A, B, C: 5637, HT1376 (EV, ARRB2 OE) and 253J (C-sh, ARRB2-sh) transfectants were treated with GEM (0 – 100 nM) in growth medium in a 72 h assay. Cytotoxicity was determined by MTT assay. MTT assay was performed after 72 h. Data: Mean ± SD; triplicate. D: Detection of genes associated with GEM resistance by qPCR analysis. E: 2 × 104 cells/well were seeded in 12-well plates and incubated with 3H-Gem (10 nCi ) plus 10 nM unlabeled Gem up to 2 h. 3H-Gem uptake was measured at indicated time intervals by liquid scintillation counting. F: Cells were cultured as in E and incubated with 3H-Gem for 2 hours and efflux into the medium was measured at indicated time intervals.