In addition, TRAT1 co-expressed genes were involved in Th1, Th2, and Th17 cell differentiation; PD-L1 expression and PD-1 checkpoint pathway in cancer; TCR, B cell receptor (BCR), NF-kappa B, JAK-STAT, PI3K-AKT, VEGF, and other signalling pathways as per KEGG analysis (Figure 4D and Table 2). The gene discussed is PDCD1; the disease is cancer.