Serum concentrations of SP1 (pregnancy-specific-beta1-glycoprotein) in healthy, nonpregnant individuals, and in patients with nontrophoblastic malignant neoplasms.

The presence of [SP1 (PSbetaG)] in healthy men and nonpregnant women was demonstrated with a highly sensitive and specific radioimmunoassay. Detectable serum levels (1-5 ng/ml) were found in 37 of 69 individuals. Concentrations of 3-10 ng/ml could be detected in 80% of the patients with a variety of nontrophoblastic malignant neoplasms and in 17% of patients with breast cancer. In 11% of these patients the serum level was raised to 10-50 ng/ml. SP1 was also found in extracts of fresh tumor tissue. In 27% of these specimens 3-15 ng/ml SP1 were found. Serum SP1 levels that were elevated before surgery fell to the normal range within a few days after tumor removal. SP1 might thus be regarded as a marker for various nontrophoblastic cancers and as such might become important as a guide to treatment.