TGFB1 and neoplasm: On the other hand, tumor cells can reduce cytotoxic T lymphocyte (CTL) infiltration in the tumor by producing immunosuppressive cytokines such as vascular endothelial growth factor (VEGF), transforming growth factor–β (TGF-β), IL-10 and by consuming IL-2, a cytokine that is critical for maintaining CTL function [48].