human breast cancer. NHPs, such as monkeys, are similar to humans and have been widely used to study human diseases, including breast cancer. However, due to the low incidence of spontaneous tumors, long incubation periods, and high costs, NHPs have not been widely used in cancer research (Xia & Chen, 2011).

      Tree shrews are a new experimental animal model and are considered advantageous because they are small in body size (100–200 g) and highly productive (2–3 offspring) (Xia et al., 2012; Xiao et al., 2017). Tree shrews exhibit several advantages. For example, they contain three pairs of breasts, reach sexual maturity at 3–4 months, with pregnancy and lactation lasting only 40–45 and 35–40 days, respectively, can breed for up to three years, and have a lifespan of 5–7 years (Fan et al., 2013). In addition, high-quality genome sequences have revealed that tree shrews are evolutionarily close to primates (Fan et al., 2019; Xiao et al., 2017). Most importantly, tree shrews develop spontaneous breast cancers with high frequency (Xia et al., 2014). Spontaneous tumors in tree shrews were actually reported as early as the 1960s (Elliot et al., 1966). Breast tumors can be induced in tree shrews by chemical carcinogens and oncogenes (details below).

      According to different requirements, different animal models have been constructed to simulate the occurrence and development of human breast cancer. These construction methods are listed in Table 1.

      ModelMethodReferences
      SpontaneousNo treatmentRao et al., 1987
      InducedChemicalDMBA or MNUChan et al., 2007
      PhysicalRadiationRusso & Russo, 1996
      BiologicalLentivirus infectionBu et al., 2009; Fisher et al., 1999
      TransplantationHomeotransplantationSpontaneous or induced breast cancer cells transplanted into same strainPaschall & Liu, 2016
      HeterograftHuman breast cancer cells or patient tumor tissues transplanted into immunodeficient animalsBurdall et al., 2003
      Genetic engineering mouse modelTransgenicOncogene activationRashid & Takabe, 2015
      KnockoutTumor suppressor gene inactivationHutchinson, 2000

      Table 1.  Summary of breast cancer animal models

    • Spontaneous tumors occur naturally in experimental animal populations. The most important characteristic of spontaneous breast cancer is that the experimental animals have not been artificially treated, and thus are similar to humans in terms of etiology.

      Spontaneous breast tumors have been frequently observed in rodents (Rao et al., 1987). Although inbred mice are mostly used in spontaneous breast cancer research, both the incidence and frequency of such tumors can vary considerably among different mouse strains (C3H, A, CBA/J, and TA2), as shown in Table 2 (Russo & Russo, 1996). For example, SHN inbred mice show a high incidence of breast cancer (Nagasawa et al., 1976). TA2 inbred mice (cultivated by Tianjin Medical University), which exhibit a stable genetic phenotype, develop spontaneous breast cancer similar to human basal breast cancer in terms of biology, morphology, and phenotype, with an average age at the time of tumorigenesis of 329.81±95.3 days (Sun et al., 2008). Zheng et al. (2014) developed a spontaneous breast tumor animal model from Kunming outbred mice and found breast tumors in 25% (89/398) of female breeding mice, with an average time of tumorigenesis of 13.5 months.

      StrainLatencyFrequencyPathologyReferences
      C3H6–10 monthsBreeding female mice: 95%; Virgin mice: 88%; Male mice: <1%ACHeston & Vlahakis, 1971; Machida et al., 2019
      ABreeding females: 80–84%Strong, 1936
      DBA/2Female mice: 72%; Virgin mice: 48%; Male mice: 1%Szymanska et al., 2014
      BALB/c12 monthsFemale mice: 5%; Virgin mice: 1%ACHeston & Vlahakis, 1971; Machida et al., 2019
      SHN6.6–8.7 monthsBreeding rats: 97.2%; Virgin rats: 88.3%ACNagasawa et al., 1976
      TA2329.81±95.3 days84.1%Sun et al., 2008
      Kunming13.5 months25%IDCZheng et al., 2014
      AC: Adenocarcinoma; IDC: Invasive ductal carcinoma.

      Table 2.  Common spontaneous mouse breast tumors

      In addition to rodents, spontaneous breast cancer has been reported in large animals, such as dogs, cats, tree shrews, and monkeys. Canines are of great value in studies as they are outbred, large in size, exhibit a high incidence of spontaneous breast cancer, live in similar environments as humans, and have an intact immune system. Dogs and humans also show more than 80% genetic similarity. Furthermore, canine breast cancers are frequently observed in pet hospitals and are often treated with therapies or under clinical trials (Mottolese et al., 1994). Peña et al. (2003) analyzed the histopathological morphology and clinical characteristics of spontaneous inflammatory breast cancer in 21 dogs and revealed that such cancer can be used as a spontaneous model of human inflammatory breast cancer. Spontaneous breast tumors have been reported in tree shrews as early as the 1960s (Elliot et al., 1966). Xia et al. (2012) also reported the occurrence of intraductal papillary tumors in tree shrews. Furthermore, Xia et al. (2014) analyzed 18 spontaneous tree shrew breast tumors with hematoxylin and eosin staining and immunohistochemistry (IHC), and identified four cases of intraductal papilloma (4/18, 22.2%), 10 cases of papillary carcinoma (10/18, 55.5%), and four cases of invasive ductal carcinoma (4/18, 22.2%). Among them, five cases of spontaneous breast tumors carried PIK3CA/PTEN mutations, which activate AKT (Xia et al., 2014). Interestingly, the well-known tumor suppressor gene TP53 showed no mutation in these tumors, suggesting that the PI3K-AKT pathway may play an important role in tree shrew breast tumor initiation. Consistently, human breast tumors also show a high frequency of PIK3CA and PTEN mutations (Koboldt et al., 2012). These findings suggest that tree shrew spontaneous breast tumor models may well mimic a subset of human breast tumors. Currently, however, there are no tree shrew strains with a pure genetic background to establish orthotopic tumor transplantation models (Xiao et al., 2017).

