Impairment of APE1 function enhances cellular sensitivity to clinically relevant alkylators and antimetabolites

Daniel R. McNeill, Wing Lam, Theodore L. DeWeese, Yung Chi Cheng, David M. Wilson

Research output: Contribution to journalArticlepeer-review

Abstract

Base excision repair (BER) is the major pathway for removing mutagenic and cytotoxic oxidative and alkylation DNA modifications. Using a catalytically inactive, dominant negative protein form of human APE1, termed ED, which binds with high affinity to substrate DNA and blocks subsequent repair steps, we assessed the role of BER in mediating cellular resistance to clinically relevant alkylating drugs and antimetabolites. Colony formation assays revealed that ED expression enhanced cellular sensitivity to melphalan not at all; to decarbazine, thiotepa, busulfan and carmustine moderately (1.2- to 2.4-fold); and to streptozotocin and temozolomide significantly (2.0- to 5.3-fold). The effectiveness of ED to promote enhanced cytotoxicity generally correlated with the agent's (a) monofunctional nature, (b) capacity to induce N 7-guanine and N3-adenine modifications, and (c) inability to generate O6-guanine adducts or DNA cross-links. ED also enhanced the cell killing potency of the antimetabolite troxacitabine, apparently by blocking the processing of DNA strand breaks, yet had no effect on the cytotoxicity of gemcitabine, results that agree well with the known efficiency of APE1 to excise these nucleoside analogues from DNA. Most impressively, ED expression produced an ∼5- and 25-fold augmentation of the cell killing effect of 5-fluorouracil and 5-fluorodeoxyuridine, respectively, implicating BER in the cellular response to such antimetabolites; the increased 5-fluorouracil sensitivity was associated with an accumulation of a basic sites and active caspase-positive staining. Our data suggest that APE1, and BER more broadly, is a potential target for inactivation in anticancer treatment paradigms that involve select alkylating agents or antimetabolites.

Original languageEnglish (US)
Pages (from-to)897-906
Number of pages10
JournalMolecular Cancer Research
Volume7
Issue number6
DOIs
StatePublished - Jun 2009

ASJC Scopus subject areas

  • Molecular Biology
  • Oncology
  • Cancer Research

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