Metformin Induces Autophagy In Prostate Cancer And Inhibits Its Growth

Objective:To verify the inhibitory effect of metformin on the proliferation and migration of prostate cancer cells,observe other influences on biological functions,and explore the possible mechanisms,both in vitro and in vivo.Methods:Two prostate cancer cell lines were treated with metformin of different concentrations.Cell viability was assessed with CCK-8.Wound-healing assay,flow cytometry and western blot(WB)were used to detect the migration ability,cell cycle and the expression level of autophagy-related proteins or other proteins of related signaling pathways.Autophagic inhibitor 3-methyladenine(3-MA)was treated together with metformin to observe whether the autophagy mediated by metformin could be rescued.Last,we construct xenograft mouse model.Treatment cohort was administered metformin(250 mg/kg/d),and physiological saline solution(PBS)to the control cohort.Changes in weight of mice and volume of tumors were recorded continuously.21 days after treatment,the subcutaneous tumor was dissected.Immunohistochemistry was used to detect the expression of proteins related.Functions of liver and kidney were detected to evaluate the safety of metformin.Results:Compared with the control cohort,metformin can inhibit the proliferation(P<0.05)and migration(P<0.05)of prostate cancer cells,and induce G0/G1 phase cell cycle arrest(P<0.05).Autophagy-related protein LC3B was up-regulated and P62 was down-regulated.3-MA partially rescued prostate cancer cells from the inhibitory effects of metformin.In the subcutaneous tumor model,the tumor volume of the metformin treatment cohort was significantly smaller than that of the control cohort after 21 days of treatment.There were no significant differences in body weight,liver and kidney functions between the two groups(P>0.05).Immunohistochemical and WB results showed that the phosphorylation of adenosine phosphate activated protein kinase(pAMPK)was activated.Conclusion:Metformin induces autophagy and cell cycle arrest in prostate cancer cells.It also inhibits the proliferation of prostate cancer cells,but has no significant impact on apoptosis.These effects may be related to the activation of AMPK.Metformin is a safe drug.