Salinomycin suppresses cancer cell stemness and attenuates TGF-β-induced epithelial-mesenchymal transition of renal cell carcinoma cells

Metastatic Renal cell carcinoma (RCC) remains a difficult oncologic challenge. Salinomycin is a monocarboxylic polyether antibiotic, which has been proved to possess anti-tumor activities in multiple types of cancer cells. However, its effects on RCC cells remains unclear. In our study, salinomycin could inhibit the proliferation and viability of RCC cell lines 786-O and ACHN. The TUNEL assay revealed that treatment with salinomycin induced DNA breaking in RCC cells. Consistently, Western blotting showed up-regulation of pro-apoptotic biomarkers (cleaved caspase3/9 and cleaved PARP1) and down-regulation of anti-apoptotic biomarker (survivin) in RCC cells after salinomycin treatment, suggesting that salinomycin could induce RCC cell apoptosis. salinomycin treatment also suppressed the sphere formation ability of RCC cells and decreased the expressions of CD105, ALDH1 and CD44, biomarkers for reflecting the stemness of RCC cells. salinomycin treatment effectively down-regulated SMO and Gli1, two key proteins in Hedghog signaling pathway, in a dose-dependent manner. Moreover, salinomycin could suppress the invasion and migration of RCC cells in the presence of TGF-β1, as observed in wound-healing and Transwell assays. salinomycin treatment attenuated TGF-β1-induced epithelial-mesenchymal transition (EMT), as evidenced by its ability to increase E-cadherin expression and decrease N-cadherin, Snail and MMP-2 expressions in RCC cells. Finally, salinomycin inhibited the tumorigenecity of RCC cells in vivo. Our study provides the evidence that salinomycin possess multiple anti-tumor activities against RCC, as it, in particular, suppressed the cancer stem cell properties and attenuated TGF-β-induced EMT. Therefore, it may serve as a potentially therapeutic candidate for metastatic RCC and improve the prognosis of RCC patients.