The role of macrophages in cancer progression: M1, M2 subtypes, and their impact on tumor microenvironment

Abstract

Macrophages are key players in the immune system, exhibiting remarkable plasticity that allows them to influence cancer progression in opposing ways. Their polarization into M1 or M2 subtypes dictates their impact on the tumor microenvironment (TME). M1 macrophages, characterized by pro-inflammatory and anti-tumor functions, release cytokines that enhance immune responses and promote tumor destruction. Conversely, M2 macrophages support tumor growth by facilitating angiogenesis, immune suppression, and tissue remodeling, thereby creating a favorable environment for cancer progression. Further classification of M2 macrophages into subtypes M2a, M2b, M2c, and M2d underscores their diverse roles in tumor development, metastasis, and immune evasion. Given their crucial role in shaping the TME, macrophages have become a major focus in cancer research. Recent therapeutic strategies aim to reprogram macrophages, shifting their phenotype from tumor-promoting to tumor-suppressive. By targeting macrophage polarization, researchers seek to develop novel immunotherapies that enhance treatment efficacy, improve patient outcomes, and combat therapy resistance in cancer.