Multiscale modeling uncovers macrophage infiltration and TNF-α signaling networks for targeting in inflammatory breast cancer tumor emboli.

PURPOSE: Inflammatory breast cancers (IBC) are characterized by diffuse clusters of cells found in dermal lymphatic vessels, known as tumor emboli. IBC needs a novel treatment because it is the most aggressive breast cancer form. We hypothesized that the interaction between tumor emboli and the tumor immune microenvironment (TiME) fosters survival signaling, leading to the aggressiveness of disease. METHODS: Ex vivo tumor emboli were generated from patient-derived cell lines cultured in a lymphatic-like platform and subjected to transcriptomic and proteomic analysis. Spatial immunophenotyping was performed on IBC patient samples with tumor emboli. A transgenic CX3cr1GFP murine model was generated for visualization of macrophages and tumor emboli within the TiME via a surgically implanted window chamber, enabling intravital imaging and targeting. RESULTS: Gene and protein analyses of tumor emboli cultures compared to 2D monolayer cultures revealed upregulation of TNFR signaling networks, CXCL8, and immune cell chemotaxis genes. Spatial immunophenotyping of tumor emboli in patient samples demonstrated high levels of CD163+ tumor-associated macrophages. Furthermore, intravital imaging of CX3cr1GFP mice confirmed macrophage movement toward tumor cell clusters. Finally, targeting macrophage-associated TNF-α-signaling using SMAC mimetic, Birinapant, inhibited the tumor emboli phenotype in vivo. CONCLUSIONS: This study, the first to our knowledge, identifies TNF-α signaling and macrophage infiltration in IBC tumor emboli. Therapeutic strategies targeting TNF-α signaling to induce cell death and reduced macrophage influence have the potential to improve IBC outcomes.