The estrogen-related receptors (ERRs) are orphan nuclear receptors (NRs) with high sequence similarity to the estrogen receptor (ER). Peroxisome proliferator-activated receptor gamma coactivator-1 beta (PERC) specifically activates ER and ERRs, thus providing a link with breast cancer growth. Here we functionally characterized a non-synonymous PERC polymorphism, rs7732671, previously associated with increased risk for familial breast cancer, and tested its clinical relevance for breast cancer progression.
A mammalian two-hybrid assay was used to identify protein interactions using full-length and truncated NR (ERα, ERRα, ERRγ) and PERC. PERC rs7732671 variant allele (649G>C_A203P) was created by site-directed mutagenesis. Expression of genes involved in cell glycolysis and/or direct ERR targets Eno1, PKM, LDHA and IDH3A, were analyzed in breast cancer cells and in breast tumors (N = 84). Cell supernatants were quantitated for lactate formation using liquid chromatography coupled mass spectrometry. PERC rs7732671 was genotyped in 896 postmenopausal early breast cancer patients treated with adjuvant tamoxifen and clinical outcome was analyzed using Kaplan-Meier and Cox regression analyses.
Truncated PERC (aa129-426) containing the 649G>C_A203P variant did not interact with ERα, but ERRα and ERRγ ligand-binding domains were activated. The PERC129-426-C allele enhanced ERRα activity by 21% and ERRγ by 67%, compared to the PERC129-426-G major allele (P<0.005). Expression of ERR downstream genes Eno1, LDHA, IDH3A and lactate concentrations were increased in MCF7 and MDA-MB-231 overexpressing PERC-C as compared to PERC-G. In breast tumors, glycolytic or ERR target gene expression was increased in patients carrying the PERC-C allele. Patients carrying the PERC-C showed higher distant recurrence rates compared with patients of the G/G genotype (P = 0.01), which was confirmed in Cox regression adjusted to tumor size, nodal status, and grade (Hazard Ratio 2.06; 95% CI 1.26-3.38, P = 0.005 per C allele).
PERC rs7732671 variant 649C_203P enhances ERRα and ERRγ signaling independent of ER. Higher lactate concentrations in cells and increased ERR target gene expression in vitro and in patients with the PERC-C allele point to a modulation of aerobic glycolysis. The ERR/PERC axis is possibly linked with disease progression in breast cancer.
Citation Format: Pilar H. Saladores, Reiner Hoppe, Wing-Yee Lo, Sibylle Cocciardi, Ute Hofmann, Ute Hamann, Peter Fasching, Marcus Schmidt, Hiltrud Brauch, Werner Schroth. Coactivator PPARGC1B Ala203Pro polymorphism is linked with estrogen-related receptor function and breast cancer outcome. [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 5485. doi:10.1158/1538-7445.AM2015-5485