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Alain Béliveau, Mélanie Bérubé, Alain Rousseau, Guy Pelletier, Sylvain L. Guérin; Expression of Integrin α5β1 and MMPs Associated with Epithelioid Morphology and Malignancy of Uveal Melanoma. Invest. Ophthalmol. Vis. Sci. 2000;41(8):2363-2372.
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purpose. Altered expression of the α5β1 integrin and matrix
metalloproteinases (MMPs) is recognized as a hallmark of invasive tumor
cells. The purpose of the present study was to investigate the
expression of integrin subunit α5, its corresponding ligand
fibronectin (FN), and the expression pattern for MMPs in four highly
proliferative human choroidal melanomas (TP17, TP31, SP8.0, and SP6.5)
to evaluate whether any correlation can be established between these
markers and cell tumorigenicity.
methods. Cell tumorigenicity was evaluated by subcutaneous injection of uveal
melanoma cell lines in immunodeficient nude mice. Anchorage dependency
was evaluated by growth assays in soft agar. The invasive ability of
each cell type was also determined using a modified Boyden chamber.
Expression of both the α5 integrin subunit and FN was determined at
the mRNA level by RT-PCR. The protein level (for α5) was determined
by flow cytometry and inhibition of adhesion assays by using an
antibody directed against the α5 subunit. Expression of MMPs was
determined by standard gelatin zymography.
results. Assays in nude mice provided evidence that the cell lines possess a
range of tumorigenic ability of TP17>TP31>SP8.0>SP6.5. Antibody
inhibition of cell adhesion and flow cytometry demonstrated that TP17
cells have no detectable membrane-bound α5β1, whereas low levels
are found in primary cultured melanocytes, as well as in SP6.5, SP8.0,
and TP31 cells. RT-PCR analyses provided evidence that both FN and α5
expression may be regulated at the transcriptional level. Gelatin
zymography revealed that all cell lines, as well as normal melanocytes,
express MMP-2 at varying levels but that only the highly invasive TP17
cell line secretes a distinctive MMP with a high molecular weight of
conclusions. Among the four melanoma cell lines selected for the completion of this
study, TP17 exhibited the most aggressive phenotype, which also
correlated with the mostly epithelioid morphology of these cells. The
cell morphology of the TP17 cell line could be related to the loss ofα
5β1, whereas its invasive properties are more likely related to
the expression of the 117-kDa MMP.
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