PDCD1 and cancer: At the single‐cell level in non‐responders, nearly all immuno‐suppressive/exhausted markers as PD‐1, CTLA4, and BTLA, along with CCR6, a receptor comprising CCR6/CCL20 axis and promoting cancer progression,[17] elevated consistently in peripheral HLA‐DR+CD8+ T cells (Figure 4H; Figure S6D and Table S7, Supporting Information).