SMAD4 and colorectal cancer: Yet, TGFβ signaling is frequently inactivated in human tumor entities including colorectal cancer (CRC) and pancreatic adenocarcinoma (PAAD) with a high proportion of mutations incapacitating SMAD4, which codes for a transcription factor (TF) central to canonical TGFβ and bone morphogenetic protein (BMP) signaling.