Establishment And Characteristics Of Orthotopic Breast Cancer Transplantation Model By Intraductal Injection

Background and purpose:Globally,breast cancer is the most commonly diagnosed cancer and the leading cause of cancer death in women.Triple-negative breast cancer(TNBC)has a more aggressive phenotype than other breast cancer subtypes,with higher metastasis and recurrence rate.Obstacles to drug discovery include the limitations of xenotransplantation models,which are currently lacking for TNBC to truly simulate clinical trials.At present,TNBC lacks a model to simulate clinical trials.TNBC has obvious heterogeneity in tumor microenvironment.In the research of breast cancer and the exploration of treatment methods,to a certain extent,we need to rely on the realization of breast cancer experimental animal model.Currently,the commonly used breast cancer models include spontaneous breast cancer animal models,induced breast cancer animal models,allograft experimental animal mammary cancer models,xenograft breast cancer models,distant metastasis of breast cancer models and Genetically engineered mouse models(GEMMs)of breast cancer.These experimental animal models of breast cancer have their own advantages,but there are still some unavoidable problems and disadvantages.Intraductal injection of tumor cells into breast can mimic the occurrence and development of breast cancer.4T1 breast intraductal injection model can restore the tumor microenvironment of breast cancer,and more importantly,it can study the role of immune system in the occurrence and development of breast cancer.On this basis,this study intends to explore the construction and characteristics of an optimized intraductal injection model of breast.The purpose of this study is to provide reference for the application of this model in breast cancer research.Method:The 4T1 breast cancer cells of different cell numbers were injected into the mammary ducts of female BALB/C mice for 6-8 weeks to establish an intraductal injection model of 4T1 breast cancer.We observed the tumorigenic rate of BALB/C mice after intraductal injection of 100000,40000,20000,10000,5000 and 2500 4T1 cells respectively.We compared the tumorigenic rate,tumorigenic time and metastasis of different cell numbers to determine the appropriate number of cells for modeling.We optimized the construction method of intraductal injection model of 4T1 cells,and observed the occurrence,development and spontaneous metastasis of tumors in different time periods of the model by mammary tissue staining,HE staining and mice magnetic resonance imaging.Graph generation and statistical analysis were done on Prism 7.0 software(GraphPad,San Diego CA).All data are expressed as the mean ± SD.A value of P < 0.05 was considered statistically significant.Result:Collectively,we explored and validated that the fourth pair of mammary glands injected unilaterally in mice could fill the entire mammary duct.The 4T1-MIND model injected with 20?l of cell culture medium containing 20,000 suspended cells had a suitable tumor formation rate and time,and a suitable treatment time window after distant metastasis.Tumor cells grew in the mammary ducts of mice 1-2 weeks after the establishment of the model,broke through the mammary ducts to become invasive breast cancer at 3-4 weeks,and metastasized distantly at 7-8 weeks.Conclusion:The 4T1 breast intraductal injection model is a model in vivo that can restore tumor development and tumor microenvironment.But at present,the research and application are few and need to be improved and optimized continuously.Find a more suitable and optimized model for translational research and the study of microenvironment in breast carcinogenesis.