Lastly, we wanted to determine if incubation of NK-92 cells in the presence of soluble factors secreted by melanoma cells, such as TGFβ, IL-10, IDO, nitric oxide (NO) and prostaglandins, molecules that have been shown to be regularly secreted by tumor cells and to induce an immunosuppressive phenotype in primary immune cells, could also weaken immune effector function of NK-92 cells [60,61,62,63]. This evidence concerns the gene IDO1 and neoplasm.