Mutator phenotype of BCR – ABL transfected Ba/F3 cell lines and its association with enhanced expression of DNA polymerase β

Abstract

Chronic myelogenous leukemia (CML) is characterized by the Philadelphia chromosome resulting from the translocation t(9-22) producing the chimeric 190 and 210 kDa BCR ± ABL fusion proteins. Evolution of the CML to the more agressive acute myelogenous leukemia (AML) is accompanied by increased cellular proliferation and genomic instability at the cytogenetic level. We hypothezised that genomic instability at the nucleotide level and spontaneous error in DNA replication may also contribute to the evolution of CML to AML. Murine Ba/F3 cell line was transfected with the p190 and p210-encoding BCR ± ABL oncogenes, and spontaneous mutation frequency at the Na-K-ATPase and the hypoxanthine guanine phosphoribosyl transferase (HPRT) loci were measured. A signi®cant 3 ± 5-fold increase in mutation frequency for the transfected cells relative to the untransfected control cells was found. Furthermore, we observed that BCR ± ABL transfection induced an overexpression of DNA polymerase b, the most inaccurate of the mammalian DNA polymerases, as well as an increase in its activity, suggesting that inaccuracy of DNA replication may account for the observed mutator phenotype. These data suggest that the Philadelphia abnormality confers a mutator phenotype and may have implications for the potential role of DNA polymerase b in this process.

Pharmacological inhibition of c-Abl compromises genetic stability and DNA repair in Bcr-Abl-negative cells

“…This contrasts the effect of imatinib observed in Bcr-Ablpositive cells. We and others found that expression of the active Bcr-Abl kinase in CML cells results in genetic instability (Canitrot et al, 1999;Salloukh and Laneuville, 2000;van der Kuip et al, 2004). This can be partially reversed by imatinib in Bcr-Abl-positive cells resulting in mutation frequencies comparable to those seen in imatinib-treated Bcr-Abl-negative cells (Figure 1b).…”

Fusion tyrosine kinases: a result and cause of genomic instability

“…Increased RAD51 also promoted aneuploidy and multiple chromosomal rearrangements. In addition, error-prone DNA polymerases, such as polymerase b, which expression is elevated in BCR/ABL cells (Canitrot et al, 1999), may eventually replace other polymerases usually involved in DNA replication during HRR (Servant et al, 2002). Interestingly, base misincorporations made during DSB repair in Saccharomyces cerevisiae were not substrates for the MMR machinery (McGill et al, 1998).…”

“…Although ROS appears to play a major role in BCR/ABL mutagenesis, other factors may be important, too. For example, DNA polymerase b is overexpressed in BCR/ABL cells, which may diminish the fidelity of BER and HRR (Canitrot et al, 1999;Matsuda et al, 2003).…”

Progressive changes in the leukemogenic signaling in BCR/ABL-transformed cells

“…Interestingly, mutations`re-activating' Akt and STAT5 occurred in cells expressing BCR/ ABL mutants but not in parental 32Dcl3 cells. This phenomenon could be explained by the ®nding that BCR/ABL confers a mutator phenotype (Canitrot et al, 1999).…”