FIGURE 1.

Interaction of myeloid-derived suppressor cells (MDSCs), platelets, and cancer cells. MDSCs inhibit the proliferation and development of T cells and natural killer (NK) cells through the production of nitric oxide (NO) and reactive oxygen species (ROS), interfere with the antigen-presenting ability of B cells, and stimulate the proliferation of regulatory T cells (Tregs) in large numbers, thereby exerting a sustained immunosuppressive effect. MDSCs derive transforming growth factor-β (TGF-β) and increase the expression of vascular endothelial growth factor (VEGF), which acts on endothelial cells (ECs) and leads to tumor microvascular malformations. TF and CP secreted by cancer cells as well as MDSCs are able to transform platelets to tumor-associated platelets (TAPs) through the PSGL1/P-selectin pathway. TAPs can drive tumor metastasis by promoting MDSCs recruitment, immunosuppression, and neovascularization. Figure was created by Figdraw (www.figdraw.com).