CD4 and neoplasm: It has been found that CD4+CD25+ regulatory T cells (Tregs), myeloid derived suppressor cells, and various immunosuppressive factors, including interleukin 10 (IL-10), transforming growth factor β (TGF-β), vascular endothelial growth factor, and prostaglandin E2, are frequently enriched in the tumor microenvironment and facilitate tumor immune evasion5.