Micro-RNAs miR125b and miR137 are frequently upregulated in response to capecitabine chemoradiotherapy of rectal cancer.

There is increasing evidence that some microRNAs change their levels in reaction to xenobiotic challenge. The aim of this study was to test the possible involvement of micro-RNAs in response to standard anticancer treatment. Tumor biopsies from 35 patients with rectal cancer before therapy and parallel tumor biopsies from 31 patients two weeks after starting preoperative capecitabine chemoradiotherapy were taken. The expression levels of single miRNA species were measured using TaqMan Micro-RNA assays after reverse transcription from isolated total RNAs. Many micro-RNAs (miR10a, miR21, miR145, miR212, miR339, miR361) responded to chemoradiotherapy in individual tumor samples, but there was profound intertumoral variability. However, other two micro-RNAs miR125b, miR137 showed a significant increase in median expression levels after starting therapy in most samples. Moreover, our results for the first time show that higher induced levels of miR125b and miR137 are associated with worse response to the therapy.