miR-211 regulates the expression of RRM2 in tumoral metastasis and recurrence in colorectal cancer patients with a k-ras gene mutation

Colorectal cancer (CRC) ranks as the third-leading cause of cancer-associated mortalities in Taiwan. The expression of ribonucleotide reductase M2 (RRM2) and p53R2 is associated with tumoral malignancy and progression in several types of cancer. The aim of the present study was to determine the association of p53R2/RRM2 with the upstream expression of microRNA (miR)-211 and the association of expression levels of p53, APC and k-ras with clinical outcomes in patients with CRC. The study consisted of 192 tumor tissue samples obtained from patients with CRC. Immunohistochemistry and direct sequencing of DNA were performed to analyze p53R2/RRM2 protein expression and p53/APC/k-ras gene mutations in these samples. The expression level of miR-211 was detected by reverse transcription-quantitative polymerase chain reaction. The results showed that the expression of p53R2 was lower and that of RRM2 was higher in patients with lymph node metastasis, distant metastasis, and late-stage CRC compared with patients without lymph node metastasis, distant metastasis and early-stage CRC. A high expression of RRM2 in patients had a negative effect on overall survival (OS) and disease-free survival (DFS) in CRC. Positive expression of RRM2 was detected in tumor tissues, and expression associated with the presence of k-ras gene mutation. Furthermore, it was detected that the upstream miR-211 expression was negatively associated with RRM2 expression in tumor tissues of patients with CRC. miR-211 expression was associated with survival and tumoral recurrence in patients with k-ras mutations. The present authors suggest that the downregulation of miR-211 and overexpression of RRM2 in tumor tissues of patients with CRC could be used to predict metastases and disease prognosis, particularly in patients with k-ras gene mutations.