Besaratinia A, Kim SI, Hainaut P, Pfeifer GP. In vitro recapitulating of TP53 mutagenesis in hepatocellular carcinoma associated with dietary aflatoxin B1 exposure.
Gastroenterology 2009;
137:1127-37, 1137.e1-5. [PMID:
19524575 PMCID:
PMC2736365 DOI:
10.1053/j.gastro.2009.06.002]
[Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Revised: 06/03/2009] [Accepted: 06/05/2009] [Indexed: 12/18/2022]
Abstract
BACKGROUND & AIMS
Dietary exposure to aflatoxin B(1) (AFB(1)), in addition to other known factors, increases risk for human hepatocellular carcinoma (HCC). HCCs from AFB(1)-exposed individuals frequently have distinct TP53 mutations, such as G to T transversions in the second guanine of codon 249 (AGG to AGT), and a characteristic mutational spectrum predominated by G:C to T:A mutations.
METHODS
To recapitulate the distinctive features of TP53 mutations in AFB(1)-associated HCC, we investigated AFB(1)-induced DNA adduction in relation to mutagenesis in transgenic mouse fibroblasts exposed to AFB(1) in vitro.
RESULTS
Immunodotblot determination of DNA adducts in the overall genome of AFB(1)-exposed cells revealed the dose-dependant formation of persistent imidazole ring-opened AFB(1)-DNA adducts. DNA footprinting analysis of the cII transgene in AFB(1)-exposed cells verified the dose-dependent and sequence-specific formation of DNA adducts. The preferential formation of AFB(1)-induced DNA adducts along the cII transgene was almost exclusively localized to guanine-containing sequences encompassing CpG dinucleotides. Mutation analysis of the cII transgene in AFB(1)-exposed cells revealed a dose-dependent induction of cII mutant frequency (P < .001) and a unique induced mutational spectrum characterized by predominant induction of G:C to T:A transversions that occurred within CpG sequence contexts. Notably, codons 42 and 45 of the cII transgene, which have identical sequence contexts to that of codon 249 of human TP53, constituted 2 frequently mutated sites in AFB(1)-exposed cells that contained the G to T transversion signature mutation at their third base positions.
CONCLUSIONS
In this model system, AFB(1)-induced DNA adduction and mutagenesis recapitulate the unique mutational features of TP53 in AFB(1)-associated human HCC.
Collapse