Cancer cells hinder the proliferation of cytotoxic T lymphocytes (CTLs) within the tumor through the production of immunosuppressive cytokines like interleukin (IL)-10, vascular endothelial growth factor (VEGF), and TGF-β, and by consuming IL-2, a critical cytokine for CTL function [63]. The gene discussed is TGFB1; the disease is cancer.