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Alain Béliveau, Mélanie Bérubé, Patrick Carrier, Caroline Mercier, Sylvain L. Guérin; Tumorigenicity of the Mixed Spindle-Epithelioid SP6.5 and Epithelioid TP17 Uveal Melanoma Cell Lines Is Differentially Related to α5β1 Integrin Expression. Invest. Ophthalmol. Vis. Sci. 2001;42(12):3058-3065.
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purpose. It has been suggested that the epithelioid morphology and high
aggressiveness that is typical of the uveal melanoma cell line TP17 is
dependent on the loss of α5β1 integrin expression at the cell
surface. The purpose of the current study was to test this hypothesis
in the TP17 cell line and investigate the role this integrin may play
in the tumorigenicity of the SP6.5 cells, a mixed spindle–epithelioid
culture-type human uveal melanoma that shows tumorigenic properties
clearly distinct from that of TP17 cells.
methods. Expression of the α5 integrin subunit was restored in the α5-TP17
cell line by stably transfecting the cells with a recombinant plasmid
encoding the integrin subunit. Flow cytometry and adhesion assays on
fibronectin (FN)-coated culture plates were used to monitor α5
expression in the cells. The effect of α5 expression on both
tumorigenicity and cell proliferation was evaluated in vivo in nude
mice. In vitro growth properties of the α5+ TP17 cells
was evaluated by cell counting and compared with that of the α5
parental TP17 cell line. The influence exerted by the α5 integrin
subunit on the tumorigenic and proliferative properties of the SP6.5
cells was evaluated in vivo in nude mice by exposing the cells to
increasing doses of a blocking antibody directed against theα
5-subunit before subcutaneous injection, and compared with the
results obtained with untreated SP6.5 cells.
results. Expression of the α5 integrin subunit in the α5-TP17 cells was
successfully achieved, as evidenced by both flow cytometry and adhesion
assays on FN-coated culture plates. Restoring expression of α5 in
TP17 cells enhanced epithelioid cell morphology and increased the
growth properties of this cell line in vivo. The ability
of the SP6.5 cells to yield subcutaneous tumors was found to be
concentration dependent and was reduced in a dose-dependent manner when
the cells were exposed to the anti-α5 blocking antibody.
conclusions. Restoring expression of α5 in the α5-negative TP17 uveal melanoma
cell line influenced the proliferative properties of these cells but
did not alter its tumorigenic potential. In contrast, the ability of
the SP6.5 cells to yield tumors in vivo in nude mice appeared to be
related to expression of this integrin.
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