In summary, we found that galectin-1 was a novel modulator of MDR1 by proteomic analysis of a model system of leukemia cell lines with a gradual increase of MDR1 expression and drug resistance, and NF-κB translocation induced by P38 MAPK activation was responsible for the enhancing effects of galectin-1 on MDR1, suggesting that galectin-1 might be a novel target for improving the efficacy of CML chemotherapy. This evidence concerns the gene ABCB1 and leukemia.