[HLA-G: a tolerance molecule implicated in the escape of tumors from immunosurveillance]

To define rational anti-tumor immunotherapy strategies, the reasons for the frequent lack of efficacy of the immune response to developing tumors must be elucidated. One hypothesis involves expression by tumor cells of molecules with local immuno-suppressive effects. HLA-G is known to be involved in tolerance of the fetus by the maternal immune system. We studied HLA-G expression in primary and metastatic melanomas (ex vivo biopsies and cell lines). We found a high level of HLA-G transcription and expression at the surface of the cells. A variety of patterns of HLA-G isoform transcription and protein expression were seen. The ability of HLA-G to inhibit the cytotoxic effect of two immunocompetent cell types involved in the antitumor response, namely natural killer cells (NK) and T-cells, suggests that HLA-G may help tumors evade the immune system.