LTBP4 deficiency induces MRC1+/CD44+ macrophages to drive cancer progression in preclinical colorectal cancer models.

Understanding the intracellular role of IL1α in regulation of immune suppressive myeloid cells in breast cancer 2260588

Breast cancer remains one of the most prevalent and deadly malignancies worldwide. The tumor microenvironment (TME) critically shapes tumor progression and immune regulation through cytokine signaling. Among these, interleukin-1 alpha (IL1α) is a key mediator of breast cancer—associated immunosuppression. We initially identified IL1α produced by CX3CR1+ macrophage subset within the TME. Deletion of IL1α reduced tumor growth and depleted this population, suggesting IL1α-driven myeloid reprogramming. We hypothesize that IL1α deficiency reprograms myeloid differentiation from monocyte-derived suppressive macrophages to inflammatory macrophage. An in vitro bone marrow—derived macrophage (BMDM) model from wild-type (WT) and IL1α knockout (KO) mice was used to assess IL1α-dependent differentiation. Flow cytometry and qPCR characterized CD11b+CD11c+MHCII+ subsets and quantified inflammatory (iNOS, CD80) versus inhibitory (Arginase-1, CD206) markers. Functional assays, including T-cell proliferation and MDSC activity, evaluated immunoregulatory capacity. Seahorse analysis and mass spectrometry assessed mitochondrial metabolism and electron transport chain (ETC) integrity. IL1α KO BMDMs showed reduced F4/80 and CX3CR1 expression, a shift from CD11b+CD11c+MHCII^low to MHCII^high cells upon LPS activation, decreased inhibitory markers, and elevated inflammatory mediators. These macrophages exhibited reduced T-cell suppression and MDSC activity. Neutralization of extracellular IL1α in WT cells did not reproduce KO effects, supporting an intracellular role. IL1α loss impaired oxidative phosphorylation, and peptide inhibitor blocking IL1α mitochondrial localization reproduced this phenotype. Our results show IL1α as a regulator of mitochondrial metabolism and myeloid differentiation. By stabilizing the ETC, IL1α sustains immunosuppressive macrophages, whereas its loss promotes inflammatory, anti-tumor myelopoiesis, identifying IL1α as a potential therapeutic target in breast cancer. n/a Innate Immune Responses and Host Defense: Molecular Mechanisms (INM)

IFIT1+ Tumor-Associated Macrophages Suppress Cancer Stemness and Enhance Chemosensitivity via the TNFSF10-TNFRSF10B Axis in Epithelial Ovarian Cancer.

BACKGROUND Epithelial ovarian cancer (EOC) is typically diagnosed at an advanced stage and is associated with high mortality due to metastasis and chemoresistance. Cancer stem cells (CSCs) are central to EOC progression, recurrence, and treatment resistance, with their functional behavior shaped by the tumor immune microenvironment. While M1 and M2 macrophages have been well-characterized, the role of interferon-stimulated gene-enriched subpopulations, particularly interferon-induced protein with tetratricopeptide repeats 1 tumor-associated macrophages (IFIT1+ TAMs), in regulating CSC properties in EOC remains largely unexplored. METHODS Single-cell RNA sequencing (scRNA-seq) was utilized to map the myeloid landscape and trace transcriptomic evolution in EOC. An in vitro indirect culture model utilizing unpolarized macrophage (M0)-conditioned medium (CM) was established to assess baseline phenotypic alterations. Furthermore, targeted siRNA silencing (si-TNFRSF10B) combined with recombinant human tumor necrosis factor ligand superfamily member 10 (TNFSF10) (rhTRAIL) treatments were employed to evaluate the specific impact of the TNF-related apoptosis-inducing ligand (TRAIL)-Death receptor 5 (DR5) signaling axis on multidrug resistance and CD44 expression. RESULTS High-resolution scRNA-seq analysis revealed a stage-dependent decline in IFIT1+ TAMs, an interferon-primed subset that robustly expresses the TNFSF10 ligand during early-stage disease. In vitro assays showed that conditioned medium from M0 macrophages suppresses CSC features and enhances expression of the tumor necrosis factor receptor superfamily member 10B (Death receptor 5) (TNFRSF10B/DR5) in EOC cells. Mechanistic studies confirmed that exogenous rhTRAIL treatment markedly diminished CD44+ cell populations and enhanced sensitivity to chemotherapeutic agents. Notably, these antitumor effects were largely abrogated following siRNA-mediated silencing of the DR5 receptor in EOC cell lines. CONCLUSIONS Our findings reveal that IFIT1+ tumor-associated macrophages intrinsically harbor anti-cancer stem cell potential through the TNFSF10 ligand. Activation of the TNFSF10-TNFRSF10B pathway suppresses cancer stemness and may enhance chemosensitivity. These insights shed light on the functional diversity of macrophages, highlighting that driving tumor-associated macrophages toward a sustained, interferon-primed IFIT1+ phenotype represents a promising therapeutic approach to target cancer stem cell populations in epithelial ovarian cancer.

