DISSECTION OF TRANSCRIPTIONAL VULNERABILITIES IN ACUTE MYELOID LEUKEMIA
Genetics and Genomics
Biochemistry, Biophysics, and Structural Biology
Acute myeloid leukemia (AML) is an aggressive blood cancer characterized by uncontrolled self-renewal and blocked differentiation of myeloid precursor cells. Some of the most recurrent oncogenic alterations in AML involve transcription factors (TFs) and epigenetic regulators, which ultimately aid in the augmentation of transcriptional dysregulation and malignant transformation. However, one caveat to consider is that the heterogeneity of the molecular subtypes driving AML pathogenesis makes it challenging to develop targeted therapeutics. One such approach to bypass this predicament in expanding effective therapeutic strategies is to identify non-oncogenic TF dependencies that AML exploits. These dependencies are generally not mutated but are required to maintain AML regulatory programs. Thus, we can identify and utilize these vulnerabilities as selective therapeutic targets for AML with varying molecular subtypes.In this thesis, I leveraged the CRISPR toolbox and molecular biology techniques to investigate the mechanism of a unique transcriptional circuit dependency in AML. Previously, a TF-focused CRISPR screen identified Myocyte Enhancer Factor 2D (MEF2D) as a selective dependency for AML with distinct molecular subtypes and high MEF2D expression. Herein, we validated this finding through genetic perturbation of MEF2D in AML and show that MEF2D is required in a subset of AML, thus we sought to investigate its functional role in transcriptional dysregulation. First, we determined its transcriptomic effects by performing RNA-seq and discovered that MEF2D downregulates a previously identified AML-TF dependency Interferon Regulatory Factor 8 (IRF8). Upon inspection of whether these two TFs have a transcription association, we found that MEF2D and IRF8 have a high correlation of expression in cancer patients as well as their dependency patterns. Beyond this, we delineated the transcriptional circuitry between MEF2D and IRF8 and their association with PU.1, and further explored the convergent and divergent functionalities of these two TFs in AML. Together, our work not only dissects the role of MEF2D as a vulnerability in AML, but also uncovered its novel cooperation with other TFs such as IRF8 and PU.1 to form an interconnected regulatory network that sustains transcriptional programs required for AML survival.