Increased Expression of the Enzyme 1-4-Galactosyltransferase is Associated with Human Parotid Neoplasms

Abstract

Human biopsy samples of parotid gland neoplasms were examined for the level of enzyme activity of the glycosyltransferase, beta 1-4-galactosyltransferase. An analysis of an adenoid cystic carcinoma, Warthin's tumor, mucoepidermoid carcinoma, and five pleomorphic adenomas all revealed elevated levels of enzyme activity. Evidence for plasma membrane beta 1-4-galactosyltransferase activity was provided by membrane fractionation as well as intact cell enzyme assays. On the other hand, the major protein of human saliva, salivary alpha-amylase, was substantially reduced in the same tissue compared with adjacent normal parotid gland tissue. The trichloroacetic acid-soluble proteins isolated from gland homogenates were also reduced in two of the carcinoma samples but increased in the pleomorphic adenomas. Additionally, the proliferation of these cells, in vitro, could be retarded by culturing in media containing the galactosyltransferase specific modifier protein, alpha-lactalbumin, or the nucleotide sugar, UDP-galactose.