The studies could provide new information that may improve the effectiveness of second-generation drugs for chronic myeloid leukemia (CML). The researchers said their findings suggest that these mutations are central to resistance to Gleevec observed in some patients with CML.

CML develops when an enzyme called Abelson tyrosine kinase (Abl) becomes overactivated by a chromosomal mixup that occurs during blood cell development. The genes ABL and BCR, which are located on different chromosomes, become fused and express a hybrid Bcr-Abl enzyme that is always active. The abnormal activity of the enzyme causes the overproliferation of white blood cells that is the hallmark of CML.

In an article published in the August 2002 issue of the journal Cancer Cell, researchers led by Charles Sawyers at the University of California, Los Angeles, and Howard Hughes Medical Institute (HHMI) investigator John Kuriyan at the University of California, Berkeley, reported that they identified 15 mutations in the BCR-ABL gene that cause resistance to Gleevec. Sawyers was selected as an HHMI investigator in May 2002 in a national competition to identify outstanding investigators who are conducting patient-oriented research.

The latest findings build on earlier work by Sawyers' group that showed that mutations in BCR-ABL underlie resistance to Gleevec, a drug that has shown remarkable potency against CML. "We had studied a handful of CML patients who had a beautiful initial response to Gleevec, but who then relapsed quite dramatically," Sawyers said. "Our biochemical studies showed that the Bcr-Abl target protein, which was inhibited when the patients responded to the drug, was turned back on. Then, we found in
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Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
13-Aug-2002