We further confirmed specificity of our findings to the colonic claudin-1 expression as similar transient overexpression of Cdx1, Cdx2 or GATA4 in human breast cancer cells (MCF-7) or renal epithelial cells (MDCK II cells) did not increase claudin-1 promoter activity (Figure 2D & E). Here, GATA4 is linked to breast cancer.