Thymidylate synthase gene polymorphism predicts toxicity in colorectal cancer patients receiving 5-fluorouracil-based chemotherapy.
OBJECTIVE
The target enzyme for 5-fluorouracil (5-FU) is thymidylate synthase (TS). The TYMS gene encoding this enzyme is polymorphic, having either double (2R) or tri-tandem (3R) repeats of a 28-bp sequence in the promoter region and a 6-bp variation in the 3'-untranslated region (3'-UTR). TS expression predicts response to 5-FU-based chemotherapy, and the expression seems to be determined by the TYMS gene promoter. The aim of this study was to investigate the utility of determining these two TYMS gene polymorphisms to predict the toxicity and efficacy of 5-FU treatment in patients with colorectal cancer.


METHODS
The determination of TYMS genotypes was performed in tumor and normal tissues by PCR amplification from 90 patients with colorectal cancer who were treated with adjuvant or palliative 5-FU-based chemotherapy. Associations between polymorphisms in the TYMS promoter and in the 3'-UTR gene and clinical outcome of these 90 patients treated with 5-FU based chemotherapy were evaluated individually. The linkage between TYMS promoter and TYMS 3'-UTR region polymorphisms was evaluated and a haplotype analysis was performed.


RESULTS
Individuals who were homozygous for the double repeat in the TYMS promoter region had more severe side effects to 5-FU. Patients with a 2R/2R, a 2R/3R, or a 3R/3R genotype had a grade 3 or 4 toxicity rate of 43, 18, and 3% respectively (P < 0.01). The TYMS promoter and TYMS 3'-UTR polymorphisms were in linkage disequilibrium, and the haplotype 2R/ins 6-bp was significantly associated with a high risk of severe side effects to 5-FU. The TYMS promoter and TYMS 3'-UTR polymorphisms were not associated with a response to 5-FU and survival of patients who received palliative 5-FU-based chemotherapy.


CONCLUSIONS
This study demonstrated that TYMS genotyping could be of help in predicting toxicity to 5-FU-based chemotherapy. TYMS genotyping might make it possible to individualize treatment for patients with colorectal cancer.
Lecomte
Thierry
T
Service de Gastroentérologie, Assistance Publique Hôpitaux de Paris, Hôpital Européen Georges Pompidou, Paris. Pierre.Laurent-Puig@biomedicale.univ-paris5.fr
Ferraz
Jean-Marc
JM
Zinzindohoué
Franck
F
Loriot
Marie-Anne
MA
Tregouet
David-Alexandre
DA
Landi
Bruno
B
Berger
Anne
A
Cugnenc
Paul-Henri
PH
Jian
Raymond
R
Beaune
Philippe
P
Laurent-Puig
Pierre
P
D020413:3' Untranslated Regions / Q000235:genetics; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000964:Antimetabolites, Antineoplastic / Q000009:adverse effects*; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000201:enzymology*; D005260:Female; D005472:Fluorouracil / Q000009:adverse effects*; D005838:Genotype; D006239:Haplotypes / Q000235:genetics; D006720:Homozygote; D006801:Humans; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic / Q000235:genetics*; D011379:Prognosis; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D013940:Thymidylate Synthase / Q000235:genetics* / Q000378:metabolism
D020413:3' Untranslated Regions; D000964:Antimetabolites, Antineoplastic; D012333:RNA, Messenger; D013940:Thymidylate Synthase; D005472:Fluorouracil