Abstract 3332: An artificial zinc finger glycosylase causes site-directed DNA damages and specifically kills the targeted cancer cells via synthetic lethality.

Abstract

Abstract Synthetic lethality is a new developed therapy, in which PARP inhibitor selectively kills BRCA-deficient cancer cells. However, BRCA-deficiency only accounts for a small fraction of cancers. We are interesting in applying synthetic lethal approach to target all cancers regardless BRCA statute. As single strand break (SSB) is the start point of the synthetic lethal, we hypothesized the targeted induction of persistent SSB at tumor unique sequences (cancer somatic mutation sequences) with assistance of synthetic lethality would specifically kill cancer cells. To test this principle we have constructed a six-zinc finger/mutant uracil glycosylase fusion protein (zinc finger glycosylase, ZFG). Upon binding to a specific 18-bp sequence by ZFG six-zinc binding domain, the mutated uracil glycosylase will remove a cytosine residue leaving an apyrimidinic site, which is subsequently convert to SSB by AP-endonuclease cleavage. The SSB lesion is capable of being repaired, however, upon repair, the zinc finger binding site is restored and the site-specific ZFG will again initiate a lesion leading to a persistent SSB. We have transfected ZFGs into BRCA2-deficient human breast cancer MCF7 and lung cancer A549 cells, the cells were then treated with PARP inhibitors. We observed increased killing of the ZFG-transfected cells compare to mock-transfected controls. Since BRCA2 deficiency causes homologous recombination (HR) repair defect, we next sought to determine if inhibitors of HR is a suitable substitute for loss of BRCA2. We are testing this concept by transfection of ZFG to BRCA2-proficient MCF7 cells with the treatment of combination of PARP and HR inhibitors, to determine whether 1. Combination of PARP and HR inhibitors treatments can achieve synthetic lethality; 2. ZFG constructs can enhance synthetic lethality. We conclude ZFG coupled with synthetic lethality is a promising direction towards the development of cancer specifically treatment. Citation Format: Hua Fung, Stanton L. Gerson, Carlos F. Barbas. An artificial zinc finger glycosylase causes site-directed DNA damages and specifically kills the targeted cancer cells via synthetic lethality. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3332. doi:10.1158/1538-7445.AM2013-3332