Vitamin D Improves The Sensitization Of Lung Cancer To Radiotherapy

Lung cancer is the leading cause of cancer related death worldwide. Radioresistance is an obstacle in treating lung cancer. The efficacy of treatments may be improved by increasing the sensitivity of cancer cells to radiation therapy. Vitamin D has been reported to have radiosensitizing effects in cancers of the breast and the prostate. The objective of this study is to explore the effects of vitamin D on radiosensitization of human lung cancer cells. Human non-small cell lung cancer cell line A549 cells were treated with 1,25(OH)(2)D-3 before irradiation with X-rays. The effect of 1,25(OH)(2)D-3 on cell-survival following irradiation was evaluated by colony-forming assay. DNA double-strand breaks were detected by immunostaining for gamma H2AX foci. Cell cycle distributions were investigated using flow cytometry. Apoptotic cells were identified on the basis of nuclear morphology. Results: 1,25(OH)(2)D-3 inhibited lung cancer cell proliferation in a dose-dependent manner. A549 cells were radiosensitized by 1,25(OH)(2)D-3. Flow cytometric analysis for DNA content indicated that 1,25(OH)(2)D-3 increased radiation-induced G2/M arrest. Apoptotic analysis demonstrated that 1,25(OH)(2)D-3 enhanced the cell apoptosis induced by irradiation. Conclusion: These findings suggest that 1,25(OH)(2)D-3 caused radiosensitization of A549 cells are associated with its enhancement effects on apoptosis and G2/M arrest induced by radiation.