Programmed death-1 gene polymorphism (PD-1.5 C/T) is associated with colon cancer

Programmed death-1 (PD-1), expressed by activated T cells, is a negative regulator of T lymphocytes. The associations of the immune response-related genes with cancer have been demonstrated. In this study, the PD-1.5 C/T (+7785) polymorphism was investigated in 200 colorectal cancer patients and 200 healthy individuals as controls by nested polymerase chain reaction-restriction fragment length polymorphism method. The genotype and allele frequencies at PD-1.5 position were not significantly different between control individuals and the overall colorectal cancer patients. However, subdivision of the patients by the location (175 colon cancer and 25 rectal cancer) revealed a significant difference between colon cancer patients and healthy individuals (p=0.026), and between colon and rectal cancer patients (p=0.017). The frequency of the CT genotype was significantly higher in colon cancer patients than in control individuals (58.3% vs. 44.8%, Bonferroni corrected p-value=0.024; OR=1.74; 95% CI=1.15-2.62), and in rectal cancer patients (58.3% vs. 28.0%, Bonferroni corrected p-value=0.012; OR=3.59; 95% CI=1.42-9.04). Characteristics of the patients including age, sex, tumor grade and stage were not associated with the PD-1.5 polymorphism. Our results show a significant association between PD-1.5 polymorphism and colon cancer. Larger numbers of patients are required to investigate comprehensively the association of rectal cancer with PD-1.5 polymorphism.