IDO1 and melanoma: Specifically, Wu et al. recently demonstrated that Sox2 is able to promote the expression of immunosuppressive genes, such as PD-L1 and IDO1, favoring melanoma CSC-mediated depletion of T cell cytotoxic activity; in line with this observation, epigenetic suppression of Sox2 was observed to synergize with anti-PD-1-based immunotherapy in melanoma mouse models [247].