Synergistic efficacy of 3n-butyrate and 5-fluorouracil in human colorectal cancer xenografts via modulation of DNA synthesis.
OBJECTIVE
Butyrate, produced in the colon lumen, maintains mucosal cell homeostasis. Poorly diffusible, its access is compromised in growing colon cancers and absent in distant metastases. Butyrate regulates DNA synthesis. We postulated that systemic administration of butyrate should reduce colon cancer growth and enhance 5-fluorouracil (5-FU) efficacy.


METHODS
A stable derivative of butyrate (3n-But) was used. The antitumoral efficacy of 5-FU and 3n-But, alone or combined, was evaluated in human colorectal cancers (hCRCs) subcutaneously, orthotopically, or intrasplenically grafted into nude mice. Thymidylate synthase (TS) and thymidine kinase (TK) mRNA expression, proliferation, apoptosis, and cell cycle alterations were studied.


RESULTS
In vivo, 5-FU alone inhibited growth of only 3 of the 12 hCRCs tested and 3n-But alone had no effect; the 5-FU/3n-But combination inhibited growth of all 16 hCRCs tested. The hCRCs differed in their p53 and microsatellite instability status. 5-FU/3n-But decreased TK and TS mRNA expression by 20- and 40-fold, respectively, and TS activity by 75%, stopped cell proliferation without affecting cell differentiation, and significantly enhanced apoptosis. 3n-But potentiated the efficacy of Tomudex and methotrexate, 2 TS inhibitors, but not that of oxaliplatin. In vitro, 5-FU/3n-But inhibited [3H]thymidine but not bromodeoxyuridine incorporation and induced apoptosis in hCRC cell lines. Cells treated with 5-FU/3n-But did not accumulate in G1 nor in S phase of the cell cycle, while 5-FU and 3n-But arrested the cycle in S and in G1 phase, respectively. 3n-But prevented the cell rescue from 5-FU-induced cytotoxicity by uridine or thymidine.


CONCLUSIONS
3n-But and TS inhibitors acted synergistically against colorectal cancers, independently of the genetic alterations of the hCRCs. The mechanism of action of 5-FU/3n-But could be enhanced reduction of TS and prevention of thymidine salvage in DNA synthesis.
Laboratoire de Cytogénétique Moléculaire et Oncologie, UMR 147 CNRS-Institut Curie, Paris, France.
R A
RA
Bras-Gonçalves
M
M
Pocard
J L
JL
Formento
F
F
Poirson-Bichat
G
G
De Pinieux
I
I
Pandrea
F
F
Arvelo
G
G
Ronco
P
P
Villa
A
A
Coquelle
G
G
Milano
T
T
Lesuffleur
B
B
Dutrillaux
M F
MF
Poupon
D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage* / Q000494:pharmacology; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D015415:Biomarkers; D002087:Butyrates / Q000008:administration & dosage / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D015179:Colorectal Neoplasms / Q000378:metabolism* / Q000473:pathology*; D004247:DNA / Q000096:biosynthesis*; D042943:Dihydrouracil Dehydrogenase (NADP); D004357:Drug Synergism; D005260:Female; D005472:Fluorouracil / Q000008:administration & dosage* / Q000494:pharmacology; D005947:Glucose / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D008113:Liver Neoplasms / Q000378:metabolism / Q000473:pathology / Q000556:secondary; D008297:Male; D008727:Methotrexate / Q000008:administration & dosage; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D009944:Organoplatinum Compounds / Q000008:administration & dosage; D000077150:Oxaliplatin; D010088:Oxidoreductases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000235:genetics; D011799:Quinazolines / Q000008:administration & dosage; D012333:RNA, Messenger / Q000378:metabolism; D013876:Thiophenes / Q000008:administration & dosage; D013940:Thymidylate Synthase / Q000235:genetics / Q000378:metabolism; D014183:Transplantation, Heterologous
D000964:Antimetabolites, Antineoplastic; D015415:Biomarkers; D002087:Butyrates; D009944:Organoplatinum Compounds; D011799:Quinazolines; D012333:RNA, Messenger; D013876:Thiophenes; D000077150:Oxaliplatin; C069135:esterbut-3; D004247:DNA; D010088:Oxidoreductases; D042943:Dihydrouracil Dehydrogenase (NADP); D013940:Thymidylate Synthase; D011505:Protein-Tyrosine Kinases; C068874:raltitrexed; D005947:Glucose; D005472:Fluorouracil; D008727:Methotrexate