Myeloid-derived Suppressor Cells in Cancer: A Review on the Pathogenesis and Therapeutic Potentials

Myeloid-Derived Suppressor Cells (MDSCs) are multifarious group of immature cells that arise from the myeloid and amass in individuals with cancer, sepsis, burns, or chronic inflammation. It has been evidenced that these group of cells are efficient in modifying adaptive and innate immune responses, coherent with their assumed key biological roles. It is evidenced that MDSCs inter-communicate with Tumor-Associated Macrophages (TAM), Tumor-Associated Neutrophils (TAN), Dendritic Cells (DCs), Receptor for Advanced Glycation End-products (RAGE), Toll-Like Receptors (TLRs), Matrix Metalloproteinase (MMPs) as well as High Mobility Group Box 1 (HMGB1) during carcinogenesis. This interaction although elaborated in various studies and reviews still does not explain in details as to how their interplay results in cancer pathogenesis. We noted that MDSC contributed to cancer immune suppressionviaTLR-4 receptor and lipopolysaccharideas (LPS). Furthermore, MDSC contributed to cancer developmentviaMMPs (MMP-9 and MMP1-12) as well as RAGE. In the cancer microenvironment, HMGB1-driven MDSC amassment expedites cancer development and metastasisviaPMN-MDSCs, macrophages, DCs and Immature Myeloid Cells (IMC). Also, HMGB1 intermediation with MDSCsviaRAGE and/or TLR-4 leading to cancer development. Nevertheless, MDSCs have already proven potent in some cancers and are currently been used as treatment options although further studies are needed in some other cancers. Our review, therefore, explores the pivotal pathogenic and therapeutic roles of MDSCs in cancer.