However, Treg, especially eTregs (with greater suppressive capacity), which have been extensively correlated with poor prognosis in several tumors, including melanoma [59], have been shown to hinder responses mediated by anti-PD-1 therapy and anti-CTLA-4 [57,58,59,60,61,62,63,64,65,66]. The gene discussed is PDCD1; the disease is melanoma.