      Spontaneous breast tumors are similar to human tumors because they occur naturally in genetically heterogeneous populations. The disadvantages of spontaneous breast cancer animal models include low incidence rates, long latency, lengthy experimental periods, and non-synchronization. Therefore, spontaneous breast cancer animal models are usually used for studying cancer etiology and treatment.

    • To increase breast tumor incidence rates and accelerate tumorigenesis, scientists can artificially treat animals with chemical, physical, and biological carcinogens through oral administration, injection, and whole-body treatment (Su et al., 2010). The most common method is administration of 7,12-dimethylbenz(a) anthracene (DMBA) or N-methyl-N-nitrosourea (MNU) (Russo & Russo, 1996; Thompson & Singh, 2000).

      In mice, DMBA, 3,4-benzopyrene, 3-methylcholan-threne (MCA), 1,2,5,6 dibenzanthracene, and urethane have been used to induce breast cancer. Most chemically induced breast tumors in mice are adenomas and type B adenocarcinomas (Russo & Russo, 1996). Fabris et al. (2014) used DMBA to induce breast tumors in female (BALB/c x DBA/2) F1 mice with an incubation period of seven months, but found that progesterone or a combination of medroxyprogesterone acetate (MPA) and DMBA can shorten the incubation period to three months and increase the incidence of breast cancer. Lanari et al. (1986) continuously administered MPA in BALB/c mice and induced mammary ductal carcinoma in 79% of mice with an incubation period of one year.

      In rats, DMBA, MNU, MCA, 2-acetylamino-fluorene, 3,4-benzopyrene, ethylnitrosourea, and butylnitrosourea are widely used to induce breast cancer (Russo & Russo, 1996; Welsch, 1987). Common inducible rat breast cancer models are shown in Table 3. DMBA and MNU-induced rat breast cancers are mostly hormone dependent (Russo & Russo, 1996). The most common method for generating induced rat breast cancer models is to treat Sprague-Dawley (SD) or Fischer 344 rats with DMBA or NMU, usually by intravenous, subcutaneous, or intragastric administration (Gullino et al., 1975; Thompson & Meeker, 1983). NMU-induced primary rat tumors are similar to ERα-positive low-grade human breast cancer (Chan et al., 2007). Following gavage administration of 20 mg of DMBA in 47-day-old SD rats, Barros et al. (2004) reported a tumor induction incubation of 8–13 weeks and an incidence of breast tumors close to 100% at 13 weeks. Furthermore, Gullino et al. (1975) found that a single intraperitoneal injection of 50 mg/kg MNU in 50-day-old SD rats induced mammary tumors in more than 73% after 86 days. This model has several advantages, such as low cost, high specificity, high reproducibility, and the induction of ERα-positive tumors.

      StrainAge (d)CarcinogenDoseRoutePrimary tumorReferences
      Incidence (%)Latency
      SD47DMBA20 mg/kgig1008–13 wBarros et al., 2004
      50NMU50 mg/kgiv7386 dGullino et al., 1975
      NSDDMBA5 mg/animalip100Russo et al., 1990
      NMU50 mg/kgiv100Russo et al., 1990
      BUF/N50NMU50 mg/kgiv8977 dGullino et al., 1975
      F34450NMU50 mg/kgiv8994 dGullino et al., 1975
      SD: Sprague-Dawley; F344: Fischer 344; NSD: Inbred S-D; BUF/N: Buffalo; iv: Intravenous; ig: Intragastric; ip: Intraperitoneal injection; d: Day; w: Week.

      Table 3.  DMBA or MNU-induced mammary tumors in female rats

      Xia et al. (2014) demonstrated that intragastric administration of DMBA can induce breast tumors in 3–4-month-old female tree shrews with a low frequency (12%), with the addition of MPA increasing the incidence to 50% after a seven month incubation period. They identified three intraductal papillary carcinomas and one invasive ductal carcinoma, with PIK3CA gene mutations detected in all tumors induced by DMBA and MPA. Consistently, these mutations were positively correlated with the activation of AKT. These genetic alterations in induced mammary tumors are similar to those in spontaneous mammary tumors in tree shrews (Xia et al., 2014). Chen et al. (2019) also found that an injection of DMBA and MPA can shorten the latency of breast lesions to 56 days in this species.

      Breast cancer can also be induced by physical approaches, such as ionizing radiation. In rats, X-ray or neutron radiation can induce breast cancer by whole-body or segmental irradiation (Broerse et al., 1985; Welsch, 1987). Among rat strains, SD and Lewis rats are most susceptible to radiation-induced tumorigenesis, whereas AxC, Fisher, Long-Evans, and Wistar/Furth rats are less susceptible. Mammary tumors from irradiated rats are usually hormone-dependent adenocarcinomas or fibroadenomas (Russo & Russo, 1996).

      Biological induction of breast cancer mainly relies on lentiviruses to overexpress oncogenes or silence tumor suppressor genes in experimental animals. This technology was originally developed by Professor Yi Li from the Baylor College of Medicine. His team developed two new retrovirus-based systems to study the role of specific genes in tumorigenesis. The principle is shown in Figure 1. The first method replies on RCAS (replication competent ALV-LTR splice acceptor) and TVA (TVA tumor virus A) to stably introduce oncogenes into somatic cells in vivo. Specifically, chicken DF-1 cells are transfected with a plasmid encoding a replication-competent subgroup of avian virus vector RCAS (vector contains viral genes gag, pol, and env and the gene of interest (gene X)) to produce a high titer virus, whose surface glycoprotein attaches to the extracellular domain of the TVA receptor on the cell surface of avian cells (Du & Li, 2007). Recombinant avian retroviruses are generated to infect TVA transgenic mice to produce various cancer models, including breast cancer (Fisher et al., 1999). The RCAS virus containing foreign genes of interest can be directly injected into the glands of MMTV-TVA or WAP-TVA transgenic mice to induce breast tumors. The MMTV-TVA transgenic mice are injected with 107 RCAS viral particles encoding the PyMT (T-antigen in mouse mammary tumor virus-polyomavirus) gene in mammary ducts, resulting in a median tumor latency of 12.5 days. Infected mice develop tumors in all infected glands within three weeks (Du et al., 2006). In addition to PyMT, several other oncogenes, including Neu and Wnt-1, can also induce breast tumors. It takes about seven months for MMTV-TVA transgenic mice infected with RCAS-Neu to induce tumors in half of infected mice (Du et al., 2006).

