MicroRNA miR-374, a potential radiosensitizer for carbon ion beam radiotherapy.

In this study, we compared the microRNA (miRNA) profiles of a control and X-ray- and carbon ion beam-resistant cells to identify miRNAs that can be used as radiosensitizers and biomarkers. Mouse squamous cell carcinoma line NR-S1, its X-ray-resistant derivative X60, and its carbon ion beam‑resistant derivative C30 were subjected to miRNA microarray analysis. Expression of miRNAs shown to be upregulated or downregulated in the microarray analysis was confirmed by qRT-PCR. Downregulated miRNAs were overexpressed in human pancreatic cancer cell lines PANC1 and MIA PaCa-2, and the resulting cells were tested for radiosensitivity using colony-forming and sphere-forming assays. Of 1,265 miRNAs analyzed, 4 were downregulated and 11 were upregulated in X-ray-resistant and carbon ion beam-resistant cells. Two of the downregulated miRNAs, miR-196 and miR-374, were selected for overexpression in PANC1 and MIA PaCa-2 cells. Overexpression of miR-374 sensitized PANC-1 and MIA PaCa-2 cells toward carbon ion beam radiation. miRNA miR-374 has the potential to be a new radiosensitizer for carbon ion beam radiotherapy and a new biomarker to determine the optimal treatment for cancer.