Myeloid-Derived Suppressor Cells and Macrophage Polarization in Cancer Immunotherapy

Abstract

Myeloid-derived suppressor cells (MDSCs) and macrophage polarization are key functional components of the immune system in shaping the tumor microenvironment (TME) and modulating immune responses. MDSCs, characterized by their heterogeneity and potent immunosuppressive functions, negatively affect anti-tumor immunity by inhibiting T cell activation, promoting regulatory T cell (Treg) expansion, and enhancing tumor growth and metastasis. Similarly, macrophage polarization into M1 (classically activated) and M2 (alternatively activated) phenotypes significantly influences tumor progression, with M2 macrophages facilitating immunosuppression, angiogenesis, and tissue remodeling. Therapeutic strategies targeting these cells focus on depleting MDSCs, reprogramming macrophages from the M2 to M1 phenotype, and disrupting their recruitment and activation signals within the TME. This chapter explores the complex biology of MDSCs and polarized macrophages, their interactions within the TME, their impact on cancer progression and treatment outcomes, and the future landscape of this field.