Fig. 3.

Impact of repeated exposure to chemotherapy on ABC transporter expression and intracellular drug accumulation. a Relative gene expression of ABC transporters as determined by qRT-PCR using HPRT1 as control gene. b Accumulation of [³H]-VCR after 4 h incubation in presence or absence of 10 μM verapamil. The BE(2)-C neuroblastoma cell line expressing high levels of P-gp was included as a positive control. Columns means of four individual experiments, bars SE. Statistics were calculated by comparing drug-treated cells with control cells, unless indicated otherwise; ^# p = 0.06; *p < 0.05; **p < 0.01; ***p < 0.001