Noguchi, T., Y. Toiyama, T. Kitajima, H. Imaoka, J. Hiro, S. Saigusa, K. Tanaka, Y. Inoue, Y. Mohri, S. Toden and M. Kusunoki (2016). “Mirna-503 promotes tumor progression and is associated with early recurrence and poor prognosis in human colorectal cancer.” Oncology 90(4): 221-231.
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OBJECTIVES: MicroRNA (miR)-503 is downregulated in several cancers and plays a tumor-suppressive role in carcinogenesis. However, the miR-503 expression pattern, its clinical significance and its molecular mechanism in colorectal cancer (CRC) have not been investigated. METHODS: We analyzed miR-503 expression in normal mucosa (n = 20), adenoma (n = 27) and CRC (n = 20). We quantified miR-503 expression in an independent cohort (n = 191) and investigated the clinical significance of miR-503 in CRC. CRC cell lines were transfected with anti-miR-503 to assess its function and target gene. RESULTS: miR-503 expression increased according to the adenoma-carcinoma sequence. High miR-503 expression was significantly associated with large tumor size, serosal invasion, lymphatic and venous invasion as well as lymph node metastasis. CRC patients with high miR-503 expression had significantly earlier relapse and poorer prognosis than those with low expression. miR-503 was an independent recurrence marker in stage I/II CRC. In vitro, attenuated miR-503 expression resulted in inhibition of proliferation, invasion and migration and acquisition of anoikis of CRC cells. The putative target gene (calcium-sensing receptor) was significantly upregulated after miR-503 attenuation. CONCLUSIONS: miR-503 acts as an ‘onco-miR’ in CRC. High miR-503 expression is associated with early recurrence and poor prognosis in CRC.