Abstract 7154: Ivospemin/doxorubicin combination modulates polyamine metabolism to improve survival in murine ovarian cancer models
Authors: Holbert Cassandra E. , Foley Jackson R. , Nwafor Ashley C. , Liu Ting-Ann , Bruckheimer Elizabeth , Simpson Jennifer K. , Stewart Tracy Murray , Casero Robert A. 
Published: March 2024

Abstract
Polyamines are small polycationic alkylamines that are absolutely required for the continual growth and proliferation of cancer cells. As cancer cells maintain elevated polyamine pools through dysregulated polyamine metabolism, its pharmacological modulation is a promising avenue in cancer therapeutics. The polyamine analogue ivospemin has shown efficacy in slowing pancreatic and ovarian tumor progression in vitro and in vivo and has demonstrated encouraging results in pancreatic cancer clinical trials. Considering nearly 75% of late-stage ovarian cancer patients develop resistant to platinum-based chemotherapies, limiting treatment options, the aim of our study is to determine the potential efficacy of ivospemin in combination with doxorubicin, a common chemotherapeutic used in platinum-resistant ovarian tumors. We have previously shown that ivospemin exposure decreases polyamine content in a variety of cancer cell lines through downregulation of the polyamine biosynthetic enzyme ornithine decarboxylase (ODC) and induction of the polyamine catabolic enzyme spermidine/spermine-N1-acetyltransferase (SSAT). Here we examine the potential of combining ivospemin with doxorubicin. Ivospemin treatment reduces cell viability in ovarian adenocarcinoma cell lines and increases the toxicity of doxorubicin regardless of cisplatin sensitivity. Cells treated with the combination exhibit a greater decrease in polyamine levels than cells treated with either single agent. This increased polyamine depletion and decreased survival is accomplished through modulation of polyamine metabolism, predominately through an additive induction of SSAT activity. Using the syngeneic VDID8+ ovarian murine model, we further evaluated the ability of ivospemin to improve response to doxorubicin at clinical and sub-clinical dosing. Ascites fluid was used as a marker for tumor burden and evaluated for polyamine content. We found that the combination treatment increases median survival, delays tumor onset, and decreases overall tumor burden compared to either clinical or subclinical doxorubicin dosing schemes. Combination treatment also decreases overall polyamine content in the ascites by 75%. N1-acetylated spermidine is enriched in ascites from combination-treated mice, consistent with an upregulation of SSAT in response to treatment. Recognizing the non-representative mutational status of the VDID8+ model as a limitation, we are currently evaluating the combination of ivospemin and doxorubicin in genetically defined murine models that better recapitulate human high-grade serous ovarian carcinomas. Ongoing studies will determine influences on the tumor microenvironment and will mechanistically evaluate the cooperativity of ivospemin and doxorubicin on pathways outside of polyamine metabolism.
Citation Format: Cassandra E. Holbert, Jackson R. Foley, Ashley C. Nwafor, Ting-Ann Liu, Elizabeth Bruckheimer, Jennifer K. Simpson, Tracy Murray Stewart, Robert A. Casero. Ivospemin/doxorubicin combination modulates polyamine metabolism to improve survival in murine ovarian cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7154.