Further research revealed that the high risk group had increased immune checkpoint expression, including PDCD1 and CTLA4The reason the body's anti-tumor response was reduced and not boosted by the increased CD8+ T cell and NK cell populations surrounding the tumor is because it's probable that an immunosuppressive mechanism enabled ccRCC to withstand the fatal effects of NK cells and CD8+ T cells. Here, PDCD1 is linked to nonpapillary renal cell carcinoma.