SMAD4 and colorectal carcinoma: Moreover, we found that the dramatically increased migration and invasion activities of circPTEN1 knockdown LoVo cells induced by TGF-β1 could be attenuated by reintroduction of full-length circPTEN1 but not the 451–50 nt deletion mutant of circPTEN1 (Supplementary Fig. 9C and D), demonstrating that the effect of circPTEN1 on the migration and invasion activities of CRC mediated by TGF-β1 was dependent on its interaction with Smad4.