PDCD1 and cancer: Given the unique characteristics of LAG3 observed in this study and the complex interplay of immune checkpoints in advanced cancers, our plan to incorporate additional functional markers (including MHC class II, PD-1/PD-L1, PRF1, Galectin-3, IL-4, IL-17, IL-21, IL-9, and IL-10) to characterize phenotypic changes in T cell subsets before/after ESCC treatment and determine their functional states (activated, helper, or inhibitory) in the future [38].