Identification of colorectal cancer recurrence-related microRNAs

Colorectal cancer (CRC) has high recurrence rate. Effective biomarkers for the detection of colon cancer are still unavailable. MicroRNA (miRNA) is an epigenetic factor that regulates cell proliferation, tumor cell growth, cancer formation, and metastasis by regulating tumor suppressor genes or oncogenes. miRNA has the potential to be used as a biomarker for the diagnosis of diverse cancers. Previously, we revealed that miR-139-3 p is downregulated and miR-338-5 p is upregulated in recurrent CRC patients. The present study further reveals that the miR-139-3 p expression level is inversely correlated with increased metastatic status in three colon cancer cell lines (SW480, SW620, and colo201), as determined using real-time polymerase chain reaction. Furthermore, in 51 pairs of CRC clinical specimens, the expression level of mir-139-3 p was significantly lower in the tumor sections than in the adjacent normal tissues (p < 0.0001), indicating that they are tumor-suppressive miRNAs. Furthermore, the expression level of mir-338-5 p in the tumor tissues of metastatic patients was significantly higher than in the tumor tissues of nonmetastatic patients (p < 0.05), indicating that mir-338-5 p is positively correlated with metastasis. All together, mir-139-3 p and mir-338-5 p may have potential use as biomarkers for the diagnosis of tumor formation and metastasis in CRC patients.