Myeloid-derived immunosuppressive pathways

Myeloid-derived immunosuppressive pathways represent a complex network of cellular and molecular mechanisms used by myeloid-derived suppressor cells (MDSCs) to dampen the host's immune response, particularly within the tumor microenvironment [1, 2]. These pathways are characterized by the production of suppressive enzymes such as Arginase 1 (ARG1) and inducible nitric oxide synthase (iNOS), which deplete essential amino acids like L-arginine and generate reactive oxygen species (ROS) that inhibit T-cell proliferation and function [3, 8]. Additionally, MDSCs utilize these pathways to secrete inhibitory cytokines like TGF-beta and IL-10, and to promote the development of regulatory T cells (Tregs), further contributing to an immunosuppressive milieu [4, 5]. In various cancers, the activation of these pathways is strongly associated with tumor progression, metastasis, and resistance to conventional therapies and modern immunotherapies [3, 7]. Drugs targeting these pathways aim to either eliminate MDSC populations, prevent their recruitment via chemokine receptor antagonism, or directly inhibit their suppressive biochemical products to restore effective anti-tumor immunity [6, 13]. For instance, chemotherapeutic agents like gemcitabine can selectively deplete MDSCs, while small molecule inhibitors of Arginase 1 or IDO target the metabolic components of these pathways [1, 3]. Understanding and modulating these pathways is a critical area of research for improving the efficacy of cancer immunotherapy and overcoming treatment resistance [5, 8].

Other names

MDSC-mediated immunosuppressionMyeloid-derived suppressor cell pathwaysMyeloid immunosuppressive mechanisms

Therapeutic strategies targeting these pathways involve the depletion of myeloid-derived suppressor cells (MDSCs), inhibition of their recruitment to the tumor microenvironment via chemokine receptor blockade, and inhibition of their immunosuppressive mediators such as Arginase 1, iNOS, and IDO to restore anti-tumor immunity.