This accumulation is detectable both within the tumor tissue (specifically in the tumor core, necrotic zones, and perivascular-rich areas) and as elevated levels in the peripheral blood of patients, and is often correlated with tumor progression and immunosuppression [74,75] MDSCs are known to inhibit T-cell activity and promote tumor progression through the secretion of immunosuppressive factors, including IL-10, TGF-β, and ARG1 [76]. This evidence concerns the gene ARG1 and neoplasm.