For instance, while we propose that the glutathione metabolite 5-oxoproline may promote tumorigenesis by reducing the proportion of CD28-CD25++ CD8+ T cells, it is necessary to confirm through animal models or in vitro co-culture experiments whether treatment with 5-oxoproline or modulation of glutathione metabolism can directly impair T cell function and accelerate tumor formation. This evidence concerns the gene CD8A and neoplasm.