Unravelling epigenetic drivers of chemo-resistance by optical editing of DNA-methylation in cells

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Aberrant DNA-methylation is a well-established driver of acquired resistance in ovarian cancer, although such epigenomic changes occur within a high background of passenger events and current epigenetic chemical biology tools generally affect the entire epigenome rather than locus specific. This makes it challenging with current biological tools to investigate the role of key locus specific methylation events in resistance mechanisms. To overcome this, epigenetic editing using CRISPRCas9 fused to epigenetic modifiers is increasingly being evaluated, although current approaches have the limitation of not being inducible. To identify key drivers of resistance and demonstrate phenotypic effects, we aim to generate novel chemical ligands that enable light-controlled positioning of DNA methylation writer and eraser (e.g. DNMTs and TETs) at specific genomic loci by means of CRISPRCas9. These chemical tools will disentangle the role of site-specific methylation in patient-derived cell-lines and xenografts. The light-controlled positioning of the epigenetic modifiers will enable temporal control of epigenetic modification, allowing evolution of resistance and its prevention or resensitisation to be studied in a time-dependent manner that is essential to study dynamic epigenetic based processes such as acquired resistance to chemotherapy.