miR-18a downregulates DICER1 and promotes proliferation and metastasis of nasopharyngeal carcinoma.

Nasopharyngeal carcinoma, common in Southeast Asia and the southern provinces of China, often has metastasized by the time of diagnosis; thus there exists the need for improved diagnosis and treatment. Accumulating evidence indicates that microRNAs (miRNAs), which post-transcriptionally regulate protein expression, contribute to the processes of tumorigenesis, including metastasis and cellular invasion. Here, we studied the effect of one miRNA, miR-18a-which is believed to target the miRNA-processing enzyme DICERl-on nasopharyngeal carcinoma. In situ hybridization revealed that miR-18a was more highly expressed in nasopharyngeal carcinoma tissues than in control tissues (P < 0.05), and the overexpression correlated with clinical stage and lymph node metastasis (P < 0.05), but not with age and gender (P > 0.05). In vitro analysis of HK1 nasopharyngeal carcinoma cells transfected with miR-18a exhibited significantly decreased expression of DICER1 mRNA and protein but significantly increased proliferation and invasion properties compared to control cells (P < 0.05). Finally, nude mice injected with miR-18a transfected-HK1 cells displayed significantly increased tumor growth and lung metastasis in vivo (P < 0.05). These findings suggest that miR-18a expression can promote proliferation and metastasis of nasopharyngeal carcinoma cells and that these activities may occur through its regulation of DICER1.