TP53 mutations induced by BPDE in Xpa-WT and Xpa-Null human TP53 knock-in (Hupki) mouse embryo fibroblasts.

TitleTP53 mutations induced by BPDE in Xpa-WT and Xpa-Null human TP53 knock-in (Hupki) mouse embryo fibroblasts.
Publication TypeJournal Article
Year of Publication2015
AuthorsKucab JE, van Steeg H, Luijten M, Schmeiser HH, White PA, Phillips DH, Arlt VM
JournalMutat Res
Volume773
Pagination48-62
Date Published03/2015
ISSN1873-135X
Keywords7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide, Animals, Benzo(a)pyrene, Cell Survival, Cells, Cultured, Codon, DNA Adducts, DNA Repair, Fibroblasts, Genes, p53, Humans, Mice, Mutagens, Mutation, Oxygen, Xeroderma Pigmentosum Group A Protein
Abstract

Somatic mutations in the tumour suppressor gene TP53 occur in more than 50% of human tumours; in some instances exposure to environmental carcinogens can be linked to characteristic mutational signatures. The Hupki (human TP53 knock-in) mouse embryo fibroblast (HUF) immortalization assay (HIMA) is a useful model for studying the impact of environmental carcinogens on TP53 mutagenesis. In an effort to increase the frequency of TP53-mutated clones achievable in the HIMA, we generated nucleotide excision repair (NER)-deficient HUFs by crossing the Hupki mouse with an Xpa-knockout (Xpa-Null) mouse. We hypothesized that carcinogen-induced DNA adducts would persist in the TP53 sequence of Xpa-Null HUFs leading to an increased propensity for mismatched base pairing and mutation during replication of adducted DNA. We found that Xpa-Null Hupki mice, and HUFs derived from them, were more sensitive to the environmental carcinogen benzo[a]pyrene (BaP) than their wild-type (Xpa-WT) counterparts. Following treatment with the reactive metabolite of BaP, benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE), Xpa-WT and Xpa-Null HUF cultures were subjected to the HIMA. A significant increase in TP53 mutations on the transcribed strand was detected in Xpa-Null HUFs compared to Xpa-WT HUFs, but the TP53-mutant frequency overall was not significantly different between the two genotypes. BPDE induced mutations primarily at G:C base pairs, with approximately half occurring at CpG sites, and the predominant mutation type was G:C>T:A in both Xpa-WT and Xpa-Null cells. Further, several of the TP53 mutation hotspots identified in smokers' lung cancer were mutated by BPDE in HUFs (codons 157, 158, 245, 248, 249, 273). Therefore, the pattern and spectrum of BPDE-induced TP53 mutations in the HIMA are consistent with TP53 mutations detected in lung tumours of smokers. While Xpa-Null HUFs exhibited increased sensitivity to BPDE-induced damage on the transcribed strand, NER-deficiency did not enhance TP53 mutagenesis resulting from damage on the non-transcribed strand in this model.

DOI10.1016/j.mrfmmm.2015.01.013
Alternate JournalMutat. Res.
PubMed ID25847421
PubMed Central IDPMC4547099
Grant List101126/B/13/Z / / Wellcome Trust / United Kingdom
101126/Z/13/Z / / Wellcome Trust / United Kingdom
C313/A14329 / / Cancer Research UK / United Kingdom