This apparent conversion in TGF-β1 function after tumor initiation is known as the “TGF-β1 paradox.” It is important to understand the downstream effectors of the TGF-β1 signaling pathway and to identify the “molecular switch” or “switches” mediating the “TGF-β1 paradox.” TGF-β1 is considered a major driver of the EMT in tumors. The gene discussed is TGFB1; the disease is neoplasm.