title: Poly(ADP-ribose) polymerase inhibitor ABT-888 potentiates the cytotoxic activity of temozolomide in leukemia cells: influence of mismatch repair status and O6-methylguanine-DNA methyltransferase activity.
abstract: The poly(ADP-ribose) polymerase (PARP) inhibitor ABT-888 potentiates the antitumor activity of temozolomide (TMZ). TMZ resistance results from increased O(6)-methylguanine-DNA methyltransferase (MGMT) activity and from mismatch repair (MMR) system mutations. We evaluated the relative importance of MGMT activity, MMR deficiency, nonhomologous end joining (NHEJ), and PARP activity in ABT-888 potentiation of TMZ. MMR-proficient and MMR-deficient leukemia cells with varying MGMT activity, as well as primary leukemia samples, were used to determine TMZ IC(50) alone and with ABT-888. ABT-888 effectively inhibited PARP activity and enhanced TMZ growth inhibition in most leukemia cells. ABT-888 potentiation was most effective in MMR-deficient cells with low MGMT activity [potentiation factor (PF) = 21]. ABT-888 also potentiated TMZ activity in MMR-deficient cells with elevated MGMT activity. Unexpectedly, ABT-888 also enhanced TMZ activity in MMR-proficient cells (PF = 3-7). ABT-888 potentiation was unrelated to NHEJ activity. ABT-888 potentiated TMZ (PF = 2-5) in two of four acute myeloid leukemia patient samples but showed little potentiation in primary acute lymphoblastic leukemia. In conclusion, although ABT-888 potentiation of TMZ was most pronounced in MMR-deficient cells with low MGMT activity, neither MMR proficiency nor MGMT overexpression completely abrogated ABT-888 potentiation of TMZ.
authors: Texas Children's Cancer Center/Baylor College of Medicine, Houston, Texas 77030, USA. tmhorton@txccc.org
authors: Terzah M
authors: TM
authors: Horton
authors: Gaye
authors: G
authors: Jenkins
authors: Debananda
authors: D
authors: Pati
authors: Linna
authors: L
authors: Zhang
authors: M Eileen
authors: ME
authors: Dolan
authors: Albert
authors: A
authors: Ribes-Zamora
authors: Alison A
authors: AA
authors: Bertuch
authors: Susan M
authors: SM
authors: Blaney
authors: Shannon L
authors: SL
authors: Delaney
authors: Madhuri
authors: M
authors: Hegde
authors: Stacey L
authors: SL
authors: Berg
mesh_terms: D018906:Antineoplastic Agents, Alkylating / Q000633:toxicity*; D001562:Benzimidazoles / Q000494:pharmacology*; D045744:Cell Line, Tumor; D053843:DNA Mismatch Repair; D003606:Dacarbazine / Q000031:analogs & derivatives* / Q000633:toxicity; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D007938:Leukemia / Q000188:drug therapy* / Q000201:enzymology; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000235:genetics / Q000378:metabolism*; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D000077204:Temozolomide
chemical_list: D018906:Antineoplastic Agents, Alkylating; D001562:Benzimidazoles; D004791:Enzyme Inhibitors; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; C521013:veliparib; D003606:Dacarbazine; D019853:O(6)-Methylguanine-DNA Methyltransferase; D000077204:Temozolomide