      Figure 1.  Biological approach to induce breast tumors

      The second method is based on the FUCGW lentiviral vector, as shown in Figure 1B. The gene is stably introduced into the mouse mammary gland by injecting a FUCGW lentiviral vector with the gene of interest to construct a breast cancer model. Compared with the RCAS-TVA system, lentiviruses can infect any cells and can accommodate larger inserts (Bu et al., 2009). Dong et al. (2016) constructed a lentivirus expressing PyMT to induce breast tumors, with all mice developing tumors within 30 days. The median incubation period is reported to be nine days and all tumors are ERα-/PR- (Bu et al., 2009; Dong et al., 2016; Mukherjee et al., 2006). Ge et al (2016) induced breast tumors in tree shrews by injecting a lentivirus expressing the PyMT oncogene into the ducts of 22 tree shrews. They reported an incubation period of three weeks and development of breast tumors in all injected animals at seven weeks, including papillary carcinomas (main tumor type) and lymph node metastasis and lung metastasis in one case (Ge et al., 2016).

      The advantages of induced breast cancer animal models include relatively high incidence rates, short latencies, and more reliable predicted results compared with spontaneous breast cancer animal models. The disadvantages are low efficiencies, long incubation times, different incidence times, and different pathological characteristics. Breast tumors induced by carcinogens are usually hormone-dependent adenocarcinomas. In addition, number of tumors, latency, and histological type in animals can be affected by age, reproductive history, and the host's endocrine environment when exposed to carcinogens (Russo & Russo, 1996). Overall, induced breast cancer animal models are used for studies on etiology and prevention (Mollard et al., 2011).

    • Transplantation models involve the transplantation of spontaneous or induced breast cancer tissues or cells into experimental animals (DeRose et al., 2011). According to the source of the transplant, models can be divided into allograft and xenograft, with the latter requiring immunodeficient mice. Transplantation sites can be divided into orthotopic and ectopic transplantations, and the latter can be divided into subcutaneous transplantation, tail vein injection to generate lung metastasis, and left ventricular injection to generate bone and brain metastasis (Mollard et al., 2011). For orthotopic transplantation, an intraductal route of transplantation is considered a better alternative to mammary fat pad transplantation. Indeed, intraductal transplantation can generate a better pathological microenvironment for breast cancer cells; however, fewer cancer cells can be injected, and it is technically challenging. Currently, the most popular animal model for testing new therapies is the transplantation model, especially the human xenograft model (Lacroix & Leclercq, 2004). The transplantation model has the advantages of short cycles, low costs, small variations, and high tumor formation rates.

    • Spontaneous or induced breast cancer cell lines can be transplanted into the same genetic strain with normal immune function (Figure 2A). Several transplantable animal breast cancer cell lines have been established, most of which are derived from mice. Breast cancer cell lines used for allogeneic transplantation have strict germline specificity. Commonly used mouse-derived breast cancer cell lines include 4T1, EMT6, TM40, and D2A1 derived from BALB/c mice; E0771 from C57BL/6 mice; and MVT1, 6DT1, and M6 from FVB mice (Yang et al., 2017), as shown in Table 4. Most mouse cell lines are derived from spontaneous breast tumors in inbred and genetically engineered mice (Yang et al., 2017). Among them, the BALB/c-derived 4T1 model is a major transplantable mouse breast cancer model for screening anti-cancer drugs and studying tumor and host-derived factors associated with spontaneous metastasis to the lung, brain, bone, and other organs (Aslakson & Miller, 1992; Kusuma et al., 2012). EMT6 is another BALB/c-derived hormone receptor-negative murine breast tumor cell line (Rockwell et al., 1972). This model has the advantage of short latency and is often used to screen and evaluate pre-clinical anti-tumor drugs (Duan et al., 2013). Additionally, Ehrlich ascites carcinoma (EAC) is a spontaneous murine mammary adenocarcinoma carried in outbred mice by serial intraperitoneal passages. EAC is an undifferentiated carcinoma, which exhibits a rapid growth rate in suspension and sensitivity to chemotherapies (Ozaslan et al., 2011).

      Figure 2.  Transplanted breast cancer animal models

      Cell lineOriginLatencyPathologyMetastasisTransfer siteReferences
      4T167NRBALB/C8–17 dLuminalYesLungJohnstone et al., 2015
      4T1.2BasalNo
      TM40DBALB/C1 wYesLungShi et al., 2001
      D2A1BALB/c14–18 dYesLung, heartMorris et al., 1993
      EMT6BALB/c3–5 dYesLungDuan et al., 2013; Rockwell et al., 1972
      E0771C57BL/6BasalYesLungJohnstone et al., 2015
      MVT1FVB/NLuminalYesLungPei et al., 2004
      6DT1FVB/NLuminalYang et al., 2017
      M6FVB/N44 dLuminalYesLungHolzer et al., 2003
      CSTFVB/N20 dBasalHámori et al., 2020
      EACOutbredYesLung, liver, heart, boneMishra et al., 2018; Ozaslan et al., 2011
      D: Day; w: Week.

      Table 4.  Basic characteristics of commonly used mouse breast cancer cell lines

      Recently, Hámori et al. (2020) introduced a newly established Brca1-/-, p53-/- mouse breast tumor cell line (CST). CST shows significant features of triple negative breast cancer (TNBC) with BRCA1 mutations, as well as sensitivity to platinum-based chemotherapy and PARP inhibitors. Following the transplantation of 1.5×106 of CST cells into the fat pads of wild-type female FVB mice, Hámori et al. (2020) reported a tumor incidence rate of 100% and an incubation period of 20 days.

