SMAD4 and colorectal carcinoma: As summarized in Figure 1A, these cells show different status of KRAS and SMAD4 mutational status, two genetic mutations frequently observed in CRC patients [27–33], as well as varying levels of CEACAM1 expression and that of two other well-known pro-metastatic CEACAM family members namely CEA and CEACAM6 [2].