The expression of microRNA-324-3p as a tumor suppressor in nasopharyngeal carcinoma and its clinical significance

OBJECTIVE: This study aimed to determine the expression, clinical significance, and possible biologic function of microRNA-324-3p in nasopharyngeal carcinoma (NPC) tissues. METHODS: In total, 54 NPC and 35 control tissues were collected. The correlation between miR-324-3p expression and the clinicopathologic characteristics was analyzed. A dual-luciferase reporter gene assay was employed to examine the predicted target gene of miR-324-3p. The miR-324-3p expression level in 5–8F cells was determined with quantitative reverse transcription-polymerase chain reaction following the transfection of miR-324-3p mimics and inhibitors. Cell proliferation and the percentage of apoptosis were measured with MTT and flow cytometry. Cell invasion ability was assessed by Transwell invasion assay. RESULTS: Our results showed that miR-324-3p was downregulated in the NPC tissues. The expression level of miR-324-3p in poorly differentiated NPC was significantly reduced in comparison with that in well/moderately differentiated NPC. The expression level in clinical stages III/IV was lower than that in clinical stages I/II. Moreover, the expression level of miR-324-3p was significantly lower in NPC patients with lymph node metastasis than that in NPC patients without lymph node metastasis. NPC patients with higher levels of miR-324-3p expression also demonstrated a longer survival time. Predictions from bioinformatics indicated the Hedgehog pathway transcription gene GLI3 as the target gene of miR-324-3p, and the dual- luciferase reporter assay showed that miR-324-3p is directly combined with the 3′-untranslated region of GLI3. The overexpression of miR-324-3p suppressed cell proliferation and invasion, and it enhanced apoptosis in 5–8F cells. CONCLUSION: miR-324-3p can act as a tumor suppressor in NPC cells by the negative regula- tion of GLI3 gene.