TGFB1 and cancer: However, Fib is not an inorganic small molecule; it is instead a set of molecules with complex bioactivity—for example, cancer cells or tumor tissues release TGFβ into the blood through exosomes (cancer-derived exosomes) (20), thereby activating the pSTAT3 signal in blood cells, and TGFβ and pSTAT3 are signaling molecules upstream and downstream of each other (21, 22), so they will induce a positive feedback response and last for a certain period of time.