Copy-number analysis of topoisomerase and thymidylate synthase genes in frozen and FFPE DNAs of colorectal cancers

Academic Article

Abstract

  • Background: Archived formalin-fixed, paraffin-embedded specimens represent an important resource for pharmacogenomic analysis in retrospective clinical studies but the quality of results from formalin-fixed, paraffin-embedded samples is of concern due to the fact of the degradation of DNAs and RNAs from formalin-fixed, paraffin-embedded tissues. Methods: In the present study, we used DNA from fresh frozen as well as formalin-fixed, paraffin-embedded tumor to detect copy-number changes in colorectal cancer, and our data shows that formalin-fixed, paraffin-embedded DNAs were able to deliver reliable copy-number data, and that quantitative PCR had the ability to detect copy-number changes from deletion to amplification, with high concordance of copy-number calls among formalin-fixed, paraffin-embedded and frozen DNAs. Results: The amplification of topoisomerase I and deletion of thymidylate synthase were found in 23% (12/52) and 27% (14/52) of colorectal cancers, but EGF receptor amplification was not common (5/52, <10%). Among 52 colorectal cancers, 31 tumors were both topoisomerase I and thymidylate synthase diploid, which may have a worse outcome for tumor chemotherapy; and there were five tumors with favorable genomics (topoisomerase I amplification and thymidylate synthase deletion). Furthermore, topoisomerase I-amplified tumors had a two-times higher RNA level and a nearly twofold higher protein expression level than did the diploid tumors (p < 0.001 and 0.01, respectively), but there were no correlations between copy-number status and RNA or protein level for thymidylate synthase. Conclusions: Our study suggests a potential pharmacogenomic influence of topoisomerase I copy-number alteration on its RNA/protein expressions, which could be reflected on tumor response to chemotherapy in human colorectal cancer. © 2008 Future Medicine Ltd.
  • Authors

    Published In

  • Pharmacogenomics  Journal
  • Digital Object Identifier (doi)

    Author List

  • Yu J; Miller R; Zhang W; Sharma M; Holtschlag V; Watson MA; McLeod HL
  • Start Page

  • 1459
  • End Page

  • 1466
  • Volume

  • 9
  • Issue

  • 10