Mechanism of CXCL8-mediated chemotaxis during transendothelial migration of melanoma cells.
Published: 2005
Language: eng
Number of pages: 280
Description: There is increasing evidence that both cell adhesion molecules and soluble factors are involved tumor metastasis. One question which remains to be answered is why tumor cells undergo directional migration through the endothelial junction. To test the hypothesis of chemoattraction during diapedesis, an under-agarose migration assay was employed to determine whether endothelial cells can secrete chemoattractants to stimulate chemotactic migration of tumor cells. Using melanoma as a model, I have found that metastatic melanoma cells undergo chemotactic migration towards endothelial cell-conditioned medium. Partial purification and characterization indicate that the chemokine CXCL8 is the main chemoattractant. The predominant endothelial CXCL8 isoform, CXCL877, is more potent and induces greater migration than the more common CXCL872. Antibody inhibition studies indicate that CXCL8 works through the receptor CXCR1 and not the more promiscuous CXCR2. Furthermore, the non-metastatic cell line WM35, which expresses a very low level of CXCR1 and does not migrate chemotactically towards CXCL8, can be induced by TNFalpha to synthesize a higher level of CXCR1, which leads to a corresponding increase in chemotactic migration and transendothelial migration in in vitro assays. Antibody inhibition of CXCL8 or CXCR1 affects both transendothelial migration and chemotaxis. Further analysis show that upon CXCL8 stimulation, CXCR1 redistributes, oligomerizes and clusters at the leading edge of cells during chemotactic migration. The redistribution of CXCR1 was likely due to the association of CXCR1 with lipid rafts and may involve the actin cytoskeleton. Subsequently, CXCR1 moves out of rafts into the bulk plasma membrane and becomes internalized via the clathrin-mediated pathway. CXCL8 activates many signaling components through CXCR1. Activation of the PI3K, MAPK and Src pathways have been found to play a role in chemotaxis, chemokinesis and transendothelial migration. Taken together, these results suggest a role for CXCL8-induced chemotaxis in the transendothelial migration of melanoma cells. In addition, the data indicate signaling differences between CXCR1 and CXCR2. This degree of separation may provide a mechanism for fine-tuning the chemokine-stimulated effects on melanoma cells and a level of control that has not been documented previously. These differences may also begin to explain the differences in chemokine involvement in tumor metastasis.
Notes: Thesis (Ph.D.)--University of Toronto, 2005.

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Source: Dissertation Abstracts International, Volume: 66-06, Section: B, page: 3119.