Identification of aberrantly expressed miRNAs in rectal cancer.

Disturbance of miRNA expression may play a key role in the initiation and progression of colorectal cancer (CRC). CRC should be viewed as a heterogeneous disease, but previous studies have only screened dysregulated miRNAs in CRC from a panel of 96, 145, 287 and 455 miRNAs, respectively. It is necessary to identify new aberrantly expressed miRNAs in rectal cancer. In this study tissue samples were derived from patients undergoing a surgical procedure to remove a portion of cancers. The expression profile of 904 miRNAs was analyzed using a miRCURY™ LNA Array from 6-paired rectal cancers and normal tissues. The expression levels of 4 miRNAs were compared by real-time PCR between colon and rectal cancer, and also the expression levels of metastatic miRNAs in different stages of rectal cancer were analyzed. We found that 67 miRNA precursors are upregulated in rectal cancer (p<0.05) and 21 of those have never been reported in colorectal cancer (CRC); 39 miRNA precursors are downregulated (p<0.05) and 24 novel dysregulated miRNAs were identified in rectal cancer. miR-31, miR-126 and miR-143 are differentially expressed between colon cancer and rectal cancer. Here, we report an miRNA profile of rectal cancer, and we identified differential expression patterns of miRNAs between rectal and colon cancers. This novel information may suggest the potential roles of these miRNAs in the diagnosis of rectal cancer.