DNA methylation, cell differentiation and genetic factors involved in radiosensitivity.

Despite its benefits in cancer treatment, ionising radiation (IR) can induce a series of adverse acute and/or long term effects. Studies on A-bomb survivors and radiotherapy patients have shown that acute whole-body exposure results in an increased risk for radiation-induced Acute Myeloid Leukaemia (r-AML), a bone marrow (BM) malignancy; whereas local-radiotherapy patients run the risk of developing acute and/or long term normal tissue reactions. Irradiated BM cells manifest persistent radiation-induced genomic instability. BM is one of the most susceptible tissues to radiation-induced cancer and one of the most radiosensitive tissues, which proposes a link between cancer susceptibility, genomic instability and radiosensitivity. The exact mechanism by which exposure of BM cells to IR leads to malignant transformation is still unclear, but the non-targeted nature of radiation-induced damage and genomic instability could suggest that an epigenetic mechanism is also involved; and DNA methylation is a good candidate. This thesis investigated genetic and epigenetic factors that may be involved in biological responses to ionising radiation exposure. Stem cell frequency is genetically determined in mouse haemopoiesis and is possibly part of the equation that defines cancer risk. Global DNA methylation levels were assessed in control haemopoietic tissues and radiation-induced leukaemias. The methylation status of haemopoietic malignancies reflects that of their untransformed tissue. Additionally, DNA methylation levels of untransformed haemopoietic tissues were found to correlate with their relative radiosensitivity in vivo. In vivo responses to ionising radiation were found to be under the influence of both genetic and epigenetic factors, highlighting the complexity of such biological reactions

QTL analyses of lineage-negative mouse bone marrow cells labeled with Sca-1 and c-Kit

Differences in the number of functionally and/or phenotypically defined bone marrow cells in inbred mouse strains have been exploited to map quantitative trait loci (QTL) that determine the variation in cell frequency. To extend this approach to the differences in the stem/progenitor cell compartment in CBA/H and C57BL/6 mice, we have exploited the resolution of flow cytometry and the power of QTL analyses in 124 F2 mice to analyse lineage negative (Lin-) bone marrow cells according to the intensity of labelling with Sca-1 and c-Kit. In the Lin- Sca-1+ c-Kit+ enriched population six quantitative trait loci (QTL) were identified – one significant and five suggestive. Whereas previous in vitro clonogenic, LTIC-IC, CAFC day 35, and flow cytometry each identified different QTL, our approach identified the same or very similar QTL at all three loci (Chromosome 1, 17 and 18) as well as QTL on chromosomes 6 and 10. In silico analyses implicate haematopoietic stem cell homing involving Cxcr4 and Cxcl12 as being the determining pathway. The mapping of the same or very similar QTLs in independent studies using different assay(s) suggests a common genetic determinant, and thus reinforces the biological and genetic significance of the QTL. These data also suggest that mouse bone marrow cell sub-populations can be functionally, phenotypically and genetically defined

Additional file 3: Figure S2. of Somatic drivers of B-ALL in a model of ETV6-RUNX1; Pax5 +/− leukemia

Accelerated tumor development in Ink4a−/−; Etv6 +/RUNX1-SB mice. (PPT 162 kb

Additional file 2: Figure S1. of Somatic drivers of B-ALL in a model of ETV6-RUNX1; Pax5 +/− leukemia

Pathway analysis showing enrichment for genes involved in early B-cell function in our model. (PPT 166 kb

Additional file 1: of Somatic drivers of B-ALL in a model of ETV6-RUNX1; Pax5 +/− leukemia

List of targeted exome baits. The file contains a list of genes that were captured as part of the targeted exome sequencing performed as part of this study. (XLSX 53 kb

Mannose metabolism inhibition sensitizes acute myeloid leukaemia cells to therapy by driving ferroptotic cell death

Resistance to standard and novel therapies remains the main obstacle to cure in acute myeloid leukaemia (AML) and is often driven by metabolic adaptations which are therapeutically actionable. Here we identify inhibition of mannose-6-phosphate isomerase (MPI), the first enzyme in the mannose metabolism pathway, as a sensitizer to both cytarabine and FLT3 inhibitors across multiple AML models. Mechanistically, we identify a connection between mannose metabolism and fatty acid metabolism, that is mediated via preferential activation of the ATF6 arm of the unfolded protein response (UPR). This in turn leads to cellular accumulation of polyunsaturated fatty acids, lipid peroxidation and ferroptotic cell death in AML cells. Our findings provide further support to the role of rewired metabolism in AML therapy resistance, unveil a connection between two apparently independent metabolic pathways and support further efforts to achieve eradication of therapy-resistant AML cells by sensitizing them to ferroptotic cell death. </p