Functional assays of uptake into the KCL22 CML cell line transfected with the hOCT1 SNPs M420del and/or M408V. (A-B) Uptake of ¹⁴C imatinib (A; n = 6) and ¹⁴C TEA⁺ (B; n = 3). Each histogram bar represent the means ± SEM. In both panels, the dark gray bars indicate unmanipulated uptake only and the light gray bars show the uptake attributable to hOCT1 activity (obtained by subtracting the uptake with the hOCT1 amantadine from the unmanipulated uptake). In both panels, * and ł denote significantly decreased uptake and hOCT1 activity, respectively, in M420del+M408 cells compared with undeleted M420+M408 cells; ** and łł denote significantly increased uptake and hOCT1 activity, respectively, in M420del+V408 cells compared with M420del+M408 cells. Individual P values are given in the panels. (C) Uptake of the fluorescent hOCT1 substrate ASP⁺ by confocal microscopy. Uptake is still apparent in the M420del+M408 line compared with mock transfected control (KCL22pcDNA), confirming the presence and activity of functional hOCT1 in this line.