Smad7 is an intracellular inhibitor of the transforming growth factor-beta (TGF-β) signaling, whose expression in colorectal cancer-infiltrating Th17 cells increases tumor necrosis factor-α (TNF-α) and interferon-γ (INF-γ) expression and decreases IL-17A expression that is responsible for effective killing of cancer cells [48]. The gene discussed is IL17A; the disease is colorectal cancer.