      Additionally, several rat breast cancer cell lines, such as UHKBR-01 and RM22-F5, are available for allograft. The UHKBR-01 cell line was initially established from DMBA-induced female SD rat breast tumors. UHKBR-01 cells show a slow growth rate in culture and are highly tumorigenic in nude mice. UHKBR-01 cells are positive for both ERα and PR (Chow et al., 2003; Mollard et al., 2011). The RM22-F5 cell line was first derived from a spontaneous malignant breast tumor in an old female Wistar rat (Nakanishi et al., 1995).

      Although allograft breast cancer models have several advantages, such as multiple characterized cell lines, rapid growth and metastasis, and immune-component microenvironment, these models also have limitations. Above all, the transplanted cancer cells are not from humans.

    • Cell-derived xenografts (CDX) can be transplanted and grown in immunodeficient mice, such as nude mice (lacking T cells), NOD-SCID mice (lacking T and B cells), and NSG mice (lacking T, B, and natural killer (NK) cells and macrophages) (Chakrabarti & Kang, 2015)(Figure 2B). Methods of xenograft include subcutaneous, intravenous, cardiac, and orthotopic inoculation. The orthotopic CDX transplantation model involves the transplanting of tumor cells into the mammary fat pads of mice to study growth and metastasis (Fantozzi & Christofori, 2006b; Hoffman, 1999). The tail vein injection is suitable for monitoring experimental lung metastases (Jiang et al., 2014).

      The characteristics of human breast cancer cell lines commonly used for xenograft transplantation are shown in Table 5. ERα-positive luminal A cell lines, such as MCF-7 and T47D, only grow in the presence of estrogen in mice. Several HER2 subtypes, including SK-BR-3 and MDA-MB-453, have weak tumorigenic potential. TNBC cell lines, such as MDA-MB-468, HCC1806, HCC1937, and MDA MB-231, are highly tumorigenic (Holliday & Speirs, 2011).

      NameOriginSubtypePathologyTransplant siteNumber of tumor cellsMouse strainLatencyMetastasisMetastasis siteReferences
      BT20BreastBasalIDCSubcutaneous6.25×106Nude mice3 wNoOzzello et al., 1974
      BT474BreastLuminal BIDCLeft ventricle1×106Nude miceYesBoneLu et al., 2009; Neve et al., 2006
      MCF-7Pleural effusionLuminal AIDCMammary gland fat pad1×106Ovariectomized female athymic nude miceb1 wYesLymph nodes, lymph vesselsHarrell et al., 2006
      MDA-MB-231Pleural effusionBasalACTail vein2×105Immunodeficient mice8~15 wYesLung, liverBos et al., 2009; Cailleau et al., 1974; Minn et al., 2005;
      Mammary gland fat pad0.5~1×1065~9 wLung, liver, brain
      Left ventricle0.1~1×1054 wBrain, bone
      MDA-MB-453Pleural effusionHER2+ACMammary gland fat pad1×105NOD/SCID4 wYesBoneCharafe-Jauffret et al., 2009; Neve et al., 2006
      MDA-MB-435Pleural effusionBasalIDCMammary gland fat pad5×106NCr-nu/nu nude miceYesLungLiby et al., 2003
      MDA-MB-361BreastLuminal BACNeve et al., 2006
      MDA-MB-468Pleural effusionBasalACNeve et al., 2006
      SUM149BreastBasalDCMammary gland fat padNOD/SCID(6-8 w)aYesLungKuperwasser et al., 2005
      SUM185Pleural effusionLuminal ADCNeve et al., 2006
      SUM190BreastBasalCMammary gland fat padNOD/SCID(6-8 w)aKuperwasser et al., 2005
      SUM1315SkinBasalIDCMammary gland fat padNOD/SCID(8-12 w)aYesLung, boneKuperwasser et al., 2005
      SUM52Pleural effusionLuminalCEthier et al., 1996
      T47DcPleural effusionLuminal AIDCMammary gland fat pad1×106NOD/SCIDCerliani et al., 2011
      SKBR3Pleural effusionHER2+ACTrempe, 1976
      ZR-75-1AscitesLuminal BIDCEngel et al., 1978
      HCC1806 BasalSubcutaneously1.7×106Nude mice5 dWang et al., 2015
      HCC1937BreastBasalDCMammary gland5×106NOD/SCID10 dJia et al., 2016; Neve et al., 2006
      AC: Adenocarcinoma; IDC: Invasive ductal carcinoma; C: Carcinoma; DC: Ductal carcinoma; a: Incubation period required for tumor to grow to about 1 cm; b: Mice were implanted with silastic pellets containing cellulose (10 mg) or 17 h-estradiol (2 mg+8 mg cellulose); c: T47D cells stably transfected with constitutively active fibroblast growth factor 2; d: Day; w: Week; m: Month.

      Table 5.  Characteristics of commonly used human breast cancer cell lines

      Due to long-term in vitro culture, human breast cancer cell lines differ from primary tumors in terms of genetic aberrations, gene expression patterns, pathological characteristics, drug responses, and tumor microenvironments. Patient-derived xenograft (PDX) models (Figure 2C) are becoming increasingly popular as they are directly derived from human tumor specimens and have never been cultured in vitro. These xenografts are very close to patients in terms of genetic abnormalities, gene expression profiles, pathological parameters, metastatic potential, and drug response (DeRose et al., 2011). PDX models are used to identify biomarkers for personalized drug selection and to overcome the limitations of CDX transplantation in clinical treatment (Cho et al., 2016; Pillai et al., 2018). Many institutions now build their own PDX model libraries. For example, the Novartis Pharmaceuticals drug screening tool released in 2015 contains more than 1 000 PDX models; NCI contains more than 300 PDX models; and EurO PDX consists of 16 European research institutions and 1 500 models (Hidalgo et al., 2014). These libraries provide great convenience for the screening of preclinical drugs and basic research.

