DRD4 and colorectal carcinoma: Furthermore, IF assays revealed co‐localization of p‐Smad2 and SNAI1, as the activation signaling of TGF‐β pathway, which were highly expressed with DRD4 in the clinical CRC samples (Figure 5D; Figure S5D, Supporting Information), and p‐Smad2 was also expressed in the clinical liver metastasis samples with high DRD4 expression (Figure 5E).