SIGLEC15 and neoplasm: Furthermore, the expression distribution of immune checkpoint genes in tumor tissues and normal tissues in PCA patients was determined, and we found that CD274 (also named PD-L1), LAG3, PDCD1LG2 (also named PD-L2), TIGIT and SIGLEC15 were significantly downregulated, while CTLA4 was significantly upregulated (Figure 8G).