LACK OF EFFECT OF DIFFERENT CYTOKINES ON EXPRESSION OF MEMBRANE-BOUNDREGULATORS OF COMPLEMENT ACTIVITY ON HUMAN UVEAL MELANOMA-CELLS

Tumor cells are protected from antibody-dependent complement-mediated lysis by membrane-bound regulators of complement activation (m-RCA). m -RCA are expressed on uveal melanoma cells. We determined whether cyto kine treatment affects expression of m-RCA on these cells in vitro. m- RCA expression on uveal melanoma cell lines was studied by flow cytome try, using monoclonal antibodies directed against CD46, CD55, and CD59 . Cytokines studied were interferon-alpha (IFN-alpha), IFN-gamma, inte rleukin-1B (IL-1B), 1L-12, and tumor necrosis factor-alpha (TNF-alpha) . All three m-RCA were expressed on the uveal melanoma cell lines (CD5 9>>CD46>CD55), although in variable amounts, With a few exceptions, th e cytokines had no effect on m-RCA expression. CD55 expression was not influenced by any of the cytokines. IFN-gamma downregulated expressio n of CD46 on one cell line (p < 0.01). TNF-alpha upregulated CD59 expr ession on two of the five cell lines (p < 0.012 and p < 0.001, respect ively), which effect was dose dependent, IFN-alpha, IFN-gamma, IL1-bet a, IL12, and TNF-alpha had limited effects on m-RCA expression on uvea l melanoma cells in vitro,