Hyperinsulinemia promotes aberrant histone acetylation in triple negative breast cancer

Excess levels of insulin relative to glucose in the blood, or hyperinsulinemia, is considered to be a poor prognostic indicator for patients with triple negative breast cancer (TNBC). While this association has been recognized for some time, the mechanistic role of hyperinsulinemia in promoting TNBC remains unclear. We show that insulin treatment leads to genome-wide increase in histone acetylation, in particular at H3K9, through the PI3K/AKT/mTOR pathway in MDA-MB-231 cells. Genome-wide analysis showed that the increase in histone acetylation occurs primarily at gene promoters. In addition, insulin induces higher levels of reactive oxygen species and DNA damage foci in cells. In vivo , hyperinsulinemia also enhances growth of MDA-MB-231 derived tumors through increased histone acetylation. These results demonstrate the impact of hyperinsulinemia on altered gene regulation through chromatin and the importance of targeting hyperinsulinemia-induced processes that lead to chromatin dysfunction in TNBC.