Studies on lung cancer-associated antigens in serum detected by mouse monoclonal antibodies Part 1. Establishment of a sandwich enzyme immunoassay and quantitative antigenic examination in various diseases

For purposes of quantitative detection of lung cancer-associated antigens in sera, a sandwich enzyme immunoassay was standardized. Four mouse monoclonal IgM antibodies (LA-3, LSI-4, LSI-a, and LSI-c) developed against human lung cancer cell lines were used for the assay. The 4 antigens in spent culture medium or cell extracts lost their antigenic reactivity after neuraminidase treatment, and the antigens were shown to be sialylated carbohydrate antigens. Serum antigen levels in 185 patients with malignancies, including 107 lung cancer patients, were measured and compared with those in 35 patients with benign respiratory diseases and 30 healthy donors. The levels of each antigen were significantly higher in the lung cancer patients than in patients with benign diseases or healthy donors. The percent of patients antigen-positive for each antigen was also significantly higher for lung cancer than with other diseases. Moreover, high antigen levels and antigen-positive rates were observed in hepatoma and pancreatic cancer patients. These results indicate that antigens detectable using these 4 antibodies are not lung cancer-specific, but may be useful in serum diagnosis of lung cancer as well as other malignancies