Correlation of thymidylate synthase, thymidine phosphorylase and dihydropyrimidine dehydrogenase with sensitivity of gastrointestinal cancer cells to 5-fluorouracil and 5-fluoro-2'-deoxyuridine.
OBJECTIVE
To determine the expression levels of three metabolic enzymes of fluoropyrimidines: thymidylate synthase (TS), thymidine phosphorylase (TP) and dihydropyrimidine dehydrogenase (DPD) in seven human gastrointestinal cancer cell lines, and to compare the enzyme levels with the sensitivity to 5-fluorouracil (5-FU) and 5-fluoro-2'-deoxyuridine (FdUrd).


METHODS
TS, TP and DPD mRNA levels were assessed by semi-quantitative RT-PCR, TP and DPD protein contents were measured by ELISA. Fifty percent inhibitory concentrations of growth (IC50), representing the sensitivity to drugs, were determined by MTT assay.


RESULTS
IC50 values ranged from 1.28 to 12.26 microM for 5-FU, and from 5.02 to 24.21 microM for FdUrd, respectively. Cell lines with lower DPD mRNA and protein levels tended to be more sensitive to 5-FU (P<0.05), but neither TS nor TP correlated with 5-FU IC50 (P>0.05). Only TS mRNA level was sharply related with FdUrd sensitivity (P<0.05), but TP and DPD were not (P>0.05). A correlation was found between mRNA and protein levels of DPD (P<0.05), but not TP (P<0.05).


CONCLUSIONS
DPD and TS enzyme levels may be useful indicators in predicting the antitumor activity of 5-FU or FdUrd, respectively.
Ma
Tao
T
Shanghai Institute of Digestive Surgery, Ruijin Hospital, Shanghai Second Medical University, Shanghai 200025, China.
Zhu
Zheng-Gang
ZG
Ji
Yu-Bao
YB
Zhang
Yi
Y
Yu
Ying-Yan
YY
Liu
Bing-Ya
BY
Yin
Hao-Ran
HR
Lin
Yan-Zhen
YZ
D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D045744:Cell Line, Tumor / Q000187:drug effects / Q000201:enzymology; D015179:Colorectal Neoplasms; D042943:Dihydrouracil Dehydrogenase (NADP) / Q000235:genetics / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D004798:Enzymes / Q000235:genetics / Q000378:metabolism*; D005467:Floxuridine / Q000494:pharmacology; D005472:Fluorouracil / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D013274:Stomach Neoplasms; D013939:Thymidine Phosphorylase / Q000235:genetics / Q000378:metabolism; D013940:Thymidylate Synthase / Q000235:genetics / Q000378:metabolism
D000964:Antimetabolites, Antineoplastic; D004798:Enzymes; D005467:Floxuridine; D042943:Dihydrouracil Dehydrogenase (NADP); D013940:Thymidylate Synthase; D013939:Thymidine Phosphorylase; D005472:Fluorouracil