INTERCELLULAR AND INTRACELLULAR SIGNALING DURING LEUKOCYTE-MEDIATED MELANOMA CELL TRANSENDOTHELIAL MIGRATION
Open Access
- Author:
- Peng, Hsin-Hsin
- Graduate Program:
- Bioengineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- December 12, 2006
- Committee Members:
- Cheng Dong, Committee Chair/Co-Chair
Andrew Thomas Henderson, Committee Member
Peter J Butler, Committee Member
Avery August, Committee Member - Keywords:
- cancer
signaling
adherens junction
chemokine
extravasation
cytokine - Abstract:
- The goal of this work is to identify key signaling pathways for melanoma-associated host cell responses during metastasis. Tumor cells have been shown to exploit leukocyte function to enhance their metastatic properties under certain circumstances. Interleukin-8 (IL-8) is a chemotactic cytokine that regulates polymorphonuclear neutrophil (PMN) mobilization and activity, and we hypothesize this cytokine influences tumor behavior. We have demonstrated that IL-8 is crucial for PMN-mediated melanoma extravasation under flow conditions. In addition, IL-8 is up-regulated in PMNs upon co-culturing with melanoma cells. Melanoma cells induce IƒÛB-ƒÑ degradation in PMNs indicating that nuclear factor ƒÛB (NF-ƒÛB) signaling is active in PMNs. Furthermore, the production of IL-8 in PMNs is NF-ƒÛB dependent. We have further identified that IL-6 and IL-1ƒÒ from PMN-melanoma co-cultures synergistically contribute to IƒÛB-ƒÑ degradation and IL-8 synthesis in PMNs. Attachment of tumor cells to the endothelium has been shown to be critical for tumor metastasis. We have shown a phospholipase C (PLC)-mediated mechanism for the redistribution of interendothelial adherens junctions in response to melanoma cell contacts with the endothelium. We demonstrate that contact of melanoma cells to human umbilical vein endothelial cells trigger rapid endothelial [Ca2+]i response through PLC-IP3 pathway. In addition, alternation of endothelial adherens junctions following contact of melanoma cells have been evidenced by the changes in immunological staining patterns of vascular endothelial (VE)-cadherin. A PLC inhibitor, U73122 is shown to significantly diminish [Ca2+]i response and reduce the occurrence of melanoma cell¡Vinduced VE-cadherin reorganization. Moreover, inhibition of PLC attenuates melanoma cell transendothelial migration. However, melanoma cell-associated VE-cadherin breakdown is not sensitive to Ly294002, an inhibitor of phosphatidylinositol- 3-kinase (PI3K), whereas inhibition of PI3K resulted in a reduction of melanoma cell transmigration. Taken together, we have shown that melanoma cells induce PMNs to secrete IL-8 through activation of NF-ƒÛB and suggest a model in which this interaction promotes a microenvironment that is favorable for metastasis. Moreover, by inducing the PLC-Ca2+ signaling pathway, melanoma cells disrupt endothelial junctions to breach the endothelium and promote transvascular homing of tumor cells. In addition to experimental approaches, a mathematic model has been established for studying the intracellular dynamics, such as Ca2+ signaling. The tool is beneficial for signaling pathway analysis and discovery.