Myeloid-Derived Suppressor Cells in Cancer: Mechanistic Insights and Targeted Therapeutic Innovations

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells that expand aberrantly in cancer and exhibit potent immunosuppressive properties. They contribute to tumor progression through both immunological and nonimmunological mechanisms. Immunologically, MDSCs suppress antitumor responses by inhibiting effector cells such as T cells and NK cells, facilitating immune evasion. Nonimmunologically, they promote tumor growth and metastasis through processes such as the epithelial‒mesenchymal transition, angiogenesis, and premetastatic niche formation. MDSC accumulation is closely linked to accelerated tumor progression, including resistance to both immunotherapies and conventional treatments, making these cells critical therapeutic targets. Clinical studies have demonstrated the potential of MDSC-targeted strategies to improve treatment efficacy. However, challenges remain in achieving specificity and effectiveness in MDSC-targeted therapies, emphasizing the need for a deeper understanding of their biology. This review summarizes the origin, classification, and biological characteristics of MDSCs, their dual roles in tumor progression, and their clinical significance. We also discuss recent advances in clinical and preclinical studies, including both traditional targeted therapies and emerging innovative strategies. By integrating current findings, we aim to provide a comprehensive perspective on the role of MDSCs in cancer and valuable insights for advancing cancer treatment and drug development.