A potential role for TGFβ in the regulation of uveal melanoma adhesive interactions with the hepatic endothelium

PURPOSE. TGF beta has been shown to have a regulatory effect on uveal melanoma invasion, but it is not known which processes are specifically influenced. The purpose of this study was to analyze the effect of TGF beta stimulation on the adhesive interactions of uveal melanomas with the extracellular matrix (ECM) and endothelium and, in addition, its effect on the secretion of collagenases. METHODS. Invasive and a noninvasive uveal melanoma cell lines, supported by short-term primary uveal melanoma cultures, were used to assess the effect of TGF beta on ECM and endothelial adhesion and degradation of the ECM. Changes in cell adhesion molecule expression were assessed by flow cytometry, and conditioned media were analyzed by gelatin zymography. Assays of adhesion to ECM substrates and endothelial cells were also performed. RESULTS. Treatment with TGF beta increased low basal levels of adhesion molecule and latent MMP-2 expression, as well as adhesion to hepatic endothelial cells by the noninvasive cell line. Conversely, TGF beta reduced adhesion to laminin and a laminin-binding integrin by invasive cells but had no effect on their adhesion to the endothelium. CONCLUSIONS. In this preliminary study, TGF beta was found to upregulate levels of MMP-2, reduce adhesion to laminin, and downregulate expression of laminin-binding integrins. Specifically, TGF beta was found to increase adhesion of noninvasive uveal melanoma cells to the hepatic, but not the dermal, endothelium and may therefore contribute to the preferential targeting of the liver by uveal melanomas.