UGT1A1 haplotypes associated with reduced glucuronidation and increased serum bilirubin in irinotecan-administered Japanese patients with cancer

Clin Pharmacol Ther. 2004 Jun;75(6):501-15. doi: 10.1016/j.clpt.2004.01.010.


Purpose: A comprehensive haplotype analysis of UGT1A1 in the Japanese population was conducted, and the effects of these haplotypes were investigated with respect to UGT1A1-related phenotypic parameters in patients with cancer who received irinotecan.

Methods: The UGT1A1 gene, including the enhancer, the promoter, and all 5 exons and their flanking regions, was sequenced from 195 Japanese subjects. The gene was divided into 2 blocks, and the haplotypes of each block were assigned. The association of these haplotypes with area under the concentration-time curve (AUC) ratios (7-ethyl-10-hydroxycamptothecin glucuronide [SN-38G]/7-ethyl-10-hydroxycamptothecin [SN-38]) and pretreatment levels of serum total bilirubin was investigated in 85 cancer patients who received irinotecan.

Results: Four haplotype groups (*1, *60, *28, and *6) were assigned in block 1, and 2 haplotype groups (*IA and *IB) were in block 2. The majority of the *IB haplotypes in block 2 were linked to either the *1 or the *60 haplotype but not to *28 in block 1. Highly significant associations were obtained between the *28 haplotypes and both a reduced AUC ratio (P =.0014, Jonckheere-Terpstra [JT] test) and an increased total bilirubin level (P =.0007, JT test). Increased total bilirubin levels in the *60 (P =.0048, JT test) and *IB groups (P =.0224, JT test) were also observed. The reduction in the AUC ratio by the *6 group was moderate (P =.0372, JT test) but was remarkable in combination with *60 (*6/*60) or *28 (*6/*28) as compared with the *1 group (*1/*1) (P =.049 and P =.0071, respectively; nonparametric Dunnett test).

Conclusion: This study identified several UGT1A1 haplotypes significantly associated with the reduced AUC ratio (*28 and *6) and with the increased total bilirubin level (*28, *60, and *IB) and suggested that the novel haplotype *IB might be functionally important. These findings will be useful for further pharmacogenetic studies on adverse reactions to irinotecan.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Bilirubin / blood*
  • Camptothecin / administration & dosage
  • Camptothecin / analogs & derivatives*
  • Camptothecin / metabolism*
  • Female
  • Genetic Linkage / genetics
  • Glucuronides / genetics
  • Glucuronides / metabolism*
  • Glucuronosyltransferase / genetics*
  • Glucuronosyltransferase / metabolism
  • Haplotypes / genetics*
  • Humans
  • Irinotecan
  • Japan
  • Male
  • Middle Aged
  • Neoplasms / blood
  • Neoplasms / drug therapy
  • Neoplasms / enzymology*
  • Neoplasms / genetics*
  • Polymorphism, Single Nucleotide / genetics


  • Glucuronides
  • Irinotecan
  • UGT1A1 enzyme
  • Glucuronosyltransferase
  • Bilirubin
  • Camptothecin