TGFB1 and cancer: Considering that the activation of in vivo cancer metastasis is a complex and multistep process depending on a series of intracellular signaling networks induced by TGF-β, EGF, PDGF and other signals [27], we sought to identify interacting partners, specifically circPTEN1-associated proteins, by circRNA pull-down to investigate how circPTEN1 functions.