Abstract 2823: CHAC1 regulates paraptosis by promoting glutathione degradation in cancer cells

Abstract Paraptosis is a type of programmed cell death characterized by cytoplasmic vacuolation, merging as a potential therapeutic strategy for cancer treatment. Paraptosis has been associated with disruption of proteostasis and redox homeostasis, however, the detailed mechanisms remain to be explored. CPYPP, a known paraptosis inducer, was employed to investigate the underlying mechanisms in breast cancer and melanoma cells. CPYPP significantly increased the production of reactive oxygen species (ROS). Treatment with N-acetyl-L-cysteine (NAC) and glutathione (GSH), but not oxidized glutathione (GSSG), mitigated CPYPP-induced cytoplasmic vacuolation and cell viability inhibition. CPYPP significantly decreased the intracellular GSH/GSSG ratio. Next-generation sequencing analysis indicated that CPYPP upregulates the expression of genes related to the cystine metabolism pathway, including SLC3A2, SLC7A11, cystathionine-γ-lyase (CTH), glutamate-cysteine ligase (GCLC, GCLM), and ChaC glutathione specific γ-glutamylcyclotransferase 1 (CHAC1). CPYPP increased the uptake of cystine. Cystine deprivation attenuated CPYPP-induced protein ubiquitination, cytoplasmic vacuolation, and cell viability inhibition. Furthermore, CHAC1 knockdown ameliorated CPYPP-induced endoplasmic reticulum stress, unfolded protein response, protein ubiquitination, cell viability inhibition, and ROS production. CHAC1 is transcriptionally upregulated by CPYPP via the PI3K-mTOR-CDK7/CDK9 axis. Taken together, these results suggest that the upregulation of CHAC1 mediates paraptosis. CHAC1 enhances the degradation of GSH, resulting in a decline in the GSH/GSSG ratio, a more oxidized intracellular state, and increased ROS production. This leads to the disruption of proteostasis, ultimately inducing paraptosis. Citation Format: Ling-Chu Chang, Shih-Kai Chiang, Shuen-Ei Chen. CHAC1 regulates paraptosis by promoting glutathione degradation in cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2823.