Monocytes in tumor: The perspectives of single-cell analysis

Abstract

Infiltration of mononuclear phagocytes into the tumor microenvironment (TME) is known to orchestrate the tumor progression and is generally considered to interfere with the efficacy of immune checkpoint blockade therapies. For a more precise definition of monocytes, we review some recent advances in the functions of monocytes and macrophages in TME based on single-cell analysis. We also summarize the details of the different subpopulations of monocytes and macrophages involved in immunotherapy and their potential applications in clinical studies. In this review, we briefly introduce the developmental trajectory of mononuclear phagocytes, including monocytes, tumor-associated macrophages, dendritic cells and myeloid-derived suppressive cells, and their functions in TME. In this review, the potential of monocytes and their derived cells as diagnostic and therapeutic targets, with regard to the interaction between monocytes and immune checkpoint therapies, is also summarized.