Epigenetic and Oncogenic Inhibitors Cooperatively Drive Differentiation and Kill KRAS <i>-</i> Mutant Colorectal Cancers

Abstract

Abstract Current treatments for KRAS-mutant colorectal cancers are often limited by cellular plasticity and rewiring responses. Here we describe a promising therapeutic strategy that simultaneously targets epigenetic and oncogenic signals. Specifically, we show that inhibitors of histone methyltransferase, EZH2, synergize with various rat sarcoma virus (RAS) pathway inhibitors and promote dramatic tumor regression in vivo. Together these agents cooperatively suppress Wingless and Int-1 (WNT)-driven transcription and drive colorectal cancers into a more differentiated cell state by inducing the Groucho/transducin-like enhancer corepressor, TLE4, along with a network of WNT pathway inhibitors and intestinal differentiation proteins. However, these agents also induce the proapoptotic protein BCL2 modifying factor (BMF), which subsequently kills these more differentiated cells. Accordingly, cell death can be prevented by activating β-catenin, by blocking differentiation, or by ablating BMF expression. Collectively, these studies reveal a new therapeutic approach for treating KRAS-mutant colorectal cancers and illustrate a critical convergence of EZH2 and RAS on oncogenic WNT signals, intestinal differentiation, and apoptosis. Significance: Combined EZH2 and RAS pathway inhibitors kill KRAS-mutant colorectal cancer cells and promote durable tumor regression in vivo. These agents function by cooperatively suppressing the WNT pathway, driving differentiation, and epigenetically reprogramming cells to permit the induction of apoptotic signals, which then kill these more differentiated tumor cells.