IP of 5-methylcytosine (5-mc) enriched DNA fragments from control, PB treated mouse livers, resulting Ctnnb1 mutated PB liver tumours and PB minus Ha-Ras mutate liver tumour

ABSTRACT: Through the analysis of mouse liver tumours promoted by distinct routes (DEN exposure alone, DEN exposure plus non-genotoxic insult with phenobarbital and non-alcoholic fatty liver disease); we report that the cancer associated hyper-methylated CGI events in mice are also predicated by silent promoters that are enriched for both the DNA modification 5-hydroxymethylcytosine (5hmC) and the histone modification H3K27me3 in normal liver. During cancer progression these CGIs undergo hypo-hydroxymethylation, prior to subsequent hyper-methylation; whilst retaining H3K27me3. A similar loss of promoter-core 5hmC is observed in Tet1 deficient mouse livers indicating that reduced Tet1 binding at CGIs may be responsible for the epigenetic dysregulation observed during hepatocarcinogenesis. Consistent with this reduced Tet1 protein levels are observed in mouse liver tumour lesions. As in human, DNA methylation changes at CGIs do not appear to be direct drivers of hepatocellular carcinoma progression in mice. Instead dynamic changes in H3K27me3 promoter deposition are strongly associated with tumour-specific activation and repression of transcription. Our data suggests that loss of promoter associated 5hmC in diverse liver tumours licences DNA methylation reprogramming at silent CGIs during cancer progression. 5-mc is a well establisehd epigenetic mark typically related to gene silencing events. Phenobarbital (PB) is a well studied non-genotoxic carcinogen with roles in epigenetic perturbation. We profile 5mC in both control mouse livers as well as in the livers of 12 week PB treated mice. We also profile 5mC in liver tumours arising in the presence of long term PB exposure (35 week: resulting in Ctnnb1 mutated tumours) to a Ha-Ras liver tumour which arose without PB. Samples: 2 control and 2 PB exposed mouse livers, 3 liver tumours resulting from long term PB exposrue and 1 liver tumour arising without PB

ORGANISM(S): Mus musculus

SUBMITTER: John Thomson 

PROVIDER: E-GEOD-77727 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress