Breast cancer cell lines treated with EZH2 inhibitor compounds

Loss of H3K27me3 repressive chromatin histone marks, maintained by the histone methyltransferase (HKMT) EZH2, may lead to reversal of epigenetic silencing in tumor cells and have therapeutic potential. Using a cell-based assay, we have identified three compounds from a HKMT inhibitor chemical library which re-express H3K27me3 mediated, silenced genes. Chromatin immunoprecipitation verified a decrease in silencing marks (H3K27me3, H3K9me3) and importantly an increase in active marks (H3K4me2/3, H3K27ac) at the promoter of re-expressed genes. Compound treated breast tumor cells induced enrichment for genome-wide changes in expression of known target genes for EZH2 and induced cell growth inhibition: with most sensitive breast tumor cell lines having low EZH2 protein expression, while a normal epithelial breast line was least sensitive. Agilent SurePrint G3 Human 8x60k two-colour microarrays were used to profile gene expression changes induced by treatment with drug compounds in MDA MB-231 cells, both at 24h and 48h. 4 replicates were used for each drug, time combination. A separate untreated control sample was used for comparison with each replicate.