EXPRESSION OF MUC2 GENE-PRODUCT IN MUCINOUS CARCINOMA OF THE BREAST -COMPARISON WITH INVASIVE DUCTAL CARCINOMA

We have previously reported that MUC2 gene product was dominantly expr essed in the non-invasive carcinomas of the pancreas and liver (Cancer 71:2191-2199, 1993; Int J Cancer 55:82-91, 1993). Mucinous carcinoma (MC) of the breast usually shows less frequent lymph node metastasis a nd a more favorable outcome compared with invasive ductal carcinoma (I DC). In the present study, we examined the expression of MUC1 gene pro duct (DF3, 139H2) and MUC2 gene product (anti-MRP, CCP58) immunohistoc hemically in 17 cases of MC (11 pure MCs, and 6 mixed MCs comprising M C and IDC) and 57 cases of IDC. Most of the pure MCs MUC1 positive (DF 3: 11/11, 11/11) and MUC2 positive (anti-MRP: 10/11, CCP58: 11/11) pat tern. Most of the mixed MCs showed MUC1 positive (DF3: 6/6, 139H2: 6/6 ) and MUC2 positive (anti-MRP: 5/6, CCP58: 6/6) pattern in the MC area s, but MUC1 positive (DF3: 6/6, 139H2: 6/6) and MUC2 negative (anti-MR P: 0/6, CCP58: 0/6) pattern in the IDC areas. In contrast, most of the IDCs showed MUC1 positive (DF3: 54/57, 139H2: 53/57) and CCP58: MUC1 positive and MUC2 positive pattern. Thus, the expression of MUC2 gene product is associated with the less aggressive biological properties o f MC than IDC through the production of abundant extracellular mucin f orming the characteristic configuration, since MUC2 glycoprotein is a secretory mucin, while MUC1 glycoprotein is membrane-associated.