The expression of microRNA-21 (miR-21) was determined in 42 patients with colorectal cancer (CRC) using real-time reverse transcription-polymerase chain reaction. The level of miR-21 in CRC tumour tissue was compared with paired normal adjacent tissue (NAT) and the relationships of miR-21 levels to clinicopathological characteristics and pathological tumour response to neoadjuvant chemotherapy were investigated. There was a significantly higher level of miR-21 in CRC tumour tissue than in NAT and high expression of miR-21 was significantly correlated with advanced clinical stage and poor cell differentiation. Receiver operating characteristic curve analysis indicated a maximum optimal cut-off cycle threshold value of 10.32 for differentiating pathological responders from non-responders, with a sensitivity of 80.0% and specificity of 88.2%. These data showed that miR-21 was significantly overexpressed in CRC tumour tissue and was associated with advanced CRC, and that miR-21 may be a potential candidate biomarker for predicting pathological tumour response to chemotherapy.
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