Abstract
Radioresistance is a challenge in the treatment of esophageal squamous cell carcinoma (ESCC). MicroRNAs (miRNAs) are known to play an important role in the functional modification of cancer cells and recent studies have reported miRNA-mediated radiotherapy resistance. However, further research is necessary to reveal the regulation mechanisms, and treatment strategies using miRNA are yet to be established for ESCC. We compared the miRNA expression profiles of ESCC parental (TE-4) and acquired radioresistance (TE-4R) cell lines using a miRNA microarray and qRT-PCR. Our data showed that miR-338-5p, one of the target miRNA biomarkers, was significantly downregulated in TE-4R. Ectopic overexpression of miR-338-5p induced apoptosis and sensitivity to radiation treatment by interfering with survivin, which is a known inhibitor of apoptosis. Overexpression of survivin reversed miR-338-5p-induced apoptosis. Tumor xenograft experiments indicated that therapeutic delivery of the miR-338-5p mimics via direct injection into tumor mass increased sensitivity to radiation therapy. In conclusion, our findings suggest that miR-338-5p is a potential radiosensitizer and may be a therapeutic biomarker for radioresistant in ESCC.