Controlling Metastasis and Immune Signaling in Breast Cancer Cells with Epigenetic Engineering

The role of chromatin-driven epigenetics in drug resistant cancers is becoming increasingly clear with the growing body of genome-wide expression data. Epigenetic therapy, a class of drugs that block enzymes that regulate protein-DNA structures (chromatin) in the nucleus, is gaining traction as a way to reactivate silenced anti-cancer genes in cancer cells. Triple negative breast cancer (TNBC) disproportionately affects African-American women and shows high rates of relapse after chemotherapy. TNBC responds moderately to leading epigenetic drugs in vitro, in vivo, and in clinical trials. Improvement of epigenetic therapy for TNBC is impeded by a lack of chromatin-targeting pharmacological mechanisms. Inhibition of hyperactive EZH2, which leads to depletion of histone H3 lysine 27 (H3K27me3), passively affects gene regulation, affects cellular processes outside of chromatin, and is therefore not ideal for targeted epigenetic control. Our goal is to engineer histone-reader-effector proteins, which are central components of the natural chromatin machinery. We set out to determine the efficacy of a H3K27me3-binding transcriptional activator, Polycomb-based Transcription factor (PcTF), in TNBC cells compared to small molecule inhibitors of EZH2. In order to determine the pharmacological potential of PcTF and inhibitors, we have designed XTT experiments to measure IC50 values for several breast cancer cell lines. So far, we have observed varying sensitivities of TNBC cells to a panel of EZH2 inhibitors. We have developed a cell-penetrating PcTF to support dose-response experiments to generate results (IC50) that can be compared with inhibitor treatments. We expect that PcTF will show anticancer effects since we previously demonstrated that transgenic over-expression of PcTF activates genes that reverse the epithelial-mesenchymal transition (EMT) and stimulate the T-cell signaling pathway. In summary, we have established a fusion protein-based strategy to expand epigenetic therapy beyond small molecule inhibitors. Efforts to extend our viability (XTT) analysis to apoptosis, invasion, and metastasis are underway.