Salinomycin reduces stemness and induces apoptosis on human ovarian cancer stem cell

OBJECTIVE Cancer stem cells (CSCs) represent a subpopulation of undifferentiated tumorigenic cells thought to be responsible for tumor initiation, maintenance, drug resistance, and metastasis. The role of CSCs in drug resistance and relapse of cancers could significantly affect outcomes of ovarian cancer patient. Therefore, therapies that target CSCs could be a promising approach for ovarian cancer treatment. The antibiotic salinomycin has recently been shown to deplete CSCs. In this study, we evaluated the effect of salinomycin on ovarian cancer stem cells (OCSCs), both alone and in combination with paclitaxel (PTX). METHODS The CD44⁺CD117⁺CSCs were obtained from the ascitic fluid of patients with epithelial ovarian cancer by using an immune magnetic-activated cell sorting system. OCSCs were treated with PTX and salinomycin either singly or in combination. Cell viability and apoptosis assays were performed and spheroid-forming ability was measured. The expression of sex determining region Y-box 2 (SOX2) and octamer-binding transcription factor 3/4 (OCT3/4) mRNA was determined using reverse transcription polymerase chain reaction, and protein expression was observed using western blot analysis. RESULTS Treatment with salinomycin alone reduced the stemness marker expression and spheroid-forming ability of OCSCs. Treatment with PTX alone did not decrease the viability of OCSCs. Treatment with a combination of salinomycin decreased the viability of OCSCs and promoted cell apoptosis. The enhancement of combination treatment was achieved through the apoptosis as determined by annexin V/propidium iodide (PI) staining, caspase-3 activity, and DNA fragmentation assay. CONCLUSION Based on our findings, combining salinomycin with other anti-cancer therapeutic agents holds promise as an ovarian cancer treatment approach that can target OCSCs.