TGFB1 and colorectal carcinoma: We also identified Smad4 as the target of circPTEN1 and showed that circPTEN1 inhibits TGF-β-mediated CRC metastasis by disrupting TGF-β/Smad signaling through binding the MH2 domain of Smad4 to disrupt its physical interaction with p-Smad2/3.