Figure 3.
FOXP4 is a direct downstream of YAP1. A, RNA-seq revealed that among the FOXP family, FOXP4 exhibits significant downregulation after the knockdown of YAP1. B, The Eukaryotic Promoter Database showed a putative YAP1/TEAD4-binding site on the FOXP4 promoter (−647 bp; P < 0.001). C, ChIP-qPCR assay (n = 3) confirmed the direct binding of YAP1/TEAD4 complex to the FOXP4 promoter. TSS, transcription start site. D, Luciferase reporter assays (n = 3) verified that YAP1 can bind with the FOXP4 promoter (wild-type binding motif). E, Western blot analysis showed that siRNA-mediated YAP1 depletion led to a significant decrease in FOXP4 protein in both gastric cancer cell lines. F, Western blot analysis revealed that the overexpression of wild-type YAP1 or constitutively active YAP (YAP5SA) increased FOXP4 expression. G and H, Administration of CA3 or VT107 inhibited the expression of YAP1 and FOXP4 dose-dependently. I, Left, workflow for generating an MNNG (N-methyl-N’-nitro-N-nitrosoguanidine)-induced gastric cancer model. d.w., drinking water. Middle and right, IHC staining showed that Yap1/Taz double-knockout mice (Yap1−/−Taz−/−) exhibited low FOXP4 expression in the MNNG-induced gastric cancer model. Scale bar, 50 μm. J and K, IHC staining confirmed a significant correlation between YAP1 and FOXP4 in both intestinal and diffuse gastric cancer types. Scale bar, 50 μm. L and M, Patient-derived organoid models further depicted that FOXP4 expression is regulated by YAP1. Scale bar, 50 μm. ***, P < 0.001.