Thymidylate Synthase Expression in Patients with Colorectal Carcinoma Using a Polyclonal Thymidylate Synthase Antibody in Comparison to the TS 106 Monoclonal Antibody

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 en...

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Published in:The journal of histochemistry and cytochemistry 2000-06, Vol.48 (6), p.755-760
Main Authors: Van Triest, Baukelien, Loftus, Barbara M, Pinedo, Herbert M, Backus, Harold H.J, Schoenmakers, Pascale, Telleman, Frank, Tadema, Thea, Aherne, G. Wynne, Van Groeningen, Cornelius J, Zoetmulder, Frans A.N, Taal, Babs G, Johnston, Patrick G, Peters, Godefridus J
Format: Article
Language:English
Subjects:
Animals
Antibodies - immunology
Antibodies, Monoclonal - immunology
Blotting, Western - methods
Colorectal Neoplasms - enzymology
Colorectal Neoplasms - pathology
Female
Humans
Immunoenzyme Techniques
Male
Middle Aged
Rabbits
Thymidylate Synthase - biosynthesis
Thymidylate Synthase - immunology
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Summary: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 anti-human 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.
ISSN:0022-1554
1551-5044
DOI:10.1177/002215540004800604