Stress-NRF2 response axis polarizes tumor macrophages and undermines immunotherapy

BACKGROUND: Tumor-associated macrophages (TAMs) can switch between immune-activating and cancer-promoting states; yet, the stress pathways that lock them into procancerous states remain obscure. Here we defined the role of transcription factor NRF2 as a mediator of procancerous macrophages. METHODS: We combined spatial transcriptomics, single-cell RNA sequencing, three-dimensional (3D) cell culture and in vivo tumor models to explore how NRF2 activation status in tumor-associated macrophages modifies responses to immunotherapy. RESULTS: In MC38 colon tumors, repeated anti-CD40 or radiotherapy created necrosis that split TAMs into peripheral Cxcl9+ and peri-necrotic Spp1+ subsets. Spatial transcriptomics, single-cell RNA sequencing, and Keap1-deficient mice showed that the latter are NRF2-imprinted "stress-TAMs", with immunosuppressive and tumor-promoting activity. The same NRF2 activation gradient separates pro-inflammatory CXCL9+ and anti-inflammatory SPP1+TAMs across diverse human cancers. NRF2-imprinted TAMs silence IFN-STAT1 programs, lose major histocompatibility complex-II and chemokine expression, fail to expand T cells, drive tumor cell invasion in 3D co-cultures, and foster metastasis. Constitutive hematopoietic NRF2 activation accelerated the growth of therapy-naïve MMTV-PyMT breast tumors and markedly impaired the efficacy of agonistic anti-CD40 antibody therapy in MC38 subcutaneous and lung-metastasis models. Conversely, macrophage-specific Nrf2 deletion restored immunogenic TAMs and potentiated anti-CD40 and anti-programmed cell death protein-1 treatments. CONCLUSIONS: Our data pinpoint a previously underappreciated cytoprotective mechanism, which inadvertently sustains immunosuppressive macrophages and confers therapy resistance. These results define stress-induced TAMs as an untapped driver of macrophage-based immune evasion. Inhibiting NRF2 activity alongside standard immunotherapies could restore a pro-inflammatory macrophage-T-cell amplification loop, potentially improving patient responses to T-cell-and macrophage-directed immunotherapies.