An investigation into the role of ULK1 in regulating chronic myeloid leukaemia stem and progenitor cell differentiation and sensitivity to tyrosine kinase inhibitors

Ianniciello, Angela (2019) An investigation into the role of ULK1 in regulating chronic myeloid leukaemia stem and progenitor cell differentiation and sensitivity to tyrosine kinase inhibitors. PhD thesis, University of Glasgow.

Abstract

Chronic Myeloid leukaemia (CML) is a stem cell driven disease, and a paradigm for cancer stem cell biology and targeted therapy. The BCR-ABL oncoprotein is expressed in the most primitive leukaemic stem cells (LSCs) and drives myeloid expansion and accumulation of mature blood cells. Front line treatment for CML, using tyrosine kinase inhibitors (TKIs), still represents one of the most effective treatment for cancer. However, autophagy embodies a key role in LSC persistence following TKI treatment. Therefore, autophagy represents an attractive target for LSCs eradication. Our study using patient-derived CD34+ CML cells indicates that ULK1, an autophagy-inducing kinase, is activated following TKI treatment, demonstrated by phosphorylation of its downstream target ATG13. Using a CRISPR-Cas9-mediated ULK1 knock-out (KO) we show that TKI treatment does not induce autophagy in ULK1 KO cells, thereby sensitising CML cells to TKI treatment in vitro and in vivo.

Here we also uncover a new combination treatment option, by exploiting a novel ULK1 kinase inhibitor (MRT403) that is under pre-clinical development. MRT403 treatment inhibited ULK1-mediated autophagy in a concentration-dependent manner, monitored by mitochondrial degradation in Parkin-dependent “enhanced mitophagy” assay. This correlates with increased mitochondrial respiration, measured by oxygen consumption rate, increased level of mitochondrial reactive oxygen species (ROS), and decreased level of glycolysis. Interestingly, using autophagy deficient cells (i.e. ATG7 KO) we show that while the effect of ULK1i treatment on mitochondrial respiration is autophagy-dependent, the effect on glycolysis is independent of autophagy.

Of clinical relevance, using robust patient-derived xenograft model, MRT403 targeted human CML CD34+133+ LSCs in vivo when used in combination with TKI treatment.

Moreover, inhibiting ULK1 kinase activity in an inducible BCR-ABL mouse model promotes differentiation of LSCs when combined with imatinib. Loss of of long-term leukaemic stem cells (LT-LSCs) resulted in increased megakaryocyte-erythroid progenitor (MEP) which contributed to rescue both disease and TKI-induced disfunction in erythroid maturation.

In conclusion, our findings describe a novel metabolic role for ULK1 in LSCs and provide a strong rationale for further clinical development of specific autophagy inhibitors as a therapeutic strategy to more effectively target TKI-resistant LSCs in CML patients.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Supported by funding from Tenovus Scotland.
• Subjects: Q Science > QR Microbiology
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Cancer Sciences
• Supervisor's Name: Helgason, Dr. Vignir
• Date of Award: 2019
• Depositing User: Mrs Marie Cairney
• Unique ID: glathesis:2019-77858
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Dec 2019 15:03
• Last Modified: 23 Jan 2024 16:41
• Thesis DOI: 10.5525/gla.thesis.77858
• URI: https://theses.gla.ac.uk/id/eprint/77858

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