title: A monoclonal antibody to a 48 K antigen in oestrogen-dependent human breast cancer cells.
abstract: A mouse was immunised with an antigen(s) purified by oestradiol-Sepharose affinity chromatography of pooled oestrogen-receptor positive cytosols from human breast cancer tissue. One antibody secreting clone was identified which precipitated labelled antigen and which also stained MCF-7 cells. Culture supernatant and ascites fluid were used for immunofluorescence, SDS-PAGE-Western blotting, photoaffinity labelling and binding studies. The antibody staining of MCF-7 cells was inhibited by preincubation in oestrogen-receptor positive cytosol but was unaffected by oestrogen-receptor negative cytosol. MCF-7 cells stained whether cultured in the presence or absence of oestradiol. The oestrogen-receptor negative cell lines MDA-MB-231 and MDA-MB-330 did not stain. Binding studies with 16-alpha-iodooestradiol using breast cancer tissue cytosols followed by immunoprecipitation showed activity only with oestrogen-receptor positive cytosols with optimal binding activity at 4 degrees C, unaffected by molybdate, but reduced at 25 degrees C or in the presence of 0.4 M KCl. Binding studies with MCF-7, MDA-MB-231 and MDA-MB-330 cytosols and nuclear fractions only showed activity with the MCF-7 cytosol and MCF-7 particulate fractions. The antibody recognised a 48 K species in both MCF-7 cytosol and nuclear fractions but not in the cytosol and nuclear extracts of oestrogen-receptor negative cell lines. Photoaffinity labelling using 16 alpha-iodooestradiol suggests the 48 K antigen does not bind oestradiol directly. The relationship of this antigen to the classical oestrogen-receptor and receptor complex awaits further clarification.
authors.affiliation: Department of Clinical Biochemistry, Christchurch Hospital, New Zealand.
authors.forename: J G
authors.initials: JG
authors.lastname: Lewis
authors.forename: J M
authors.initials: JM
authors.lastname: Robertson
authors.forename: P A
authors.initials: PA
authors.lastname: Elder
mesh_terms: D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm / Q000032:analysis*; D001943:Breast Neoplasms / Q000032:analysis*; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D008970:Molecular Weight; D009376:Neoplasms, Hormone-Dependent / Q000032:analysis*; D011960:Receptors, Estrogen / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D011960:Receptors, Estrogen