Abstract 640: SIRT2 deacetylates peroxiredoxin and increases sensitivity to oxidative stress in human breast cancer cells

SIRT2, the mammalian ortholog of yeast Hst2, is a predominantly cytosolic and nuclear member of sirtuins, which is the class III, NAD+ dependent, histone deacetylase (HDAC) family. Sirtuins play a key role in modulating cellular stress resistance, longevity and cancer transformation. SIRT2 is known to deacetylate FOXO1 and FOXO3, thereby regulating FOXO-regulated stress resistance. In the cytosol, SIRT2 co-localizes with microtubules and deacetylates α-tubulin at the lysine-40, indicating a role in proper cytokinensis. Here, we determined other biologically important SIRT2 targets and their functions. Knockdown and overexpression of SIRT2 in HEK293 cells significantly altered the acetylation status of many proteins, including a group of proteins ranging in molecular weight from 23-50 kDa. In cells with knockdown of SIRT2, differential in-gel electrophoresis of cytosolic extract of cells followed by mass spectrometric analysis identified several significantly hyper-acetylated proteins, notably peroxiredoxin 1. Peroxiredoxins are ubiquitous family of evolutionarily conserved, thiol-dependent peroxidases, which catalyze the reduction of hydrogen peroxide. SIRT2 co-immunoprecipitated with peroxiredoxin 1, and ectopic overexpression of SIRT2 attenuated acetylation of peroxiredoxin 1 in HEK 293 cells. While acetylation activates, reduced acetylation is known to inhibit the activity of peroxiredoxins. Ectopic overexpression of SIRT2, but not the catalytically dead SIRT2 mutant, markedly increased reactive oxygen species (ROS) levels as well as increased the sensitivity of the human breast cancer MCF7 and MDA MB231 cells to oxidant stress induced by hydrogen peroxide. SIRT2 overexpression in breast cancer cells also increased their sensitivity to ROS generating agents such as arsenic trioxide and menadione. These findings demonstrate that SIRT2 plays an important role in regulating oxidative stress in cells by modulating the activity of peroxiredoxin 1. The findings also highlight the possibility that increased SIRT2 levels and activity can be therapeutically exploited for augmenting the antitumor effects of therapeutic agents that induce cancer cell death by increasing intracellular ROS levels. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 640.