TGFB1 and neoplasm: Studies in genetically engineered mouse models and preclinical studies using TGFβ pathway antagonists support the pro-metastatic function of TGFβ, although this activity may depend on multiple factors, such as the nature of the tumor-initiating mutation, the precise mechanism of TGFβ inactivation, and the timing of TGFβ signaling [4, 12–13, 16].