PDCD1 and colonic neoplasm: Immune infiltration analyses revealed that colon cancer in cluster 1 was characterized by higher immune scores, higher immune infiltration levels (e.g., CD8+ T cells), increased active immune function (e.g., inflammatory promotion and cytolytic activity), and overexpression of immune checkpoints such as CTLA4, TIME3 (HAVCR2), LAG3, and PD-1 (PDCD1) than in cluster 2 [8].