Combination of salinomycin and radiation effectively eliminates head and neck squamous cell carcinoma cells in vitro

The antibiotic drug salinomycin has been reported to mediate cancer cell-specific cytotoxicity, especially regarding cancer stem cells. Since salinomycin has also been reported to arrest cancer cells in the G2 phase, it may have possible radiosensitizing effects. Radiotherapy is a common therapeutic strategy for head and neck squamous cell carcinoma (HNSCC). The aim of the present study was to evaluate a possible influence of salinomycin on the radiosensitivity of the HNSCC cell line HLaC-78 in vitro. HLaC-78 cells were incubated with 5 µM salinomycin or control medium for 24 h and then received 5-Gy irradiation. Subsequently, analysis of cell viability, apoptosis, necrosis and motility through an MTT and a colony formation assay, as well as an Annexin V/propidium-iodide test, a consecutive cell count for four days and a scratch assay were conducted. Additionally, interleukin-8 secretion was assessed using ELISA, due to its role in tumor progression and angiogenesis. Combined treatment with salinomycin and radiation revealed a significantly higher reduction of tumor cell viability, proliferation, motility and secretory capacity compared to cells receiving only one of the treatments alone. Therefore, it is postulated that radiation and salinomycin are an effective combination therapy against HNSCC, a hypothesis which warrants further investigation in cell lines, as well as in an animal model.