Differential expression of ICAM-1 and response to TGF-beta among cultured human uveal melanoma cells of varying cellular morphology

Purpose. Intercellular adhesion molecule (ICAM-1) is a cell adhesion molecule expressed on melanoma cells which is thought to play a role in tumor embolization. Among skin melanomas, the level of ICAM-1 expression correlates with the metastatic potential of the tumor. We investigated whether human uveal melanoma cells of differing cellular morphology had differing levels of ICAM-1 expression. We also investigated whether the level of ICAM-1 expression among these cells could be altered by transforming growth factor-beta, a multifunctional mitogen present in the intraocular tumor environment. Methods. Five different lines of human uveal melanoma cells of differing cellular morphology (2 spindle, 2 epithelioid, 1 mixed) were cultured for 48 hrs in complete media or in serum-free media, in the presence or absence of TGF-beta2 (2ng/ml). The cells were fixed in formalin and the level of ICAM-1 expression was determined by FACS analysis. Results. All five cell lines expressed ICAM-1. The two epithelioid cell lines (OCM3, OM431) had higher ICAM-1 expression than the two spindle cell lines (OCM1, Mel202) in the presence or absence of serum or TGF-beta. A mixed morphology cell line (OCM8) had intermediate level of ICAM-1 expression. TGF-beta2 lowered ICAM-1 expression of cells with epithelioid or mixed morphology but had no effect on spindle cells. Conclusions. Cultured human uveal melanoma cells of epithelioid morphology have higher ICAM-1 expression than those of spindle morphology. In addition, TGF-beta can down-regulate ICAM-1 expression of epithelioid cells but has no effect on ICAM-1 expression of spindle cells.