Graduation Date

Spring 5-4-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Programs

Biochemistry & Molecular Biology

First Advisor

R. Katherine Hyde, Ph.D.

Abstract

Inversion of chromosome 16 [inv(16)] acute myeloid leukemia (AML) generates a fusion gene CBFB-MYH11. Approximately half of inv(16) AML patients eventually relapse mainly due to the existence of leukemia stem cells (LSCs). Previous work using a Cbfb-MYH11 knockin mouse model showed that the LSCs are enriched within CSF2RB- population. Another gene upregulated by Cbfb-MYH11 encodes the cytokine receptor IL1RL1. Using Cbfb-MYH11 knockin mice, we showed that LSCs exist in multiple sub-populations defined by their immunophenotype, and IL1RL1 is expressed by cell populations with high LSC activity. We also found that treatment of IL-33, the ligand for IL1RL1, promoted cell survival in vitro. Our results imply that therapeutic approaches based on a single cell surface molecule antigen may not work against the entire, diverse population of LSCs.

The CBFB-MYH11 fusion gene is expressed in all LSCs but not in normal cells. Thus, targeting CBFB-MYH11 may have potential as a therapeutic strategy. Here, we used a new knockin mouse model allowing for deletion of Cbfb-MYH11 after leukemic transformation and demonstrated that the loss of the Cbfb-MYH11 caused apoptosis and decreased colony-forming ability in vitro. By transducing leukemia cells from Cbfb-MYH11 knockin mice with doxycycline inducible short hairpin RNA (shRNA) targeting MYH11 and transplanting into recipient mice. We found that Cbfb-MYH11 knockdown significantly reduced the leukemic burden in vivo. Thus, our data indicates that Cbfb-MYH11 is required for the survival of inv(16) leukemia cells.

Given the role of Cbfb-MYH11 in leukemia cell survival, it is important to develop targeted therapies to inhibit the fusion gene activity. In collaboration with Dr. David Oupicky’s laboratory, we tested a polymeric CXCR4 antagonist (PCX) which can deliver short interfering RNA (siRNA). We found that PCX exerts a cytotoxic effect in leukemia cells and successfully delivered siRNAs into leukemia cells, as well as caused apoptosis. Our results imply that using PCX to deliver siRNAs targeting key genes is a potential strategy for the treatment of AML. Overall, our results provide insights into promising molecular therapeutic agents for treating AML patients in the future.

Available for download on Sunday, April 18, 2021

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