Neutrophil-mediated Melanoma Adhesion and Migration in Shear Flow
Open Access
- Author:
- Slattery, Margaret June
- Graduate Program:
- Bioengineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- December 20, 2005
- Committee Members:
- Cheng Dong, Committee Chair/Co-Chair
William O Hancock, Committee Member
Peter J Butler, Committee Member
Andrew Thomas Henderson, Committee Member - Keywords:
- polymorphonuclear leukocytes
cancer
beta2-integrin
ICAM-1
interleukin-8 - Abstract:
- An in vitro flow-migration chamber was developed and used to investigate the cellular and molecular mechanisms of PMN-mediated melanoma cell extravasation under dynamic shear-flow conditions. In general, melanoma cells lack the adhesion molecules necessary to interact with the endothelium in a manner similar to leukocytes. It is hypothesized here that melanoma cells exploit the adhesive ability of leukocytes to improve their adhesion to and migration through the vascular endothelium under flow conditions. Polymorphonuclear leukocytes (neutrophils; PMNs) were found to increase melanoma cell extravasation under flow conditions via an adhesion-dependent mechanism, specifically ICAM-1/B2-integrin interactions. The migration was characterized over a range of shear stresses and shear rates. The hydrodynamics of PMN-melanoma adhesion and migration correlate with the inverse of shear rate, in contrast to PMN-endothelial adhesion that correlates with both shear stress and shear rate. PMN-facilitated melanoma migration can be described as a two-step process. PMNs must first adhere to the endothelial substrate, which is followed by tumor cell adhesion to a previously adhered PMN. Melanoma cells were also found to alter PMNs’ phenotype and biochemical secretion by cytokine communication using interleukin-8 (IL-8) and possibly other inflammatory mediators. IL-8 secretion is induced in PMNs but not melanoma cells when they are cultured together. In addition, the cell surface adhesion molecule CD11b, a subunit of the B2-integrin Mac-1, is upregulated on PMNs when they are co-cultured with melanoma cells. Blocking the IL-8 receptors CXCR1 and CXCR2 on the PMNs prevents this upregulation of CD11b. Blocking the IL-8 receptors or neutralizing soluble IL-8 also attenuates the increase in melanoma migration due to PMN-facilitation. This suggests that a self-stimulatory microenvironment is created between melanoma cells and PMNs that potentially elicits immuno-editing by tumor cells. Finally, a mathematical model, based on population balance analysis, was developed to simulate tumor cell and PMN aggregation near a substrate. The model successfully predicted aggregation results of tumor cells and PMNs over a range of shear rates and two antibody treatments. The model was not successful at modeling changes in the population ratio of tumor cells to PMNs. The model provides a method to simulate collisions near a substrate but does not accurately model adhesion to the substrate, which is a requisite step in PMN-facilitated melanoma migration. PMN-facilitated melanoma adhesion is a complex multi-step process that is regulated by both micro-fluid transport and biological signaling. Together, the flow migration assay and biological data could possibly aid in the identification of pharmaceutical targets for cancer metastasis therapies.