CD274 and esophageal squamous cell carcinoma: Figure 2H depicts the IHC results. We further analyzed the expression of PD-L1 and PD-1, a key immune checkpoint molecule, in tumor versus normal tissues. As shown in Supplementary Figure S1, PD-L1 expression was significantly higher in ESCC tissues compared to normal tissues (P < 0.001), consistent with its role in tumor immune evasion.