Monoclonal antibody‐based ELISA to detect glycoprotein tumor‐associated‐antigen‐specific immune complexes in cancer patients

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Abstract
This report describes the development and applicability of a tumor‐assocaited‐antigen‐specific immune complex (IC) detection assay to denote th presence oftumor cells in a cancer host. This assay utilizes a murine monoclonal antibody, AD1‐40F4, which was produced to a glycoprotein tumor‐associated antigen (TAA). In Western blot, the murine monoclonal antibody recognized a 90–10 kD subunit of the antigen. This antigen is immunogenic in cancer patients and induces formation of endogenous antigen‐antibody complexes. Analysis of 250 sera from normal individuals and 419 sera from cancer patients revealed that a significantly (P <.0005) greater proportion (234/419; 55.9%) of cancer sera was positive for the marker than the normal sera (8/250; 3.2%). The incidence of the 90 kD‐TAA‐specific‐IC was consistently and significantly higher in melanoma (58.5%; 38/65), Sarcoma (52.9%; 83/157), and carcinoma of breast (50.9%; 83/157), and carcinoma of breast (50.9%; 58/114), lung (68.2%; 30/44), and colon (64.1%, 25/39) than in the normal group. The age of serum donors did not affect the incidence of teh reactivity. Also, at least in the cancer group the gender ofthe serum donor did not affect the incidence of the 90 kD‐TAA‐specific‐IC positivity. In a retrospective study where sequential serum samples obtained postoperatively from 105 patients with melanoma were analyzed, the 90 kD‐TAA‐specific‐IC could be detected in 72 (69%) of patients several years before the appearance fo clinically detectable disease. These results indicate that the 90 kD‐TAA‐specific‐IC assay represents a new type of tumor marker of enhanced specificity and broad crossreactivity among a wide spectrum of different histological types of human neoplasms. This assay may be useful to assess prognosis and detect residual disease after surgical treatment.