Non-small cell lung cancer (NSCLC) is characterized by early metastasis and has the highest mortality rate among all solid tumors, with the majority of patients diagnosed at an advanced stage where curative therapeutic options are lacking. In this study, we identify a targetable mechanism involving TGFb elevation that orchestrates tumor progression in this disease. Substantial activation of this pathway was detected in human lung cancer tissues with concomitant downregulation of BAMBI, a negative regulator of the TGFb signaling pathway. Alterations of epithelialto-mesenchymal transition (EMT) marker expression were observed in lung cancer samples compared with tumor-free tissues. Distinct alterations in the DNA methylation of the gene regions encoding TGFb pathway components were detected in NSCLC samples compared with tumor-free lung tissues. In particular, epigenetic silencing of BAMBI was identified as a hallmark of NSCLC. Reconstitution of BAMBI expression in NSCLC cells resulted in a marked reduction of TGFb-induced EMT, migration, and invasion in vitro, along with reduced tumor burden and tumor growth in vivo. In conclusion, our results demonstrate how BAMBI downregulation drives the invasiveness of NSCLC, highlighting TGFb signaling as a candidate therapeutic target in this setting. Cancer Res; 76(13); 3785-801. Ó2016 AACR.

Expression of CEACAM1 was an independent prognostic factor in our patient population and can be used to stratify patients with adenocarcinomas of the lung into low-risk and high-risk groups. In contrast, the expression of sialyl Lewis X was of no prognostic relevance because it was expressed in 97% of all investigated tumors, and most likely has no influence on the function of CEACAM1 in this tumor entity.