MicroRNA­342­3p suppresses proliferation and invasion of nasopharyngeal carcinoma cells by directly targeting Cdc42.

Deregulated microRNAs play an important role in the development and progression of various types of cancer. In our previous study, we observed that microRNA­342­3p (miR­342­3p) was one of the most markedly downregulated microRNAs in two nasopharyngeal carcinoma (NPC) cell lines compared to non­neoplastic cells by using whole genome small RNA sequencing. In the present study, we confirmed that the expression of miR­342­3p was significantly reduced in NPC tissues compared with normal nasopharyngeal epithelial tissues. Overexpression of miR­342­3p inhibited proliferation, epithelial­mesenchymal transition (EMT), migration and invasiveness of NPC cells. In addition, we observed that Cdc42, a Rho GTPase family member involved in cell proliferation and metastasis, is a direct target of miR­342­3p. Additionally, ML141, a small­molecule inhibitor of Cdc42, efficiently suppressed the invasion of NPC cells compared with the control cells. Finally, we analyzed NPC tissues derived from 10 NPC patients and subjected them to quantitative RT­PCR and immunohistochemistry assays for concomitant determination of the expression levels of miR­342­3p and Cdc42. Our results revealed that miR­342­3p levels were significantly inversely correlated with the protein levels of its target Cdc42. The results of the present study indicated that miR­342­3p inhibited NPC tumor growth and invasion by directly targeting the Cdc42 pathway.