MTT assay for cell survival analysis

Bladder cancer cells (T24, BIU87, 5637) and other cells (293, PC12, A498, HepG2, BGC823) were plated in 96-well plates (5 × 10³ cells/well) and incubated for 24 h at 37°C in a humidified 5% CO₂ chamber. Then, the cell lines were infected with RGDAd-UPII-TK or RGDAd-UPII-Null. At 24 h post-transfection, the cells were treated or not treated with GCV (0.02 μg/ml). After incubation for 12 h at 37°C, 20 μl of MTT (Sigma) in PBS (5 mg/ml) was added to each well, followed by an additional 4 h of incubation. Subsequently, the supernatant was removed, and 150 μl DMSO (Sigma) was added to each well and mixed thoroughly. The optical density (OD) was measured at 490 nm using a microplate reader. Cell viability was measured as the absorbance of the experimental group compared to the GCV-treated control group.