IDO1 and skin cancer: Specifically, we found that synergistic interactions of HH/GLI with pro-inflammatory IL6/STAT3 or IFNγ/STAT1 signaling drive high levels of IDO1 expression in melanoma and non-melanoma skin cancers, resulting in suppression of effector T cells via IDO1-mediated production of the immunosuppressive metabolite kynurenine.