[Monocytes and cancer: fundamental insights and therapeutic perspectives]

Monocytes, circulating mononuclear phagocytes, play a fundamental role in innate immunity and the maintenance of tissue homeostasis. Using advanced technologies like flow cytometry, the characterization of monocytes has evolved from a simplistic view of a homogeneous population to a more complex understanding of a heterogeneous system comprising three main subtypes: classical monocytes (CD14++CD16-), intermediate monocytes (CD14++CD16+), and non-classical monocytes (CD14+CD16++). The identification of these subpopulations has enabled precise characterization of their functional profiles, enhancing the understanding of their roles in various pathological contexts, particularly in oncology. While anti-tumoral functions of monocytes have been clearly established in certain categories of cancers through tumor antigen presentation, induction of cytotoxic responses, and inhibition of metastatic progression, their role in promoting the development and progression of other cancers has also been highlighted during recent years. The utilization of monocytes in cancer immunotherapy presents promising opportunities, particularly by reprogramming their activity to enhance anti-tumoral responses or suppress their pro-tumoral functions. This review provides a comprehensive analysis of recent advances in the phenotypic and functional diversity of monocytes and their role in tumor progression, while highlighting emerging therapeutic strategies targeting these cells to optimize cancer treatment.