Table of Contents

Israeli Principal Investigator

Amir Eden, Hebrew University, Jerusalem

DKFZ Principal Investigator

Frank Lyko, Division of Epigenetics, German Cancer Research Center

Approaches and Achievements

Drug-induced demethylation of the L1-cMet promotor region. Bisulfite sequencing demonstrates almost complete (99%) methylation in HCT116 colon carcinoma cells, which becomes substantially reduced following treatment with the demethylating drugs decitabine (DAC, 59%) and azacytidine (AZA, 22%). Open circles represent unmethylated CpG dinucleotides, closed circles represent methylated CpG dinucleotides. | © dkfz.de

DNA methylation plays an important role in development and disease. More specifically, proper genomic methylation patterns are required for faithful epigenetic programming and for the maintenance of genome stability. Results from the Israeli Principal Investigator raised the possibility that demethylating drugs (azacytidine and decitabine) induced the expression of an illegitimate LINE1-cMet fusion transcript (L1-cMet) from the antisense LINE-1 promoter. This observation was of great importance, because it provided a potential paradigm for studying epigenetic side effects of demethylating drugs. We have now performed a comprehensive analysis for epigenetic activation of illegitimate transcripts in human cancer cell lines. Using bisulfite sequencing and quantitative real-time PCR we have obtained evidence for the drug-induced generation of illegitimate transcription at several loci in the human genome. We have confirmed drug-induced epigenetic changes by chromatin immunoprecipitation and have shown that induction of the LINE1-cMet fusion transcript is associated with profoundly reduced cMet signalling. Our results have thus uncovered a major safety issue for epigenetic therapy with demethylating drugs.