ARG1 and neoplasm: In addition, MDSCs also express immunosuppressive and trophic factors, including vascular endothelial growth factor (VEGF), interleukin (IL) 1/2/10, transforming growth factor‐β (TGF‐β), programmed death‐ligand (PD‐L) 1/2, indoleamine 2,3‐dioxygenase (IDO), inducible nitric oxide synthase (iNOS), and arginase‐1 (ARG‐1), to assist in immunosuppression, angiogenesis, and tumor progression.6