Charlotte Helena Rivas

Triple-negative breast cancer (TNBC) has high rates of recurrence despite chemotherapy and immune checkpoint blockade. Tumor-associated macrophages (TAM) can either suppress or support antitumor immunity, but the mechanisms governing these states and therapeutic targets remain unclear. In this study, which integrates public single-cell RNA sequencing (scRNA-seq) datasets with TNBC cohorts, we identify a prognostic myeloid signature defined by CXCL9-high programs, which is associated with improved survival and enrichment of lymphocyte activation pathways. Using immunocompetent p53-null syngeneic TNBC models spanning basal-like (2153L) and claudin-low (T12) subtypes, we show that immunomodulatory cyclophosphamide (CTX) reprograms hematopoiesis toward the monocytic lineage and induces an interferon (IFN)-conditioned tumor milieu that supports CXCL9+ monocyte-derived macrophages (Mo.Mac) in basal-like disease. Combining CTX with the next-generation MERTK-selective inhibitor UNC2371 (MRX-2843) drives complete remission in both models, but durable long-term responses occurred selectively in the basal-like subtype model. Antigen-presenting CXCL9+ Mo.Macs expand and C1Q+ TAMs are reduced in responding tumors. Mechanistically, MERTK inhibition relieves MAPK/SOCS1-mediated restraint of IFN signaling driving CXCL9 induction. Functionally, tumor control requires CXCL9–CXCR3-dependent CD4+ T-cell recruitment and correlates with the accumulation of stem-like memory CD4+ T cells and germinal center–associated lymphoid organization in tumor-draining lymph nodes. PD-1 blockade further increases durability, preventing recurrence in most treated basal-like tumors. Together, these findings define an IFN-licensed, MERTK-regulated myeloid checkpoint that can be therapeutically targeted to convert suppressive TNBC microenvironments into durable adaptive immunity, supporting clinical translation of CTX + MRX-2843–based combinations in basal-like TNBC.

Table S3 from ICAM1high Neutrophils Sculpt Tumor Evolution and Metastasis Through Symbiotic Adhesion and Reverse Migration

Supplementary figure for ICAM1high neutrophils promote metastasis of epithelial cancer cells through reverse transendothelial migration

Supplementary figure for EMT disrupts the symbiotic interaction

Supplementary figure for clinical association of ICAM1high neutrophils in indicated cancer types

Supplementary figure for the symbiotic interaction between neutrophils and epithelial cancer cells

Supplementary figure for ICAM1high neutrophils may promote metastasis of epithelial cancer cells through reverse transendothelial migration

Supplementary figure for interaction among tumor cells, neutrophils and endothelial cells in human TNBC exhibits potential racial disparity