Lipid analysis and surfactant-associated protein expression in lung adenocarcinoma cells from pleural effusion

Primary lung adenocarcinomas originate from the progenitor cells of peripheral airway cells. Alveolar type II cells and Clara cells are the major progenitor cells of peripheral airway cells. Alveolar type II cells produce a lipid-protein complex called surfactant, which contains surfactant proteins SP-A, SP-B, SP-C and SP-D. Phosphatidylcholine (PC) and phosphatidylglycerol (PG) are believed to be essential for the surfactant function. Clara cells also express SP-A, SP-B and SP-D but not SP-C. In this study we examined the properties of the cancer cells isolated from the pleural effusion of a patient with primary lung adenocarcinoma by analyzing lipids, proteins and mRNAs. The cancer cells, designated as LC117 cells, were isolated from the pleural effusion of a patient with primary lung adenocarcinoma. The percent distributions of [14C]-acetate incorporated into PC and PG in the cancer cells were 55.7 and 1.1%, respectively. The disaturated species in total PC was 46.2%. Immunoblotting analysis using anti-SP-D monoclonal antibody revealed that the pleural effusion from a patient with lung adenocarcinoma contained SP-D. We determined the concentrations of SP-A and SP-D by enzyme-linked immunosorbent assay. The pleural effusions from this patient and the media incubated with cancer cells exhibited significant levels of SP-D as well as SP-A. Reverse transcriptase-polymerase chain reaction demonstrated that the tumor cells expressed mRNAs for SP-C as well as the other surfactant proteins. The results demonstrate that tumor cells from lung adenocarcinoma express all of surfactant-associated proteins, indicating that LC117 cells originate from alveolar type II cells. This study indicates that the combination of analyses of lipids, proteins and mRNAs in the cancer cells isolated from pleural effusion is useful to understand the property of lung adenocarcinoma.