Single cell analyses reveals a non-canonical EZH2 activity as main driver of RA resistance in PLZF/RARA leukemia [ChIP-seq]

Resistance to treatment is due to the heterogeneity of the tumor which contains a subset of cancer cells that escape treatment and are responsible for the relapse. We took advantage of the PLZF/RARA retinoic acid (RA) resistant acute promyelocytic leukemia (APL) model to catch relapse-initiating cell features and their vulnerabilities. By developing an integrative single-cell multi-omics analysis (scRNA-seq and scATAC-seq), we uncovered transcriptional and chromatin heterogeneity of the PLZF/RARA APL blasts. We highlighted a subset of cells insensitive to RA-induced differentiation with a strong DNA repair signature ("Rep" cluster) and exhibiting a fine tuned transcriptional network targeting the histone methyltransferase Ezh2. Combining epigenomic profiling with mouse-derived models for Ezh2 catalytic inhibition or total KO, we revealed an independent methyltransferase Ezh2 activity linked to RA resistance. These findings demonstrate the power of single-cell multi-omics integration to highlight paths to sensitize therapy-resistant leukemia cells ChIPseq for H3K27ac, H3K27me3, H3K4me3, H3K4me1 performed on murine purified promyelocytes expressing the PLZF/RARA oncogonic fusion