A demethylation screen identifies novel targets of epigenetic regulation in lung cancer

Abstract

Lung cancer is the leading cause of death by cancer worldwide. There is an urgent need to expand the range of molecular targets and therapies, as well as biomarkers to diagnose disease, stratify high-risk patients and predict response to therapy. The importance of epigenetic transcriptional silencing as a mechanism of tumour suppressor gene inactivation is well recognized. DNA methylation is the dominant process necessary for this epigenetic inactivation and represents a valuable source of new biomarkers and therapeutic targets. The objective of this project was to seek de novo, candidate lung cancer tumour suppressor genes that are subject to transcriptional silencing by means of promoter methylation. Selected candidates would have their potential as prognostic biomarkers in non-small cell lung cancer characterized and any functional consequences of their silencing investigated. A genome-wide, microarray-based screen involving methylation and gene expression analysis in a panel of cell lines, incorporating treatment with the demethylating agent 5-aza-2′-deoxycytidine, was completed. From this, the TGF-β accessory receptor Endoglin and the transcription factor ZNF655 were identified and confirmed as novel genes subject to methylation-dependent silencing in lung cancer. Methylation of both genes was detected in primary lung cancer tissues. There was a strong trend towards shorter survival for patients with methylated Endoglin in two separate cohorts. Functional experiments demonstrated that silencing of Endoglin leads to increased invasion and epithelial to mesenchymal transition (EMT) in 2 NSCLC cell lines in vitro. In summary, I have validated the use of a high-throughput microarray screening strategy to identify novel epigenetically silenced tumour suppressor genes. I have identified Endoglin and ZNF655 as common targets of epigenetic silencing in lung cancer and have shown a functional role for Endoglin silencing in lung cancer progression.

Date of Award	2014
Original language	English
Awarding Institution	University of Brighton