ABCG2 mRNA expression by quantitative real-time RT-PCR in cell lines.

(A) ABCG2, (B) β-actin. RNA from parental AML3, clone 3.3, and clone 6.2 cells was analyzed by real-time RT-PCR. Amplification plots of real-time RT-PCR depict the fluorescent signal (y-axis) compared to reaction cycle number (x-axis). Ct values are defined as the reaction cycle number at which fluorescent signal crosses the threshold over background. To normalize for RNA loading, the Ct value for ABCG2 is subtracted from the Ct for β-actin, to obtain the ΔCt. The resulting ABCG2 level of clone 3.3 was used as the reference point for all subsequent real-time RT-PCR experiments.