Expression of gastric gland mucous cell-type mucin in normal and neoplastic human tissues

Gastric gland mucous cells produce class III mucin, which is also found in Brunner's glands and mucous glands along the pancreaticobiliary tract, and in metaplasia and adenocarcinomas differentiating towards gastric mucosa. Recently, we showed that class III mucin possesses GlcNAcalpha1-->4Galbeta-->R, formed by alpha1,4-N-acetylglucosaminyltransferase (alpha4GnT). Examining the tissue-specific expression of mucin epitopes is useful to clarify cell-lineage differentiation and to identify the site of origin of metastatic carcinomas in histological specimens. Formalin-fixed, paraffin-embedded tissue sections from esophagus, stomach, colon, liver, pancreas, lung, kidney, prostate, breast, and salivary gland resected for carcinoma, as well as salivary gland adenoma, colon adenoma, and metastatic adenocarcinoma of lymph nodes from stomach, pancreas, colon, and breast, were immunostained for MUC6, alpha4GnT, and GlcNAcalpha1-->4Galbeta-->R. These were all expressed in normal, metaplastic, and adenocarcinoma tissues of stomach, pancreas, and bile duct, and in pulmonary mucinous bronchioloalveolar carcinomas. Cells expressing alpha4GnT uniformly expressed GlcNAcalpha1-->4Galbeta-->R. Only MUC6 was expressed in normal salivary glands, pancreas, seminal vesicles, renal tubules, and colon adenomas, and in normal tissue and adenocarcinomas of prostate and breast. No tissues showed immunoreactivity for alpha4GnT alone. Immunohistochemistry (IHC) profiles were similar for metastatic carcinomas and primary carcinoma tissues. The IHC profiles for MUC6, alpha4GnT, and GlcNAcalpha1-->4Galbeta-->R may be diagnostically relevant.