Data from DNA Methyltransferase Inhibition Reverses Epigenetically Embedded Phenotypes in Lung Cancer Preferentially Affecting Polycomb Target Genes

Abstract

<div>Abstract<p><b>Purpose:</b> Cancer cell phenotypes are partially determined by epigenetic specifications, such as DNA methylation. Metastasis development is a late event in cancerogenesis and might be associated with epigenetic alterations.</p><p><b>Experimental Design:</b> An <i>in vivo</i> selection approach was used to generate highly aggressive non–small cell lung cancer (NSCLC) cell lines (A549 and HTB56) followed by genome-wide DNA methylation analysis. Furthermore, the therapeutic effects of the epigenetic agent azacytidine on DNA methylation patterns and the <i>in vivo</i> phenotypes were explored.</p><p><b>Results:</b> Widespread changes of DNA methylation were observed during development of highly aggressive cell lines. Up to 2.5% of the CpG-rich region was differentially methylated as identified by reduced representation bisulfite sequencing compared with the less aggressive parental cell lines. DNA methyltransferase inhibition by azacytidine reversed the prometastatic phenotype; this was highly associated with the preferential loss of DNA methylation at sites that were hypermethylated during the <i>in vivo</i> selection. Of note, polycomb (PRC2) binding sites were particularly affected by DNA methylation changes after azacytidine exposure that persisted over time.</p><p><b>Conclusions:</b> We could show that metastatic capability of NSCLC is closely associated with DNA methylome alterations. Because inhibition of DNA methyltransferase reversed metastasis-prone phenotype, epigenetic modulation seems to be a potential therapeutic approach to prevent metastasis formation. <i>Clin Cancer Res; 20(4); 814–26. ©2013 AACR</i>.</p></div>