Abstract
Allele frequencies are rather constant among different ethnic groups in many genetic polymorphisms, but some polymorphisms vary in the allele frequency depending on the time when the germ-line base exchanges occurred in the history of humans and on the adaptability of the phenotypes to given environment. This review documented the allele frequencies of polymorphisms pertaining to cancer risk for Japanese, Koreans, and Chinese. Twenty-five polymorphisms of 21 genes whose allele frequencies were available for at least two out of the three ethnic groups were selected. They were ALDH2 Glu487Lys, COMT Val158Met, CYP1A1 MspI and Val/Ile, CYP1B1 Leu432Val, CYP2E1 RsaI, CYP17 T-34C, ER C975G, GSTM1, GSTT1, GSTP1 Ile105Val, IL-1B C-511T, IL-1RN 86-bp VNTR (variable number of tandem repeats), MTHFR C677T and A1298C, NAT1, NAT2, NQO1 Pro187Ser, OGG1 Ser326Cys, p21 Ser31Arg, p53 Arg72Pro, TNF-A G-308A and G-238A, and XRCC1 Arg194Trp and Arg399Gln. The allele frequencies were found for 24 in Japanese, 16 in Koreans, and 24 in Chinese. All of the polymorphisms had similar allele frequencies for these ethnic groups, except the following polymorphisms; ALDH2 Glu487Lys whose Lys allele was more common for Japanese and Taiwanese, COMT Val158Met whose Met allele was more common for Japanese, and NAT2 rapid/slow whose slow alleles were more common for Chinese. When compared with the allele frequencies among Caucasians, the following minor alleles were more frequent among Japanese/Koreans/Chinese; ALDH2 478Lys, CYP1A1 m1 and m2, CYP2E1 c2, ER 975G, GSTT1 null, NAT1 *10, NQO1 187Ser, OGG1 326Cys, p21 31Arg, and XRCC1 194Trp, and less frequent in COMT 158Met, GST-P1 105Val, IL-1RN non-4R, MTHFR 1298C, and TNF-A - 308A. The differences in genetic background may affect the impact on the lifestyle factors and/or genotypes examined in epidemiological studies. However, the influences of the variations in the allele frequency seemed to be limited among Japanese, Koreans, and Chinese. The substantial differences in the allele frequency from Caucasians could modify the influences of lifestyle factors and polymorphism genotypes, resulting in the inconsistent results of epidemiologic studies.
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