The activation of ABL tyrosine kinase in BCR/ABL-positive chronic myelogenous leukemia (CML) leads to a diversity of biological changes related to the pathogenesis of the disease. In CML patients, we determined the expression of growth factor independence-1 (Gfi1), a transcription repressor with weak oncogenic activity. Our data demonstrated that the Gfi1 mRNA level in both the mononuclear cells and purified CD34(+) cells from CML were significantly higher as measured by quantitative real-time PCR. Using flow cytometry and Western blot, we also showed that the Gfi1 protein content was increased in CML CD34(+) cells. The expression of Gfi1 was correlated with BCR/ABL significantly. Gfi1 may be implicated in the pathogenesis of CML and can serve as a potential target for the management of the disease. Copyright (C) 2009 S. Karger AG, Basel