Uveal melanoma: no expression of HLA-G.
OBJECTIVE
To investigate whether uveal melanoma cells express HLA-G, a nonclassical HLA class I molecule that has been shown to be a critical mediator in the inhibition of natural killer (NK) cell-mediated cytolysis.


METHODS
Eleven human uveal melanoma cell lines were analyzed for the expression of HLA-G by flow cytometry, immunocytochemistry, Western blot analysis, and RT-PCR followed by Southern blot analysis. Two HLA-G-specific monoclonal antibodies were used, 87G and MEM-G/1. In addition, HLA-G expression was determined on frozen tissue sections of 17 primary uveal melanomas.


RESULTS
With all HLA-G detection methods, no evidence for HLA-G expression by uveal melanoma cells was found. In contrast, the trophoblast cell line JEG-3 clearly expressed HLA-G transcripts and protein in all cases. Furthermore, interferon-gamma did not induce HLA-G expression in the uveal melanoma cell lines. Notably, all cell lines expressed HLA-E, and this expression was significantly enhanced by interferon-gamma.


CONCLUSIONS
Because none of the uveal melanoma cell lines nor any of the primary uveal melanomas displayed expression of HLA-G, it is unlikely that HLA-G plays a role, direct or indirect, in the modulation of cellular immunity against uveal melanoma tumors.
Hurks
H M
HM
Department of Ophthalmology, J3-S, Leiden University Medical Center, PO Box 9600, 2300 RC Leiden, The Netherlands. h.m.m.hurks@lumc.nl
Valter
M M
MM
Wilson
L
L
Hilgert
I
I
van den Elsen
P J
PJ
Jager
M J
MJ
D015153:Blotting, Western; D005434:Flow Cytometry; D006680:HLA Antigens / Q000032:analysis* / Q000235:genetics; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I / Q000032:analysis* / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry; D008545:Melanoma / Q000276:immunology*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D014604:Uveal Neoplasms / Q000276:immunology*
D006680:HLA Antigens; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I; D012333:RNA, Messenger