miR-138 suppresses the proliferation of oral squamous cell carcinoma cells by targeting Yes-associated protein 1

Aberrant microRNA expression has been suggested to be an important event in the pathologies of various types of cancer. MicroRNA-138 (miR-138) has been reported to be frequently downregulated in various types of human cancer, including oral squamous cell carcinoma (OSCC). However, the precise molecular mechanism of miR-138 underlying OSCC remains largely unknown. The aim of the present study was to investigate the expression of miR-138 in OSCC tumor tissues and several OSCC cell lines and validated its interaction with the 3'-untranslated region (3'-UTR) of Yes-associated protein 1 (YAP1). The results showed that, miR-138 was significantly downregulated in OSCC tumor tissues and cell lines. Overexpression of miR-138 inhibited cell proliferation of OSCC cells whereas the downregulation of miR-138 promoted cell proliferation. A direct interaction between miR-138 and 3'-UTR of YAP1 was validated by dual-luciferase reporter assay. Moreover, overexpression of miR-138 in OSCC cells significantly decreased the expression of YAP1 and downregulation of miR-138 inhibited the expression of YAP1. Specifically, the inhibitory effect of miR-138 on the proliferation of OSCC cells was eliminated by transfection with YAP1 overexpression vectors that did not harbor any specific miR-138 binding specific sequences in 3'-UTR. In addition, the miR-138-overexpressing OSCC cells exhibited a low growth rate in the xenograft tumor assay with a decreased expression of YAP1 in tumor tissues. The results suggest that miR-138 is a tumor suppressor miRNA in OSCC through targeting YAP1, which serves as a promising therapeutic target for the treatment of OSCC.