1. ¹Division of Gastroenterology and Hepatology, Department of Medicine, Radboud University Medical Center Nijmegen, The Netherlands
2. ²Department of Medicine, Division of Gastroenterology, Kantonspital, Aarau, Switzerland
3. ³Department of Surgery, Otto-von-Guericke University, Magdeburg, Germany
4. ⁴Department of Laboratory Medicine and Pathobiochemistry, Charité, Virchow-Klinikum, Universitätsmedizin Berlin, Berlin, Germany
5. ⁵TIB MOLBIOL, Berlin, Germany
6. ⁶Department of Gastroenterology, Charité, Virchow-Klinikum, Universitätsmedizin Berlin, Berlin, Germany
7. ⁷Institute of Biology and Medical Genetics – University Hospital Motol and 2nd School of Medicine of Charles University, Prague, Czech Republic

Correspondence: Dr H Witt, Department of Gastroenterology, Charité, Virchow-Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany. E-mail: heiko.witt@charite.de

Received 8 September 2006; Revised 26 November 2006; Accepted 12 December 2006; Published online 27 February 2007.

Abstract

UDP-glucuronosyltransferases (UGT) catalyze the glucuronidation of various compounds and thus inactivate toxic substrates. Genetic variations reducing the activity of UGT1A7 have been associated with various gastrointestinal cancers. Most recently, the UGT1A7*3 allele has been reported as a significant risk factor for pancreatic disorders, but we could not confirm these data. This study focused on the possible causes for the noted discrepancy. UGT1A7 genotypes were assessed in 37 samples, which were previously analyzed for UGT1A7 polymorphisms by others. We determined genotypes by melting curve analysis and by DNA sequencing. Additionally, we produced UGT1A7*1 and *3 constructs with or without a mutation at position - 57 of UGT1A7 and analyzed various combinations of these constructs. In 14/37 samples UGT1A7 genotyping results differed. The discrepancy could be explained by polymerase chain reaction bias owing to an unbalanced allelic amplification which was caused by a -57T>G variant located within the sequence of the chosen primer template in previous studies. Our findings indicate that most of the previously reported genetic associations between UGT1A7 and gastrointestinal cancers are based on primer-dependent genotyping errors.