Abstract 1589: Characterization of polyaminohydroxamic acids and polyaminobenzamides as inhibitors of HDAC10

Abstract Elevated polyamine levels are essential for continual proliferation of cancer cells. Cytosolic histone deacetylase-10 (HDAC10) specifically deacetylates the modified polyamine N8-acetylspermidine (N8-AcSpd), of which extracellular sources can be abundant, particularly in the colonic lumen. We previously demonstrated that exogenously supplied N8-AcSpd can support tumor cell growth through HDAC10-mediated deacetylation into spermidine, which is then redistributed within the polyamine interconversion pathway to maintain homeostasis.In the current study, we investigate the utility of polyamine-based hydroxamic acids (PAHAs) and benzamides (PABAs) as pharmacological inhibitors of HDAC10-mediated polyamine deacetylation. Incorporation of the polyamine moiety enables these compounds to enter the cell selectively through the polyamine transport system, which is upregulated in cancer cells. A total of 42 compounds, including 21 PAHAs and 21 PABAs, were screened for HDAC10 inhibition using a cell-based growth assay in which polyamine-depleted, growth-arrested cells are exposed to N8-AcSpd: in the presence of HDAC10 activity, this polyamine is deacetylated and proliferation is restored. Several compounds in our screen inhibited HDAC10 activity in this assay, as indicated by a lack of growth rescue, and were selected for further analysis in which treatment was expanded over a range of doses, thereby allowing a dose-dependent evaluation and comparison of sensitivity. HPLC-based analysis of cell lysates functionally confirmed that deacetylation of N8-AcSpd into spermidine was inhibited by the test compounds. Finally, specificity of the selected PAHAs and PABAs for HDAC10 was evaluated by immunoblotting for increased acetylation of the substrates of related HDACs, including histones H3 and H4, and alpha-tubulin. These studies provide a basis for future drug design strategies targeting the polyamine deacetylase activity of HDAC10 as an antitumor strategy, which may be particularly important in the context of polyamine-blocking therapies. Citation Format: Tracy Murray Stewart, Jackson R. Foley, Patrick M. Woster, Robert A. Casero. Characterization of polyaminohydroxamic acids and polyaminobenzamides as inhibitors of HDAC10 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1589.