Humar, R. | bioRxiv Science

bioRxiv2025

A stress-NRF2 response axis polarises tumor macrophages and undermines immunotherapy

Tumor-associated macrophages (TAMs) can switch between immune-activating and cancer-promoting states; yet, the stress pathways that lock them into pro-cancerous states remain obscure. 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-seq, and Keap1-deficient mice showed that the latter are NRF2high "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. NRF2high TAMs silence IFN-STAT1 programmes, lose MHC-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-naive MMTV-PyMT breast tumors and markedly impaired anti-CD40 efficacy in MC38 subcutaneous and lung-metastasis models. Conversely, macrophage-specific Nrf2 deletion restored immunogenic TAMs and potentiated anti-CD40 and anti-PD-1 treatments. Thus, NRF2 constitutes a stress-response axis that fixes TAMs in a pro-cancer, therapy-resistant state; inhibiting it could revive the macrophage-T-cell amplification loop and broaden immunotherapy responses. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=139 SRC="FIGDIR/small/662726v1_ufig1.gif" ALT="Figure 1"> View larger version (63K): org.highwire.dtl.DTLVardef@728b03org.highwire.dtl.DTLVardef@4a473org.highwire.dtl.DTLVardef@c8a209org.highwire.dtl.DTLVardef@60681_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2021

Heme-stress activated NRF2 signaling skews fate trajectories of bone marrow cells from dendritic cells towards red pulp-like macrophages

Heme is an erythrocyte-derived toxin that drives disease progression in hemolytic anemias, such as sickle cell disease. During hemolysis, specialized bone marrow-derived macrophages with a high heme-metabolism capacity orchestrate disease adaptation by removing damaged erythrocytes and heme-protein complexes from the blood and supporting iron recycling for erythropoiesis. Since chronic heme-stress is noxious for macrophages, erythrophagocytes in the spleen are continuously replenished from bone marrow-derived progenitors. Here, we hypothesized that adaptation to heme stress progressively shifts differentiation trajectories of BM progenitors to expand the capacity of heme-handling monocyte-derived macrophages at the expense of the homeostatic generation of dendritic cells, which emerge from shared myeloid precursors. This heme-induced redirection of differentiation trajectories may contribute to hemolysis-induced secondary immunodeficiency. We performed single-cell RNA sequencing with directional RNA velocity analysis of GM-CSF-supplemented mouse bone marrow cultures to assess myeloid differentiation under heme stress. We found that heme-activated NRF2 signaling shifted the differentiation of bone marrow cells towards antioxidant, iron-recycling macrophages, suppressing the generation of dendritic cells in heme-exposed bone marrow cultures. Heme eliminated the capacity of GM-CSF-supplemented bone marrow cultures to activate antigen-specific CD4 T cells. The generation of functionally competent dendritic cells was restored by NRF2 loss. The heme-induced phenotype of macrophage expansion with concurrent dendritic cell depletion was reproduced in hemolytic mice with sickle cell disease and spherocytosis and associated with reduced dendritic cell functions in the spleen. Our data provide a novel mechanistic underpinning of hemolytic stress as a driver of hyposplenism-related secondary immunodeficiency. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=89 SRC="FIGDIR/small/454342v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@1995a26org.highwire.dtl.DTLVardef@eda1b8org.highwire.dtl.DTLVardef@11441c3org.highwire.dtl.DTLVardef@e9a95c_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