Multiscale Modeling Uncovers Macrophage Infiltration and TNF-α Signaling Networks for Targeting in Inflammatory Breast Cancer Tumor Emboli.

PURPOSE

Inflammatory breast cancer (IBC) tumors are characterized by diffuse, clusters of cells found in dermal tissue and lymphatic vessels, known as tumor emboli. This study investigates the interaction between tumor emboli and the tumor immune microenvironment (TiME) that can foster survival signaling.

EXPERIMENTAL DESIGN

Spatial immunophenotyping was performed on clinical IBC samples. Ex vivo tumor emboli were generated from patient-derived cell lines cultured in a lymphatic-like platform and subjected to transcriptomic and proteomic analysis. A transgenic 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 analysis of tumor emboli cultures compared to 2D monolayer cultures revealed upregulation of TNFR signaling networks, CXCL8, and immune cell chemotaxis genes. Spatial immunophenotyping of IBC patient tumors demonstrated high levels of CD163+ tumor-associated macrophages (TAMs). Furthermore, intravital imaging of mice confirmed macrophage movement toward tumor cell clusters. Finally, targeting macrophage-associated TNF-α-signaling using Birinapant, a SMAC mimetic, inhibited the tumor emboli phenotype .

CONCLUSIONS

This study, the first to our knowledge, identifies TNFα signaling and macrophage infiltration in IBC tumor emboli. Strategies targeting TNFα signaling to induce cell death and reduce macrophage influence has the potential to improve IBC outcomes.

TRANSLATIONAL RELEVANCE

The overall survival rates for patients with inflammatory breast cancer (IBC) are dismal, and these rates have not changed in the last decade. IBC is associated with high metastatic propensity, with nearly 30% individuals presenting with metastatic disease at diagnosis. The distinct presentation of diffuse tumor cell clusters spreading collectively (emboli) is postulated to be responsible for the poor survival in patients with IBC. Despite over 50 molecular profiling studies in the past decade, the intrinsic molecular mechanisms underlying the IBC tumor emboli phenotype remain unclear. Here, we utilize both preclinical and patient biospecimen to gain insight into the tumor emboli microenvironment and identify targets for future therapeutics. Our findings demonstrate enrichment of genes linked to chemotaxis and TNFR network of signals in the tumor cells and increased macrophage infiltration in the IBC tumor emboli microenvironment. Using a transgenic murine model, we demonstrate that treatment with Birinapant, a SMAC mimetic that enhances TNFα-mediated cell death, may be effective in targeting the tumor emboli phenotype.