Telomerase: An exploration toward the end of cancer.

Abstract

The distinguishing feature of cancer cells is their ability to proliferate indefinitely, which is in contrast to the restricted cell multiplication potential for somatic cells. A better understanding of this contrasting behavior was provided in the early 1990s with the discovery of a relationship between telomeres, telomerase, aging, and cancer. Telomeres (tandem repeat DNA sequence TTAGGG) are protective caps at the ends of human chromosomes. Normal human cells experience telomere shortening with each successive cell division. However, in tumor cells, an overexpression of telomerase confers limitless replicative potential to tumor cells by continuous elongation of telomeres. The objective of this review was to systematically assess the data available on telomerase expression in oral cancer, with special reference to its role in diagnosis, prognosis, and treatment. A systematic review of studies that investigated the telomerase expression in oral squamous cell carcinoma (OSCC) was registered with PROSPERO. Subsequent to registration, a predetermined search strategy in accordance with PRISMA guidelines was formulated, and a literature search was conducted using online databases along with hand searching. Eighty-nine articles from PubMed, 83 from Scopus, 5 from BioMed Central, 43 from Google Scholar, and 2 from hand search were identified. A total of 21 articles were shortlisted that met strict inclusion and exclusion criteria and quality assessment. Each study was evaluated for the markers under study, type of sample used, study design/methodology, and statistical analysis. The studies were then grouped into three subheads depending on their implications in the diagnosis, prognosis, and treatment of OSCC. This review explains the basic biology and the clinical implications of telomerase-based diagnosis and prognosis, the prospects for its use in anticancer therapy, in the context of oral cancer.