Frequently studied PD-1 polymorphisms, PD-1.1 (rs36084323), PD-1.3 (rs11568821), PD-1.5 (rs2227981), PD-1.9 (rs2227982), and PD-1 rs7421861, and their associations in the risk of susceptibility to different types of cancer are mentioned in this review, as are studies highlighting the significance of conducting genetic association studies in different ethnic populations.
However, there were no significant associations between either PD-1.9 (rs2227982) or PD-1 rs7421861 polymorphisms and cancer risks in all genetic models and alleles.
The results of meta-analysis: the PDCD-1.5 (rs2227981) and PDCD-1.3 (rs11568821) polymorphisms were associated with decreased risk of cancer (rs2227981: OR = 0.75, 95% CI: 0.64-0.86, P < 0.0001 for TT vs TC + CC; rs11568821: OR = 0.79, 95% CI: 0.65-0.96, P = 0.02 for TC vs TT), while no significant associations were found for the other 3 polymorphisms (PDCD-1.9 [rs2227982] polymorphism: OR = 1.03, 95% CI: 0.90-1.18, P = 0.66 for CC + TC vs TT; PDCD1 rs7421861 polymorphism: OR = 1.10, 95% CI: 0.96-1.25, P = 0.16 for CC + TC vs TT; PDCD-1.6 [rs10204525] polymorphism: OR = 0.93, 95% CI: 0.82-1.05, P = 0.24 for GG + GA vs AA).