Introduction: Background: Oral cancer is known as the sixteenth most common cancer around the world, and oral squamous cell carcinoma (OSCC) comprises 90% of them with more frequency in South-Asian countries. The most commonly discovered risk factors are tobacco and alcohol consumption, and human papillomavirus (HPV) infection. The current therapeutic approaches are chemotherapy, radiotherapy, chemo/radiotherapy, and surgery. Although many studies have been developed to provide definitive biomarkers for early diagnosis, prognosis, and therapy, the five-year survival rate remains poor at 50%. In this way, it is essential to provide novel diagnostic tools and targeted therapies.
Methods: Literature review: The genes involved in molecular pathways of the tumorigenesis process are regulated by some non-coding RNAs such as microRNAs (miRNAs or miRs). miRNAs are small-length sequences (21-23nt) that regulate gene expression at the post-transcriptional level by degrading or suppressing target messenger RNAs (mRNA) according to the partial complementary base pairing sites. miRNAs commonly bind to the 3' untranslated region (3' UTR) of target mRNA by degrading them or rarely attaching to the 5' UTR to suppress promoter activation. Based on previous studies, deregulation of miRNAs affects downstream gene expression and plays a role in the pathological processes of oral cancer. The miRNAs can repress tumor suppressor gene expression by the oncogenic role that is named onco-miRs or inhibit the expression of oncogenic genes. This idea of application of them as potential biomarkers was manifested for early diagnosis, prognosis, and the development of novel therapeutic approaches. In addition, miRNAs can be involved in epigenetic modification by binding to the histones during methylation. One of the key findings in recent studies is the evaluation of miRNAs in body fluid in mentioned strategies for oral cavity cancers.
Results: The body fluid contains a signature profile of markers that change their expression during the tumorigenesis process, metastasis, and invasion. The biofluid collection is non-invasive, available, economical, safe, and valid. Micro-RNAs (miRNAs) are one of the critical cell-free nucleic acid elements in body fluids such as saliva, serum, plasma, and urine. Despite the potential roles of circulating miRNAs, challenges remain related to the exact regulation of mentioned miRNAs before using them in targeted therapy. Since one miRNA can bind to multiple mRNA targets, and one mRNA can attach by different miRNAs, discovering a definitive miRNA biomarker is the main challenge. Evaluating potential biofluid markers in the clinical setting would allow us for early diagnosis, prediction of treatment response, improvement in treatment candidates, and disease monitoring for early detection of tumor recurrence.
Conclusion: Conclusion: A panel of candidate distinct miRNAs may indicate clinicopathological features, the result of personalized treatment, and provide new signature profiles of oral cancer. miRNA signatures can be applied as potential biomarkers for early oral cancer diagnosis, and prognosis and as novel molecular therapies in oral cancer.
Keywords: Keywords: miRNAs, Oral cancer, Biomarkers, Epigenetics, Early diagnosis