PDCD1 and diffuse large B-cell lymphoma: Finally, the correlations between PIK3R4 expression and immune checkpoint molecule expression were calculated, and the results showed that PIK3R4 mRNA expression was significantly associated with BTN3A2, BTN3A1, PRF1, CXCL9, PDCD1, and TIGIT expression in DLBCL (Figure 8, all P < 0.05).