Correlation between telomerase activity and telomeric-repeat binding factors in gastric cancer

Telomeres of a specific length are essential for continuous cell proliferation. The length of telomeres must be maintained by telomerase action and the telomeric DNA-repeat binding protein must be protected. Therefore, there seems to be a relationship between cell immortality due to telomerase activity and telomeric DNA-repeat binding protein. We examined telomerase activity and the expression of telomeric-repeat binding factor 1 and 2 (TRF1 and TRF2) in gastric cancer. Telomerase activity was semi-quantified using the f-TRAP technique in 53 cancerous and non-cancerous gastric tissue specimens. TRF1 and TRF2 were also studied using an immunohistochemical method to determine the frequency of these factors in cell nuclei. Telomerase activity was observed in 79.2% of the cancerous tissue and in 39.6% of the non-cancerous tissue. The average semi-quantitative values for telomerase activity were 67.3 total product generated (TPG) unit/microg protein in cancerous tissue and 6.0 TPG unit/microg protein in non-cancerous tissue. Moreover, T0/1 tumor had the same incidence of telomerase activity as T2 or deeper tumors. These results indicated that the activation of telomerase begins at an early stage of carcinogenesis. TRF1 and TRF2 were detected in 45.1% and 42.9% of the cancerous tissue and in 70.6% and 65.6% of the non-cancerous tissue, respectively. In addition, low positive staining ratios were found for TRF1 and TRF2 when cancer had more deeply invaded. However, telomerase activity did not correlate with either TRF1 or TRF2. These findings suggest that optimal conditions for efficient telomerase are produced as cancer progresses, via suppression of TRFs.