Rikke and colleagues have established a B16 melanoma model overexpressing IDO (B16-IDO) and found that MDSCs sorted from B16-IDO tumors showed significantly higher ARG1 expression, increased NO production, and upregulated TNF-α, IL- 10, IL-4, IL-6, IL-2, IFN-γ, IL-13, MIG, MCP-1, MIP-1α, IP-10, VEGF, and GM-CSF that related to MDSC recruitment, amplification, activation, and function. Here, IDO1 is linked to melanoma.