126. Telomerase as a diagnostic tool in colon cancer

Abstract

Objectives Reactivation of telomerase is believed to play an important role in immortalization and carcinogenesis. Design To investigate the expression of three components of telomerase complex (hTR, hTERT, TP1) along with telomerase activity in malignant and normal cells. Methods Cells isolated from gastric and colon cancer, and normal mucosa from stomach and colon of corresponding patients. In addition established cell lines from gastric and colon cancer have been studied. Expression of hTERT, hTR and TP1 has been studied by reverse tanscriptase PCR technique. Telomerase repeat amplification protocol-TRAP and PCR-ELlSA was used for analysis telomerase activity. FISH technique was used to detect possible TERT gene amplification. Results The all telomerase components were consistently expressed in colon and gastric cancer cells. Neoplastic RNA produced consistently very strong amplification signals either for hTR hTERT and TP1. The expression of hTR was observed in RNA isolated from all normal mucosa samples and from peripheral blood lymphocytes. The expression of TP1 and hTERT has been found in the majority of normal cells, however the amplification signals produced were usually much weaker then in malignant cells. The limiting dilution experiments indicated that the cancer cells have at least 100-fold higher telomerase activity and at least 25-fold higher TP1 and hTERT expression in comparison to normal cells. FISH analysis revealed amplification of TERT gene in malignant cells. Conclusions It can be concluded that all cancer cells tested have higher telomerase expression and activity, as compared to normal cells. The high expression and activity of telomerase in cancer cells can be explained by amplified TERT gene. Therefore telomerase can be a good cancer marker provided quantitative analysis is carried out. Grant support: The work was sponsored by KBN grants No 4P05B 072 17 and 6P05E 102 20.