Responses of serum from breast cancer patients to murine mammary tumor virus: fact or artifact?

For determination of whether breast cancer patients possessed specific serological responses to murine mammary tumor virus (MuMTV), IgG-binding levels were monitored by antibody binding to electrophoretically separated viral proteins (Western blotting and immunodetection) and by the enzyme-linked immunosorbent assay (ELISA) against a panel of five structural proteins (gp55, gp34, p28, p18, and p12) purified from milk-borne MuMTV of the RIII isogeneic mouse strain. No significant antibody reactions were found for sera from 30 cancer patients by the immunoblotting assay, and comparative ELISA studies of 111 patients with malignant mastopathies and 122 healthy, age-matched women revealed no significantly increased mean antibody responses against gp55, gp34, p28, or p12 in breast cancer patients as compared to the responses in the control group. Only for p18 was there a significant increase in mean IgG-binding levels in cancer patients. Additional assays of antibody binding to viral antigens were performed by the cellular immunofluorescence test on MuMTV-expressing cells. These studies also failed to demonstrate greater immunoreactivity of sera from patients as opposed to the immunoreactivity of sera from healthy controls.