Abstract 1859: Targeting APE-1/Ref-1 activity for prevention of non-melanoma skin cancer

Abstract

Abstract Apurinic/apyrimidinic endonuclease-1/Redox Factor-1 (APE-1) is a dual function protein and novel target for chemoprevention of ultraviolet (UV) light-induced skin carcinogenesis. Each of the primary functions of APE-1, base excision repair of DNA damaged by oxidation and transcription factor reduction after exposure to an oxidizing stimulus like UV, is performed through the activity of a unique functional domain and plays a potential role in skin cancer promotion and progression. Our hypothesis was that APE-1 activity would correlate with survival after UV irradiation due to enhanced AP-1 activity and DNA repair. Preliminary experiments with HaCaT keratinocytes, an initiated cell line with characteristic UV-signature hotspot mutations in p53, using APE-1 siRNA demonstrated that downregulation of APE-1 increased cell sensitivity to UV-induced apoptosis. We then PCR amplified APE-1 from reverse transcribed HaCaT cell RNA and cloned it into an EGFP-tagged expression vector to generate two stable APE-1 overexpressing HaCaT cell lines, HGA9 (high expressing) and HGA10 (low expressing) cells. As expected, HGA9 and HGA10 cells were less sensitive than HaCaT cells to UV-induced apoptosis by 49.6 and 43.6%, respectively. Collectively, these data indicate that APE-1 activity does in fact play a significant role in the cellular response to UV and suggest that inhibiting APE-1 activity could be an effective means of eliminating initiated cells from the skin and preventing tumor development and growth. To further evaluate APE-1 as a therapeutic target, a library of molecules was screened for their ability to dock within one of two known binding pockets on the surface of APE-1 using an in silico docking algorithm. The first pocket screened lies within the AP endonuclease domain of APE-1. Initially, five individual molecules were chosen because they were predicted to bind APE-1 better than resveratrol, a known inhibitor that has been shown to interact with APE-1 directly. These molecules are predicted to have a higher specificity for APE-1 than resveratrol and have been assessed for their ability to inhibit DNA repair in vitro using recombinant human APE-1. Novel molecules that inhibit APE-1 activity could prove valuable in preventing UV-induced skin carcinogenesis by promoting the death of initiated keratinocytes that would otherwise undergo clonal expansion and progress to skin tumors. This work was supported by NIH grants: 5P01CA027502 and 5P30CA023074 and by a generous gift from Alliance Beverage Distributing Company. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1859. doi:10.1158/1538-7445.AM2011-1859