Mucin glycoproteins in colonic neoplasia.
Gastrointestinal Research Laboratory, Veterans Affairs Medical Center, San Francisco, CA 94121, USA.
Mucins are high molecular weight glycoproteins which are heavily glycosylated with many carbohydrate side chains. In epithelial cancers such as colorectal cancer, both qualitative and quantitative alterations in carbohydrate and polypeptide moieties of mucin glycoproteins occur. These changes in mucin glycoproteins are one of the most common phenotypic markers of colorectal carcinogenesis and may play an important pathobiological role. The expression of some of the sialylated carbohydrate antigens appears to correlate with a poor prognosis and increased metastatic potential in colorectal cancer. The increased exposure of peptide epitopes of mucin glycoproteins in colorectal cancer appears to be due to either abnormal glycosylation and/or altered levels of mucin gene transcription. In addition, dysregulation of tissue specific mucin genes occurs in colorectal cancers. This information is currently being exploited for further elucidation of the molecular mechanisms involved in carcinogenesis, tumor progression and metastasis, and the development of novel methods of colorectal cancer diagnosis and therapy.