A SURVIVOR OF BREAST-CANCER WITH IMMUNITY TO MUC-1 MUCIN, AND LACTATIONAL MASTITIS

The human mucin, MUC-1, is a transmembrane glycoprotein that is produc ed by both normal an malignant epithelium. The MUC-1 produced by malig nant epithelium is underglycosylated, which leads to the expression by tumors of novel T and B cell epitopes on the mucin polypeptide core. Similar underglycosylation occurs in the lactating breast. In this rep ort, we describe a long-term survivor of breast cancer whose tumor str ongly expressed the T- and B-cell-stimulatory epitopes. Five years aft er presenting with the tumor, the patient had her first pregnancy, at which time she developed fulminant lymphocytic mastitis. We demonstrat e that the lactating breast produced mucin expressing the same ''tumor -specific'' epitopes as the original cancer. The patient had circulati ng anti-mucin antibodies of both the IgM and IgG isotypes (these areno t found in normal controls), and mucin-specific cytotoxic T lymphocyte s in the peripheral blood. Limiting - dilution analysis for mucin - sp ecific cytotoxic T lymphocytes in three different experiments yielded frequencies of 1 in 3086, 1 in 673, and 1 in 583, compared to approxim ately 1 in 10(6) in normal controls. The patient remains clinically fr ee of carcinoma after 5 additional years of follow-up. We propose that the original tumor primed the patient's immune response against the m ucin epitopes, and that the reexpression of these epitopes on the lact ating breast evoked a secondary immune response. It is tempting to spe culate that the vigor of her anti-mucin immunity may have helped prote ct this patient against recurrent tumor.