It is well established that Smad4 play a role in activating transforming growth factor-β (TGF-β) signalling pathway and translocating to the nucleus as a transcriptional cofactor to facilitate the transcription of TGF-β-responsive genes in cancer cells [9], thereby regulating a variety of critical processes, including tumor development [10] and immunotherapy [11]. The gene discussed is SMAD4; the disease is cancer.