title: ABT-737 overcomes Bcl-2 mediated resistance to doxorubicin-DNA adducts.
abstract: Doxorubicin is an anthracycline anticancer agent that functions primarily by inhibiting topoisomerase II, but also forms covalent DNA adducts depending on the cellular availability of formaldehyde. The combination of formaldehyde-releasing prodrugs (such as AN-9) with doxorubicin has been shown to result in synergistic doxorubicin-DNA adduct formation and synergistic apoptosis in HL-60 leukemic cells, offering the potential for lower concentrations of doxorubicin to be used clinically in order to minimize side-effects. However, the overexpression of Bcl-2 confers resistance to doxorubicin/AN-9 DNA adduct forming treatments, thus limiting the therapeutic potential of this drug combination. The small molecule inhibitor, ABT-737, which binds to and inhibits Bcl-2, Bcl-xL and Bcl-w, was used in combination with doxorubicin/AN-9 treatments to overcome resistance to doxorubicin-DNA adducts in Bcl-2 overexpressing HL-60 cells (HL-60/Bcl-2). The combination treatment of doxorubicin and AN-9 (and all single agent controls) failed to induce an apoptotic response in HL-60/Bcl-2 cells, however, the addition of low nanomolar (sub-lethal) concentrations of ABT-737 was able to greatly increase apoptosis levels. Various control compounds were used to demonstrate that the mechanism of cell kill in response to the 'triple treatment' (doxorubicin, AN-9 and ABT-737) is dependent on DNA adduct formation. Therefore, the ability of ABT-737 to inhibit Bcl-2 renders previously resistant HL-60 cancer cells highly sensitive to doxorubicin-DNA adducts, leading to a classical apoptotic response. In conclusion, the data obtained provides promising evidence that the anticancer activity of doxorubicin-DNA adducts can be substantially enhanced in Bcl-2 overexpressing cancers with the use of the small molecule Bcl-2 inhibitor, ABT-737.
authors.affiliation: Department of Biochemistry, La Trobe University, Victoria 3086, Australia. mugarenko@students.latrobe.edu.au
authors.forename: Michal
authors.initials: M
authors.lastname: Ugarenko
authors.forename: Abraham
authors.initials: A
authors.lastname: Nudelman
authors.forename: Ada
authors.initials: A
authors.lastname: Rephaeli
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Kimura
authors.forename: Don R
authors.initials: DR
authors.lastname: Phillips
authors.forename: Suzanne M
authors.initials: SM
authors.lastname: Cutts
mesh_terms: D001713:Biphenyl Compounds / Q000737:chemistry / Q000494:pharmacology*; D018736:DNA Adducts / Q000737:chemistry / Q000494:pharmacology*; D004317:Doxorubicin / Q000737:chemistry / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000502:physiology*; D018922:HL-60 Cells; D006801:Humans; D009596:Nitrophenols / Q000737:chemistry / Q000494:pharmacology*; D010879:Piperazines / Q000737:chemistry / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors* / Q000502:physiology*; D013449:Sulfonamides / Q000737:chemistry / Q000494:pharmacology*
chemical_list: C501332:ABT-737; D001713:Biphenyl Compounds; D018736:DNA Adducts; D009596:Nitrophenols; D010879:Piperazines; D019253:Proto-Oncogene Proteins c-bcl-2; D013449:Sulfonamides; C031902:doxorubicin-DNA; D004317:Doxorubicin