Telomerase expression, telomerase activity and cell doubling time.

<p>(A) Telomerase mRNA levels relative to 21M primary cells were detected by real-time PCR. Telomerase-transduced primary (21M+hTERT) and HCEnC-21 cells (HCEnC-21T) showed strongly elevated telomerase mRNA levels. Importantly, non-transduced HCEnC-21 cells also expressed significantly higher levels of telomerase mRNA than 21M primary cells. (B) Telomerase activity indicated as template copy number was measured in cell extracts using the telomeric repeat amplification protocol (TRAPeze RT). Heat-inactivated extracts served as negative controls. No specific telomerase activity was detected in 21M primary cells, while HCEnC-21T cell lysates contained strongly elevated telomerase activity. Note that HCEnC-21 intrinsically upregulated endogenous telomerase activity. (C) Cell doubling time of earlier (19–24) and later (32–41) passages of HCEnC-21 and HCEnC-21T. Cells were plated in 12-well plates at a density of 50,000 cells/well and counted after 2, 3, and 4 days using a hemocytometer. HCEnC-21T showed a higher proliferation rate compared to HCEnC-21 in long-term cultures. Error bars indicate mean ± SEM. *, P<0.05.