MCAT and colorectal carcinoma: MTs are a family of cysteine-rich low molecular-weight proteins, which play a critical role in zinc homeostasis, protection against heavy metals, anti-inflammatory reactions, immunomodulation and reactive oxygen species scavengers.54, 55 Normal-appearing mucosa from healthy individual and CRC patients showed high expression of MTs, whereas cells at the lower basal layers of the crypt exhibit negative staining for MTs,35, 56 suggesting that MT downregulation is an early step in CRC progression.