Paclitaxel induces mdr1a.fLUC expression via PXR-independent mechanism. (A) pxr+/+ (WT) and pxr−/− (KO) mice that were heterozygous for the mdr1a.fLUC allele were given 10 mg/kg paclitaxel (Pac) or Cremophor EL (Veh) by i.p. injection at times 0, 48, and 120 hours after the initial injection as indicated by dashed arrows. Results are from a single experiment, with expression quantified as in previous figures. (B–D) Normalized luminescence intensities at the 8-hour time points after each dosing cycle. Data from all mice from one single-dosing experiment with the KO mice (included in dose 1 only) and one multidosing experiment with WT and KO mice (included in doses 1–3) are pooled and averaged (± S.E.M.). Panels show comparisons as in Fig. 1. WT + Pac (n = 9 for all doses), KO + Pac (n = 20 for dose 1, n = 8 for doses 2 and 3), WT + Veh (n = 9 for doses and 2, n = 8 for dose 3), KO + Veh (n = 19 for dose 1, n = 8 for doses 2 and 3). *P ≤ 0.05; **P ≤ 0.01.