Previous researches had reported that the TGF-β pathway regulated the invasion and migration of cancer cells via epithelial-mesenchymal transition (EMT) (Xu et al., 2009; Schneider et al., 2011; Ma et al., 2015; Zhao et al., 2018; Camerlingo et al., 2019) and TGF-β could form a complex with Smad4 and translocate into the nucleus to regulate gene transcription (Wang et al., 2015; Yang et al., 2019), which suggested that the TGF-β pathway was vital in carcinogenesis. The gene discussed is SMAD4; the disease is cancer.