ZD1839 (Iressa) modifies the activity of key enzymes linked to fluoropyrimidine activity: rational basis for a new combination therapy with capecitabine.
OBJECTIVE
The efficacy of new oral fluoropyrimidines, including capecitabine, is improved in cells expressing high levels of thymidine phosphorylase (TP) and low levels of thymidylate synthase (TS) and dihydropyrimidine dehydrogenase. We used a human head and neck cancer cell line (CAL33) to examine the influence of cell cycle modifications on TS, TP, and dihydropyrimidine dehydrogenase activity.


METHODS
Cells were exposed to the epidermal growth factor receptor tyrosine kinase inhibitor ZD1839 (Iressa(2)) and 5'-deoxy-5-fluorouridine (5'-DFUR), alone and in combination, for up to 96 h, and modifications in cell cycle, enzyme activity, and gene expression were examined.


RESULTS
ZD1839 (24- to 72-h exposure) markedly reduced proliferation and caused a rapid increase in G(0)-G(1) and a decrease in S phase; a 40-fold decrease in TS activity at 24 h and a 2.5-fold increase in TP activity at 48 h were observed. A significant link between TP activity and expression was observed (r(2) = 0.98; P = 0.0068). Additional investigations pointed out an increased cellular production of 5-fluorouracil anabolites from 5'-DFUR when cells were preincubated with ZD1839. Dose-effect curves of ZD1839 and 5'-DFUR, alone and in combination, were examined. Combination indices for ZD1839 + 5'-DFUR were 0.58 +/- 0.1 and 0.63 +/- 0.1 for 50% survival and 25% survival, respectively. Additional investigations pointed out an increased cellular production of 5-fluorouracil anabolites from 5'-DFUR when cells were preincubated with ZD1839.


CONCLUSIONS
These data demonstrate a strong synergistic interaction between ZD1839 and 5'-DFUR when ZD1839 is applied before or concurrently with 5'-DFUR. Such a drug combination would have two advantages: (a) the theoretical advantage of tumor selectivity of epidermal growth factor receptor-targeted therapy; and (b) the practical advantage of a combination therapy that could be administered p.o.
Oncopharmacology Unit, Centre Antoine Lacassagne, 06189 Nice Cedex 2, France.
Nicolas
N
Magné
Jean-Louis
JL
Fischel
Alain
A
Dubreuil
Patricia
P
Formento
Joseph
J
Ciccolini
Jean-Louis
JL
Formento
Céline
C
Tiffon
Nicole
N
Renée
Sandrine
S
Marchetti
Marie-Christine
MC
Etienne
Gérard
G
Milano
D000284:Administration, Oral; D000964:Antimetabolites, Antineoplastic / Q000627:therapeutic use*; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D000971:Antineoplastic Combined Chemotherapy Protocols; D000069287:Capecitabine; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division; D045744:Cell Line, Tumor; D002470:Cell Survival; D017931:DNA Primers / Q000737:chemistry; D003841:Deoxycytidine / Q000008:administration & dosage* / Q000031:analogs & derivatives*; D005467:Floxuridine / Q000627:therapeutic use*; D005472:Fluorouracil / Q000031:analogs & derivatives; D000077156:Gefitinib; D006258:Head and Neck Neoplasms / Q000188:drug therapy*; D006801:Humans; D008956:Models, Chemical; D016133:Polymerase Chain Reaction; D011743:Pyrimidines / Q000737:chemistry*; D011799:Quinazolines / Q000008:administration & dosage*; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic
D000964:Antimetabolites, Antineoplastic; D000970:Antineoplastic Agents; D017931:DNA Primers; D011743:Pyrimidines; D011799:Quinazolines; D012333:RNA, Messenger; D005467:Floxuridine; D003841:Deoxycytidine; D012313:RNA; C029269:5-fluoropyrimidine; D000069287:Capecitabine; D000077156:Gefitinib; D005472:Fluorouracil; C025034:doxifluridine