Corruption of Transcription Factor Networks in Acute Myeloid Leukaemia

Transcription factors form highly regulated and complex networks. In Acute Myeloid Leukaemia, driver and secondary mutations result in major rewiring of these circuits, resulting in a cancer phenotype. In this thesis, we examined two prominently rewired nodes in AML, Wilms Tumour 1 (WT1) and the Activator Protein-1 (AP-1) family of Transcription factors in order to elucidate the genomic regions at which these factors bind, how perturbation affects transcription and what cellular phenotype is conferred. We studied these transcription factors in the context of two main AML subtypes, t(8;21) and FLT3-ITD mutated AML as well as in healthy CD34+ stem cells. We blocked AP-1 binding through the expression of a dominant negative FOS peptide which resulted in decreased leukaemic growth in vitro and in vivo. We found that one main mechanism for this reduced growth was a G1 cell cycle arrest, through regulation of the Cyclin D2 (CCND2) gene. This finding was then exploited therapeutically through use of the small molecule inhibitor Palbociclib to inhibit leukaemic growth. We also found that overexpression of endogenous WT1 led to increased leukaemic growth whilst knockdown of WT1 led to decreased leukaemic growth. These effects upon leukaemic growth occurred in an isoform-specific fashion with WT1 +KTS isoforms increasing leukaemic growth in contrast to WT1 –KTS isoforms which decreased leukaemic growth. By assessing the binding sites of these isoforms and differential splicing we uncovered distinct alterations to the epigenome and transcriptome. This also enabled us to propose models of how these factors act within a signalling network