SMAD4 and colorectal carcinoma: Six principal driver genes—adenomatous polyposis coli (APC), v-Raf murine sarcoma viral oncogene homolog B1 (BRAF), phosphoinositide-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), SMAD family member 4 (SMAD4), KRAS, and TP53—represent potential biomarkers for CRC metastasis and therapeutic targets (112).