MDR1 GENE-EXPRESSION IN MYELODYSPLASTIC SYNDROME AND IN ACUTE MYELOID-LEUKEMIA EVOLVING FROM MYELODYSPLASTIC SYNDROME

The expression of the MDR1 gene, a multidrug resistance gene, was dete rmined in patients (N=24) with myelodysplastic syndrome or acute myelo id leukemia evolving from it. MDR1 RNA expression of the mononuclear c ells was detected in 14 (58%) patients. Among patients who had progres sed to acute myeloid leukemia (sAML) (N=14), MDR1 RNA expression was s een in 8 (57%) patients. Expression was observed in the 2 patients who had been pretreated with MDR drugs. These findings indicate that the MDR1 gene is frequently expressed in MDS or sAML and suggest that mult idrug resistance might be involved in the clinical drug resistance of these diseases.