Expression of surfactant protein B precursor and surfactant protein B mRNA in adenocarcinoma of the lung.

Surfactant protein B (SP-B) is a 79-amino acid, hydrophobic protein that plays important roles in surfactant function and homeostasis. SP-B is produced in the respiratory epithelium by proteolytic processing of a glycosylated precursor (pro-SP-B) of relative molecular mass 42,000 to 46,000. To develop diagnostic markers for pulmonary adenocarcinomas, we examined the incidence and distribution of pro-SP-B and SP-B mRNA in paraffin sections of 35 non-small cell lung carcinomas (15 adenocarcinomas, 15 squamous cell carcinomas, and 5 large cell carcinomas), using immunohistochemical techniques and in situ hybridization. Fifteen nonpulmonary adenocarcinomas were used as controls. Pro-SP-B and SP-B mRNA were detected in 60% and 53% of pulmonary adenocarcinomas, respectively. Expression was seen in adenocarcinomas with acinar, papillary, bronchioloalveolar, and solid growth patterns. Squamous cell and large cell carcinomas of the lung and nonpulmonary adenocarcinomas did not contain pro-SP-B immunoreactivity or SP-B mRNA. The specificity of SP-B gene expression in adenocarcinomas of the lung supports the usefulness of pro-SP-B and SP-B mRNA in the study and diagnosis of these neoplasms.