Urinary (A) and fecal (B) excretion of topotecan lactone in male C57BL/6 (WT), Abcc2−/−, Abcc4−/−, Abcb1−/−, Abcg2−/−, Abcc2;Abcg2, Abcc4;Abcg2−/− and Abcc2;Abcb1−/− mice, over 24 h after IV administration of 1 mg/kg and 4 mg/kg topotecan. The statistical differences were determined using the One-Way ANOVA with Tukey's multiple comparison (GraphPad Prism version 5.04) tests to compare inter-strain differences. Data are expressed as percentage of dose ± SD (n = 5–9; *, P < 0.05; **, P < 0.01; compared with wild-type).