Donna Degeer
BSc McMaster University, 2007
March 5, 2010. 9:00 a.m. – 12:00 p.m. Terry Fox
Laboratories: 13th Floor Seminar Room. B.C. Cancer Research Centre. 675 W 10th
Ave, Vancouver, B.C.
“A Novel AHI-1-BCR-ABL-JAK2 Interaction Complex Mediate
Cellular Resistance to Tyrosine Kinase Inhibitors in CML”
Donna Degeer MSc Programme (pdf)
EXAMINING COMMITTEE
Chair: Dr. Rob Kay (Medical Genetics)
Supervisory Committee: Dr. Xiaoyan Jiang, Research
Supervisor (Medical Genetics) & Dr. Gregg Morin (Medical Genetics,
Biochemistry & Molecular Biology)
University Examiner: Dr. Keith Humphries (Medical Genetics,
Pathology & Laboratory Medicine)
SUPERVISORY COMMITTEE
Dr. Xiaoyan Jiang, Dr. Gregg Morin, & Dr. Sandra Dunn
ABSTRACT
Chronic myeloid leukemia (CML) is a clonal, multilineage,
myeloproliferative disorder characterized by the reciprocal translocation
between chromosomes 9 and 22 creating a constitutively active tyrosine kinase
BCR-ABL that is involved in activating several signaling cascades. The current
first line treatment for patients diagnosed with CML involves administration of
the ABL kinase inhibitor Imatinib mesylate (IM). However, early relapses and
acquired drug resistance resulting from acquired mutations within the kinase
domain of ABL remain a current impediment to successful treatment for many
patients. AHI-1 (Abelson helper integration site 1) is a recently discovered
oncogene that is highly deregulated in murine lymphomas and leukemias, and
overexpressed in several human leukemias and lymphomas We have demonstrated a
direct interaction between AHI-1 and BCR-ABL at endogenous levels in a CML
representative cell line, the K562 cells. To further investigate AHI-1’s involvement
in mediating this cellular resistance to IM, AHI-1 was either stably overexpressed
or suppressed in K562 cells. Interestingly, an increase in cellular proliferation
and colony formation and a decrease in apoptosis was observed in the presence
of imatinib when AHI-1 was overexpressed, and the opposite was true when AHI-1
was suppressed. Phosphorylation and total protein expression levels of several
proteins known to be involved in BCR-ABL signaling were quantified by Western
blot analysis. Interestingly, elevated phosphorylation and total protein expression
levels of several of these proteins were observed when AHI-1 was overexpresessed,
in particular the NFκB and JAK2/STAT5 pathways were strongly affected. Due to
the strong effects AHI-1 had on the JAK2/STAT5 signalling cascade, we then
inhibited JAK2 activity using a tyrosine kinase inhibitor, TG101209, that is highly
effective and specific at inhibiting the JAK2/STAT5 pathway. AHI-1 overexpression
lead to a reduction in the cellular response to the inhibitor while suppression
of AHI-1 caused an increase in sensitivity in viability, apoptosis, and colony
forming cell assays. Finally, a combination of Imatinib and TG101209 was examined
in the same K562 cells lines mentioned previously. Results from a viability, apoptosis,
and colony forming cell assay suggest that using a combination treatment approach
was more effective at inhibiting cellular viability and colony forming ability
in all cell lines tested. These findings together suggest that AHI-1 may play
an important role in mediating cellular resistance to IM through activation of
several signalling proteins involved in BCR-ABL signalling pathways, especially
through NFкB and JAK2/ STAT5 signalling, and that it may be a vital target in
eradicating the malignant leukemic cells arising in CML.
PUBLICATIONS
Liang L. Zhou, Yun Zhao, Ashley Ringrose, Donna DeGeer, Erin
Kennah, Ann E.-J. Lin, Guoqing Sheng, Xiao-Jiang Li, Ali Turhan, and Xiaoyan
Jiang. AHI-1 interacts with BCR-ABL and modulates BCR-ABL transforming activity
and imatinib response of chronic myeloid leukemia progenitor cells. Journal of
Experimental Medicine. (11). 2657-2671.
AWARDS
UBC Entrance Scholarship
PRESENTATIONS
American Society of Hematology, 2009. (New Orleans, LA).
GRADUATE STUDIES
Field of Study: Chronic myeloid leukemia (CML)
COURSES
MEDG 520: Advances in Human Molecular Genetics, Dr. Matthew
Lorincz
MEDG 530: Human Genetics, Dr. Lorne Clarke
MEDG521: Molecular and Cellular Biology of Cancer, Dr.
Sandra Dunn
MEDG548: Directed Studies, Dr. Xiaoyan Jiang
MEDG549: MSc Thesis, Dr. Xiaoyan Jiang
Donna Degeer MSc programme (pdf)
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