Involvement of Nrf2 activation in resistance to 5-fluorouracil in human colon cancer HT-29 cells.
Acquisition of drug resistance by cancer cells is attributed to various factors including alterations in apoptotic pathways, enhanced expression of multidrug resistance-associated proteins, altered drug metabolism or uptake and/or overexpression of cytoprotective genes. Thus, potential induction of defence pathways by anticancer drugs might have a marked incidence on cancer cell resistance. 5-Fluorouracil (5-FU) remains the most commonly used anticancer drug for the treatment of colorectal cancer, although objective response rates are as low as 20%. The aim of our study was to investigate the effects of 5-FU on cytoprotective systems in human colon HT-29 cells. Our results demonstrate that 5-FU induced the expression of mRNAs encoding glutathione transferases and antioxidant enzymes. To further determine the mechanisms involved in 5-FU effects, we investigated whether it activates the Nrf2/antioxidant response element pathway which is implicated in the regulation of several genes involved in cytoprotection. Translocation of Nrf2 into the nucleus after 5-FU exposure was demonstrated by immunocytochemistry and western blotting. Using an ARE-driven reporter gene assay, activation of the luciferase activity by 5-FU was also evidenced. Moreover, transfection of HT-29 cells with siRNA directed against Nrf2 inhibited induction of Nrf2 target genes and increased 5-FU cytotoxicity. In conclusion, we demonstrate for the first time that 5-FU activates the Nrf2/ARE pathway which in turn induces cytoprotective genes and modulates chemosensitivity of HT-29 colon cancer cells. Therefore, we postulate that Nrf2 might represent a potential therapeutic target in 5-FU treatment of colon cancer.
Akhdar
Hanane
H
INSERM U620/EA MDC, Faculté de Pharmacie, 35043 Rennes, France.
Loyer
Pascal
P
Rauch
Claudine
C
Corlu
Anne
A
Guillouzo
André
A
Morel
Fabrice
F
D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis / Q000235:genetics; D003110:Colonic Neoplasms / Q000188:drug therapy*; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005260:Female; D005472:Fluorouracil / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic; D019073:HT29 Cells; D006801:Humans; D008297:Male; D051267:NF-E2-Related Factor 2 / Q000187:drug effects / Q000378:metabolism*
D000964:Antimetabolites, Antineoplastic; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D005472:Fluorouracil