In a first step, we thus measured mRNA expression levels of the potential imatinib transporters in PBMCs of healthy volunteers as well as in the immortalized CML cell line K562, derived from a BCR-ABL-positive CML patient in blast crisis.25 In both cell types mRNA for OCT1 (1/ΔCt= 0.07 and 0.07, NS), OCT2 (0.08 and 0.07, NS), and MATE1 (0.09 and 0.07, NS) in PBMC and K562 cells, respectively, were expressed at similar levels (Figure 1c). This evidence concerns the gene SLC22A1 and chronic myelogenous leukemia, BCR-ABL1 positive.