      PDX models can predict clinical outcomes and have been used in preclinical drug assessment, biomarker identification, biological research, and personalized medicine (Hidalgo et al., 2014). However, PDX models are also expensive, difficult, and time-consuming to prepare because NSG mice and humanized matrix components are usually required (DeRose et al., 2011).

      Patient-derived organoids (PDOs) are derived from primary human tumors and cultured in vitro, which preserves the complex histological architecture and heterogeneity of tumor tissue. PDOs can solve the long cycle and high cost of PDX model establishment and are suitable for mass anti-tumor drug screening (Neal et al., 2018). Duarte et al. (2018) successfully combined a well-defined genetic model of BRCA1 and BRCA2 breast cancer with organoid culture technology to develop a three-dimensional cancer organoid, with the orthotopically transplanted organoids producing breast tumors that retained the epithelial morphology and drug response of the original tumor.

      Tumors in immunodeficient mice cannot faithfully copy the microenvironment of human tumors, which makes these models unsuitable for immunotherapy. Therefore, a humanized PDX (Hu-PDX) model, which recapitulates the human immune system, has been developed recently. Most humanized mice are injected intravenously with peripheral monocytes (PBMCs) or CD34+ hematopoietic stem cells (HSCs) before or after tumor transplantation (Meraz et al., 2019). The Hu-PDX model can be used for tumor immunotherapy research, such as evaluating the efficacy of anti-PD-L1/PD-1 antibodies in the treatment of breast cancer. However, humanized mouse models are expensive, time consuming, and require integration of multidisciplinary expertise (Meraz et al., 2019).

    • GEMMs of breast cancer are created using transgenic technology (Hanahan et al., 2007). Conventional transgenic mice are constructed by implementing tissue-specific expression of transgenes through tissue-specific promoters (Borowsky, 2011; Park et al., 2018). Multiple copies of oncogenes are then randomly integrated into the mouse genome.

      Promoters commonly used in transgenic animal models of breast cancer include mouse mammary tumor virus long terminal repeat (MMTV-LTR) and whey acidic protein (WAP) promoters (Taneja et al., 2009). The MMTV is an important virus causing mammary tumors in mice. The MMTV promoter drives transgene expression in ducts and alveolar cells at all developmental stages of the mammary gland. The MMTV promoter is hormone-activated and its activity is significantly enhanced during pregnancy (Pattengale et al., 1989). Drawbacks of this promoter include uneven mosaic pattern activation (Stamp et al., 1992) and leakage (Liu et al., 2018). The WAP promoter is only active in the breast during mid-pregnancy. It is activated by lactogenic hormones in mouse breast tumors, and preferentially drives the expression of transgenes in alveolar cells during small alveolar differentiation (Hutchinson & Muller, 2000). Both promoters can be used to achieve specific expression of foreign genes in breast epithelial cells to avoid tumor induction in other organs. The phenotype exhibited by WAP and MMTV transgenes may depend on the developmental stage of the individual mouse. Other less common promoters include the C3(1) promoter (5' flanking region of the C(3)1 component of the rat prostate steroid binding protein) (Maroulakou et al., 1994) and the metallothionein (MT) promoter (Törnell et al., 1991).

      Overexpression of breast-specific oncogenes, such as HER2/ERBB2 (erythroblast leukemia viral oncogene homolog 2), PyMT, Wnt, Myc, Ras, and PIK3CA, has been the primary approach for studying breast cancer in transgenic mice. The most commonly used single transgenic mouse models are listed in Table 6. These models can develop breast carcinoma in situ, and even distant metastasis at later stages (Jonkers & Derksen, 2007).

      PromoterTransgenePrimary tumorMetastasisPathologyReferences
      LatencyIncidence (%)Incidence (%)LatencyMetastatic site
      MMTV-LTRTGFα6–13 m40ACHalter et al., 1992; Matsui et al., 1990
      Wild-type-ErbB-2 (HER2,Neu)7 m100728 mLungACGuy et al., 1992b
      H-ras5 w–6 mACSinn et al., 1987
      c-rel19.9 m31.6LungACRomieu-Mourez et al., 2003
      PyMT4–8 w10084–9014 wLymph node, lungIDCAlmholt et al., 2005
      c-Myc4–8 mACStewart et al., 1984
      Cyclin D122 m40Wang et al., 1994
      Wnt-16 m50Lymph node, lungACLi et al., 2000; Tsukamoto et al., 1988
      WAPTGFα6–12 m100ACRose-Hellekant & Sandgren, 2000b; Sandgren et al., 1995
      Ras24 w10014LungACNielsen et al., 1991
      c-Myc5–10 m10020LungACRose-Hellekant & Sandgren, 2000a
      SV408–9 mACLi et al., 1996; Santarelli et al., 1996
      C(3)1SV4016 w10015LungIDCGreen et al., 2000
      AC: Adenocarcinoma; IDC: Invasive ductal carcinoma; d: Day; w: Week; m: Month.

