ICOS and neoplasm: This observation prompted us to further analyze gene sets related to Tregs — particularly, tumor-associated Tregs recently identified in various tumor contexts, variously designated as intratumoral Tregs, activated Tregs, or effector Tregs (33–37) — that express specific signatures including cytokine/chemokine receptors ST2 (IL1RL1) and CCR8; immune checkpoints CTLA-4, PD-1 (PDCD1), ICOS, and OX40 (TNFRSF4); and cytokines IL-10, TGF-β, and IL-35.