IFNG and neoplasm: Secretion of sPD-1 after ICI treatment may be caused, at least partially, by enhanced production of cytokines such as IFN-α, IFN-γ, or TNF-α due to ICI-mediated anti-tumor response because altered levels of sPD-1 after treatment of ipilimumab corresponded to changes in the circulating cytokines (30).