Increased fragmention of MUC 5AC mucins in gastric juice of patients with ulceration and carcinoma

Gastric cancer, a fatal malignancy, is prevalent in the Western Cape region of South Africa. We have compared the mucins in gastric juice of cancer pa tients with those of gastric ulcer patients and asymptomatic volunteers as controls. Mucins from naso-gastric aspirates were extracted in proteolytic inhibitors and purified by precipitation with cetylpyridinium chloride. Muc ins were analysed by gel filtration, SDS-PAGE and Western blotting methods. There was significantly more mucin in gastric juice of controls than in pa tients with carcinoma of the stomach. Mucins from gastric ulcer and gastric cancer patients were significantly less polymeric than in control specimen s as shown by Sepharose 2B gel filtration. Indeed, 4 of 7 of the carcinoma specimens had no polymeric mucins, suggesting that there is greater fragmen tation of mucin in diseased states than in healthy subjects. In addition, S DS-PAGE studies and Western blot analysis with M1 antibodies showed that th e mucin fragments were of the MUC 5AC type. M1 monoclonal antibodies reacte d more positively with gastric cancer mucin than with that from gastric ulc er and controls. Gastric mucin from carcinoma patients was more degraded th an in ulcerous and healthy subjects. The greater cross-reactivity of a poly clonal antibody to human cancer mucin (from crude mucus scrapings) with muc in from cancer and ulcer gastric juice specimens confirmed that intralumina l mucins and their fragments are largely the product of MUC 5AC, which is s ecreted by healthy gastric epithelia.