Platinum accumulation on DNA in Tca/cisplatin and Tca8113. DNA was extracted from Tca/cisplatin cells (blue) and Tca8113 cells (pink) after treatment with 200 μM cisplatin for 0, 30, 60 and 120 min. The platinum concentration in isolated DNA was measured by ICP. Each point is the mean of three independent experiments. Significant differences were observed at 60 min (P = 0.008, Student's t test) and 120 min (P = 0.002, Student's t test), which are marked with asterisks.