MARCKS Drives Immunosuppressive Signaling in Tumor-Associated Macrophages to Promote Lung Cancer Progression 2258297

By driving TGF-β- and SPP1-mediated interactions with tumor and immune compartments, MARCKS emerges as a key regulator of TAM-driven immunosuppression and a potential therapeutic target in lung cancer.

Midkine-activated TRPA1+ cancer-associated fibroblasts promote immunotherapy resistance in gastric cancer through a WNT5A-mediated treg circuit.

Stk11 loss in lung adenocarcinoma increases tumor CXCL16 and is associated with an expansion of Areg+ CXCR6+ IL-17-producing γδ T cells 2310280

gd T cells have been shown to both promote tumor growth/metastasis and to efficiently kill tumor cells. These contrasting roles have been attributed to their different functional subsets, with gdT1 cells being associated with anti-tumor immunity, while gdT17 cells are associated with tumor growth and metastasis. However, the factors that regulate the activation and expansion of these functional subsets, as well as the mechanisms through which they regulate tumor growth are still unclear. To investigate these questions, we developed a novel inducible model of Scgb1a1-linked Kras-driven lung adenocarcinoma with or without an Stk11 co-mutation and used multi-color flow cytometry to characterize the tumor-immune microenvironment and single-cell RNAseq to examine both the gd T cells and the tumor lung epithelium. Upon tumor induction KrasG12D/Stk11fl (KS) mice exhibited significantly higher tumor burden and faster disease progression than KrasG12D (K) mice. The more rapid disease progression in these mice was associated with a significant increase in Vg4 and Vg6 gdT17 cells, but not Vg1 gdT1 cells. scCITEseq revealed significant changes in the transcriptional diversity of the KS lung gdT17 cells that was associated with an expansion of an Areg+ Vg6 gdT17 subset. There was no significant difference, however, in gd T cell proliferation. Investigation of the Scgb1a1+ lung epithelium revealed that KS tumors upregulate the expression of numerous immune-relevant chemokines and cytokines, including Cxcl16. When cultured in vitro, tumor cells but not healthy epithelial cells from KS mouse lungs produced significant levels of CXCL16. Finally, we demonstrated that lung gdT17, but not gdT1 cells, express the CXCL16 receptor CXCR6. Taken together, these data show that tumor-intrinsic Stk11 loss in lung adenocarcinoma is associated with an expansion of lung gdT17 cells and supports a model in which these pro-tumor cells are recruited to the KS mouse lung via a CXCL16-CXCR6 axis. n/a Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)

Pannexin-1 promotes CD8+ T cell antitumor immunity against colorectal cancer in a gender-dependent way 2256739

Colorectal cancer (CRC) is the second leading cause of cancer death in the U.S., with stage IV patients showing poor five-year survival. Immune checkpoint blockade shows limited efficacy in CRC, highlighting the need to better understand how CD8+ T cells are regulated by the tumor microenvironment (TME). In the TME, CD8+ T cells often become exhausted and lose cytotoxic function. Terminally exhausted cells express high inhibitory receptors, PD-1, Tim-3, and low proliferative capacity; whereas stem-like exhausted cells can self-renew and respond well to checkpoint blockade. Metabolic regulation is critical for CD8+ T cells, including membrane channels that export metabolites. Our lab studies Pannexin-1 (PANX1), a channel that exports ATP and promotes memory CD8+ T cell survival via AMPK signaling. We found that PANX1 is crucial for effective antitumor CD8+ T cell responses in CRC. High PANX1 expression correlates with increased CD8+ T cell infiltration and better prognosis in stage IV CRC patients. Using CRC mouse models, CD8-specific Panx1 knockout males, but not females, fail to control MC38 tumors, with tumor-infiltrating CD8+ T cells showing higher exhaustion, fewer stem-like cells in lymph nodes, and lower AMPK activity. Single-cell RNAseq and InfinityFlow confirm enhanced exhaustion signatures in PANX1-KO tumor-infiltrating stem-like exhausted cells, while wild-type tumors accumulate more effector-like (Zeb2+) CD8+T cells. Preliminary data suggests that AMPK overactivation (AICAR) significantly restores PANX1-KO exhausted CD8+ T cells. Finally, the gender-specific discrepancies may involve androgen receptor signaling, elevated in PANX1-KO exhausted cells. Ongoing studies examine whether PANX1-mediated AMPK activity regulates androgen receptor expression. Together, these findings suggest PANX1 promotes CD8+T cell-driven anti-tumor immunity in CRC in a gender-dependent manner, potentially explaining sex-based differences. n/a Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)