Abstract
Epithelial-mesenchymal transition (EMT) program, which facilitates tumor metastasis, stemness and therapy resistance, is a reversible biological process that is largely orchestrated at the epigenetic level under the regulation of different cell signaling pathways. EMT state is often heterogeneous within individual tumors, though the epigenetic drivers underlying such heterogeneity remain elusive. In colon cancer, hyperactivation of the Wnt/beta-catenin signaling not only drives tumor initiation, but also promotes metastasis in late stage by promoting EMT program. However, it is unknown whether the intratumorally heterogeneous Wnt activity could directly drive EMT heterogeneity, and, if so, what are the underlying epigenetic driver(s). Here, by analyzing a phenotypically and molecularly heterogeneous colon cancer cell line using single-cell RNA sequencing, we identified two distinct cell populations with positively correlated Wnt activity and EMT state. Integrative multi-omics analysis of these two cell populations revealed RUNX2 as a critical transcription factor epigenetically driving the EMT heterogeneity. Both in vitro and in vivo genetic perturbation assays validated the EMT-enhancing effect of RUNX2, which remodeled chromatin landscape and activated a panel of EMT-associated genes through binding to their promoters and/or potential enhancers. Finally, by exploring the clinical data, we showed that RUNX2 expression is positively correlated with metastasis development and poor survival of colon cancer patients, as well as patients afflicted with other types of cancer. Taken together, our work revealed RUNX2 as a new EMT-promoting epigenetic regulator in colon cancer, which may potentially serve as a prognostic marker for tumor metastasis.