Nonhomologous end joining is essential for cellular resistance to the novel antitumor agent, beta-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 DNA-dependent protein kinase catalytic subunit (DNA-PKcs) for NHEJ. Alterations in these repair processes can cause drug/radiation resistance and increased genomic instability. beta-Lapachone (beta-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 beta-lap leading to reactive oxygen species generation, DNA breaks, gamma-H2AX foci formation, and hyperactivation of poly(ADP-ribose) polymerase-1, which is required for cell death. Here, we report that beta-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 beta-lap lethality. These studies give insight into the mechanism by which beta-lap radiosensitizes cancer cells and suggest that NHEJ is a potent target for enhancing the therapeutic efficacy of beta-lap alone or in combination with other agents in cancer cells that express elevated NQO1 levels.

• Authors: Melissa S Bentle, Kathryn E Reinicke, Ying Dong, Erik A Bey, David A Boothman
• Journal: Cancer research (Cancer Res) Vol. 67 Issue 14 Pg. 6936-45 (Jul 15 2007) ISSN: 0008-5472 [Print] United States
• PMID: 17638905 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• Antineoplastic Agents
• Naphthoquinones
• Reverse Transcriptase Inhibitors
• beta-lapachone
• PARP1 protein, human
• Poly (ADP-Ribose) Polymerase-1
• Poly(ADP-ribose) Polymerases

Topics

• Antineoplastic Agents (pharmacology)
• Cell Line, Tumor
• Cell Survival
• Comet Assay
• DNA Breaks
• DNA Damage
• DNA Repair
• Dose-Response Relationship, Drug
• Humans
• Models, Biological
• Naphthoquinones (pharmacology)
• Poly (ADP-Ribose) Polymerase-1
• Poly(ADP-ribose) Polymerases (metabolism)
• Reverse Transcriptase Inhibitors (pharmacology)
• Time Factors