Ethnic variation in the thymidylate synthase enhancer region polymorphism among Caucasian and Asian populations

Thymidylate synthase (TS) regulates the production of DNA synthesis precurs ors and is an important target of cancer chemotherapy. A tandem repeat sequ ence in a TS promoter enhancer region (TSER) was recently identified. Polym orphic variation affected in vitro expression levels of the gene. We evalua ted the influence of ethnicity on TSER genotype. Allele frequency was simil ar in Caucasian and Southwest Asian subjects. However, homozygous triple re peat subjects were tn-ice as common in Chinese subjects (67%) than in Cauca sian subjects (38%). This demonstrates significant ethnic variation in a TS gene regulatory element which may have significant impact on pyrimidine ho meostasis and drug therapy. (C) 1999 Academic Press.