Molecular Pathways: Tumor-Infiltrating Myeloid Cells and Reactive Oxygen Species in Regulation of Tumor Microenvironment

Tumor-associated myeloid cells are the major type of inflammatory cells involved in the regulation of antitumor immune responses. One key characteristic of these cells is the generation of reactive oxygen (ROS) and reactive nitrogen species (RNS) in the tumor microenvironment. Recent studies have shown the important role of ROS and RNS, especially peroxynitrite, in immune suppression in cancer. ROS and RNS are involved in induction of antigen-specific T-cell tolerance, inhibition of T-cell migration to the tumor site, and tumor cell evasion of recognition by cytotoxic T cells. In preclinical settings, a number of potential therapeutic agents showed activity in blocking ROS/RNS in cancer and in improving the efficacy of cancer immune therapy. A better understanding of ROS/RNS-associated pathways in myeloid cells will help to identify more specific and direct targets to facilitate the development of more effective immune therapy for cancer.