Abstract 3103: Spatial proteomics reveals vasculature and immune modulation for overcoming doxorubicin resistance in breast cancer

Abstract Therapeutic resistance hinders the efficacy of single-agent cancer treatments, often mediated by the tumor microenvironment. Significant endothelial cell enrichment following local doxorubicin treatment has been proposed as a resistance mechanism in breast cancer. Here, we apply the tumor vasculature normalization principle using an anti-angiogenic drug combination delivered locally using the high-throughput multiplex implantable microdevice assay in mouse models of breast cancer. Spatial single-cell proteomic profiling paired with unsupervised learning methods confirmed doxorubicin-mediated pro-angiogenic changes, including pericyte detachment and sprouting angiogenesis. A combination with cabozantinib depleted endothelial cells and increased tumor antigenicity by inducing immunogenic cell death with recruitment of leukocytes including neutrophils, and T cells. Leveraging this immune modulatory activity, we tested a systemic triple combination with anti-PD1 immunotherapy, which led to a significant and complete tumor regression. Our study demonstrates a rational drug combination that improves doxorubicin efficacy to overcome microenvironment-driven resistance for long-term breast cancer control. Citation Format: Gautami Gaidhani,Juraj Jakubik,Leoni Moldaner,Yishu Xu,Zuzana Tatarova. Spatial proteomics reveals vasculature and immune modulation for overcoming doxorubicin resistance in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 3103.