Proteomic signatures of adipocyte recruitment in breast cancer.

The tumor microenvironment (TME) is increasingly recognized as a dynamic regulator of breast cancer progression, with adipocytes functioning as active contributors rather than passive bystanders. Here, we investigated the proteomic and morphologic reprogramming of breast cancer-associated adipocytes (BrCAAs) in response to triple-negative breast cancer (TNBC). Using conditioned medium from HCC1143 cells, we established an in vitro BrCAA model and performed mass spectrometry-based proteomics. Comparative profiling revealed 256 differentially expressed proteins, enriched for pathways including fatty acid degradation, carbon metabolism, and glycogen turnover, consistent with a metabolic shift from energy storage to energy supply. Gene ontology and protein-protein interaction analyses further identified cytoskeletal remodeling, adhesion dynamics, and secretory pathway activation, supporting BrCAA-driven microenvironmental remodeling. In the MMTV-PyMT mouse model, morphometric analysis demonstrated progressive size reduction and increased contour irregularity of adipocytes adjacent to tumors, correlating with proteomic evidence of metabolic stress. Importantly, BrCAAs localized at tumor interfaces were associated with increased microvessel density and CD105+ endothelial activation compared to desmoplastic zones. Proteomic enrichment highlighted pro-angiogenic remodeling, with validation of basigin (BSG), integrin αV (ITGAV), and 2,4-dienoyl-CoA reductase 1 (DECR1). Collectively, our findings establish BrCAAs as metabolically and structurally reprogrammed stromal components that promote tumor metabolism and localized angiogenesis, representing potential therapeutic targets in aggressive breast cancer.