Downregulation of miR-34a contributes to the proliferation and migration of laryngeal carcinoma cells by targeting cyclin D1

Laryngeal carcinoma is one of the most common head and neck cancers. MicroRNAs are a class of small non-coding RNAs 18-25 nucleotides in length that post-transcriptionally regulate gene expression and have a pivotal role in many biological processes including cancer development. In this study, we investigated the role of miR-34a in laryngeal carcinoma and confirmed the regulation of cyclin D1 (CCND1) by miR-34a. We examined miR-34a expression levels in 71 laryngeal carcinoma patient specimens by quantitative reverse transcription-PCR, and analyzed the clinicopathological significance of the obtained data. Then, functional assays were performed to investigate the potential effects of miR-34a on cancer cell proliferation and migration. In addition, western blotting, luciferase reporter assay and several algorithms were conducted to confirm that CCND1 is directly regulated by miR-34a. We demonstrated that the miR-34a expression level was significantly downregulated in laryngeal carcinoma clinical specimens compared with that observed in their paired adjacent normal tissues. Additionally, miR-34a expression was also inversely correlated with lymph node metastasis and clinical stage. Functional assays showed that ectopic expression of miR-34a inhibited cell proliferation and migration in laryngeal carcinoma cells. Bioinformatic analysis identified CCND1 as a potential target of miR-34a. Moreover, we confirmed that miR-34a inhibited the expression of CCND1 by directly binding to its 3'-untranslated region. Silencing of CCND1 induced effects similar to those of miR-34a ectopic expression, and in laryngeal carcinoma tissues, miR-34a and CCND1 were inversely correlated. Our data suggest that tumor suppressor miR-34a could serve as a new potential diagnostic marker and that ectopic expression of miR-34a may be used as a therapeutic target for laryngeal carcinoma.