CD44 and colorectal carcinoma: Additionally, knockdown of Smad4 promoted the expression of stem cell markers CD44, Sox2, Oct4, and Nanog, while the treatment with CD55-Smad4 downregulated their expression in both HCT116 and HCT116-Smad4−/− cells, implying that CD55-Smad4 suppresses CRC stemness by inhibiting the Wnt/β-catenin cascade (Figure 4E).