Salinomycin triggers human colorectal cancer HCT116 cell death by targeting unfolded protein responses and autophagy pathways

The autophagy and unfolded protein responses (UPR) are important pathways in colorectal tumorigenesis and drug resistance, which make them potential therapeutic targets for treatment of this cancer. As an ionophoric polyether antibiotic, salinomycin has anti-cancer effects and overcome drug resistance in cancer cells. Considering the low information on the molecular action mechanism of salinomycin in colorectal cancer, this study was designed to investigate the effect of this compound on autophagy and UPR pathways in colorectal cancer cells.

The in vitro cytotoxicity of salinomycin on CRC cell line HCT116 was determined using MTT assay by treating the cells with different concentrations of salinomycin for 24 and 48 h. The gene expression analysis of three main autophagy biomarkers Beclin1, LC3 and P62 and two UPR biomarkers, XBP-1s and CHOP was performed using quantitative real-time polymerase chain reaction (RT-PCR). Data were statistically analyzed with GraphPad Prism 8 software.

Salinomycin had cytotoxic effects on HCT116 cells in a time and dose dependent manner. The expression analysis of the UPR and autophagy related genes described the UPR activation at both 24 h and 48 h (increase of XBP-1s and CHOP), autophagy activation at 24 h (increase of Beclin 1, LC3II and decrease of P62) and autophagy flux inhibition at 48 h (increase of Beclin 1, LC3II and P62).

The anticancer activity of salinomycin against HCT116 cell line seems to be through triggering cell death by targeting UPR and autophagy pathways. Further studies are required to confirm our obtained results.