MiRNA signature analysis in LSCC gene expression profiles indicates hsa-miR-299-5p as a new tumor suppressor

Given the importance of epigenetic mechanisms in the downregulation of tumor suppressor genes and the activation of oncogenes, herein we focused on microRNA silencing as a cause of oncogene activation in laryngeal squamous cell carcinoma (LSCC). In our study, we aimed at identifying regulatory microRNA signatures in LSCC mRNA profiles from our previous analysis. By this approach, we identified 14 overexpressed genes that shared a common regulatory hsa-miR-299-5p signature in LSCC samples. Subsequent RT-qPCR analysis confirmed the downregulation of hsa-miR-299-5p as well as the overexpression of 3 out of 14 genes: PATZ1, PURB, and TFAM in both LSCC cell lines and tumor samples compared to non-cancerous controls. Further, we have demonstrated a direct interaction between hsa-miR-299-5p and TFAM 3'UTR using dual luciferase assay. Importantly, we have shown decreased TFAM protein level after mimicry of hsa-miR-299-5p expression in three LSCC cell lines. Moreover, cell lines with restored activity of hsa-miR-299-5p demonstrated reduced viability compared to cell lines treated with the negative control. In conclusion, we point to hsa-miR-299-5p as a tumor-suppressive microRNA with the potential to regulate TFAM and consequently influence cell viability.