Abstract 4664: Impact of TP53 mutations, single nucleotide variants and global methylation patterns on pre-menopausal breast cancer risk

Abstract INTRODUCTION: Li-Fraumeni Syndrome (LFS) is a cancer predisposition syndrome that confers a high lifetime risk of developing malignancies, including pre-menopausal breast cancer. Over 80% of LFS patients harbor germline mutations of the TP53 tumor suppressor gene. OBJECTIVE: We sought to determine if the spectrum of TP53 variants, as well as global methylation methylation patterns, correlates with the presence of TP53 mutations or influences cancer risk in pre-menopausal breast cancer patients. METHODS: Constitutional DNA was obtained from peripheral blood lymphocytes (PBL) of 10 patients with pre-menopausal breast cancer harboring germline TP53 mutations, 10 patients diagnosed with pre-menopausal breast cancer that are non-mutation carriers, 15 TP53 mutation carriers who do not have cancer, and 15 healthy female controls. Genome-wide methylation analysis of PBL-derived DNA was performed using the Illumina 450K array. Sanger sequencing of exons 2-11, and flanking intron regions of the TP53 gene was performed. RESULTS: The most commonly observed single nucleotide polymorphism (SNP) in TP53 across all samples was at c.215C>G (p.Pro72Arg) in exon 4 (rs1042522). We observed a G allele frequency of 66.0% in our study group. Three additional low-frequency variants in TP53 were observed: the exon 4: c.108G>A (p.Pro36Pro) variant was found in 2 patients, exon 6: c.639A>G (p.Arg213Arg) was found in 9 patients and intron 9: c.993+12T>C was found in 4 patients. Methylation patterns were not associated with a specific TP53 mutation or variant; however, distinct methylation patterns were observed in TP53 mutation carriers when compared to either TP53 wild-type healthy individuals or patients with early-onset breast cancer. DISCUSSION: This study represents an epigenome-wide analysis and targeted genetic survey of germline TP53 in early-onset, pre-menoupausal breast cancer. As a result of the mutation frequency observed, germline mutations in TP53 may need to be included in the genetic work-up of patients with early-onset breast cancer. Parallel studies of genome-wide methylation demonstrate these patterns may serve as an independent biomarker of early-onset breast cancer risk. Note: This abstract was not presented at the meeting. Citation Format: Nardin Samuel, Mathieu Lemire, Ana Novokmet, Thomas J. Hudson, David Malkin. Impact of TP53 mutations, single nucleotide variants and global methylation patterns on pre-menopausal breast cancer risk. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4664. doi:10.1158/1538-7445.AM2015-4664