SMAD7 and colorectal cancer: Furthermore, SMAD7 expression was found to be lower in colorectal cancers than in adenomas regardless of 18q copy number status [11] and the risk allele at rs12953717 was significantly associated with lower SMAD7 expression in lymphoblastoid cell lines [3], suggesting that allele-specific expression of SMAD7 is likely to be the biological mechanism underlying the association between variations in 18q21 and CRC risk.