Purification and characterization of a new 85-kDa glycoprotein antigen from human breast tumor

A new breasttumorassociated antigen (BTAA) was purified and partially characterized from human breast tumor. By DEAE-cellulose discontinuous NaCl-gradient chromatography of a crude extract of human malignant breast tumor, 3 major protein peaks were obtained. Circulating antibodies against one of the protein peaks, HF₁, was observed in breastcancer patients. The antibodies were absent in patients with carcinoma of the uterine cervix, lung, stomach and liver or with benign breast diseases and in healthy women. Absorption of the sera of breastcancer patients with normal human breast tissue pellet did not remove the HF₁-reactive circulating antibodies. The BTAA was partially purified from HF₁ by subjecting the fraction to SDS-PAGE and eluting the band 3 (HF₁-3). Westernblot analysis confirmed the presence of the BTAA in HF₁-3. Using an affinity column of protein-A-Sepharosebound IgG, purified from breastcancer patients' sera, the BTAA was also recovered from HF₁. Purification of the BTAA was achieved by subjecting HF₁ to sizeexclusion highperformance liquid chromatography (SE-HPLC). The antigen was characterized as a glycoprotein with MW of approximately 85 kDa and appeared not to be related either to murine mammarytumor virus (MuMTV) structural antigens or to human fetal antigens. The BTAA-reactive circulating antibodies in the breastcancer patients were of lgG₂ subtype, and the level of these antibodies significantly decreased in patients following surgical removal of the breast tumors. © 1995 Wiley-Liss, Inc.