Abstract 5993: Temporal dynamics of ferroptosis vulnerability in a resistant cancer cell state
Authors: Loftus Luke , Pienta Ken , Amend Sarah 
Published: March 2024

Abstract
Once cancer has metastasized it remains incurable as a result of evolved resistance to nearly all systemic therapies. Our group has demonstrated that an endocycling cancer cell state is an underappreciated mechanism of therapeutic resistance in many cancer settings. Cells in this state uncouple DNA replication from cell division to obtain abnormally high genomic content and cell size (over 40x volume). Resulting polyploidy and cellular hypertrophy provide survival advantages such as elevated genomic content, higher oxidative buffer capacity, increased autophagy, and heightened resistance to chemotherapy. Endocycling cancer cells are induced by multiple different classes of chemotherapy and present in vivo at increased frequencies both in metastatic sites and following chemotherapy. We hypothesize elimination of this overlooked resistant cancer cell state is critical for sustained anticancer therapies. Cancer cells, including those in the endocycling cancer cell state, leverage canonical cell cycle and cell death programs to evade apoptosis from external stressors including all classes of chemotherapy. Engaging cell cycle-independent death pathways is an alternative therapeutic strategy that circumvents cancer’s trademark manipulation of the cell cycle1. Ferroptosis is a cell cycle agnostic form of cell death that occurs due to dysregulation of cellular iron and subsequent lipid peroxidation. While ferroptosis is emerging as a vulnerability in resistant cancers, efficacy of ferroptosis induction is highly heterogeneous depending on tissue type, cellular metabolism, and many other factors. We characterized oxidative damage, labile iron, lipid content, and signaling pathways in cells pre- and post-chemotherapy to assess vulnerability to ferroptosis. By inhibiting GPX4, the sole lipophilic antioxidant enzyme, we show induction of ferroptotic cell death across multiple cell lines and chemotherapies with cells in the endocycling state being more susceptible. Importantly, targeting cells in the endocycling cancer cell state (as opposed to untreated cell lines), also affords a more uniform elimination by ferroptosis. Ferroptosis also has a capacity to be immunogenic that may direct anti-cancer immune licensing in addition to direct cytotoxicity. These studies will directly contribute to development of ferroptosis engaging therapeutic strategies for resistant cancer cell states, particularly concerning the timing of intervention. 1Loftus, L.V.; Amend, S.R.; Pienta, K.J. Interplay between Cell Death and Cell Proliferation Reveals New Strategies for Cancer Therapy. Int. J. Mol. Sci. 2022, 23, 4723. https://doi.org/10.3390/ijms23094723
Citation Format: Luke Loftus, Ken Pienta, Sarah Amend. Temporal dynamics of ferroptosis vulnerability in a resistant cancer cell state [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 5993.