OBJECTIVETo investigate the expression of microRNA-221 (miR-221) and CDKN1C/P57 in colorectal carcinoma (CRC) and adjacent non-cancerous tissues. The effect of miR-221-specific inhibitor on cell proliferation and apoptosis in CRC cells was also assessed.

METHODSThe expression of miR-221 was detected by real-time RT-PCR. CDKN1C/P57 mRNA and corresponding protein expression pattern were detected by semi-quantitative RT-PCR and Western-blot. The specific 2'-methoxy-modified RNA oligonucleotide of miR-221(miRNA inhibitor,anti-miR-221) was designed, synthesized and transfected into Caco2 cell by liposome. Finally, the status of CRC cell proliferation and apoptosis were detected by MTT assay and flow cytometry.

RESULTSThe expression of miR-221 was significantly up-regulated in CRC tissues as compared to the adjacent non-cancerous tissues(2.041±1.401 vs. 0.806±0.341, P<0.01). There was no significant difference in CDKN1C/P57 mRNA expression between CRC and non-cancerous tissues, whereas CDKN1C/P57 protein markedly decreased in CRC (3.019±1.708 vs. 0.972±0.316, P<0.01). miR-221-specific inhibitor significantly enhanced CDKN1C/P57 protein expression, inhibited proliferation of CRC cells and induced apoptosis of CRC cells(P<0.01).

CONCLUSIONSmiR-221 inhibits CDKN1C/P57 expression by post-transcriptional gene silencing to promote CRC development and progression. miR-221-specific inhibitor potentially inhibits the growth of CRC cells. Therefore, it may be a new target for the biologic therapy for CRC.