SOX9 and esophageal squamous cell carcinoma: As a transcriptional co-activator, YAP regulates transcription mainly through interacting with DNA-binding transcription factors (TEAD1-4) because of the lack of a DNA-binding domain.31 To elucidate if YAP-induced transcriptional function was crucial for stemness-related genes expression, TEAD1-4 were knocked down with their specific siRNAs in indicated ESCC cells, which reduced the protein expression of YAP targeted genes, including SOX9, SOX2, OCT4, and NANOG (Fig. 2k, l).