Inhibition of mitochondrial translation as a therapeutic strategy
for acute myeloid leukemia
Marko Škrtić
Doctor of Philosophy
Institute of Medical Science
University of Toronto
2012
Abstract
Intro: Acute myeloid leukemia (AML) therapies have remained unchanged for 20 years, and thus new therapies are needed.
Objective: To identify FDA-approved agents with anti-leukemia stem cell activity, we performed a screen and identified the antimicrobial tigecycline (TIG).
Methods: Primary AML mononuclear cells were isolated by Ficoll centrifugation from peripheral blood. Flow cytometry dye; JC-1, Carboxy-H2DCFDA, Mitotracker GreenFM. Leukemia stem cell activity was assayed by human AML engraftment in NOD/SCID mice.
Results: TIG induced cell death in primary AML patient samples (LD50, 3-6μM n=14), preferentially over normal hematopoietic cells. Likewise, in colony assays, TIG (5μM) reduced the clonogenic growth of AML samples (n=7) by 93%, demonstrating an effect on leukemia progenitor cells, but not normal hematopoietic cells (34% reduction, n=5). A yeast genome-wide screen identified mitochondrial translation inhibition as the mechanism of tigecycline-mediated cell death in eukaryotic cells. TIG decreased the expression of mitochondrial peptides, enzyme activity and membrane potential preferentially in AML cells over normal hematopoietic cells. ShRNA knockdown of TuFM mitochondrial translation factor in leukemia cells reproduced TIG anti-leukemia target effects previously described. We discovered that primary AML CD34+/CD38- stem cells have greater mitochondrial mass (3-fold, n=5) than normal CD34+ cells (n=4). Higher baseline mitochondrial mass in primary AML samples was predictive for tigecycline sensitivity in vitro (r=-0.71, p<0.05). We assessed the effect of TIG on primary AML stem cells defined by their ability to initiate leukemic engraftment in vivo. NOD/SCID mice treated with TIG had decreased human AML engraftment (n=3 AML patients) compared to control.
Conclusions: We identified mitochondrial translation inhibition as a novel therapeutic strategy for AML. Currently, a Phase I clinical trial of tigecycline in hematological malignancies is underway.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/34929 |
| Date | 07 January 2013 |
| Creators | Skrtic, Marko |
| Contributors | Schimmer, Aaron D. |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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