DOI
https://doi.org/10.25772/Z5DN-NE92
Defense Date
2022
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Integrative Life Sciences
First Advisor
Robert Tombes
Second Advisor
Sarah Rothschild
Abstract
Acute myeloid leukemia (AML) is the most common type of adult acute leukemia and accounting for for 50% of all leukemic deaths and causing more than 11,000 fatal outcomes in the US in 2020. Standard treatment includes chemotherapy and stem cell transplantation, but for aging patients and those with impaired immune function these rigorous therapies are not always possible. Furthermore, AML patients harboring a chromosomal rearrangement involving the mixed lineage leukemia (MLL) gene resulting in the production of an MLL fusion protein (FP) have particularly poor prognoses. Development of treatments for this subclass of AML, termed MLL-r AML, have progressed slowly which highlights the need for new therapies. In recent years, zebrafish have emerged as a powerful model organism for studying human blood malignancies due to the conservation of hematopoiesis between humans and zebrafish. In this dissertation transient transgenic zebrafish models were developed with myeloid specific expression of known AML-associated MLL fusion protein genes, MLL fused with eleven-nine leukemia (MLL-ENL) and MLL fused with AF9 (MLL-AF9) were developed. Myeloid specific expression of MLL-ENL or MLL-AF9 (collectively, MLL-FPs) induced an expansion of MLL-FP expressing cells on the yolk from 30 hours post fertilization (hpf) to 7 days post fertilization (dpf), and induced an expansion of myeloperoxidase (mpx), spi-1 proto-oncogene b (spi1b), and macrophage expressed (mpeg) expressing cells on the yolk at 48 hpf. Double colorimetric whole mount in situ hybridization (WISH) revealed that MLL-FP expression colocalized with mpx, spi1b, and mpeg expression at 48 hpf and 72 hpf, which suggests the affected cells are of the myeloid lineage and is indicative of an AML-like phenotype. Furthermore, MLL-FP expression led to an expansion of B-cell lymphoma 2 (bcl2) and cyclin dependent kinase 9 (cdk9) expressing cells on the yolk—both are upregulated in AML patients. Finally, MLL-FP expressing embryos were treated with two drugs that are either approved for AML treatment or are currently being used in human AML trials, venetoclax (BCL2 inhibitor) and flavopiridol (CDK9 inhibitor). While individual treatment with either drug reduced MLL-ENL expression, co-treatment significantly reduced the number of MLL-ENL expressing cells on the yolk compared to individual treatments or controls. Treatment of MLL-AF9 expressing embryos did not yield a significant change in the number of MLL-AF9 expressing cells. Together, these data suggest that a transient transgenic MLL-r zebrafish model exhibiting AML-like characteristics was developed and highlight the effectiveness of using zebrafish for drug screens to identify novel AML therapeutic combinations.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
8-12-2022