Investigation of autophagy as a survival factor for chronic myeloid leukaemia

Karvela, Maria (2013) Investigation of autophagy as a survival factor for chronic myeloid leukaemia. PhD thesis, University of Glasgow.

Abstract

Tyrosine kinase inhibitors (TKIs) have revolutionised the treatment of chronic myeloid
leukemia (CML), however, fail to cure the disease due to the persistence of a refractory
fraction of stem/progenitor cells. Autophagy is a recycling mechanism utilised by the cell
as a survival mechanism under stressful conditions, and its induction has been suggested to
have a cytoprotective role in cancer cells.
In this study we demonstrate that autophagy is triggered in CML upon TKI-mediated
inhibition of BCR-ABL, and protects from cell death. In order to evaluate if specific
autophagy inhibition enhances TKI effects, we stably transduced primary CML
stem/progenitor cells with a vector carrying a short-hairpin against the key autophagy gene
ATG7. Knock-down of basal ATG7/autophagy levels in CML stem/progenitor cells
inhibited by approximately 50% the survival of the cells in a clonogenic assay, and
reduced by 75% their erythroid differentiation potential. Furthermore, ATG7 knock-down
enhanced the effects of TKIs imatinib (IM; 1st), dasatinib (DAS; 2nd), nilotinib (NIL; 2nd)
and ponatinib (PON; 3rd generation), reducing by 92-98% the survival of these cells in a
clonogenic assay. In contrast, ATG7 knock-down in normal stem cells, with or without
TKI treatment, did not have a significant effect on survival and proliferation.
ATG7 was also knocked-down in final disease stage, blast crisis (BC), patient-derived
K562 and KCL22 cell lines. Both cell lines appeared to depend significantly on autophagy
for survival as indicated by high apoptosis levels (70-100%) after ATG7 knock-down.
Interestingly, ATG7 knock-down cells appeared to be more differentiated compared to the
control (scrambled shRNA).
Our findings suggest a role for basal autophagy in the survival, differentiation decisions
and clonogenicity of CML cells, and support the combined use of autophagy inhibition
with TKIs for the eradication of CML stem/progenitor cells. This could be partially
attributed to a bypass of the differentiation block upon autophagy inhibition, which
facilitates TKI-targeting. We underline the necessity for the development of specific
autophagy inhibitors that in combination with TKIs could potentially eradicate the fraction
of persistent CML stem/progenitor cells and offer a curative option for CML patients.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Chronic myeloid leukaemia, tyrosine kinase inhibitors, autophagy, stem cells
• Subjects: R Medicine > RC Internal medicine > RC0254 Neoplasms. Tumors. Oncology (including Cancer)
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Cancer Sciences > Paul O'Gorman Leukemia Research Centre
• Supervisor's Name: Holyoake, Prof. Tessa and Helgason, Dr. Vignir
• Date of Award: 2013
• Depositing User: Dr M Karvela
• Unique ID: glathesis:2013-4271
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 22 May 2013 14:29
• Last Modified: 22 May 2013 14:29
• URI: https://theses.gla.ac.uk/id/eprint/4271