The kinase inhibitor STI571 reverses the Bcr–Abl induced point mutation frequencies observed in pre-leukemic P190^Bcr–Abl transgenic mice

Abstract 

Chronic myelogenous leukemia (CML) and 25% of adult onset acute lymphoblastic leukemia (ALL) are associated with the expression of Bcr–Abl, a constitutively activated protein tyrosine kinase. Bcr–Abl associated leukemias are characterized by a high degree of chromosomal and genomic instability. It is unclear if the phenotype of genomic instability is a primary consequence of Bcr–Abl expression or if it is acquired secondarily. We have attempted to answer this question in previous studies by measuring the frequency of point mutations in double heterozygote transgenic mice derived from mating homozygous P190^Bcr–Abl transgenic mice (line 623) and the Big Blue Mice^® (Stratagene). Our results showed a 2–3-fold increase in the point mutation frequency in pre-leukemic (i.e. about 100 days before the onset of leukemia) P190 mice, compared to control mice (C57/BL6). In the present report, we extended these prior studies to ascertain if Bcr–Abl induced point mutations is a reversible phenotype. Pre-leukemic P190^Bcr–Abl/Big Blue double homozygous and C57/BL6 control mice were injected with the c-Abl specific kinase inhibitor STI571 for 10 consecutive days. We observed a decrease in the Bcr–Abl induced mutation frequencies in spleen and kidney tissue from mice treated with STI571. These results confirm that Bcr–Abl can directly and reversibly induce an increase in point mutation frequencies that could contribute to the genomic instability observed in Bcr–Abl positive leukemias.

Abbreviations:  CML, chronic myelogenous leukemia, Ph, Philadelphia chromosome, Bcr, break cluster region, ALL, acute lymphocytic leukemia, Rb, retinoblastoma, RFC, replication factor C, X-gal, 5-bromo-4-chloro-3-indolyl-β-d-galactopyranoside, CNL, chronic neutrophilic leukemia

Keywords:  Bcr–Abl, STI571, Big Blue assay system, Genomic instability, Chronic myelogenous leukemia, Mutation frequency