Abstract LB-121: Polymorphic variants in PPARGC1A and PCMTD1 associate with earlier age of onset in ER-negative breast cancer

Abstract

Abstract Background: Breast cancer is the most frequent cancer and leading cause of cancer death among women worldwide. As <10% of breast cancers are due to mutations in BRCA1 and BRCA2, other perturbations such as single nucleotide polymorphisms (SNPs) may be genetic contributors. Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PPARGC1A) enhances estrogen receptor (ER) and estrogen related receptor gamma (ERRγ) activity by acting as a coactivator. ERRγ has been demonstrated to regulate vascular endothelial growth factor mRNA expression in both ER-positive and ER-negative breast cancer cell lines, indicating that it may accelerate angiogenesis and metastasis. PCMTD1 encodes protein-L-isoaspartate O-methyltransferase domain-containing protein 1, a S-adenosylmethionine-dependent methyltransferase whose biological relevance is largely unknown to present. SNPs in PPARGC1A have been correlated with metabolic diseases, but within the three studies evaluating cancer phenotypes for this gene, only Thr612Met (76873 C→T) revealed a significant association with familial breast cancers. Experimental Procedure: SNPs in PPARGC1A and PCMTD1 were selected using a bioinformatics approach based on SNP associations with drug response in NCI-60 cell lines and evidence of selection bias for haplotype frequencies. Allelic discrimination assays were performed on genomic DNA isolated from whole blood from over 900 Caucasian breast cancer patients with ductal carcinomas. Clinical information was linked to genotypes to search for genotype-phenotype correlations, and statistical analyses were carried out. Results: Analysis of PPARGC1A rs4619879 revealed a mean age of diagnosis of ER-negative cases for CC and AA carriers at 50.1 and 43.8 years, respectively (p=0.019). The difference was less striking in ER-positive ductal carcinomas, with only a 2.7year earlier onset for AA carriers (p=0.013). For PCMTD1 rs9298462, the mean age at diagnosis of ER-negative cases for CC carriers was 41.2, compared to 48.8 for the TT carriers (p=0.004). No significant difference was seen in ER-positive ductal carcinomas (p=0.15). Conclusions: Our results indicate that polymorphisms in PPARGC1A and PCMTD1, two transcriptional regulators, may play a role in age at diagnosis in breast cancer, particularly ER-negative ductal carcinomas. We are performing functional studies to further evaluate these findings and to elucidate the molecular mechanisms underlying these observations. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-121. doi:10.1158/1538-7445.AM2011-LB-121