Expression of telomerase activity in 4NQO induced carcinoma in rat tongue

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Correlation between telomerase activity and apoptosis was examined in chemically induced tongue carcinomas using 5-week-old male Sprague-Dowley rats. Animals were given 50 ppm 4-nitroquinoline 1-oxide solution as drinking water for 4, 8, 12, 16, 20, and 24 weeks and sacrificed. Tongue tissue was prepared to investigate apoptotic cells and p53 positive cells by TUNEL method and immunohistochemical method, respectively. Telomerase activity was also examined by stretch PCR method. Namely, telomerase containing solution was extracted from each group of rats, and stretch reaction by telomerase was performed at 30℃. After amplification by PCR with rTaq, samples were applied to an acrylamide gel. Electrophoresis was carried out at 100V under a constant temperature. The gel was stained with SYBRgreen and observed. Epithelial tissue of the tongue showed hyperplastic change in 8 weeks, dysplastic change in 12 weeks, and carcinogenesis in 16 weeks after the beginning of 4NQO administration. p53 overexpression increased in 4 weeks and was kept high level through experimental period. Apoptotic cells also increased till 16 weeks, but decreased thereafter. Telomerase activity was observed in all animals including 4-week group. As a result, telomerase activity began to appear coincident with p53 overexpression proceeding the initiation of histological changes. So it is suggested that apoptosis and immortalization of the tissue should be equally involved in the early stage of chemically induced carcinoma.