Salinomycin, A Novel Carcinostatic Agent, Inhibits Prostate Cancer Stem Cell Via Regulation Of β-catenin And MTOR Pathway

Objective:To study the roles of β-catenin and mTOR pathway in prostate cancer stem cells proliferation and salinomycin treatment.Methods:Human prostate cancer cell line PC-3were treated with salinomycin and the forming colonies were counted. The proportions of CSCs in PC-3cells with/without salinomycin treatment were then analyzed with flow cytometry. By comparing with the un-treated group, the activation of β-catenin and mTOR pathway was detected both at the protein level and mRNA level by using Western blotting and Real-time quantitative PCR respectively. Next, the ALDH marked PC-3cells were sorted by FACS ARIA cell sorter to separated into ALDHhigh group and ALDHlow group. The formation of colonies were checked. In the last part, GSK3inhibitor and Rapamycin pre-treatment was used to active or inhibit β-catenin and mTOR pathway and subsequently the proportion of CSCs was analyzed with flow cytometry.Results:Salinomycin can inhibit the capability of colony formation of PC-3and reduce the proportion of prostate CSCs. Salinomycin can down-regulate β-catenin and mTOR pathway at protein levels. ALDH is a marker for prostate cancer stem cell,ALDHhigh prostate cancer cells display enhanced clonogenicity. Salinomycin can selectively work on ALDHhigh subpopulation. Inhibitor of GSK3can increase prostate CSCs and decrease the effects of salinomycin. Rapamycin can reduce prostate CSCs and enhance the effects of salinomycin.Conclusion:These results link β-catenin and mTOR pathway to salinomycin-induced apoptosis in prostate cancer stem cells for the first time. Salinomycin may become a potential chemotherapeutic agent for the prostate cancer therapy.