PDCD1 and esophageal squamous cell carcinoma: In the present study, we showed that the frequencies of PD-1+ or TIM-3+CD4+ T cells were significantly higher in patients with cStage IV ESCC compared to those at other cStages (Figure 1b), and the PD-1+CD4+ and TIM-3+CD8+ T-cell populations were significantly higher in ESCC patients treated with CRT compared to those in patients who underwent other treatments (Figure 2b).