Biosynthesis and secretion of mucin-related products in Hs746T gastric cancer cells.

We have previously studied the biosynthesis and secretion of mucin in the normal human stomach and reported that the tetramer of the 60-kDa subunit of mucin core protein was synthesized and highly glycosylated, and that only high molecular weight mucin was secreted. In this study, we investigated the mucin-related products of a gastric cancer cell line (Hs746T). Analysis of intracellular and extracellular products immunoprecipitated with an anti-apomucin monoclonal antibody revealed that a 110-kDa protein, the dimer of the 55-kDa subunit, was synthesized and secreted. Tunicamycin treatment inhibited the secretion of the 110-kDa protein. These findings suggest that N-glycosylation may be involved in the secretory mechanism of the mucin-related product.