Metformin Inhibits Prostate Cancer Cell Migration And Invasion And Increases The Sensitivity Of The Cancer Cells To Paclitaxel

Background:Prostate cancer (PCa) is the most common cancer in men and the second cause of cancer-related death in western countries. Although PCa incidence is relatively lower in China than in western countries, the incidence is dramatically rising in recent years due to multiple reasons. From a micro perspective, the etiology of the PCa is diverse like most of the tumors, which involves multiple genes. Chromosome aberration plays a leading role, and the activation of oncogenes and the inactivation of the tumor suppress genes are also significant factors. From a macro perspective, the incidence of PCa is affected by age, race and family inheritance, but also related to hormones and nutrition. In the treatment of PCa, androgen deprivation therapy (ADT) is used in the early stage due to the androgen-dependent of the progression of PCa and it is effective. But after a period of ADT treatment, the PCa cells change into the androgen-independent form, resulting in chemo-resistance and poor prognosis.Metformin is a kind of first class drugs used for type 2 diabetes patients for oral hypoglycemic drugs. In 2005, metformin was reported to reduce incidence of tumor in diabetes. Then the drug has become popular for its potential anti-cancer effects. At present, metformin has been reported to have anti-cancer effects in a variety of cancers including hepatocellular carcinoma, lung cancer, breast cancer, esophageal cancer, nasopharyngeal carcinoma, colon cancer and malignant melanoma. These effects were achieved by inhibition of cancer cell proliferation, induction of apoptosis and cell cycle arrest. But there are a few studies on PCa. Here, we reported that metformin inhibited PCa cell migration and invasion and increased the sensitivity of the cancer cells to paclitaxel.Objectives:1) We aim to study the effects of metformin on PCa cell proliferation; 2) investigate the roles of metformin on migration and invasion in PCa; 3) study the effects of metformin on chemo-resistance of PCa cells.Methods:1) To determine the effects of metformin on PCa cell proliferation by using MTS assay.2) To test the effects of metformin on PCa cell migration and invasion by using wound healing assay and invasion assay.3) To determine the changes of EMT marker expressions by using Western blot.4) Explore the possible signaling pathways by using Western blot.Results:The results of MTS showed that metformin inhibited proliferation of the parental cells and multidrug resistant cells, and this inhibition was in time-and dose-dependent manners. In all PCa cell lines except PC3, comparing with paclitaxel alone group, the paclitaxel plus metformin group significantly decreased the cell viability. The wound healing assay indicated that the average migration distance of group with metformin decreased significantly at 15h and 24h (P<0.05) in contrast with control group. The invasion cell numbers of the metformin group significantly reduced comparing with the control group in the four cell lines (p<0.05). The results of Western blot revealed that metformin reversed EMT in PCa and further influenced the biological function in PCa. We showed that metformin upregulated the expression of P-AMPK in parental cell lines including DU145 and PC3, and the total protein level of AMPK remained unchanged. By contrast, P-AMPK maintained unchanged in DU145-TxR and PC3-TxR. In DU145-TxR cell line, P-4E-BP1 showed constant expression level, but expressions of other cell lines decreased, and the total 4E-BP1 remained unchanged.Conclusion:Metformin inhibited the proliferation of PCa cells diminished the capacity of migration and invasion. Moreover, metformin sensitized PCa cells to paclitaxel. This may be relevant to reversing EMT. And the process may be regulated by activating the AMPK signaling pathway and blocking mTOR signaling pathway.