Significance of Telomerase Activity and Gene Expression in Colorectal Cancer

Introduction: Telomerase is a ribonucleoprotein synthesizing telomeric DNA onto the chromosomes which has two functional subunits: hTERT (human telomerase reverse transcriptase) and hTR (human telomerase RNA). Activation of telomerase appears to be associated with unlimited replicative potential. Telomerase activity and expression of telomerase components may have significant roles in diagnosis or/and prognosis of malignancies. PCR-based TRAP assay is very sensitive for the detection of enzymatic activity of telomerase even if a few number of cancerous cells are available. The diagnostic or prognostic value of telomerase activity and its expression in colorectal cancer are still unclear. Material and Methods: Protein extraction was performed from specimens of matched normal and colon cancer specimens. Protein concetrations were determined by Bradford assay. Optimized protein concentrations were used for TRAP Assay (Telomeric repeat amplification protocol) which is a PCR-based assay. TRAP products were seperated by vertical gel electrophoresis on 12.5% polyacrylamide gel and visualized by silver staining. Gene expression of hTERT was determined by qPCR analysis. Results: The results demonstrated that all tumor tissues were telomerase positive whereas all corresponding normal tissues were telomerase negative. Among clinicopathological findings, telomerase activity was found to be associated with stage, histology, localization, distant metastasis and lymph node metastasis of tumor. The expression of hTERT was observed both in tumor and normal tissues, however; tumor tissues expressed 4.33 fold more hTERT than normal tissues. Although all of the clinicopathological findings differed in the expression of hTERT compared to normal tissues, they did not differ from each other significantly. Conclusion: Telomerase activity could be a promising tumor marker for colorectal cancer and there is a close association between the enzymatic activity and the expression of its catalytic subunit.