CD4 and cancer: The PDAC samples from the different cuproptosis-related clusters had significantly different infiltration levels of several key immune cell types, including activated CD4+ T cells, activated CD8+ T cells, CD56dimNK cells, eosinophils, neutrophils, and T helper 2 (TH2) cells, indicating a potential role of cuproptosis in PDAC cancer immunology (Supplementary Figure S4).