Alterations in TGF-β signaling in cancer can manifest across various key levels: (1) the expression and activation of TGF-β ligands, (2) the expression, post-translational modification, and occurrence of inactivating mutations of TGF-β receptors, (3) the expression, post-translational modification and occurrence of inactivating mutations within Smads, (4) perturbations in Smad co-regulators, and (5) the activation of non-canonical TGF-β pathway signaling. Here, TGFB1 is linked to cancer.