Roles of Tumor-Recruited Myeloid Cells in Immune Evasion in Cancer

Myeloid cells, including tumor-associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs) represent a major cellular component in tumor tissues that play a key role in tumor development and progression. Recruitment of myeloid cells to the tumor vicinity is a constant process fueled by the increased secretion of chemokines by both malignant as well as by stromal cells, which causes the mobilization of bone marrow-derived myeloid cell precursors from bone marrow and extravasation from the circulation into the tumor. Following entry into tumor tissue myeloid cells, due to tolerogenic cytokine milieu in the tumor microenvironment, differentiate into immunosuppressive TAMs and MDSCs. Tumor-recruited myeloid cells have been shown to exert supportive tumor-promoting effects via multiple pathways that stimulate local immune suppression/tolerance, tumor angiogenesis, tissue remodeling, and cancer inflammation.

While a very substantial progress has been made in recent years in immunotherapy of human cancers, the mechanisms of immune escape and immune resistance to cancer immunotherapy are not fully understood. The objective of this Research Topic is to evaluate the roles of tumor-recruited myeloid cells in mechanisms of immune evasion and immune exclusion employed by human and experimental animal tumors that allow malignant cells to escape from immune recognition and immune-mediated elimination. We welcome researchers to submit Reviews, Opinions, or Original Research articles focusing on the contribution of myeloid cells and myeloid cell differentiation in development and progression of cancer.

We are particularly interested in clinical and pre-clinical studies with novel findings that highlight the mechanisms of recruitment of myeloid cells (or myeloid precursors) to the tumor tissue, interaction of recruited myeloid cells with malignant cells or tumor stroma, targeting myeloid cells, as well as the molecular and cellular mechanisms associated with myeloid cell differentiation/polarization in the tumor micro-environment or those implicated in the immune suppression/tolerance and/or mechanisms of immune resistance to cancer immunotherapy mediated by myeloid cells.