The impact of ABCC1 for CML is less clear in the clinic (11–13); nevertheless, in a small group of CML treatment-refractory patients, we described increased expression and activity of ABCC1 in 11 and ABCB1 in 12 out of 13 individuals (14, 15). This evidence concerns the gene ABCC1 and chronic myelogenous leukemia, BCR-ABL1 positive.