miRNAs as Biomarkers and Therapeutic Targets in Non-Small Cell Lung Cancer: Current Perspectives

Lung cancer is the most common cancer worldwide. Up to 85% of lung cancer cases are diagnosed as non-small cell lung cancer (NSCLC). The effectiveness of NSCLC treatment is expected to be improved through the implementation of robust and specific biomarkers. MicroRNAs (miRNAs) are small, non-coding molecules that play a key role in the regulation of basic cellular processes, including differentiation, proliferation and apoptosis, by controlling gene expression at the post-transcriptional level. Deregulation of miRNA activity results in the loss of homeostasis and the development of a number of pathologies, including lung cancer. During lung carcinogenesis, miRNAs exhibit dual regulatory function: they act as oncogenes to promote cancer development or as tumour suppressors. Unique miRNA sequences have been detected in malignant tissues and corresponding healthy tissues. Furthermore, stable forms of tumour-related miRNAs are detectable in the peripheral blood of patients with NSCLC. The potential benefits of using extracellular miRNAs present in body fluids as part of the diagnostic evaluation of cancer include low invasiveness (compared with tumour cell/tissue sampling), and the repeatability and ease of obtaining the specimens. Apart from the diagnostic applications of altered miRNA expression profiles, the dual regulatory role of miRNA in cancer might drive the further development of personalised therapies in NSCLC. The clinical usefulness of miRNA expression analysis to predict the efficacy of various treatment strategies including surgery, radio- and chemotherapy, and targeted therapies has been evaluated in NSCLC. Also, the capacity of a single miRNA to regulate the expression of multiple genes simultaneously presents an opportunity to use these small molecules in personalised therapy as individualised therapeutic tools.