RAMP3 is associated with macrophage-driven immune exclusion and promotes resistance to PD-1 blockade in breast cancer: integrated in vivo and single-cell transcriptomic analyses
Year: 2026
Type: article
Abstract: BACKGROUND: Receptor activity-modifying protein 3 (RAMP3) has been implicated in stromal regulation in cancer. However, its role in tumor microenvironment (TME) remodeling and immune checkpoint resistance remains unclear. In this study, we aimed to define the role of RAMP3 in shaping the immunosuppressive TME and evaluate its potential as a therapeutic target to enhance immunotherapy responses. METHODS: We used syngeneic mouse models of breast cancer with genetic manipulation of RAMP3 to investigate tumor progression, immune remodeling, and response to immune checkpoint blockade in vivo. Tumor growth, metastasis, and survival were evaluated. Single-cell RNA sequencing was performed on murine tumor tissues, and a publicly available spatial transcriptomic dataset was analyzed to characterize immune cell states and spatial organization within the TME. Human breast cancer datasets from The Cancer Genome Atlas were analyzed to assess the clinical relevance of RAMP3-associated immune signatures. RESULTS: T cell infiltration, and reduced T cell exhaustion. Mechanistically, RAMP3 deficiency was associated with reduced IL-4/STAT6 signaling in macrophages and decreased expression of immunosuppressive genes, including the chemokine CCL8. Pharmacological inhibition of CCL synthesis phenocopied the effects of RAMP3 deficiency, and RAMP3 deficiency enhanced the efficacy of PD-1 blockade. Spatial transcriptomic analysis demonstrated co-localization of RAMP3 and CCL8 within the TME. In the TCGA-BRCA cohort, a higher weighted RAMP3/CD163/CD8A risk score was associated with poorer overall survival and remained significantly associated with overall survival in complete-case multivariable Cox models adjusted for clinicopathological variables. CONCLUSIONS: RAMP3 was identified as a potential regulator of the immunosuppressive TME and its functional impact was demonstrated in vivo. Integration with human clinical datasets supports further investigation of RAMP3 as a potential therapeutic target for overcoming resistance to immune checkpoint therapy in breast cancer.
Institution: Shinshu University
Language: English
Subfield: Oncology
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $3,890
Funders: Takahashi Industrial and Economic Research Foundation, Okinaka Memorial Institute for Medical Research, Japan Association for Diabetes Education and Care, Santen, Daiichi Sankyo Foundation of Life Science, Foundation for Promotion of Cancer Research, Ono Medical Research Foundation, Yamaguchi Endocrine Research Foundation, Shinshu Public Utility Foundation for Promotion of Medical Sciences, Japan Diabetes Foundation, Life Science Foundation of Japan, Novo Nordisk Pharma, Japan Society for the Promotion of Science, JST-Mirai Program
OpenAlex ID: W7214422574