The accumulation [3H]-MX (A) in empty vector transfected HEK293/pcDNA3.1, ABCG2 vector transfected wild-type ABCG2-482-R2, and mutant ABCG2-482-T7 or [3H]-paclitaxel (B) in parental KB-3-1 and ABCB1 overexpressing KB-C2 cells was measured as described in Materials and Methods. Columns are the mean of triplicate determinations; bars, SD. *, P < 0.05 versus the control group. Experiments were done three independent times, and a representative experiment is shown.