IDO1 and melanoma: Importantly, this association was even stronger among metastatic melanomas, suggesting the existence of a more intense immunosuppression in these tumors (e.g., in primary melanoma, PD-1, p = 1.14e−35, Pearson’s rho = 0.887; LAG3, p = 1.03e−45, Pearson’s rho = 0.930; IDO1, p = 3.05e−08, Pearson’s rho = 0.513.