Tumor Extracellular Vesicles Regulate Macrophage-Driven Metastasis through CCL5.

Area of Science:

• Oncology
• Immunology
• Cell Biology

Background:

• Triple-negative breast cancer (TNBC) is an aggressive subtype with limited therapeutic options.
• Tumor-associated macrophages (TAMs) play a complex role in breast cancer progression.
• The mechanisms by which tumor cells educate macrophages remain incompletely understood.

Purpose of the Study:

• To investigate how tumor cells, specifically via CCL5 signaling, alter macrophage biology within the TNBC tumor microenvironment.
• To determine the role of tumor-derived extracellular vesicles (EVs) in programming macrophages.

Main Methods:

• Bone marrow-derived macrophages (BMDMs) were treated with CCL5, tumor cell conditioned media, or tumor EVs.
• Macrophage-conditioned media was used to assess TNBC invasion.
• Cytokine secretion profiles of educated macrophages were analyzed.
• Tumor CCL5 expression was manipulated to study its effect on EV-mediated macrophage education.

Main Results:

• Tumor EVs are essential for reprogramming macrophages to a pro-metastatic phenotype.
• Tumor cell CCL5 expression regulates EV biogenesis, cargo, and subsequent macrophage education.
• EV-educated macrophages (TEMs) secreted factors (e.g., CXCL1, HGF, TGFB) that remodel the tumor stroma and immune infiltrate.
• Macrophages educated by metastatic tumor EVs promoted lung metastasis in vivo.

Conclusions:

• Tumor-derived EVs are critical mediators in educating macrophages towards a pro-metastatic state.
• EVs play a significant role in modulating the tumor immune infiltrate and potentially therapeutic responses in TNBC.