Project description:The histone methyltransferases DOT1L (H3K79me1,2,3 KMT, "activating" chromatin mark) and EZH2 (H3K27me1,2,3 KMT, "silencing" mark) have both been shown to be required for growth and survival of KMT2A rearranged AML cells. Both KMTs have been shown to modulate expression of HOXA cluster genes, albeit for EZH2 this has not been shown in the context of KMT2A rearranged AML, but in other subtypes of AML. We asked what transcriptional effects dual inhibition of DOT1L and EZH2 has in KMT2A rearranged AML.
Project description:The histone methyltransferases DOT1L (H3K79me1,2,3 KMT, "activating" chromatin mark) and EZH2 (H3K27me1,2,3 KMT, "silencing" mark) have both been shown to be required for growth and survival of KMT2A rearranged AML cells. Both KMTs have been shown to modulate expression of HOXA cluster genes, albeit for EZH2 this has not been shown in the context of KMT2A rearranged AML, but in other subtypes of AML. We asked what transcriptional effects dual inhibition of DOT1L and EZH2 has in KMT2A rearranged AML.
Project description:Doxorubicin is a widely used chemotherapeutic drug that intercalates between DNA base-pairs and posions Topoisomerase II, although the mechanistic basis for cell killing remains speculative. Here we show that both anthracyclines and Topoisomerase II poison cause enhanced DNA double-strand breaks around CpG island promoters of active genes genome-wide. We propose that torsion-based enhancement of nucleosome turnover exposes promoter DNA, ultimately causing DNA breaks around promoters that contributes to cell killing. We have analyzed mouse squamous cell carcinoma cells treated with doxorubicin, aclarubicin and etoposide. The direct in situ Breaks Labeling, Enrichment on Streptavidin (BLESS, PMID 23503052) method was used for mapping DNA double-strand breaks genome-wide.
Project description:Acute myeloid leukemia (AML) is a disease with poor outcome but patients harbouring certain chromosomal rearrangements or complex karyotypes have particularly adverse prognosis. For these patients, targeted therapies have not yet made a significant clinical impact. To understand the molecular landscape of poor risk AML we profiled 55 poor risk AML patients using a multiomics approach that included transcriptomics (n=39), proteomics (n=55), phosphoproteomics (n=55) and an ex vivo drug sensitivity screening (482 compounds tested in at least 30 patients). We identified a phosphoproteomics signature that define two biologically distinct groups of KMT2A rearranged leukaemia, which we term MLLGA and MLLGB. MLLGA presented increased DOT1L phosphorylation, HOXA gene expression, CDK1 activity and phosphorylation of proteins involved in RNA metabolism, replication and DNA damage when compared to MLLGB and no KMT2A rearranged samples. MLLGA was particularly sensitive to 15 compounds including genotoxic drugs and inhibitors of mitotic kinases and IMPDH relative to other cases. The expression of IMPDH2 and multiple nucleolar proteins was higher in MLLGA and correlated with the response to IMPDH inhibition in KMT2A rearranged leukaemia, suggesting a role of the nucleolar activity in sensitivity to IMPDH inhibition. In summary, our multilayer molecular profiling of poor risk AML matched to the response to hundreds of compounds identified a phosphoproteomics signature that define two biologically and phenotypically distinct groups of KMT2A rearranged leukaemia. These data provide a rationale for the development of specific therapies for KMT2A subgroups characterised by the MLLGA phosphoproteomics signature identified in this study.
Project description:Mapping physiological double strand breaks (DSBs) in cancer cells uncovers transcription-coupled repair mechanism at oncogenic super-enhancers in which RAD51 of the homologous recombination pathway plays a key role supporting the hyper-transcription of related oncogenes.
Project description:Activating mutations in kinase/PI3K/RAS signaling pathways are common in acute leukemia with KMT2A rearrangements (KMT2A-R). These mutations are often subclonal and their biological impact remain unclear. Using a retroviral acute myeloid leukemia model, we demonstrate that NRASG12D, FLT3ITD, and FLT3N676K accelerates KMT2A-MLLT3 leukemia onset. Importantly, also the presence of subclonal FLT3N676K in KMT2A-R leukemic cells shorten disease latency, possibly by providing stimulatory factors such as Mif. Acquired de novo mutations in Braf, Cbl, Kras, and Ptpn11 were identified in KMT2A-MLLT3 driven leukemia and favored clonal expansion. KMT2A-MLLT3 leukemia with an activating mutation enforce Myc- and Myb transcriptional modules, whereas KMT2A-MLLT3 leukemias lacking activating mutations displayed upregulation of signal transduction pathways. Our results provide new insight into the biology of KMT2A-R leukemia and highlights the importance of activated signaling as a contributing driver in this disease.
Project description:High concentration of NaCl increases DNA breaks both in cell culture and in vivo. The breaks remain elevated as long as NaCl concentration remains high and are rapidly repaired when the concentration is lowered. Repair of the breaks after NaCl is reduced is accompanied by formation of foci containing phosphorylated H2AX (γH2AX), which occurs around DNA double-strand breaks and contributes to their repair. By chromatin immunoprecipitation using anti-γH2AX antibody, followed by massive parallel sequencing (ChIP-Seq), we find that during repair of double–strand breaks induced by high NaCl, γH2AX is predominantly localized to regions of the genome devoid of genes (“gene deserts”), indicating that the high NaCl-induced double-strand breaks are located there. Localization to gene deserts helps explain why the DNA breaks are less harmful than are the random breaks induced by genotoxic agents such as UV radiation, ionizing radiation and oxidants. We propose that the universal presence of NaCl around animal cells has directly influenced the evolution of the structure of their genomes.