Tumor-associated macrophages promote invasion while retaining Fc-dependent anti-tumor function

Area of Science:

• Immunology
• Oncology
• Cell Biology

Background:

• Tumor-associated macrophages (TAMs) are linked to tumor progression and poor prognosis.
• The precise phenotype and function of TAMs, particularly in antibody-dependent cytotoxicity, remain incompletely understood.

Purpose of the Study:

• To investigate the dual role of TAMs in breast cancer, examining their protumor properties and Fc-dependent anti-tumor functions.
• To elucidate the plasticity of TAMs and their potential for therapeutic targeting.

Main Methods:

• Isolation and characterization of CD11b(+)CD14(+) TAMs from human breast tumors.
• In vitro differentiation of human monocytes into tumor-conditioned macrophages using breast cancer cell-conditioned media.
• Comparison of tumor-conditioned macrophages with M1 and M2a macrophages.
• Assessment of Fcγ receptor expression and phagocytosis of tumor cells in the presence of tumor-targeting monoclonal antibodies (mAbs).
• In vivo studies involving macrophage depletion in a xenograft mouse model.

Main Results:

• TAMs exhibit protumor properties, promoting tumor cell invasion and expressing M2a markers.
• Despite protumor characteristics, TAMs express Fcγ receptors and can phagocytose tumor cells when targeted by mAbs, indicating tumoricidal capacity.
• Macrophage depletion in vivo impaired the efficacy of anti-CD142 therapy against tumor xenografts.
• M-CSF in tumor-conditioned media drives macrophage differentiation with both pro- and anti-tumor functions.

Conclusions:

• TAMs possess a plastic phenotype, capable of promoting tumor progression while retaining Fc-dependent anti-tumor functions.
• Targeting TAMs in conjunction with mAbs may represent a viable therapeutic strategy by leveraging their tumoricidal capacity.
• Understanding TAM plasticity is crucial for developing effective immunotherapies for breast cancer.