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The role of RUNX3 in acute myeloid leukaemia and normal human haematopoietic development

Menezes, Ana Catarina 2020. The role of RUNX3 in acute myeloid leukaemia and normal human haematopoietic development. PhD Thesis, Cardiff University.
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Abstract

The t(8;21)(q22;q22) is a common abnormality in acute myeloid leukaemia (AML). This translocation encodes the RUNX1-ETO fusion protein which blocks the differentiation of human CD34+ haematopoietic stem and progenitor cells (HSPC) and promotes their self-renewal, hallmarks of AML. Transcriptional repression of RUNX3 by RUNX1-ETO has been identified in t(8;21) AML but is strongly expressed in AML without core binding factor abnormalities. This study examines RUNX3 expression during normal and malignant human haematopoiesis and the consequences of increased and reduced RUNX3 expression for erythroid and myeloid cell development. Analysis of transcriptomic data showed that RUNX3 mRNA expression is downregulated during normal haematopoietic development. In AML, variable RUNX3 expression across different subtypes was observed, with core binding factor AML being associated with RUNX3 downregulation whilst AML patients with complex cytogenetics overexpressed RUNX3 compared to normal karyotype. The impact of altering RUNX3 expression on haematopoiesis was determined by transducing human HSPC with RUNX3 overexpression or shRNA knockdown vectors. RUNX3 overexpression inhibited both erythroid and myeloid growth and differentiation. Colony forming ability was also reduced but accompanied by increased self-renewal of progenitors. Reduced RUNX3 expression negatively impacted the survival of erythroid cells but did not cause significant effects in erythropoiesis and myelopoiesis. Attempts were also made to show whether RUNX3 could rescue the suppression of haematopoietic development seen in RUNX1-ETO-expresing cells. Further RNA-sequencing analysis showed that RUNX3 overexpression dysregulates the HSPC transcriptome, characterised by the repression of important erythroid-related genes, including KIT and LMO2. Differentiation markers GYPA, CD36 and ITGAM were also downregulated by RUNX3, validating the RUNX3-induced phenotypic changes during erythroid and myeloid development. In addition, cross-regulation among RUNX proteins was observed, as RUNX3 overexpression downregulated RUNX1 and RUNX2 levels in HSPC. In conclusion, this study shows that downregulation of RUNX3 expression is important for normal human erythroid and myeloid development. The ability of RUNX3 overexpression to inhibit differentiation suggest that RUNX3 could be a driver of leukaemogenesis.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Medicine
Date of First Compliant Deposit: 22 January 2021
Last Modified: 22 Jan 2021 15:54
URI: http://orca.cardiff.ac.uk/id/eprint/137896

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