The Combination of Trametinib, a MEK Inhibitor, and Temsirolimus, an mTOR Inhibitor, Radiosensitizes Lung Cancer Cells

Background/Aim: We evaluated the radiosensitizing effect of the combination treatment of trametinib, a MEK inhibitor, and temsirolimus, an mTOR inhibitor, on non-small cell lung carcinoma (NSCLC) cells. Materials and Methods: The effects of combining trametinib and temsirolimus with radiation in NSCLC cell lines were evaluated using clonogenic survival and apoptosis assays. DNA double-strand breaks and cell cycle distribution were analyzed using flow cytometry. Tumor volume was measured to determine the radiosensitivity in lung cancer xenograft models. Results: Exposure of lung cancer cells to a combination of trametinib and temsirolimus reduced clonogenic survival and promoted radiation-induced apoptosis. Combined inhibition of MEK and mTOR induced prolonged expression of gamma H2AX after irradiation and resulted in prolonged G(2)/M cell cycle arrest after irradiation in A549 cells. In vivo studies revealed that co-administration of the drugs sensitizes lung cancer xenografts to radiotherapy. Conclusion: The combination of trametinib and temsirolimus can enhance lung cancer radiosensitivity in vitro and in vivo.