Elevation of sialyl stage-specific mouse embryonic antigen levels in pleural effusion in patients with adenocarcinoma of the lung

Abstract

Sialyl stage-specific mouse embryonic antigen (SSEA-1) levels were measured in pleural effusions obtained from patients with lung cancer and benign pulmonary disease, using a solid-phase immunoradiometric sandwich assay. The mean (+/- SEM) levels (unit/ml) of pleural fluid sialyl SSEA-1 were 3620 +/- 1419 in adenocarcinoma (n = 25), 123 +/- 30 in nonadenocarcinoma (n = 13) and 95 +/- 19 in benign pulmonary disease (n = 13), respectively. The positive rate was 64% in adenocarcinoma, 7.7% in nonadenocarcinoma, and 0% in benign pulmonary disease, respectively, when a cutoff level was defined as the mean + 3 SD value (300 unit/ml) based on pleural fluid sialyl SSEA-1 levels in benign pulmonary disease. There was a significant positive correlation between pleural fluid levels of sialyl SSEA-1 and those of carcinoembryonic antigen in adenocarcinoma patients (r = 0.8246, P less than 0.01). Pleural fluid sialyl SSEA-1 levels correlated with cytologic findings in adenocarcinoma patients. These observations suggest that sialyl SSEA-1 in pleural effusion is a useful marker to discriminate malignant from nonmalignant and adenocarcinoma from nonadenocarcinoma of the lung.