Detection of thrombomodulin in human lung cancer cells

Thrombomodulin (TM), which usually exists in vascular endothelial cells and exerts an anticoagulant activity, was detected by Western blot analyses and immunocytochemical staining using three anti-TM monoclonal antibodies in cultured cell lines derived from a squamous cell carcinoma and an adenocarcinoma of the lung, but was not detected in a cell line derived from a small cell carcinoma. Functional assays indicated that TM detected in these cells was functionally active. The presence of TM in 22 specimens of surgically removed lung cancer tissue was also examined by an immunohistochemical method. TM was present along the cell membranes in 4 (36%) of 11 squamous cell carcinomas examined, but was not detected in 10 adenocarcinomas and 1 large cell carcinoma examined. Because TM is identical to fetomodulin, which modulates embryogenesis, the authors have concluded that TM is an oncodevelopmental antigen. The authors have also suggested that functionally active TM on lung cancer cells may modulate cancer cell behaviors in such ways as exhibiting anticoagulant activity.