Dual inhibition of the homologous recombinational repair and the nonhomologous end-joining repair pathways in chronic lymphocytic leukemia therapy.

Resistance to chlorambucil in chronic lymphocytic leukemia (CLL) has been associated with increased DNA repair. Specifically, inhibition of either c-abl, which modulates Rad51 directed homologous recombination or DNA-PK dependent nonhomologous end joining has been shown to sensitize primary CLL lymphocytes to chlorambucil. Here we report that inhibition of c-abl can result in a compensatory increase in DNA-PK and thus inhibition of both c-abl and DNA-PK optimally sensitizes CLL lymphocytes to chlorambucil. In this paper we report a drug-induced compensatory change between two DNA repair pathways with potential therapeutic implications in CLL therapy.