HLA-cw polypmorphism and killer cell immunoglobulin-like receptor (KIR) gene analysis in Korean patients with colorectal cancer.

Abstract

525 Background: Many kinds of genetic and environment factors are involved in colorectal cancer development. Natural killer cells (NK cells) play important roles to protect from viral infections and the early development of cancers, and it is activated or inhibited by killer cell immunoglobulin-like receptors (KIR) which bind to HLA class I. KIR genes are encoded on chromosome 19q13.4. And there are 7 kinds of activating KIRs, and another 7 kinds of inhibiting KIRs. The genetic polymorphisms of KIR genes effect the expression of KIR on NK cells, and there are ethnic differences. In this study, we were trying to investigate the KIR genotype of Korean colorectal cancer patients. Methods: DNAs were extracted from the peripheral bloods from normal populations and Korean colorectal cancer patients. KIR genes were amplified using PCR-SSP methods, and HLA-Cw genes were characterized using PCR methods. The results were analyzed between cancer patients and normal control group. Results: KIR2DL2 and KIR2DS2 were found at low rate and KIR2DL3 were found at high rate compare to the Eastern studies, but the rates were similar with Japan study. In this study, KIR2DS5 (33.2% vs. 20.8%, p-value<0.007) was increased in colorectal cancer group, and in rectal cancer subgroup, KIR3DL1 (93.2%, vs. 98.1%, p-value<0.05), KIR2DS2 (7.8% vs. 19.5%, p-value<0.01), KIR2DS4 (93.2% vs. 98.1%, p-value<0.05) were decreased significantly. HLA-Cw6 (9.1% vs. 15.7%, p-value<0.05) and HLA-Cw7 (17.4% vs. 27.7%, p-value<0.02) were decreased in colorectal cancer group, but no difference was found when they were classified to HLA-C1 and HLA-C2 group. Among the patients with HLA-C1 homozygote, KIR2DS2 was decreased significantly (5.8% vs. 14.5%, p-value<0.004). Conclusions: There are ethnic differences of KIR genotypes. KIR2DS5 is increased in Korean colorectal cancer patients, and in rectal cancer subgroup, KIR3DL1, KIR2DS2 and KIR2DS4 are decreased, so there are immunologic differences between colon and rectal cancers. And among the patients with HLA-C1 homozygote, KIR2DS2 is decreased. Therefore KIR2DS2 in presence of their ligand (HLA-C1 group) may have protective effect against colorectal cancer.