SMAD4 and neoplasm: Based on this, in order to study whether the demethylation drugs arsenic trioxide and 5-azacitidine can regulate the TGF-β signaling pathway, thereby affecting the growth activity of tumor cells, we employed qRT-PCR for detecting the effects of arsenide trioxide and 5-azacitidine on the classical molecular markers of the TGF-β signaling pathway, including Smad2, Smad3, and Smad4.