A miR-centric view of head and neck cancers

Head and Neck Squamous Cell Carcinomas (HNSCCs) constitute the sixth most common cancer worldwide with an average 5-year survival rate of around 50%. Several microRNAs, small non-coding RNAs involved in post-transcriptional gene regulation, have been linked to HNSCC based on their differential expression in tumors. Here, we present a compilation of multiple types of information on each HNSCC linked miRNA including their expression status in tumors, their molecular targets relevant to cancer, results of gene manipulation studies and association with clinical outcome. Further, we use this information to devise a new scheme for classifying them into causal and non-causal miRNAs in HNSCC. We also discuss the possibility of using miRNAs as prognostic and diagnostic biomarkers for HNSCC, based on existing literature. Finally, we present available evidence that shows how altered expression of specific miRNAs can contribute to various "hallmarks of cancer" phenotypes such as limitless replicative potential owing to abnormal cell cycle regulation, evasion of apoptosis, reduced response to anti-growth signals, and Epithelial-Mesechymal transition (EMT).