Abstract 6002: Increased ferroptosis sensitivity and epithelial to mesenchymal transition of breast cancer cells overcoming chemotherapeutic mediated apoptotic caspase activation
Authors: Hausman Rachel , Brown Wells , McDonald Paul , Awrey Shannon , Sun Gongping , Montell Denise , Dedhar Shoukat 
Published: March 2024

Abstract
The survival of cancer cells post chemotherapeutic treatment can lead to the presence of recurrent tumors and continues to be a barrier to effective cancer treatment. The majority of chemotherapeutics kill cells through the induction of executioner caspases and subsequent apoptotic death, and resistance to apoptosis can lead to the presence of anastatic cancer cells. Executioner caspase release was previously thought to be the point of no return from apoptotic cell death, however, it has been shown that removal of the reagent causing caspase release can lead to recovery of cells from apoptotic signaling, a phenomenon which has been termed ``Anastasis``. This presents a need for a better understanding of the underlying mechanisms behind cancer cell survival and the mechanisms that lead to cell recovery and recurrent tumors. We have hypothesized that when treated with chemotherapeutics, some cells will evade cell death even when executioner caspases have been activated. By identifying surviving anastatic cells and the pathways involved in their evasion of cell death, we hope to propose novel therapeutic strategies to prevent their survival. The novel CasExpress system, developed by the Denise Montell lab group, was used to identify and isolate a population of cells surviving caspase-3 activation as a result of chemotherapeutic treatment in Triple Negative Breast Cancer (TNBC) cell lines. The CasExpress system permanently labels these cells with GFP post caspase-3 activation. Analysis of this population of SUM159 anastatic cells, identified by their GFP expression, demonstrates that these cells have an increased resistance to further chemotherapeutic treatment, a decrease in levels of active caspase-3, an up-regulation of Cancer Stem Cell marker CD44, and a more mesenchymal phenotype. Furthermore, these “anastatic cells” express decreased levels of GPX-4, an enzyme that mitigates ferroptosis via lipid peroxide reduction, and are more sensitive to GPX-4 and xCT inhibitor mediated ferroptosis cell death.To investigate the link between Epithelial to Mesenchymal Transition (EMT) and ferroptosis mediated cell death, we used TGF-b to stimulate EMT in NMe mouse epithelial cells. We found that TGF-b induced EMT is associated with increased sensitivity to ferroptosis mediated by GPX-4 inhibition. Furthermore, the TGF-b induced EMT cells have a marked decrease in the expression of GPX4, similar to what was observed in the TNBC anastatic cells. These results indicate a potential link between EMT and an increased sensitivity to ferroptosis, and provide novel strategies for identifying and targeting chemotherapeutic resistant tumor cells.
Citation Format: Rachel Hausman, Wells Brown, Paul McDonald, Shannon Awrey, Gongping Sun, Denise Montell, Shoukat Dedhar. Increased ferroptosis sensitivity and epithelial to mesenchymal transition of breast cancer cells overcoming chemotherapeutic mediated apoptotic caspase activation [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 6002.