Regulation of telomerase activity in cancer

Recently, in addition to environmental effects, researches focused on effects of genetic factors on carcinogenesis. The telomerase activity is required for immortality of tumor cell and carcinogenesis process. In human cancers, telomerase is up regulated where it serves to increase tumor proliferation by helping to protection of functional telomeres.In our study, gene expression levels of hTERT, pontin, reptin and dyskerin measured with RT-PCR method which telomerase related molecules in normal and tumor tissues in colon, gastric, breast and soft tissue cancers. In addition 8OHdG levels in urine and MDA levels in serum were measured which cancer related oxidative stress markers.In total patient group, mean expression levels of pontin, reptin and dyskerin in tumor tissues were significantly higher than normal tissues (p=0.008, p=0.006 and p=0.042, respectively). Also mean expression levels of hTERT in tumor tissues were higher than normal tissues but it was not significant level (p=0.214). When we evaluated according to the types of cancer, average gene expression levels of tumor tissues in all cancer groups were higher than in normal tissues, except hTERT expression in gastric cancer. Hovewer, significantly increased levels were obtained for pontin in colon cancer and for reptin in breast cancer (p=0.001 and p=0.043, respectively).In our study, while the levels of MDA and 8OHdG/creatinine in total patient group and all types of cancer were higher compared to control group, significant increases were only in MDA levels in total, colon and gastric cancer groups (p=0.001, p=0.049 and p=0.007, respectively).We did not find any correlation between hTERT and reptin, while all other genes were in positive correlations in total patient group. There was a positive correlation between MDA and reptin according to correlations between oxidative stress markers and gene expressions.Results obtained in this study reveal that increasing expressions of pontin, reptin and dyskerin in tumor tissues may be suppporting the telomerase activity in cancer, especially in the early stage of disease. Additionally, positive correlations observed between only a few of the studied genes and oxidative stress markers which were shown to have increasing levels in cancer patients lead us to suggest that oxidative stress may be partially effective in telomerase activity.