Lung cancer is a major health-care problem in industrialized countries. With reference to its therapeutic consequences and major histological variations, it is divided into two subgroups - SCLC (small-cell lung cancer) and NSCLC (non-small-cell lung cancer). As an important factor of cell-cell and cell-substratum interaction, cell adhesion molecules (CAMs) seem to play a key role in tumor-cell migration and invasion that lead to metastases. We investigated human lung tumor cell lines established from histologically documented neoplastic lesions taken in our operating theater. Immunohistological screening showed differences in E-cadherin expression with no clear predominance of SCLC or NSCLC cell lines. Using an invasion model with Matrigel Matrix and a migration assay, we could demonstrate a more aggressive behavior pattern in E-cadherin-negative cell lines. We transfected E-cadherin cDNA into a formerly negative cell line showing strong invasive behavior in the initial tests in order to investigate the role of E-cadherin in this process. In this study, we examined E-cadherin cDNA transfection in human bronchial carcinoma cells. At present, transfection is stable with a follow-up time of one year. We could demonstrate that cell lines were remarkably less invasive after transfection of E-cadherin in the invasion model with Matrigel Matrix. These results indicate that the E-cadherin CAM plays an important role in lung tumor invasion and metastasis. Further studies are in progress to confirm these findings and to describe a possible role of this CAM in tumor therapy.