PDCD1 and neoplasm: The NAC combination used in our study differentially preserved the tumour-infiltrating CD8+ T cell population but significantly reduced both the circulating and tumour-infiltrating FOXP3+, CTLA-4+ (stromal), and immune checkpoint PD-1+ T cells, thereby preventing the secretion of inhibitory cytokines (IL-4, IL-10, and TGF-β) and disrupting the PD-1/PD-L1 pathway.