The effect of the long-term culture with anti-cancer drugs on the telomerase activity. The telomerase activity was observed by a modified-TRAP assay. Top: A ladder pattern after acrylamide gel electrophoresis. Bottom: the band intensity was measured using an NIH-Image software package and telomerase activity (TA: band intensity of the TRAP products/band intensity of the ITAS) was also calculated. Thereafter, the TA was converted to the relative value (TA at 0 PDL = 1.0). All experiments were repeated at least three times and representative results are shown in this figure.