Official reprint from UpToDate®
www.uptodate.com ©2017 UpToDate, Inc. and/or its affiliates. All Rights Reserved.

Medline ® Abstract for Reference 81

of 'Enterotoxicity of chemotherapeutic agents'

Association of thymidylate synthase enhancer region polymorphisms with thymidylate synthase activity in vivo.
de Bock CE, Garg MB, Scott N, Sakoff JA, Scorgie FE, Ackland SP, Lincz LF
Pharmacogenomics J. 2011 Aug;11(4):307-14. Epub 2010 Jun 08.
Two known polymorphisms in the 5' enhancer region (ER) of the thymidylate synthase (TS) gene, a variable number of tandem repeats of a 28 bp sequence (2R/3R) and a further G>C single nucleotide substitution within the repeats, result in genotypes with 0-5 functional upstream stimulatory factor (USF) E-box consensus elements. However, the relationship between these polymorphisms, regulation of TS expression and patient response to fluoropyrimidine treatment has been inconsistent. In this study, seven possible TSER allele configurations showed similar patterns of luciferase gene expression regardless of cell type or USF-1 content, with no significant difference in promoter activity between the wild-type 2RGC and 3RGGC (1.40±0.37 vs 1.43±0.32, P=0.90), whereas the minor alleles, 2RCC and 3RGCC, were significantly reduced (0.84±0.17, P=0.01) and increased (3.19±0.72, P=0.001) respectively. Patient plasma levels of 2'-deoxyuridine, a surrogate marker of TS activity, were significantly different between genotypes (P<0.001) and inversely related to luciferase activity (P=0.02) but not to the absolute number of functional repeated elements (P=0.16), suggesting that the position, rather than the number of functional USF E-box repeats in the TSER, is responsible for determining gene expression in vitro and TS activity in vivo.
Leukaemia Foundation Laboratory, Division of Cancer and Cell Biology, Queensland Institute of Medical Research, Brisbane, Queensland, Australia.