Correlation between the expression of telomerase reverse transcriptase and proliferative activity in breast cancer cells using an immunocytochemical restaining method

Telomerase activity is thought to contribute to the immortality of cancers. Recently, some investigators described a correlation between the activity of telomerase and the proliferative activity of cancer cells. The aim of this study was to evaluate the correlation between the expression of telomerase-associated protein and proliferative activity. Telomerase reverse transcriptase (TERT) is one of the proteins that correlates with telomerase activity. We investigated TERT protein and its mRNA, and examined the correlation between the TERT protein and Ki-67, which reflects proliferative activity with immunostaining, and its mRNA, which correlates with telomerase activity, using in situ hybridization. Imprint smears from 17 invasive ductal adenocarcinomas were investigated. In most cases positive for TERT mRNA, the percentage of TERT protein-positive cells was also high and was closely related to mRNA (P=0.024). The positive rates of TERT for the cases with lymph node metastasis were significantly higher than those for the cases without metastasis (P=0.046). The positivity of TERT protein also correlated significantly with the Ki-67-positive rate (r=0.82). As the proliferation activity increased, the number of cells positive for both proteins also increased (r=0.89). In conclusion, it was suggested that the expression of TERT protein is associated with the expression of Ki-67, and is concerned with maintenance of the high proliferative activity in cancer cells with aggressive proliferation.