CD4 and melanoma: TH9 cells have recently been proposed to harbor superior anticancer properties compared with TH1, TH2 or TH17 in vivo in the B16 melanoma tumor model.4 6 Given that our results showed that STING ligands enhance TH9 cell differentiation, we examined the ability of naive CD4 T cells stimulated with control or cGAMP and differentiated into TH9 cells to prevent cancer tumor growth in vivo.