Experimental Study Of MiR-17 Regulation Balb/c Mice Breast Cancer Progression And Metastasis In Vivo

Breast cancer is a malignancy occurred in the breast tissue, which can metastasize to distant organs. Each year about 200000 new cases in China, and its morbidity and mortality increased year by year.Although breast cancer treated by surgery, chemotherapy, radiotherapy and endocrine and molecular target therapy effectively cure the clinical carcinoma in situ,the overall treatment effect and prognosis of breast cancer patients are still poor for distant metastasis occurred.Breast cancer cells can metastasize to lung, pleura, bones, liver and brain through blood or lymphatic channel.In patients with distant organ metastasis is the leading cause of death.A lot of research shows that miRNAs has an important regulatory role for occurrence, development and diffusion transfer of breast cancer.Further research on the origin and development of breast cancer molecular mechanism, is the key to seek treatment countermeasures.miR- 17-92 cluster is one of the most widely research of miRNAs.miR-17-92 cluster functions involve the normal development and cancer, immune diseases, cardiovascular disease and neurodegenerative diseases, etc.miR-17-92 cluster on chromosome 14 in mice,human chromosome13q13- q32.It includes six independent members:miR-17、miR-18、miR-19a、miR-19b、miR-20 a and miR-92 a.The expression effect of each member are not identical,balance the expression.A number of studies show miR-17 has tumor suppressor function.Through the target cancer gene,tumor-suppressor gene, apoptotic protein and cytokines, miR-17 affect cancer cell growth, proliferation, migration and the infiltration process.miR-17-92 cluster retrovirus expression vector infected Balb/c mice,can result in mice splenomegaly,spleen cell hyperplasia, and induced hematopoietic stem cell proliferation.These pluripotent hematopoietic stem cells in vivo and in vitro can differentiate into T cells and B cells and various kinds of blood cells.the low expression of miR-17 can influence the increased expression of Bim protein as one of the main members of Bcl-2 protein family.Bim can combine with Bcl-2protein replacement Bax protein.Bax protein promote cell apoptosis.This is a classic pathway of Bcl-2 family proteins to promote apoptosis.So the purpose of this study is to investigate miR-17 can adjust the Bcl-2 apoptotic pathways,promote T, B lymphocyte proliferation,enhance the body’s immune response inhibition the development and transfer mechanism of breast cancer. Plant 4T1 breast cancer cells in adult Balb/c mice mammary gland. 4T1 cells can metastasize to lung.At different time points for the mice miR-17 lentivirus,divided into three groups, one group for a week before planting tumor injection of miR-17 slow virus, a group for planting tumor injection of miR-17 slow virus at the same time, a group to plant a week after the injection of tumor of miR-17 slow virus.The size of the tumor measured once a week.In the fifth week the mice was executed after growing tumors.By comparing the size of the tumor tissue, size, and number of pulmonary metastases,we determine if miR-17 can inhibit the growth and metastasis of breast cancer in mice.By western blot test spleen Bcl-2 and Bax protein expression, we determine if miR-17 can adjust Bcl-2apoptotic pathways.By flow cytometry detecting the content of CD4, CD8,CD19, CD34 cells,we determine if miR-17 can increase the content of T and B cells.Through the CD8 antibody immunohistochemical staining of the tumor,we determine if miR-17 can promote CD8 cells infiltrating invasion of tumor cells.Through the above experiment, we observed given miR-17 treatment ofmice with small tumor tissue compared with model group, and less pulmonary metastases, metastatic tumour area is lesser.That miR-17 inhibit the growth and metastasis of breast cancer, rise the expression of Bcl-2,decrease the expression of Bax,and miR- 17 inhibit the apoptosis of spleen cells through Bcl-2 apoptotic pathway,increase the content of CD4,CD8,CD34 cells,and miR-17 promote lymphatic cells and hematopoietic stem cell proliferation, promote the body’s immune function. The longer miR-17 injection,the effect of inhibition of breast cancer more obvious.This suggests that miR-17 can raise Bcl-2 expression, cut Bax expression, inhibit lymphocyte apoptosis,promote CD4, CD8 cell hyperplasia, CD34 stem cell hyperplasia, boost the immune system response,thus inhibiting the growth and metastasis of breast cancer.