Nonhomologous End Joining Is Essential for Cellular Resistance to the Novel Antitumor Agent, β-Lapachone

Abstract

Commonly used antitumor agents, such as DNA topoisomerase I/II poisons, kill cancer cells by creating nonrepairable DNA double-strand breaks (DSBs). To repair DSBs, error-free homologous recombination (HR), and/or error-prone nonhomologous end joining (NHEJ) are activated. These processes involve the phosphatidylinositol 3 ¶-kinase-related kinase family of serine/threonine enzymes: ataxia telangiectasia mutated (ATM), ATM-and Rad3-related for HR, and DNAdependent protein kinase catalytic subunit (DNA-PKcs) for NHEJ. Alterations in these repair processes can cause drug/ radiation resistance and increased genomic instability. BLapachone (B-lap; also known as ARQ 501), currently in phase II clinical trials for the treatment of pancreatic cancer, causes a novel caspase-and p53-independent cell death in cancer cells overexpressing NAD(P)H:quinone oxidoreductase-1 (NQO1). NQO1 catalyzes a futile oxidoreduction of B-lap leading to reactive oxygen species generation, DNA breaks, ;-H2AX foci formation, and hyperactivation of poly(ADP-ribose) polymerase-1, which is required for cell death. Here, we report that B-lap exposure results in NQO1-dependent activation of the MRE11-Rad50-Nbs-1 complex. In addition, ATM serine 1981, DNA-PKcs threonine 2609, and Chk1 serine 345 phosphorylation were noted; indicative of simultaneous HR and NHEJ activation. However, inhibition of NHEJ, but not HR, by genetic or chemical means potentiated B-lap lethality. These studies give insight into the mechanism by which B-lap radiosensitizes cancer cells and suggest that NHEJ is a potent target for enhancing the therapeutic efficacy of B-lap alone or in combination with other agents in cancer cells that express elevated NQO1 levels. [Cancer Res 2007;67(14):6936-45]

eIF2 kinases mediate β-lapachone toxicity in yeast and human cancer cells

“…Initially it was reported that b-lap cytotoxicity did not involve DNA damage, but recently we and others groups have demonstrated that b-lapinduced cell death is initiated by the induction of DNA damage and checkpoint activation. 22,26 To further characterize the molecular mechanism of b-lap-induced cell death, we analyzed the profile of gene expression of WT yeast cells treated with the drug. As expected, categories as ROS response and electron transport were present in this analysis (Table 1).…”

Preclinical study of the DNA repair inhibitor Dbait in combination with chemotherapy in colorectal cancer

“…For example, molecules inhibiting damage signaling have been designed to target poly(ADP-ribose) polymerase (PARP) [25][26][27], ATM [28], and the partner of DNA-PKcs Ku70 [29][30][31]. DNA repair inhibitors target base excision repair via O(6)-methylguanine-methyltransferase (MGMT) inhibition [32], homologous recombination repair via Rad51 inhibition, or non-homologous end joining (NHEJ) via DNA-PK inhibition [29,[33][34][35][36]. All these strategies are designed to target key enzymes and may therefore be thwarted by target mutation or the activation of another repair pathway.…”

Reduction of doxorubicin-induced genotoxicity by Handroanthus impetiginosus in mouse bone marrow revealed by micronucleus assay

“…However, it is also possible that β-lapachone induced a small number of DNA strand breaks owing to its ability to produce activated oxygen species (Docampo et al, 1979;Molina Portela and Stoppani, 1996;Molina Portela et al, 1996). β-lapachone (3,4-dihydro-2,2-dimethyl-2H-naphthol[1,2-b] pyran-5,6-dione, ARQ 501), a natural o-naphthoquinone and a major component in an ethanol extract of H. impetiginosus bark, displayed promising antitumor activity in various tumor cells (Pardee et al, 2002;Tagliarino et al, 2003;Terai et al, 2009;Tan et al, 2012) and has been tested as an antitumor drug in phase I, II, and III clinical trials in combination with other chemotherapeutic agents (Pardee et al, 2002;Bentle et al, 2007). The anticancer activity of β-lapachone may involve its catalysis by NAD(P) H:quinone oxidoreductase (NQO1, DT-diaphorase), which used NAD(P)H or NADH as an electron source to yield the two-electron reduction of β-lapachone (Pardee et al, 2002;Reinicke et al, 2005).…”