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.

Background Lung cancer is the leading cause of cancer-related death in most western countries in both, males and females, accounting for roughly 20–25% of all cancer deaths. For choosing the most appropriate therapy regimen a definite diagnosis is a prerequisite. However, histological characterization of bronchoscopic biopsies particularly with low tumor cell content is often challenging. Therefore, this study aims at (a) determining the value of DNA methylation analysis applied to specimens obtained by bronchoscopic biopsy for the diagnosis of lung cancer and (b) at comparing aberrantly CpG loci identified in bronchoscopic biopsy with those identified by analyzing surgical specimens. Results We report the HumanMethylation450-based DNA methylation analysis of paired samples of bronchoscopic biopsy specimens either from the tumor side or from the contralateral tumor-free bronchus in 37 patients with definite lung cancer diagnosis and 18 patients with suspicious diagnosis. A differential DNA methylation analysis between both biopsy sites of patients with definite diagnosis identified 1303 loci. Even those samples were separated by the set of 1303 loci in which histopathological analysis could not unambiguously define the dignity. Further differential DNA methylation analyses distinguished between SCLC and NSCLC. We validated our results in an independent cohort of 40 primary lung cancers obtained by open surgical resection and their corresponding controls from the same patient as well as in publically available DNA methylation data from a TCGA cohort which could also be classified with high accuracy. Conclusions Considering that the prognosis correlates with tumor stage at time of diagnosis, early detection of lung cancer is vital and DNA methylation analysis might add valuable information to reliably characterize lung cancer even in histologically ambiguous sample material.

<p>Activity of the TGF-beta pathway in tumor-free lung and lung cancer (S1); Validation of the microarray data for individual targets with qRT-PCR assay (S2); Expression of EMT-related proteins in human lung tumor tissues and tumor-free lung (S3); Secretion of TGF-beta and expression of the pathway components in NSCLC cell lines (S4); Activation of TGF-beta pathway members and expression of EMT markers in lung cancer cells with BAMBI reconstitution (S5); Verification of DNA methylation values determined by HumanMethylation450K BeadChip analysis by performing bisulfite pyrosequencing (S6); siRNA-mediated knockdown of BAMBI expression in A549 cell line enhances TGF-beta-induced signaling (S7); siRNA-mediated knockdown of BAMBI expression in the squamous cell carcinoma cell line SK-MES1 enhances TGF-beta-induced signaling (S8); Human alveolar epithelial cells type II (AECII) cells express low amount of SMAD3 (S9); GFP- and BAMBI-GFP-positive A549 cells are present in the mice lungs at the time of sacrifice (S10).</p>