Retinoid and Pentoxifylline-Induced Modulation of Human Melanoma Cell Metastasis

Alexander, Claire Low (1998) Retinoid and Pentoxifylline-Induced Modulation of Human Melanoma Cell Metastasis. PhD thesis, University of Glasgow.

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Successful metastasis of a tumour cell involves a series of complex steps comprising of several cell-cell and cell extracellular matrix (ECM) interactions. All-trans retinoic acid (RA) and pentoxifylline (PX) have previously been shown to modulate various stages of metastasis, and this study examines the ability of either drug to modulate tumour cell growth, adhesion of tumour cells to various components of the ECM, tumour lysis by lymphokine-activated killer (LAK) cells, and plasminogen activator expression. Pretreatment of the A375, Hs294T and C8161 human melanoma cell lines for up to 7 days with a range of concentrations of RA (10-10M - 10-5M) failed to alter tumour cell growth. In contrast, PX induced a time and dose dependent decrease in tumour cell numbers, reducing C8161 cells numbers by 67.5%, Hs294T cell numbers by 65.4% and decreasing the numbers of A375 cells by 37.2% after 4 days treatment with 250mug/ml PX. Neither PX nor RA had any effect on tumour cell morphology. Pretreatment of the C8161 cells for 4 days with 10-6M RA had no effect on adhesion of the cells to fibronectin, laminin, collagens type I and type IV or matrigel basement membrane. Although adhesion of C8161 cells pretreated with 250mug/ml PX to collagens type I and IV, and laminin was not altered, a 24.2% reduction in adhesion to fibronectin was observed by 30min. The ability of either drug to modulate tumour cell lysis by LAK cells was determined using the Chromium-51 release assay over a range of effector to tumour cell ratios (E:T). Neither drug modulated lysis of the A375 cells but lysis of the Hs294T and C8161 cells pretreated for 4 days with 10-6M RA was increased 1.4-fold and 2.8-fold respectively at an E:T ratio of 40:1.4 days pretreatment of the tumour cells with PX (250mug/ml) failed to alter lysis of the A375 cells yet increased lysis of the C8161 cells 1.8-fold and in contrast, decreased lysis of the Hs294T cells 1.8-fold at the 40:1 ratio. The involvement of intercellular adhesion molecule-1 (ICAM-1, CD54) in the modulation of tumour cell lysis by either RA or PX was subsequently examined. ICAM-1 is expressed on several cell types including melanoma cells and acts as a ligand for lymphocyte function associated antigen (LFA-1, CD11 a/CD18) present on the surface of lymphocytes. Analysis of alterations in membrane ICAM-1 (mICAM-1) by flow cytometry revealed RA (10-10M - 10-7M) had no effect on mICAM-1 expression in the Hs294T and C8161 cells whereas at the higher concentrations (10-6M - 10-5M), a slight increase in mICAM-1 levels became evident. Using the A375 cell line, 4 days pretreatment with 10-10M - 10-7M RA induced only a marginal increase in mICAM-1 expression, which further increased with 10-6M - 10-5M RA. Despite the RA-induced increase in mICAM-1 levels, PX (10mug/ml - 250?g/ ml) failed to alter mICAM-1 expression in any of the three cell lines. Addition of blocking ICAM-1 antibody over a range of concentrations to the cytotoxicity assays at the 40:1 ratio reduced lysis of the C8161, A3 75 and Hs294T cells. Usingthe C8161 cells, blocking ICAM-1 antibody at the optimum concentration of 10mug/ml induced a 2.3-fold reduction in lysis of the tumour cells. In the Hs294T cell line, an optimum 1.8-fold reduction in lysis was observed using 5|ig/ml blocking ICAM-1 antibody. Using the A3 75 cells, 10mug/ml blocking ICAM-1 antibody induced an optimum 2-fold reduction in lysis. This antibody also reduced lysis of RA-pretreated C8161 cells 3-fold using 10mug/ml antibody, and the Hs294T cells 1.3-fold using 5mug/ml. Lysis of PX-pretreated C8161 and Hs294T cells was also reduced 2.1-fold (5mug/ml) and 1.5-fold (10mug/ml) respectively. Despite showing weak expression of the major histocompatibility complex (MHC) class 1 on all 3 cell lines, blocking of this molecule using a specific antibody had no effect on tumour cell lysis. Collectively, this data shows that ICAM-1 is partially involved in the lysis of RA/ PX-treated and untreated tumour cells but other molecules involved in the tumour/LAK cell interaction must also be altered to account for the observed RA/PX induced modulation of tumour lysis. (Abstract shortened by ProQuest.).

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: Michael Edward
Keywords: Medicine, Cellular biology, Oncology
Date of Award: 1998
Depositing User: Enlighten Team
Unique ID: glathesis:1998-75920
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Nov 2019 17:26
Last Modified: 19 Nov 2019 17:26

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