UNIVERSITY OF CALGARY Colitis-Associated Cancer

UNIVERSITY OF CALGARY
The Role of Myeloid Derived Suppressor Cells in the Interleukin-10 Model of
Colitis-Associated Cancer
by
Manmish Singh Bawa
A THESIS
SUBMITTED TO THE FACULTY OF GRADUATE STUDIES
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE
DEGREE OF DOCTOR OF PHILOSOPHY
GRADUATE PROGRAM IN GASTROINTESTINAL SCIENCES
CALGARY, ALBERTA
JULY 2015
© Manmish Singh Bawa 2015

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Abstract
Chronic inflammation in the colon is a risk factor for developing colorectal
cancers, one of the leading causes of cancer related deaths in Canada. A
hallmark feature of inflammation is the recruitment of leukocytes. Of interest in
this thesis are the heterogenous population of Gr1+/CD11b+ Myeloid Derived
Suppressor Cells (MDSC). These cells are recruited to tumour sites, but have
recently also been shown to be increased during inflammation. A key regulator of
inflammation and leukocyte recruitment to the gut is the innate immune receptor
TLR4. In this thesis we use the IL-10-/- mouse model to examine the role of
MDSC in colitis-associated cancer.
Our preliminary data in an IL-10 TLR4 double knock out mouse revealed an
increased cancer incidence in the absence of TLR4. We hypothesized that
MDSC contributed to cancer development in the IL-10-/- and TLR4 signaling
modulates cancer development through an effect on MDSC function or
recruitment.
Our studies demonstrated enhanced numbers of Gr1+/CD11b+ cells in the colons
of IL-10-/- mice. Characterization of these cells revealed an active
immunosuppressive phenotype demonstrated by activity of NOS II and Arginase
I enzymes and suppression of T-cell proliferation. Pharmacological targeting of
MDSC decreased dysplasia development. Enriching the MDSC pool using

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adoptive transfer was associated with enhanced neoplasia development in the
IL-10-/- mice. These data suggest that MDSC contribute to inflammation
associated tumour development.
In the absence of TLR4, IL-10-/- mice recruited increased levels of MDSC to the
colon. MDSC numbers correlated with the levels of cancer development in this
model. TLR4 competence did not affect the immunosuppressive function of
MDSC. We identified MCP-1 and SDF-1 as MDSC chemoattractants.
Examination of colonic tissue demonstrated increased MDSC chemoattractant
expression levels in the absence of TLR4 before tumour development in the IL-
10 deficient model.
Our data identify a link between TLR4 signaling and MDSC recruitment to the gut
during inflammation and demonstrate that MDSC recruitment drives cancer
development.

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Acknowledgements
I would like to acknowledge the love and support of my family that has made it
possible for me to achieve everything that I have. My wonderful parents, Daljit
and Baljinder, have always nurtured and supported me to the best of their ability
and beyond. My brother and my best friend, Gharandip, has been a constant
companion, source of guidance and inspires me to life in service. The love of my
life, Navkiran, who went from being my girlfriend to fiancé and finally, wife, during
the course of my graduate study years, is my reason for being.
I would also like to acknowledge the support of my supervisor, Dr. Donna-Marie
McCafferty. Donna-Marie has provided me with invaluable mentorship and
guidance over the last 6 years. I would like to thank my supervisory committee:
Dr. Joe Davison, Dr. Paul Beck and Dr. Oliver Bathe. Under the combined
supervision of Donna-Marie and my committee, I have expanded my knowledge
of the scientific method and how to put it into practice. It has been a privilege to
be mentored and guided along in my career by these and many other individuals
that I greatly admire.
I would like to thank all members of the McCafferty lab over the years, especially,
Ronald Chan, Dr. Rui Zhang, Dr. Ying Gao, Kelvin Ng and Dr. Maitham Khajah. I
thank Dr. Stephan Urbanski for his great help with my project.

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I would like to thank the Queen Elizabeth II graduate scholarships for their
support during my graduate career. Finally, I would like to thank the
Gastrointestinal Research Group, the Department of Physiology and
Pharmacology and the University of Calgary for providing an excellent
environment to learn, do research, to interact and collaborate other scientists.