The article discusses the complex role of myeloid-derived suppressor cells (MDSCs) in cancer, highlighting their dual functions as both suppressors of immune responses and facilitators of tumor growth. MDSCs are defined as immature myeloid cells that can be further categorized into mononuclear (M-MDSCs) and polymorphonuclear (PMN-MDSCs) subtypes. These cells suppress immune responses through various mechanisms, including production of arginase, inducible nitric oxide synthase (iNOS), transforming growth factor-β (TGF-β), interleukin-10 (IL-10), and cyclooxygenase-2 (COX2). They also support tumor growth by remodeling the tumor microenvironment, promoting angiogenesis, and facilitating epithelial-to-mesenchymal transition (EMT). The article reviews recent progress in understanding the regulation of MDSC accumulation and activation in cancer, including the role of growth factors, proinflammatory cytokines, and transcription factors like STAT3 and HIF-1α. It also discusses the clinical significance of MDSCs as biomarkers for tumor progression and responsiveness to therapy, and explores therapeutic strategies targeting MDSCs, such as direct depletion, functional inhibition of their suppressive machinery, and skewing myelopoiesis away from MDSC production. Overall, the article emphasizes the importance of MDSCs in cancer and suggests that they may serve as valuable prognostic factors and therapeutic targets in the treatment of human cancer.The article discusses the complex role of myeloid-derived suppressor cells (MDSCs) in cancer, highlighting their dual functions as both suppressors of immune responses and facilitators of tumor growth. MDSCs are defined as immature myeloid cells that can be further categorized into mononuclear (M-MDSCs) and polymorphonuclear (PMN-MDSCs) subtypes. These cells suppress immune responses through various mechanisms, including production of arginase, inducible nitric oxide synthase (iNOS), transforming growth factor-β (TGF-β), interleukin-10 (IL-10), and cyclooxygenase-2 (COX2). They also support tumor growth by remodeling the tumor microenvironment, promoting angiogenesis, and facilitating epithelial-to-mesenchymal transition (EMT). The article reviews recent progress in understanding the regulation of MDSC accumulation and activation in cancer, including the role of growth factors, proinflammatory cytokines, and transcription factors like STAT3 and HIF-1α. It also discusses the clinical significance of MDSCs as biomarkers for tumor progression and responsiveness to therapy, and explores therapeutic strategies targeting MDSCs, such as direct depletion, functional inhibition of their suppressive machinery, and skewing myelopoiesis away from MDSC production. Overall, the article emphasizes the importance of MDSCs in cancer and suggests that they may serve as valuable prognostic factors and therapeutic targets in the treatment of human cancer.