Interestingly, the expanded products of CD137+ T cells in vitro secreted multiple cellular cytokines, including IFN-γ, TNF-α and IL-2, after co-culture with a mixture of preferentially expressed antigen in melanoma-derived peptides, a specific tumor antigen upregulated in melanoma obtained from the peripheral blood of healthy donors (77). Here, TNFRSF9 is linked to melanoma.