Salinomycin and IR780-loaded upconversion nanoparticles influence biological behavior of liver cancer stem cells by persistently activating the MAPK signaling pathway

The combination of chemotherapy and phototherapy has emerged as a promising therapeutic approach for enhancing the efficacy of cancer treatment and mitigating drug resistance. Salinomycin (SAL), a polyether antibiotic, exhibits potent cytotoxicity against chemotherapy-resistant cancer cells. IR780 iodide, a novel photosensitive reagent with excellent near-infrared (NIR) light absorption and photothermal conversion abilities, is suitable for use in photothermal therapy for cancers. However, both SAL and IR780 exhibit hydrophobic properties that limit their clinical applicability. Upconversion nanoparticles (UCNPs) are an emerging class of fluorescent probe materials capable of emitting high-energy photons upon excitation by low-energy NIR light. The UCNPs not only function as nanocarriers for drug delivery but also serve as light transducers to activate photosensitizers for deep-tissue photodynamic therapy. Here, to enhance the targeting and bioavailability of hydrophobic drugs in liver cancer stem cells (LCSCs), we employ distearoyl phosphorethanolamine-polyethylene glycol (DSPE-PEG) to encapsulate SAL and IR780 on the surface of UCNPs. Cell viability was evaluated using the CCK-8 assay. Cell migration was assessed by the Transwell Boyden Chamber. The activation of the mitogen-activated protein kinase (MAPK) signaling pathway was measured via western blot. The results demonstrated successful loading of both IR780 and SAL onto the UCNPs, and the SAL and IR780-loaded UCNPs (UISP) exhibited a robust photothermal effect under NIR light irradiation. The UISP effectively inhibited the viability of HCCLM3 and LCSCs. Under NIR light irradiation, the UISP further suppressed HCCLM3 viability but had no impact on LCSC viability; however, it could further inhibit LCSC migration. Meanwhile, under NIR light irradiation, the UISP persistently activated the MAPK pathway more significantly in LCSCs. These findings suggest that exposure to NIR light results in persistent activation of the MAPK pathway by UISP, thereby influencing the biological behavior of LCSCs and enhancing their therapeutic efficacy against liver cancer.