Investigating The Role Of Epigenetic Enzymes In Breast Cancer

The past 40 years of research greatly transformed our understanding of breast cancer disease. The results of basic scientific findings were successfully translated into the development of therapeutic agents. Although enormous progress has been made, many important questions still remain. Developing specific inhibitors targeting cellular epigenetic program becomes one of the most active areas of current drug discovery efforts. Many new epigenetic enzymes become drug targets for cancer intervention. The work presented here was focused towards understanding the role of KDM5s and EZH2 epigenetic enzymes in breast cancer as potential targets for breast cancer intervention. These enzymes are known to regulate histone H3 lysine 4 and 27 trimethylation states, which largely affect genome wide transcriptional programs. Our preliminary studies have identified breast cancer patient groups whose survival outcome correlated with expression of KDM5s and EZH2 bound genes and respective H3K4me3 and H3K27me3 gene loci. In order to link deregulation of KDM5 and EZH2 proteins to breast cancer development, we looked for the evidence of correlation between the expressions level of KDM5s and EZH2 and breast cancer disease aggressiveness. This data informs development of strategies reducing expression levels of these enzymes as well as targeting their enzymatic activity. To test the effects of reduced expression level on breast cancer cell growth, we generated knock down of KDM5s and EZH2 in a variety of cancer cell lines and compared it to non-transformed mammary epithelial cells. By performing a variety of cell culture-based assays as well as conducting gene expression studies, we next aimed at the identification of cancer cell characteristics controlled by these epigenetic enzymes. Decrease in expression of these enzymes resulted in less aggressive cancer phenotype affecting cell proliferation, invasion, migration and survival. We further investigated the potency of selective EZH2 inhibitors on reducing breast cancer cell growth. Based on these results, we applied CRISPR-Cas9 genome engineering system to generate a breast cancer genome encoding catalytically inactive forms of KDM5s and EZH2. This novel epigenetic cancer model enables studies into causal role of epigenetic activities in breast cancer tumorigenesis, which will move our outstanding of cancer epigenetic mechanisms beyond incremental knowledge.