Presence of elevated levels of platelet-derived growth factor (PDGF) in lung adenocarcinoma pleural effusions.

Significant tumor stroma development is a specific feature of adenocarcinoma of the lung in comparison to small-cell lung cancer (SCLC). The fibrotic component of tumor stroma is thought to result from the migration and local replication of mesenchymal cells in response to the presence of cytokines. One of them, platelet-derived growth factor (PDGF), is a chemotactic and growth factor for mesenchymal cells. Since several lung adenocarcinoma cell lines, but not SCLC cell lines, have been shown in vitro to express PDGF genes, we evaluated pleural effusions for the presence of PDGF in patients with adenocarcinoma of the lung, SCLC, or nonmalignant pleural effusions. In adenocarcinoma of the lung, PDGF levels in pleural effusions were higher than in SCLC and in nonmalignant pleural effusions and were associated with the presence of a growth-promoting activity for fibroblasts due, in part, to the presence of PDGF. This observation suggests the role of PDGF in tumor stroma formation in adenocarcinoma of the lung.