Telomerase activity in the occurrence and progression of oral squamous cell carcinoma.

Chronic inflammation is considered to be one of the risk factors for carcinogenesis. It was recently reported that telomerase plays an important role in inducing such chronic inflammation. Although high telomerase activity is detected in cancer tissues, the activator of telomerase is still unknown. In this study, we used an immunohistochemical method to examine the expression of human telomerase reverse transcriptase (hTERT) in the dysplasia-carcinoma sequence in the oral cavity. Furthermore, the effects of inflammatory cytokines on the telomerase activity and migration of oral cancer cell lines (Ca9-22, HSC-3, and HSC-4) were examined. Immunoreactivity for hTERT was observed in squamous intraepithelial neoplasia 3 and squamous cell carcinoma. Telomerase activity in Ca9-22 cells was increased by treatment with TNF-α and INF-γ, while its activity in HSC-4 cells was decreased by IL-1β. Although inflammatory cytokines did not affect the proliferative activity of any of the oral cancer cell lines, cytokines and hTERT siRNA promoted the migration of HSC-3 cells. These results suggest that the presence of long-term chronic inflammation may increase telomerase activity and therefore contribute to malignant transformation of the oral mucosal epithelium. Furthermore, inhibition of telomerase activity by inflammatory stimuli increases the invasion of certain types of oral squamous cell carcinomas.