Reprogramming oncogene levels through gene body hypermethylation in RTK-driven cancer

While promoter epigenetic modifications have been linked to tumor suppressor silencing in cancers, modifications in gene body regions has been largely neglected. Using a genetic setting in which subtle enhanced levels of non-oncogenic receptor tyrosine kinases (RTKs) become progressively pathological, we show that reprogrammed CpG island (CGI) methylation locks cells into tumorigenicity. By focusing on gene bodies, we found an enrichment of hypermethylated CGI similar to that reported in cancer patients. Gene body CGI hypermethylation correlates with decreased H3K27me3 modification and enhanced transcription for a proportion of genes, which act as oncogenes in cancer cells. Collectively, our results illustrate that tumorigenesis is ensured by an increase dosage of a set of oncogenes through an epigenetic reprogramming involving gene body CGI hypermethylation. Overall design: Genomic DNA from dissected Alb-R26Met tumors (n=10) and control livers (n=3) was used to analyze the DNA methylation profile