microRNA-27a functions as a tumor suppressor in esophageal squamous cell carcinoma by targeting KRAS.

microRNAs (miRNAs) have been suggested to play a vital role in regulating tumor progression and invasion. However, the expression of miR-27a in esophageal squamous cell carcinoma (ESCC) and its effect on the tumorigenesis of ESCC are unclear. In the present study, we found that miR-27a was downregulated in esophageal carcinoma cell lines and ESCC specimens with lymph node metastasis. Furthermore, we demonstrated that miR-27a binds to the 3'-untranslated region (UTR) of KRAS and inhibits the expression of the KRAS protein. miR-27a levels were inversely correlated with levels of KRAS mRNA and protein in ESCC specimens. Both in vitro and in vivo assays revealed that miR-27a attenuated ESCC proliferation, invasion and tumor growth in nude mice. miR-27a exerts its tumor suppressor function through inhibition of the KRAS-related ERK pathways. Our findings suggest, for the first time, that miR-27a suppresses tumorigenesis of ESCC by targeting KRAS.