Morphologic and immunocytochemical characterization of four human uveal cell lines (melanoma- and melanocytes-derived).

PURPOSE: To characterize three cell lines from human uveal melanomas and one ocular melanocyte cell line to study the specificity of several antigens in the malignant transformation of melanocytic uveal cells.
METHODS: Light microscopy (LM), transmission electron microscopy (TEM), and immunocytochemical techniques were used in the characterization of OCM-1, SP 6.5, and MKT-BR human uveal melanoma cell lines and UW-1 normal melanocyte cell line from human uvea. Several monoclonal antibodies (MoAbs) S-100, HMB-45, MNF-116, PAL-M1, NK1/C-3, IND-1, and MAAMA were used.
RESULTS: All cell lines showed an epithelioid/spindle morphology with occasional multinucleated cells, and nuclear pleomorphism. TEM showed intracytoplasmatic premelanosomes. Incubation with HMB-45 MoAb was positive in all cell lines. PAL-M2, NK1/C-3, MAAMA, and IND-1 MoAbs stainings were positive with variable intensity. MNF-116 MoAb showed negative staining in the four lines, and S-100 MoAb was also negative except for the UW-1 cell line.
CONCLUSIONS: Human uveal melanoma cell lines OCM-1, SP 6.5, and MKT-BR and the ocular melanocyte cell line UW-1 exhibited maintenance of some structural and ultrastructural characteristics of melanocytic cells. All four MoAbs, PAL-M2, NK1/C3, IND-1, and MAAMA against cutaneous melanoma-associated antigens stained positively all melanoma cell lines as well as the melanocytic cell line, suggesting that in vitro proliferation of melanocytes could modify their antigenic expression.