Date of Award

4-2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Program

Biomedical Sciences

Track

Microbiology, Immunology, and Biochemistry

Research Advisor

Joseph T. Opferman, Ph.D

Committee

David R. Nelson, PhD Stacey K. Ogden, PhD Shondra M. Pruett-Miller, PhD Gerard P. Zambetti, PhD

Abstract

Anti-apoptotic MCL1 is one of the most frequently amplified genes in human cancers and its elevated expression confers resistance to many therapeutics including the BH3-mimetic agents ABT-199 and ABT-263. The anti-malarial, dihydroartemisinin (DHA) translationally represses MCL-1 and synergizes with BH3-mimetics. To explore how DHA represses MCL-1, a genome-wide CRISPR screen identified that loss of genes in the heme synthesis pathway renders mouse BCR-ABL+ B-ALL cells resistant to DHA-induced death. Mechanistically, DHA disrupts the interaction between heme and the eIF2α kinase heme regulated inhibitor (HRI) triggering the integrated stress response. Genetic ablation of Eif2ak1, which encodes HRI, blocks MCL-1 repression in response to DHA treatment and represses the synergistic killing of DHA and BH3-mimetics compared to wild-type leukemia. Furthermore, BTdCPU, a small-molecule activator of HRI, similarly triggers MCL-1 repression and synergizes with BH3-mimetics in mouse and human leukemia including both Ph+ and Ph-like B-ALL. Lastly, combinatorial treatment of leukemia bearing mice with both BTdCPU and a BH3-mimetic extended survival and repressed MCL-1 in vivo. These findings reveal that the HRI-dependent cellular heme-sensing pathway can modulate apoptosis in leukemic cells by repressing MCL-1 and increasing their responsiveness to BH3-mimetics. This signaling pathway could represent a generalizable mechanism for repressing MCL-1 expression in malignant cells and sensitizing them to available therapeutics.

Declaration of Authorship

Declaration of Authorship is included in the supplemental files.

ORCID

https://orcid.org/0000-0002-9981-7883

DOI

10.21007/etd.cghs.2021.0529

2021-002-Smith-DOA.pdf (321 kB)
Declaration of Authorship

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