      Table 6.  Basic situation of common breast cancer transgenic mouse models

      At present, the PyMT transgenic mouse model is commonly used because mammary tumors develop rapidly (Rashid & Takabe, 2015). MMTV-PyMT transgenic mice show obvious tumors at 4–8 weeks of age, and 84%–90% of mice develop lung metastases at 14 weeks of age (Guy et al., 1992a, 1992b; Lin et al., 2003). The pathology of these tumors is very similar to that of human breast cancers, involving hyperplasia, adenoma, and early or advanced cancer. MMTV-Wnt-1 transgenic mice are another common model used for studying TNBC and screening drugs (Li et al., 2000). This model includes extensive ductal hyperplasia in the early stage, and about 50% of female transgenic mice develop breast adenocarcinoma by the age of six months. When the tumor is first detected, there is little metastasis to the lung or proximal lymph node, but metastasis often occurs after the primary tumor is removed (Li et al., 2000). ErbB2/HER2/Neu is another well-known oncogene in human breast cancers. The HER2 gene is amplified or over-expressed in about 20% of human primary breast cancers (Allred et al., 1992; Park et al., 2008). Guy et al. (1992b) constructed a MMTV/wild-type-neu transgenic mouse model and reported focal breast tumors after an incubation period of 205 days, a tumor incidence rate of 100%, and the development of secondary metastatic tumors in the lungs of 72% of transgenic mice after eight months. Bouchard et al. (1989) constructed a MMTV-c-neu transgenic mouse model that carried activated c-neu under the control of the MMTV promoter, which resulted in the asynchronous appearance of poorly differentiated breast adenocarcinomas at 5–10 months.

      Davies et al. (1999) constructed MMTV-Neu and MMTV-TGFα transgenic SD rat breast cancer models. When these MMTV-Neu transgenic rats underwent repeated pregnancy and lactation cycles, they developed multiple focal hyperplasia and benign lesions, including lobular and ductal hyperplasia, fibroadenomas, cystic dilatations, and papillary adenomas. In addition to these lesions, ductal carcinoma in situ (DCIS) and other malignant lesions also developed with a low frequency. Similar phenotypes have also been observed in MMTV-TGFα transgenic rats (Davies et al., 1999). Moreover, some transgenic rats are highly susceptible to carcinogens, e.g., Hras128 transgenic rats. Hras128 carries a human c-Ha-ras proto-oncogene, including its own promoter region. Twenty-two Hras128 transgenic female rats treated with 50 mg/kg MNU rapidly developed multiple and large mammary carcinomas within eight weeks; in contrast, non-transgenic rats developed no or only small tumors within this period (Nohmi et al., 2017).

    • In addition to transgenic animal models, there are also tumor suppressor knockout breast cancer animal models. Knockout of tumor susceptibility genes, such as p53, BRCA1/2, and pTEN, in the genome of experimental animals can create breast cancer models. Breast tissue-specific gene knockout can be achieved using the Cre/loxP recombinase system (Ding & Gan, 2012) and MMTV-Cre or WAP-Cre tool mice.

      P53 is a classic tumor suppressor gene, and P53 knockout (p53-/-) mice can spontaneously develop breast cancers and a variety of other malignant tumors (Liu et al., 2012). Breast-specific p53 knockout mice show spontaneous tumors after about 10 weeks and rapid tumor development after 15–20 weeks (Clarke, 2000). PTEN is a common mutated tumor suppressor gene in human cancers. When Pten+/- mice are older than six months, they develop a series of tumors, 50% of which are breast cancers (Stambolic et al., 2000).

      With the development of technology, spatiotemporal specific knockout and transgene expression can be achieved (Kim et al., 2018). The most frequently used promoters are Tet-off/Tet-on and tamoxifen systems (McLellan et al., 2017; Nagy, 2000). Construction of inducible conditional gene knockout animals can solve the problem of lethality of embryos caused by conventional gene knockout and can achieve gene knockout at a specific time. For example, Xu et al. (1999) used the Cre-loxP system to construct Brca1 conditional knockout mouse models Brca1Ko/CoWap-Cre and Brca1Ko/CoMMTV-Cre. About 30% of Brca1Ko/CoMMTV-Cre mice and 15% of Brca1Ko/CoWap-Cre mice developed multiple types of breast tumors at 10–13 months of age (Xu et al., 1999). Liu et al. (2011) used the Tet-off/Tet-on system to construct a mouse model of breast cancer with conditional expression of human PIK3CAH1047R, in which transgene expression is under the control of the tetracycline-inducible promoter TetO and the specific construction method is to hybridize TetO PIK3CAH1047R mice with MMTV-rtTA mice. After this, doxycycline (2 mg/ml) is administered to the drinking water of the double transgenic mice to induce the expression of PIK3CAH1047R. Results showed a breast tumor incidence of 95% and average incubation period of seven months, with pathological adenocarcinoma and adenosquamous carcinoma phenotypes of primary tumors (Liu et al., 2011).

      Knockout animal models can also be efficiently constructed using the CRISPR-Cas9 system (Shao et al., 2016). CRISPR-Cas is a new genetic engineering technology with RNA-guided endonucleases. It has been used to generate genetically modified mouse models, including knockout (KO) and knockin (KI) animal models and somatic genome editing models (Dow, 2015; Flynn et al., 2015). Large-scale genome-modified mice have been successfully generated using the CRISPR-Cas9 system (Shao et al., 2016). Compared with traditional gene targeting strategies, CRISPR-Cas9 greatly improves efficiency and can knock out multiple genes at the same time (Shao et al., 2016). Li et al. (2013) used the CRISPR-Cas9 system to simultaneously edit the Tet1, Tet2, and Tet3 genes in rats, and obtained three-gene mutant rats with an efficiency of 59.1%.

    • Several genetically engineered mice have been generated, including transgenic mice expressing high levels of specific oncogenes and knockout mice in which specific tumor suppressor genes have been depleted or mutated via homologous recombination. In combination, complex transgenic breast cancer mouse models can be created (Hutchinson & Muller, 2000). Study of these models not only highlights specific genetic events in disease progression but also the complex, multi-step nature of breast cancer progression.

      Double transgenic mice developed from crossing MMTV-c-Myc and MMTV-TGFα mice exhibit breast tumors with 100% incidence at an average age of 66 days (Amundadottir et al., 1995). Similarly, MMTV-Neu and WAP-p53172 R-H double transgenic mice develop multifocal breast tumors with a shorter latency (154 days) than MMTV-Neu single transgenic mice (234 days) (Li et al., 1997). p53-deficient mice have been crossed with a variety of transgenic mice, including Wnt1 and Ras. Hundley et al. (1997) reported that p53 knockout and MMTV-Ras transgenic mice develop tumors with a shorter average incubation period (2.2 months vs 8.5 months); however, p53 deficiency alters the distribution of tumor types. Similar results have been observed in PTEN+/-/Wnt-1 transgenic female mice (Stambolic et al., 2000).

