Genome-wide maps of transcriptomic and epigenomic state in melanoma cell lines

A mechanistic relationship between tumor epigenetic plasticity and nongenetic adaptive resistance to therapy is described, with MAPK inhibition of BRAF-mutant melanoma cells providing the model system. Upon inhibition, these largely melanocytic cells undergo reversible cell-state changes, ultimately yielding a drug-resistant mesenchymal-like phenotype. Epigenomic and transcriptomic kinetic studies, coupled with information theory and dynamic system modeling, revealed that, after just 3-days of treatment, RelA drives chromatin remodeling to establish an epigenetic program encoding long-term phenotype changes. Specifically, RelA transcriptionally inhibits SOX10 and NFKBIE through recruiting KDM5B and HDAC1 to down-regulate histone marks H3K4me3 and H3K27ac at their promoter regions. Suppression of SOX10 mediates melanoma regression towards drug-refractory phenotypes. These findings were confirmed in melanoma patients under MAPK inhibitor treatment, providing mechanistic insights into resistance-leading epigenetic reprogramming triggered following drug exposure.