Abstract B031: aKG-mediated carnitine synthesis promotes chemoresistance in CCNE1-high ovarian cancers via enhancing histone acetylation

Abstract DNA damaging agents remain the mainstay for high grade serous ovarian cancer (HGSOC) therapy. While many HGSOCs are sensitized to DNA damaging agents via dysregulated DNA repair, those patients harboring tumors with amplification or overexpression of CCNE1 (encoding cyclin E1) respond poorly in part due to proficiency in the homologous recombination (HR) DNA repair pathway. Here, we put forth a novel paradigm that HR proficiency of CCNE1-driven HGSOCs is promoted by altered cellular metabolism. We found that alpha-ketoglutarate (aKG) is upregulated in cyclin E1-driven HGSOC cells, and suppression of aKG sensitized these cells to DNA damaging agents both in vitro and in vivo, demonstrating that aKG drives chemoresistance in these models. aKG is required for the activity of aKG-dependent dioxygenases (aKGDD). There are >60 known aKGDD, and prior work has almost exclusively focused on aKGDD-mediated histone demethylation. Through a targeted CRISPR knockout library, we discovered that Trimethyllysine Hydroxylase Epsilon (TMLHE), the first and rate-limiting enzyme in de novo carnitine synthesis, is necessary for chemoresistance to DNA damaging agents in cyclin E1-driven cells. Unexpectedly, aKG-mediated TMLHE-dependent carnitine synthesis was required for histone acetylation, while histone methylation was affected but dispensable. These data point to a previously unrecognized role for aKG in acetylation reactions. The increase in histone acetylation via aKG-dependent carnitine synthesis promoted HR-mediated repair through site-specific histone acetylation. Additionally, analysis of HGSOC patient samples demonstrated that TMLHE positively correlates with histone acetylation, and both high tumor TMLHE or high serum acetylcarnitine are associated with worse progression free survival (PFS) in HGSOC patients treated with DNA damaging agents. Pharmacological targeting of carnitine synthesis via mildronate in vivo was sufficient to decrease tumor burden >30% in combination with cisplatin. Since mildronate is a non-toxic and extensively used drug in humans, this combination shows potential applicability of inhibition of this axis in humans. These data demonstrate for the first time that HR-proficiency in cyclin E1-driven HGSOCs is mediated through a metabolic axis that directly influences histone acetylation and highlight the translational potential of targeting this axis to induce HR deficiency and sensitize these tumors to DNA damaging agents. Citation Format: Apoorva Uboveja, Nathaniel W. Snyder, Katherine M. Aird. aKG-mediated carnitine synthesis promotes chemoresistance in CCNE1-high ovarian cancers via enhancing histone acetylation [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Ovarian Cancer Research; 2025 Sep 19-21; Denver, CO. Philadelphia (PA): AACR; Cancer Res 2025;85(18_Suppl):Abstract nr B031.