      The advantages of GEMMs are that the target is clear, the animal's immune function is usually intact, and the genetic alterations are similar to breast cancer patients. Therefore, GEMMs are widely used for etiology and preventive studies. However, there are several disadvantages of GEMMs. First, breast tumors developed from GEMMs are different from human breast tumors in histology. Second, GEMMs are usually expensive and time consuming. Additionally, MMTV promoter activity is not strictly limited to the breast and the WAP promoter requires pregnancy for activation. Finally, gene editing occurs in almost all mammary ductal epithelial cells, which does not reflect the actual situation of cancer initiation.

    • Metastasis is the leading cause of death in breast cancer patients. Priority sites for human breast metastasis include the lymph node, bone, lung, liver, and brain (Fantozzi & Christofori, 2006). After human breast cancer cells are injected into blood circulation of immunodeficient mice, distant metastases may develop. For example, intravenous tail vein injection primarily causes lung metastasis, whereas intracardiac injection results in bone metastases (Chakrabarti & Kang, 2015). This approach bypasses the early steps of migration and invasion and can generate distant metastasis more efficiently.

    • An experimental animal model of breast cancer metastasis can be established by inoculating breast cancer cells subcutaneously, orthotopically, or through tail vein injection (Vargo-Gogola & Rosen, 2007). Mouse 4T1 cancer cells will easily develop lung metastasis after inoculation in the breast of BALB/c mice (Kij et al., 2018; Qin et al., 2015). EO771.LMB is a spontaneous breast tumor derived from a female C57BL/6 mouse isolated from a rare spontaneous lung metastasis of an EO771 tumor-bearing mouse. EO771.LMB cells spontaneously metastasize to the lung and show increased invasiveness compared to parental EO771 (Johnstone et al., 2015). MDA-MB-231-LM2 cells, derived from the MDA-MB-231 human breast cancer cell line, are prone to lung metastasis when injected into the mammary fat pad of immunodeficient mice (Aceto et al., 2014). The MMTV-PyMT transgenic mouse model develops breast tumors with lung metastasis (Kaya et al., 2019). Studies have shown that in situ inoculation of MDA-MB-435 cells into SCID mice can successfully establish a spontaneous lung metastasis model (Bagheri-Yarmand et al., 1999).

    • Breast cancer has the highest incidence of bone metastases and has a long survival time relative to visceral metastases. There are three types of bone metastasis models: local injection to replicate bone metastasis, in situ implantation of breast cancer, and blood flow (intravenous and left ventricle) injections. A commonly used model of bone metastasis is via left ventricular injection (Minn et al., 2005). Injection of human MDA-MB-231 or MCF7 cell lines or mouse 4T1-2, Py8119, or E0771 cells into the left ventricle or carotid artery in a suitable mouse strain results in breast tumor cells primarily located in the long bone spine and jaw (Ottewell et al., 2014; Suva et al., 2011; Wright et al., 2016).

      After 4T1 cells are inoculated into the mammary fat pads of BALB/c mice, they can spontaneously migrate to the bone, leading to 40%–60% of animals with bone metastases (Lee et al., 2014). Injection of 4T1, Py8119, or E0771 cells into the tibia or femur of BALB/c, FVB/N, or C57BL/6 mice, respectively, results in the development of osteolytic tumors in the corresponding bone (Tulotta et al., 2019; Wright et al., 2016).

      Bone-targeted subcloning technology can achieve a higher rate of bone metastasis. After MDA-MB-231 cells are injected into the left ventricles of nude mice, MDA-MB-231-B subclones are obtained after repeated cycles. MDA-MB-231-B can cause bone metastasis in all experimental nude mice in only four weeks (Wetterwald et al., 2002). Nutter et al. (2014) developed a new MDA-MB-231 breast cancer bone-seeking clone (MDA-IV). After injection of 1x105 MDA-IV cells into the tail vein of nude mice, tumors only formed in the long bones of mice and large tumors were clearly visible in 83% of mice (Nutter et al., 2014).

    • An experimental animal model of liver metastasis of breast cancer can be established by portal vein inoculation and intrahepatic inoculation of tumor tissue (Price, 1996). Goddard et al. (2016) developed a mouse portal vein injection method that delivers tumor cells directly to the liver. This model can cause concurrent metastases to other organs or complications of splenectomy. Three different metastatic breast cancer cell lines (high metastatic 4T1 cells, medium metastatic D2A1 cells, and low metastatic D2.OR cells) are injected into BALB/c mice via portal vein injection to establish liver metastasis models of breast cancer, which could be an important tool for studying breast cancer liver metastasis (Goddard et al., 2016).

    • Intracarotid artery injection mainly produces brain metastasis (Kim et al., 2004). Breast cancer brain metastasis models are usually modeled using TNBC cell lines. Yoneda et al. (2001) applied MDA-MB-231 for peripheral inoculation in nude mice, and repeated the sequential passage of metastatic cells obtained from the mouse brain to produce the breast cancer cell line MDA-MB-231BR, which showed preferential transfer to the brain. This cell line only produces brain metastases after intracardiac injection in nude mice (Yoneda et al., 2001). Other human breast cancer cell lines are rarely used due to the long incubation period and low specificity of brain metastases. In addition to ventricular inoculation, 4T1 subline 4TBM has been used to prepare an in situ model of breast cancer brain metastasis (Erin et al., 2013).

