[Potentiation of 5-fluorouracil efficacy. Molecular mechanisms playing a role in the cytotoxic action of 5-fluorouracil and 5-ethyl-2'-deoxyuridine (EUdR) combination].
Pharmacologic modulation of 5-fluorouracil (5-FU) metabolism provides a possibility for the enhancement of its clinical efficacy.


OBJECTIVE
The purpose of the present work was to study the effect of 5-ethyl-2'-deoxyuridine (EUdR), a potent 5-FU modulator, on different molecular mechanisms, influenced by 5-FU itself, and to obtain further data about the mode of action of the combination.


METHODS
SW620 cell line was used for the experiments. Cytotoxicity was studied by MTT test, cell kinetic changes by FACStar flow cytometer, apoptosis by fluorescent microscope after staining the cells with acridine orange and ethydium bromide, DNA fragmentation by PAGE electrophoresis after RNase and proteinase-K digestion, thymidine incorporation with 3H-thymidine, p53 and PCNA protein expression by Western blotting.


RESULTS
The cytotoxicity of 5-FU was potentiated dose dependently by EUdR. One hundred muM concentration of EUdR resulted in a 40% decrease of the IC50 value of 5-FU. Cell cycle arrest in the G2/M transition phase was most pronounced after combined treatment with 5-FU+EUdR. EUdR potentiated the incorporation of 3Hthymidine into DNA. In addition to the increase of apoptosis rate, the expression of p53 protein, caused by 5-FU was further potentiated by UdR.


CONCLUSIONS
This study demonstrated a potential novel approach to increase the efficacy of 5-FU by EUdR, which incorporated two complementary molecular actions, the selective modulation of TS inhibition and potentiation of the p53 protein expression, consequently leading to an increase in the apoptotic rate.
Katona
Csilla
C
Onkoradiológia, Uzsoki utcai Kórház, Budapest, Hungary.
Timár
Ferenc
F
Oláh
Júlia
J
Bocsi
József
J
Budai
Barna
B
Otvös
László
L
Kralovánszky
Judit
J
D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis; D015153:Blotting, Western; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000188:drug therapy*; D053938:DNA Fragmentation; D003857:Deoxyuridine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D004357:Drug Synergism; D004591:Electrophoresis, Polyacrylamide Gel; D005434:Flow Cytometry; D005472:Fluorouracil / Q000494:pharmacology*; D006801:Humans; D008856:Microscopy, Fluorescence; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis; D013997:Time Factors; D016159:Tumor Suppressor Protein p53 / Q000032:analysis
D000964:Antimetabolites, Antineoplastic; D018809:Proliferating Cell Nuclear Antigen; D016159:Tumor Suppressor Protein p53; C022811:edoxudin; D005472:Fluorouracil; D003857:Deoxyuridine