The heterogeneity of tumor-associated macrophages and strategies to target it

Tumor-associated macrophages (TAMs) are emerging as targets for tumor therapy because of their primary role in promoting tumor progression. Several studies have been conducted to target TAMs by reducing their infiltration, depleting their numbers, and reversing their phenotypes to suppress tumor progression, leading to the development of drugs in preclinical and clinical trials. However, the heterogeneous characteristics of TAMs, including their ontogenetic and functional heterogeneity, limit their targeting. Therefore, in-depth exploration of the heterogeneity of TAMs, combined with immune checkpoint therapy or other therapeutic modalities could improve the efficiency of tumor treatment. This review focuses on the heterogeneous ontogeny and function of TAMs, as well as the current development of tumor therapies targeting TAMs and combination strategies.