Detection of a 67-kD glycoprotein in human tumor cell lines by a monoclonal antibody established against a recombinant human endogenous retrovirus-K envelope-gene-encoded protein.

Endogenous retroviruses in humans are discussed as putative etiologic agents in tumorigenesis. Molecular mimicry of cellular epitopes by retroviruses may be of importance for the genesis of autoimmune diseases. A group of human endogenous retroviruses, HERV-K, which is related to the mouse mammary tumour virus, has been characterised previously and open reading frames have been found covering their gag, pol, prt and env genes. Transcription of HERV-K genomes at the mRNA level as well as antibodies in human sera directed against HERV-K env have been detected recently. We have generated a monoclonal antibody (mAb), anti-HERV1, against a recombinant HERV-K Env protein. This mAb is capable of immunoprecipitating a 67-kD glycoprotein from the human breast carcinoma cell line T47D, the amount of which is strongly enhanced after stimulation with estradiol followed by progesterone. The same band could be precipitated from other carcinoma cell lines (Hep2, MCF7 and HeLa), but not from the human B-lymphoblastoid cell line Raji and from cultured human fibroblasts. Incubation of this antigen in the presence of endoglycosidase F indicates the presence of N-linked carbohydrate moieties of at least 7-9 kD.