PDCD1 and cancer: As shown in Figure 8A, the proportions of CD3+CD8+ cytotoxic T lymphocytes (CTLs), which have been reported to play pivotal roles in killing cancer cells (Peng et al., 2024), are significantly increased after being treated with Cis plus anti-PD-1, and the proportions of CTLs in the knockdown group are much higher than those in the NC group.