Abstract 3681: Aspirin acetylates glucose 6 phosphate dehydrogenase and inhibits its activity in colon cancer cells.

Abstract Epidemiological studies have demonstrated a significant correlation between regular aspirin use and reduced colon cancer incidence and mortality. Although a consensus is emerging on the view that aspirin has significant anti-cancer properties, it is not yet clear which pathways or molecular targets might be involved. We hypothesized that aspirin's anti-cancer effect may occur through acetylation of a panel of protein targets, including novel candidates with modulated functional activity, as a result of aspirin-mediated acetylation. In the present study, using anti-acetyl lysine antibody, we determined aspirin-mediated protein acetylation profiles in three different colon cancer cell lines namely HCT-116, HT-29 and GC3/c1, by treating cells with aspirin at different concentration, and analyzing them in Western Blot. We observed that in all cell lines tested, aspirin induced acetylation of multiple proteins in a concentration dependent fashion spanning a molecular weight range from 20 to 200 kDa. Aspirin's acetylation targets included the tumor suppressor protein p53, and glucose 6 phosphate dehydrogenase (G6PD), an enzyme in the pentose phosphate pathway. Mass spectrometry analysis of the recombinant G6PD, treated with aspirin in vitro, revealed acetylation of up to 14 distinct lysine residues, including lysine 235 at its active site. In vitro G6PD assay in lysates isolated from the cancer cell lines showed that aspirin caused a 70% decrease in the G6PD enzyme activity in HCT116 cells; however, the reduction in the enzyme activity was less in HT-29/GC3/c1 cells (up to 30%). Inhibition of G6PD activity leading to a reduction in ribonucleotide synthesis and cell proliferation may represent an important mechanism by which aspirin exerts its anticancer effects. Citation Format: Guoqiang Ai, Fred K. Hagen, Jayarama B. Gunaje. Aspirin acetylates glucose 6 phosphate dehydrogenase and inhibits its activity in colon cancer cells. [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 3681. doi:10.1158/1538-7445.AM2013-3681