Investigation of telomerase activity and gene expression in colorectal cancer

İzgi, Ahu
Human telomerase is a reverse transcriptase which synthesizes telomeric repeat sequences at the ends of chromosomes. The telomerase enzyme has two essential subunits to be functional which are called telomerase reverse transcriptase (hTERT) and human telomerase RNA (hTR). Telomerase uses its RNA subunit as a template for the addition of hexameric repeats at the ends of chromosomes. The activity of telomerase has been detected in immortal cells but not in most normal somatic cells. Therefore, its activity could serve as diagnostic or prognostic marker in malignancies. Telomeres are heterochromatic DNA sequences bound by a number of telomere binding proteins in order to maintain the stability of chromosomes. Protection of telomere 1(POT1) is a single stranded telomere binding protein which is thought to have significant role in the recruitment of telomerase to telomeres. The objective of the current study to investigate telomerase activity and gene expression of hTERT and hPOT1 in human colorectal cancer tissues. The activity of telomerase was examined in colorectal tumors and normal adjacent specimens by and improved telomeric repeat amplification protocol (TRAP)-Silver Staining Assay. The expression levels of hTERT and hPOT1 genes was analysed by qPCR. The results showed that colorectal cancer tumors showed significantly high telomerase activity whereas normal adjacent tissues were found to be telomerase negative. Among clinicopathological parameters; the stage, histological type, distant metastasis and lymph node metastasis status of tumors were found to show significant differences in terms of telomerase activity. Moreover, the expression of human telomerase reverse transcriptase (hTERT) was found to be overexpressed in tumor tissues compared to normal adjacent tissues. Likewise, colorectal tumors expressed high level of hPOT1 compared to normal tissues. Both the expression of hTERT and hPOT1 correlated with telomerase activity. It can be concluded from the results of the current study that high telomerase activity and overexpression of hTERT and hPOT1, may indicate that they could serve as diagnostic or prognostic indicators in colorectal cancer.


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Citation Formats
A. İzgi, “Investigation of telomerase activity and gene expression in colorectal cancer,” M.S. - Master of Science, Middle East Technical University, 2012.