Increased TGFβ₁ plasma level in patients with lung cancer: Potential mechanisms

Background: Plasma transforming growth factor β₁ (TGFβ₁ levels are elevated in patients with lung cancer. As TGFβ₁ is mainly found in platelets and as nonmalignant pulmonary diseases (NMPD) are frequently associated with lung cancer, we investigated the potential contribution of platelet degranulation and/or of a concomitant NMPD to the increased plasma levels of TGFβ₁ reported in patients with lung cancer. Materials and Methods: Blood samples were collected in duplicate from 30 healthy subjects, 14 patients suffering from NMPD and 37 patients with lung cancer. The platelet count was determined and the samples were processed to obtain plasma. One sample was collected in EDTA (EDTA plasma) and the other in a mixture inhibiting platelet degranulation (PIM plasma). TGFβ₁ concentrations and β-thromboglobulin (βTG) levels, an index of platelet degranulation, were measured in both plasma samples. Results: TGFβ₁ and βTG plasma levels measured in PIM plasma were lower than those obtained in EDTA plasma. With respect to PIM plasma, both TGFβ₁ and TG levels were higher in patients with lung cancer than those with NMPD and in healthy individuals. In patients with NMPD, only TGFβ₁ levels were increased as compared to healthy controls, βTG levels being similar. Conclusion: Methods for collecting and processing blood samples are critical in determining reliable circulating TGFβ₁ levels. Increased TGFβ₁ plasma levels observed in patients with lung cancer are related, at least partly, to concomitant NMPD and also to platelet degranulation as proved by increased βTG levels.