Hyperinsulinemia‐Induced Changes In Chromatin Acetylation In Triple Negative Breast Cancer

Abstract

Obesity‐associated hyperinsulinemia or insulin‐resistance is considered as a poor prognostic factor for triple negative breast cancer (TNBC), a particularly aggressive breast cancer subtype, constituting about 15–20% of all breast cancers. As a growth factor, insulin can activate the PI3K/AKT/mTOR pathway that is associated with the increased proliferation rate of TNBC cells. While this association has been recognized for some time, the mechanistic role of insulin‐resistance in promoting TNBC remains unclear. mTOR signaling enhances mitochondrial biogenesis and activity thereby potentially increasing acetyl‐CoA precursors; pyruvate and citrate. Acetyl‐CoA, in turn, can be utilized by nuclear acetyltransferases for histone acetylation. We hypothesize that hyperinsulinemia‐induced metabolic changes lead to altered chromatin structure in TNBC through genome‐wide changes in histone acetylation. To test this hypothesis, we used quantitative ChIP‐seq (ChIP‐Rx), RNA‐seq, western blot and immunofluorescence analyses on MDA‐MB‐231 (TNBC) cells treated with insulin. Insulin treatment leads to global increase in chromatin‐associated histone acetylation levels, particularly at H3K9. Using inhibitors targeting kinases in the PI3K/AKT/mTOR signaling pathway, we demonstrate its role in insulin‐induced histone hyperacetylation. ChIP‐Rx confirmed the global increase in histone acetylation at gene promoters that could potentially alter chromatin accessibility and/or gene expression. Comparison of ChIP‐seq and RNA‐seq data revealed that insulin upregulated genes accumulate higher levels of H3K9ac as compared to downregulated genes after insulin treatment. In addition, insulin induces higher levels of reactive oxygen species and DNA damage foci in cells. Moreover, peripheral blood mononuclear cells from insulin‐resistant women show higher levels of H3K9ac and DNA damage marker gamma‐H2AX relative to those from insulin‐sensitive women. These results demonstrate the significance of targeting hyperinsulinemia‐induced processes that lead to chromatin dysfunction through mitochondria in TNBC.Support or Funding InformationThis work was supported by the NCI (R01 CA220693) and a City of Hope CCSG pilot award.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.