Neutrophils in cancer and other inflammatory conditions

This thesis focuses on neutrophils in cancer, acute and chronic inflammation. The
first part of this thesis describes how intravital microscopy (IVM) can be used in
biomedical research to study dynamic processes at cellular and subcellular resolution
in their environment and how different imaging windows including the abdominal
imaging window (AIW), dermal imaging window (DIW) and cranial imaging window
(CIW) can be implanted for facilitating the tracking of cells for different research
purposes (chapter 2). To investigate the role of neutrophils in biopsy-induced
tumor progression, we intravitally imaged the behavior of glioblastoma cells
before and after biopsy via implanted CIW in neutrophil depleted mice (chapter 4).
Different parameters, such as percentage and speed of migratory tumor cells, were
measured to check if neutrophil play a role in biopsy-induced tumor progression.
To confirm the hypothesis that neutrophil promote tumor progression, transwell
assays and wound assays were also performed with human neutrophils in vitro.
Although two- and three-dimensional in vitro studies of tumor cell lines are widely
used and important for increasing our knowledge on tumor growth, behavior and
metastasis formation, the complexity of in vivo microenvironment is not taken into
consideration. Therefore, to better understand tumor cell behavior, we imaged
tumors which developed from different common human and mouse breast tumor
cell lines in living mice by intravital microscopy (chapter 3). Cell morphology,
cell-cell interaction, polarity and motility of those tumor cell lines were measured.
This data can serve as a resource to instruct researchers on the appearance and
migratory behavior of the widely used breast tumor cell lines and warrants caution
to the use of in vitro characterization of tumor invasiveness. The more traditional
role of neutrophils is to phagocytose pathogens and clear damage upon acute
inflammation. During inflammation, neutrophil phenotypes appear in the blood
which are not present during homeostasis and they display different bacterial
containment capacities. To explain the mechanism behind this difference, we first
optimized neutrophil survival in a 3D in vitro model and then performed this assay
with or without bioparticle phagocytosis and in the presence or absence of an MPO
inhibitor (chapter 6). Apart from neutrophil heterogeneity in acute inflammation,
neutrophil heterogeneity in cancer, COPD and trauma were also investigated and
compared (chapter 5). Different maturation and activation markers were examined
to further understand the similarities and differences of neutrophil populations
under different conditions. Finally, in chapter 7, we summarize and discuss our
main findings in the context of the aim of this thesis.