What role do tumor-associated macrophages play in the tumor microenvironment?

Tumor-associated macrophages (TAMs) primarily contribute to the tumor microenvironment by promoting tumor growth and suppressing anti-tumor immunity. These macrophages are often polarized towards a M2 phenotype, which is associated with tissue repair and immunosuppression. In this state, they secrete various factors that can enhance tumor cell proliferation, angiogenesis (the formation of new blood vessels), and metastasis while simultaneously inhibiting the function of cytotoxic T lymphocytes and natural killer cells that would typically contribute to anti-tumor responses.

This dual role allows TAMs to create an environment that is supportive of tumor progression, by nurturing cancer cells and shielding them from the host's immune system. Their involvement in such processes underscores the complexity of the immune system's interaction with tumors and highlights why targeting TAMs and their pathways has become an area of interest in cancer therapy.