Proliferation capability of hTERT-transfected normal and G6PD-deficient fibroblasts. Normal fibroblasts HFF3 (Panel A) and G6PD-deficient fibroblasts HFF1 (Panel B) were infected with retroviral vector pBABE-Puro or pBABE-Puro-hTERT, and G418-resistant clones were obtained as described in legend to Fig. 1. These G418-resistant cells were cultivated by successive passages with 1:8 spliting. The telomerase activity of hTERT-transfected T5 and GT3 cells at various passages (p13 to p72) was determined by TRAP and shown in Panel C. Lanes labeled with N, P, H in Panel C are negative control with no cell extract, positive control with cell extract from a telomerase-positive HT-1080 cells, and heat-inactivated HT-1080 cell extract, respectively.