Low doses of the carcinogen furan alter cell cycle and apoptosis gene expression in rat liver independent of DNA methylation.
BACKGROUND
Evidence of potent rodent carcinogenicity via an unclear mechanism suggests that furan in various foods [leading to an intake of up to 3.5 microg/kg body weight (bw)/day] may present a potential risk to human health.


OBJECTIVE
We tested the hypothesis that altered expression of genes related to cell cycle control, apoptosis, and DNA damage may contribute to the carcinogenicity of furan in rodents. In addition, we investigated the reversibility of such changes and the potential role of epigenetic mechanisms in response to furan doses that approach the maximum estimated dietary intake in humans.


METHODS
The mRNA expression profiles of genes related to cell cycle, apoptosis, and DNA damage in rat liver treated with furan concentrations of 0.1 and 2 mg/kg bw were measured by quantitative polymerase chain reaction (PCR) arrays. We assessed epigenetic changes by analysis of global and gene-specific DNA methylation [methylation-specific PCR, combined bisulfite restriction analysis (COBRA), and methylated DNA immunoprecipitation chip] and microRNA (miRNA) analyses.


RESULTS
The expression profiles of apoptosis-related and cell-cycle-related genes were unchanged after 5 days of treatment, although we observed a statistically significant change in the expression of genes related to cell cycle control and apoptosis, but not DNA damage, after 4 weeks of treatment. These changes were reversed after an off-dose period of 2 weeks. None of the gene expression changes was associated with a change in DNA methylation, although we detected minor changes in the miRNA expression profile (5 miRNA alterations out of 349 measured) that may have contributed to modification of gene expression in some cases.


CONCLUSIONS
Nongenotoxic changes in gene expression may contribute to the carcinogenicity of furan in rodents. These findings highlight the need for a more comprehensive risk assessment of furan exposure in humans.
Chen
Tao
T
School of Biosciences, University of Birmingham, Birmingham, United Kingdom.
Mally
Angela
A
Ozden
Sibel
S
Chipman
J Kevin
JK
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D002274:Carcinogens, Environmental / Q000008:administration & dosage / Q000633:toxicity*; D002453:Cell Cycle / Q000187:drug effects*; D019175:DNA Methylation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005663:Furans / Q000008:administration & dosage / Q000633:toxicity*; D015870:Gene Expression / Q000187:drug effects*; D008099:Liver / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D035683:MicroRNAs / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344
D002274:Carcinogens, Environmental; D005663:Furans; D035683:MicroRNAs; D012333:RNA, Messenger; C039281:furan