Hiding in Plain Sight: Epigenetic Plasticity in Drug-Induced Tumor Evolution

Abstract

Cancer is a heterogeneous disease with key differences at the cellular and molecular levels. Acquisition of these differences during the course of tumor development manifests into functional and phenotypic heterogeneity leading to tumor diversity, also referred to as intra-tumor heterogeneity (ITH). Within a tumor, there are subpopulations of cells capable of tumor initiation and maintenance. These cells often exhibit resistance to standard-of-care anti-cancer drugs. However, the role of various subpopulations (clones) in drug resistance remains to be investigated. Moreover, the jury is still out about whether drug resistance is a result of clonal selection of preexisting cells, or the cells acquire resistance by dynamic re-wiring of their epigenome. Therefore, we investigated the drug-induced tumor evolution in patient-derived primary cells of head and neck squamous cell carcinoma. Our data demonstrated the role of a preexisting poised epigenetic state in drug-induced adaptive evolution of tumor cells. Importantly, the combination of chemotherapy and epigenetic inhibitors can prevent/delay drug-induced tumor evolution.

Keywords: cellular reprogramming; drug-resistance; epigenetic plasticity; single cell RNA-sea; tumor evolution.

Figure 1.

Implication of epigenetic plasticity in drug resistance. Tumor cells exist in the continuous of epithelial to mesenchymal cell states. Cells can acquire drug resistance by Darwinian selection of preexisting cell states (increase epithelial or mesenchymal properties) or by adapting to different cell states (epithelial to mesenchymal). Preexisting poised chromatin state provides a platform for epigenetic plasticity–mediated cellular reprogramming during drug-induced tumor evolution.