The expression of microRNA-744-3p and its functional role in laryngeal carcinoma

Abstract

Larynx is an indispensable organ in human. The major functions of larynx include respiration, airway protection and phonation. Laryngeal carcinoma is one of the most common head and neck cancers in Hong Kong. Cancer in the laryngeal region will impair the laryngeal function. Therapeutically, disease control and post-therapeutic survival are the primary goals of treatment. In addition, maximal preservation of laryngeal function is vital for improving the quality of life of patients. In order to find out novel and more effective approach for laryngeal carcinoma treatment, identifying the mechanisms contributing to laryngeal carcinoma progression and metastasis is essential.

MicroRNA is a short noncoding RNA which functions as post-transcriptional regulator. Deregulated microRNA expression has been reported in the tumorigenic process of multiple human malignancies including laryngeal carcinoma. In this study, we first employed microRNA microarray to identify the differential microRNA expression pattern in laryngeal carcinoma cell lines and normal epithelial cells in the head and neck region. Further, the results were validated by examining laryngeal carcinoma tissues using real-time polymerase chain reaction.

Three microRNAs (miR-196a, miR-196b and miR-744-3p) are differentially expressed in the laryngeal carcinoma cell lines and clinical samples. Of which, overexpression of miR-744-3p is significantly associated with the regional lymph node metastasis of patients. In silico analysis showed that mature miR-744-3p could target the mRNA transcript of programmed cell death 4 (PDCD4) and phosphatase and tensin homolog (PTEN). In the laryngeal carcinoma tissues, miR-744-3p level is inversely correlated with PDCD4 and PTEN, both of which are the upstream regulators of matrix metallopeptidase 9 (MMP-9) expression. PDCD4 is involved in the PI3K/AKT/mTOR pathway and NF-κB (p65) signaling cascade. PTEN on the other hand is a known tumor suppressor gene which can antagonize the action of PI3K.

MiR-744-3p suppressing laryngeal cells showed reduced migration and metastatic ability in both cell line and mouse xenograft models. Physical interactions between miR-744-3p and PDCD4/PTEN were confirmed by AGO2 immunoprecipitation assay and luciferase reporter assay. Suppressing miR-744-3p in laryngeal carcinoma cells could inhibit MMP-9 expression. Finally, the efficacy of Everolimus (an oral inhibitor of mTOR) and miR-744-3p shRNA in suppressing MMP-9 was compared. Our results showed that suppressing miR-744-3p expression was an effective approach in suppressing MMP-9 in laryngeal carcinoma cells.

In conclusion, miR-744-3p is a promising target in laryngeal carcinoma treatment. Further studies are warranted to explore the clinical utilities of miR-744-3p in the management of laryngeal carcinoma patients.