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IRG1/itaconate/NRF2/GSH axis in tumor-associated macrophages drives therapy resistance and immune evasion in BRCA1-deficient breast cancer

Nan, Y.; O'keefe, S.; He, X.; Luo, Q.; Wu, X.; Ni, J.; Zou, Y.; Meade, J. M.; Li, Y.; Ji, R.; Mohammad, A.; Kumar, P.; Wang, Q.; Zhao, J. J.

2025-10-15 cancer biology
10.1101/2025.10.14.682312 bioRxiv
Show abstract

Tumor-associated macrophages (TAMs) are major contributors to immunosuppression and therapeutic resistance, including resistance to PARP inhibitors (PARPi) in BRCA1-deficient breast cancer. However, the mechanisms underlying TAM-mediated PARPi resistance remain unclear. Here, we demonstrate that TAM-derived glutathione (GSH) impairs the efficacy of PARPi by protecting tumor cells from DNA damage and ferroptosis while suppressing STING-mediated immune activation. Mechanistically, STAT5-driven upregulation of the IRG1/itaconate axis in TAMs rewires mitochondrial metabolism and activates NRF2-dependent GSH biosynthesis. GSH is subsequently released into the tumor microenvironment, where it is taken up by tumor cells, protecting them from PARPi-induced cytotoxicity and dampening immune responses. Pharmacological inhibition of IRG1 reverses these effects, restoring PARPi sensitivity and enhancing anti-tumor immunity in BRCA1-deficient tumor models. Collectively, these findings uncover a TAM-specific immunometabolic program that limits PARPi efficacy and highlight the IRG1/NRF2/GSH axis as a promising therapeutic target to improve treatment outcomes in BRCA1-associated breast cancer.

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