miR-216b suppresses tumor growth and invasion by targeting KRAS in nasopharyngeal carcinoma

MicroRNAs (miRNAs) are small noncoding RNAs that are involved in various diseases, including cancer. In the present study, we found that miR-216b was downregulated in nasopharyngeal carcinoma (NPC) cell lines and specimens. Decreased expression of miR-216b was directly related to advanced clinical stage and lymph node metastasis. miR-216b levels correlated inversely with levels of KRAS protein during nasopharyngeal tumorigenesis. Furthermore, we demonstrated that miR-216b can bind to the 3' untranslated region (UTR) of KRAS and inhibit expression of the KRAS protein. Both in vitro and in vivo assays revealed that miR-216b attenuated NPC cell proliferation, invasion and tumor growth in nude mice. miR-216b exerts its tumor suppressor function through inhibition of the KRAS-related AKT and ERK pathways. Our findings provide, for the first time, significant clues regarding the role of miR-216b as a tumor suppressor by targeting KRAS in NPC.