Increased DNA repair is not a major mechanism of resistance in these cell lines. (A, B, E, F) The six breast cancer cell lines were treated as in Figure 1B, C, E, F. The decrease in adduct levels at several time points after removal of drug at 4 h (carboplatin) or 24 h (oxaliplatin) was used to determine a rate of DNA repair in adducts/108 nt/h for each cell line. (C, D, G, H) The six cell lines were classified as sensitive (blue) or resistant (red) to carboplatin and oxaliplatin (Table 1) and combined to determine average DNA repair rates.