    • Animal models can be applied for studies on the biological understanding of breast cancer to the development of new therapies. Preclinical animal models are primarily used to predict the safety and efficacy of candidate drugs prior to use in humans (Clarke, 2009). Breast cancer animal models are useful in many different contexts and will continue to contribute to our understanding of disease progression, treatment response, and resistance mechanisms (Holen et al., 2017). Spontaneous and induced breast cancer models are rarely used in routine screening of anti-tumor drugs. Currently, transplantation and transgenic models are the most common. Xenograft models and GEMMs are widely used to elucidate the underlying mechanisms of drug resistance, pathogenesis of breast cancer and metastasis, and drug efficacy and toxicity (Park et al., 2018).

      Current treatments of breast cancer are based on receptor status (Cardiff & Kenney, 2011). Personalized medicine has achieved considerable success in the treatment of breast cancers. Commonly used targeted drugs for ERα-positive metastatic breast cancer include anti-estrogens (e.g., tamoxifen and fulvestrant), aromatase inhibitors (e.g., letrozole and anastrozole), CDK4/6 inhibitors (e.g., palbociclib, ribociclib, and abemaciclib) (Palmieri et al., 2013), and PI3Kα inhibitors (Keegan et al., 2018). For HER2-positive breast cancer patients, trastuzumab and pertuzumab are the most effective agents (Luque-Cabal et al., 2016; Swain et al., 2015). TNBC patients are usually treated with chemotherapy, including anthracyclines, taxanes, and platinum, and targeted therapies, including PARP inhibitors (e.g., olaparib and talazoparib) for BRCA1/2 mutation carriers and anti-PD-L1 mAb (e.g., atezolizumab) for PD-L1-positive patients (Lebert et al., 2018). Different breast cancer animal models have been used for drug efficacy evaluation, biomarker identification, and resistance research (Table 7).

      Breast Cancer TypingTherapyDrugModelReferences
      Hormone receptor positive breast cancer (HR+) (ERα+/PR+HER2-)AntiestrogensTamoxifenCDX model (MCF-7)Osborne et al., 1985
      FulvestrantCDX model (MCF-7)Lee et al., 1995
      Aromatase inhibitorLetrozoleCDX model (MCF-7)Brodie et al., 1998; Wakeling et al., 1991
      AnastrozoleCDX model (MCF-7)Brodie et al., 1998
      CDK4 / 6 inhibitorPalbociclibCDX model (MDA-MB-435, ZR-75-1)Fry et al., 2004
      RibociclibCDX model (MDA-MB-435)Vora et al., 2014
      AbemaciclibCDX model (MDA-MB-231)Knudsen et al., 2017
      HER2-positive breast cancer (ERα-PR-HER2+)Monoclonal antibodiesTrastuzumabCDX model (BT474)Baselga et al., 1998
      Epidermal growth factor tyrosine kinase inhibitorLapatinibCDX model (BT474)Rusnak et al., 2001
      Triple negative breast cancer (ERα-PR-HER2-)Chemotherapy drugsCisplatinGEMM (Brca1 mutant breast cancer mice)Shafee et al., 2008
      ADP ribose polymerase (PARP) inhibitorsOlaparibGEMM (BRCA1Co/Co - MMTV-Cre-p53+/− mice)To et al., 2014
      PD-L1 positive patientsImmune checkpoint inhibitorPembrolizumabHu-PDX modelWang et al., 2018

      Table 7.  Breast cancer animal models for drug research and development

      GEMMs have been successfully used in "preclinical breast cancer trials". For example, the Brca1 and p53 conditional double knockout mouse model of hereditary breast cancer is a good model for drug development (Liu et al., 2007). Based on this mouse model, Rottenberg et al. (2007, 2008) revealed that breast tumors lacking BRCA1 are highly sensitive to the PARP inhibitor AZD2281 alone and in combination with platinum drugs. These results have accelerated the clinical application of PARP inhibitors in patients with BRCA1 gene deletion or mutation (Rottenberg et al., 2007, 2008). Jaspers et al. (2013) and Gogola et al. (2018) used the same model to illustrate how tumors become resistant to PARP inhibitors. The efficiency and resistance of topoisomerase I inhibitors topotecan and SN-38 (active metabolite of irinotecan) have also been studied using the above mouse model (Zander et al., 2012). Furedi et al. (2017a) used this model to demonstrate that pegylated liposomal doxorubicin increases the recurrence-free survival rate (by six times) and overall survival rate (by three times) compared with traditional doxorubicin. The same research group also showed that primary cancer cells from these tumors can be used to test new drug candidates (Füredi et al., 2017b). Therefore, disease-specific genetic and syngeneic models (especially transplantation of GEMM tissue into recipient strain-matched mice), along with PDX models, have great potential for assessing monotherapy versus combination therapy or neoadjuvant therapy versus adjuvant therapy after surgical resection.

    • In summary, no breast cancer animal model is perfect, with each showing its own advantages and disadvantages. Breast cancer is highly heterogeneous, and even within the same tumor heterogeneity can be marked. Therefore, no single model can fully reflect the heterogeneity and drug reactivity of all breast cancers. Each animal model can only imitate certain aspects of human breast cancer. Thus, it is necessary to combine different models to understand breast cancer biology and develop prevention and therapy methods. The xenograft model remains the primary tool for therapeutic drug discovery and evaluation, and combined PDX and GEM models will work better.

      For animal species, mice are still the most widely used animal. The establishment of mouse models of breast cancer has greatly assisted in the research, prognosis, clinical drug screening, and development of new therapeutic methods for breast cancer, especially for studies on breast cancer metastasis mechanisms and the discovery of targeted drugs. In the future, it will be necessary and worthwhile to utilize other animals. In this respect, tree shrews exhibit considerable potential given their close relationship to primates. Thus, the development of gene editing techniques in tree shrews is critical.

      Immunotherapy is gaining more and more attention. Mouse allograft models, humanized PDX models, and GEMMs will play increasingly important roles. However, the establishment of ERα-positive breast cancer mouse models and of tissue-specific metastasis models remain a challenge.

    • The authors declare that they have no competing interests.

    • L. Z. prepared the draft. C.S.C. and W. L. revised the manuscript. All authors read and approved the final version of the manuscript.

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