Thymidylate synthase expression in patients with colorectal carcinoma using a polyclonal thymidylate synthase antibody in comparison to the TS 106 monoclonal antibody

Baukelien Van Triest, Barbara M. Loftus, Herbert M. Pinedo, Harold H J Backus, Pascale Schoenmakers, Frank Telleman, Thea Tadema, G. Wynne Aherne, Cornelius J. Van Groeningen, Frans A N Zoetmulder, Babs G. Taal, Patrick G. Johnston, Godefridus J. Peters

Research output: Contribution to journalArticlepeer-review

Abstract

Colorectal cancer is one of the most common human cancers, for which 5- fluorouracil (5FU) is usually part of the treatment. Thymidylate synthase (TS), the target enzyme for 5FU, can be predictive for the outcome of 5FU- based therapy. TS levels in tumor samples can be determined with radiochemical enzyme assays, RT-PCR, and immunohistochemical staining. We validated TS immunohistochemistry with a polyclonal rabbit antihuman TS antibody using the avidin-biotin method. This antibody can be used on paraffin-embedded, formalin-fixed material using an antigen retrieval method with citrate buffer and microwave treatment. The antibody shows a granular cytosolic staining pattern. The reproducibility in cross-sections from colorectal tumors from 50 patients was 90% and the interobserver variability was acceptable with a kappa of 0.45. On Western blotting it detects purified TS at 36 kD, while in 5FU-treated cells the ternary complex between FdUMP, TS, and 5,10-methylene-tetrahydrofolate is clearly visible at 38 kD, with no other interfering bands. In a separate set of tumors, immunostaining was compared with enzyme levels; Western blots correlated with enzyme levels. Because both this polyclonal antibody and the monoclonal antibody TS-106 are being used for large-scale studies, we also determined whether they could be used interchangeably. No differences were observed. This polyclonal antibody is specific and gives reproducible results. A study on a larger scale is ongoing to determine the role of TS as a predictive parameter in patients with colorectal cancer treated either with postoperative adjuvant 5FU/levamisole or with surgery only.

Original languageEnglish (US)
Pages (from-to)755-760
Number of pages6
JournalJournal of Histochemistry and Cytochemistry
Volume48
Issue number6
StatePublished - Jun 2000
Externally publishedYes

Keywords

  • Colorectal cancer
  • Immunohistochemistry
  • Polyclonal antibody
  • Thymidylate synthase

ASJC Scopus subject areas

  • Anatomy
  • Cell Biology

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