In vitro and in vivo release of soluble erbB-2 protein from human carcinoma cells.

An enzyme-linked immunosorbent assay (ELISA) was developed to measure soluble erbB-2 protein in culture supernatants of various human cell lines and sera of patients suffering from recurrent breast carcinoma. Soluble erbB-2 protein was demonstrated in culture supernatants of cell lines that expressed high levels of erbB-2 protein as shown by western blot analysis of cell lysates. Increased levels of the protein, 40- to 190-fold higher than in healthy controls, were demonstrated in sera of 3 out of 12 patients with breast carcinomas. On immunohistological study of tumor tissues from 9 patients, high immune reaction with the anti-erbB-2 protein antibody was observed in 2 cases. These were two of the three patients who had elevated levels of erbB-2 protein in serum (a sample was not available from the third patient). These results raise the possibility that soluble erbB-2 protein level in serum can be used as an indicator for spread of carcinomas that overexpress erbB-2 protein.