SMAD4 and colorectal carcinoma: Indeed, some studies showed that the deletion of the long arm of chromosome 18 (loss of 18q or LOH of 18q) is the most common cytogenetic abnormality in CRC and seems to be associated with poor prognosis as 18q contains several important tumor suppressor genes, such as SMAD2, SMAD4, and SMAD7 that are transcriptional mediators in the TGF-β signaling pathway [37].