Trichostatin A And Tamoxifen Inhibit Breast Cancer Cell Growth Via MiR-204 And ERα To Suppress AKT/mTOR Pathway

Breast cancer is the leading cause of cancer related death in women. The breast cancer cells could rapidly acquire resistance against numerous cytotoxic drugs and become treatment refractory. About 30% of breast cancer patients are recurrent and metastatic. Once the cancer is metastatic, majority of the cases are chemotherapy refractory. Seeking new strategies to increase cancer cell sensitivity to chemotherapeutic agents are urgent task. In breast cancer, ER influence the development and progression of hormone-related cancer by exerting distinct biological functions. ERα protein expression correlates with low tumor grade and negative lymph node status, and ER-positive tumors are usually less invasive and have a more favorable prognosis. ERα is the principal biomarker for the response of breast cancer to TAM treatment. This is associated with the ability of TAM to inhibit the expression of ERα target genes that regulate cell cycle and apoptosis.miRNA, non-coding RNA molecules that regulate gene expression at the post-transcriptional level through sequence-specific base pairing with 3’UTRs of target m RNA, are considered as important regulators of broad biological processes,and have been linked to the development of drug resistance in several cancers.Their functions in cancer are studied in renal clear cell carcinoma, head and neck tumor, lung cancer and ovarian cancer. A variety of studies have showed that miRNAs are associated with poor clinical outcome in cancer, along with miRNAs that regulate a variety of processes, such as cell differentiation, apoptosis, proliferation,and invasiveness. miR-204 is reported to associate with tumor cells. In some tumor tissues, miR-204 is frequently lost in 44.6% of ovarian cancer, 28% of breast cancer,and 40% of pediatric renal tumors. In gastric cancer, over-expression of miR-204 decreases the ability of cultured gastric cells to form colonies and to migrate.Trichostatin A is effective to acetyl transfer enzyme inhibitors(HDACs), its source in Streptomyces metabolites. TSA can improve many anti-cancer transcription factor levels of acetylation, inhibit a variety of tumor cell growth and induce its apoptosis.In order to study the function of TSA in breast cancer, the animal model of breast cancer and breast cancer was used for TSA. the expression level of mi R-204 and ERαfor the detection of breast cancer cell by RT-PCR, clarify the TSA mechanism of the inhibition of the proliferation of breast cancer cells.Part I: The molecular mechanism of TSA inhibiting the proliferation of MCF-7 and MDA-MB-231 breast cancer cells Objective To study the inhibitory effect of TSA in MCF-7 and MDA-MB-231 cells from the molecular biology level. Methods To detect the cell viability /IC50 and ER/miR-204 expression levels by RT-PCR in MCF-7 and MDA-MB-231 cells after TSA was used. the expression level of ER was measured after mi R-204 trans- fection.Results 1) The TSA alone or combination with TAM in MCF-7 and MDAMB-231 cells have obvious inhibitory effection; 2) TSA reduced breast cancer cell miR-204 expression, also increased the expression level of ER; 3) miR-204 downregulation can increase the sensitivity of TAM in MDA-MB-231 cells. Conclusion TSA may inhibit the proliferation of breast cancer cell by downregulation miR-204 and increase the expression of ER.par Ⅱ : The effect of TSA combined with AKT on the TAM signaling pathway in breast cancer cells.Objective To study cell signal pathway in breast cancer of TSA from the level of cell biology. Methods To detect the expression levels of Caspase-3, Mcl-1 and Akt phosphorylation of breast cancer cell apoptosis by RT-PCR and inhibition of the Akt signaling pathway in breast cancer cell proliferation for TSA. Results TSA and TAM inhibited breast cancer cell apoptosis and increased Caspase-3 expression,decreased Mcl-1 and phospho Akt expression by anti-miR-204. conclusion TSA and TAM inhibit the proliferation of breast cancer cells by blocking the phosphorrylation of Akt and inhibition of the Akt signaling pathway.partⅢ: TSA combined with TAM to inhibit the proliferation of MCF-7 and MDA-MB-231 cells in nude mice Objective To detect the inhibitory effect of TSA and TAM on the proliferation of human breast cancer cells in vivo. Methods To construct the animal model of breast cancer in nude mice and to measure the volume of the tumor after TSA and TAM intervention. Results TSA reduced the volume of breast cancer cells in nude mice,and the inhibitory effect was more significant when combined with TAM. at the same time, the expression of ER was increased after TSA intervention of breast cancer.Conclusion TSA can inhibit the proliferation of breast cancer cell, which may promote the expression of ER.