Loss of estrogen-related receptor α promotes hepatocarcinogenesis development via metabolic and inflammatory disturbances.

Estrogen-related receptor α (ERRα) is a key regulator of mitochondrial function and metabolism essential for energy-driven cellular processes in both normal and cancer cells. ERRα has also been shown to mediate bone-derived macrophage activation by proinflammatory cytokines. However, the role of ERRα in cancer in which inflammation acts as a tumor promoter has yet to be investigated. Herein we show that global loss of ERRα accelerates the development of diethylnitrosamine (DEN)-induced hepatocellular carcinoma. Biochemical and metabolomics studies revealed that loss of ERRα promotes hepatocyte necrosis over apoptosis in response to DEN due to a deficiency in energy production. We further show that increased hepatocyte death and associated compensatory proliferation observed in DEN-injured ERRα-null livers is concomitant with increased nuclear factor κB (NF-κB)-dependent transcriptional control of cytokine expression in Kupffer cells. In particular, we demonstrate that loss of ERRα-dependent regulation of the NF-κB inhibitor IκBα leads to enhanced NF-κB activity and cytokine gene activation. Our work thus shows that global loss of ERRα activity promotes hepatocellular carcinoma by independent but synergistic mechanisms in hepatocytes and Kupffer cells, implying that pharmacological manipulation of ERRα activity may have a significant clinical impact on carcinogen-induced cancers.

Integrated multi-omics analysis of adverse cardiac remodeling and metabolic inflexibility upon ErbB2 and ERRα deficiency.

Functional oncogenic links between ErbB2 and ERRα in HER2+ breast cancer patients support a therapeutic benefit of co-targeted therapies. However, ErbB2 and ERRα also play key roles in heart physiology, and this approach could pose a potential liability to cardiovascular health. Herein, using integrated phosphoproteomic, transcriptomic and metabolic profiling, we uncovered molecular mechanisms associated with the adverse remodeling of cardiac functions in mice with combined attenuation of ErbB2 and ERRα activity. Genetic disruption of both effectors results in profound effects on cardiomyocyte architecture, inflammatory response and metabolism, the latter leading to a decrease in fatty acyl-carnitine species further increasing the reliance on glucose as a metabolic fuel, a hallmark of failing hearts. Furthermore, integrated omics signatures of ERRα loss-of-function and doxorubicin treatment exhibit common features of chemotherapeutic cardiotoxicity. These findings thus reveal potential cardiovascular risks in discrete combination therapies in the treatment of breast and other cancers.

Estrogen-related receptor-α coordinates transcriptional programs essential for exercise tolerance and muscle fitness.

Muscle fitness is an important determinant of health and disease. However, the molecular mechanisms involved in the coordinate regulation of the metabolic and structural determinants of muscle endurance are still poorly characterized. Herein, we demonstrate that estrogen-related receptor α (ERRα, NR3B1) is essential for skeletal muscle fitness. Notably, we show that ERRα-null animals are hypoactive and that genetic or therapeutic disruption of ERRα in mice results in reduced exercise tolerance. Mice lacking ERRα also exhibited lactatemia at exhaustion. Gene expression profiling demonstrates that ERRα plays a key role in various metabolic processes important for muscle function including energy substrate transport and use (Ldhd, Slc16a1, Hk2, and Glul), the tricarboxylic acid cycle (Cycs, and Idh3g), and oxidative metabolism (Pdha1, and Uqcrq). Metabolomics studies revealed impairment in replenishment of several amino acids (eg, glutamine) during recovery to exercise. Moreover, loss of ERRα was found to alter the expression of genes involved in oxidative stress response (Hmox1), maintenance of muscle fiber integrity (Trim63, and Hspa1b), and muscle plasticity and neovascularization (Vegfa). Taken together, our study shows that ERRα plays a key role in directing transcriptional programs required for optimal mitochondrial oxidative potential and muscle fitness, suggesting that modulation of ERRα activity could be used to manage metabolic myopathies and/or promote the adaptive response to physical exercise.

ERBB2 deficiency alters an E2F-1-dependent adaptive stress response and leads to cardiac dysfunction.

The tyrosine kinase receptor ERBB2 is required for normal development of the heart and is a potent oncogene in breast epithelium. Trastuzumab, a monoclonal antibody targeting ERBB2, improves the survival of breast cancer patients, but cardiac dysfunction is a major side effect of the drug. The molecular mechanisms underlying how ERBB2 regulates cardiac function and why trastuzumab is cardiotoxic remain poorly understood. We show here that ERBB2 hypomorphic mice develop cardiac dysfunction that mimics the side effects observed in patients treated with trastuzumab. We demonstrate that this phenotype is related to the critical role played by ERBB2 in cardiac homeostasis and physiological hypertrophy. Importantly, genetic and therapeutic reduction of ERBB2 activity in mice, as well as ablation of ERBB2 signaling by trastuzumab or siRNAs in human cardiomyocytes, led to the identification of an impaired E2F-1-dependent genetic program critical for the cardiac adaptive stress response. These findings demonstrate the existence of a previously unknown mechanistic link between ERBB2 and E2F-1 transcriptional activity in heart physiology and trastuzumab-induced cardiac dysfunction.

Curcumin inhibits tumor growth and angiogenesis in glioblastoma xenografts.

Among the natural products shown to possess chemopreventive and anticancer properties, curcumin is one of the most potent. In the current study, we investigated the effects of this natural product on the growth of human glioma U-87 cells xenografted into athymic mice. We show here that curcumin administration exerted significant anti-tumor effects on subcutaneous and intracerebral gliomas as demonstrated by the slower tumor growth rate and the increase of animal survival time. While investigating the mechanism of its action in vivo, we observed that curcumin decreased the gelatinolytic activities of matrix metalloproteinase-9. Furthermore, treatment with curcumin inhibited glioma-induced angiogenesis as indicated by the decrease of endothelial cell marker from newly formed vessels and by the diminution of the concentration of hemoglobin in curcumin-treated tumors. We also demonstrate, using an in vitro model of blood-brain barrier, that curcumin can cross the blood-brain barrier to a high level. These are the first results showing that curcumin suppresses tumor growth of gliomas in xenograft models. The mechanisms of the anti-tumor effects of curcumin were related, at least partly, to the inhibition of glioma-induced angiogenesis.

Transcriptional control of the ERBB2 amplicon by ERRalpha and PGC-1beta promotes mammary gland tumorigenesis.

Overexpression of ERBB2 and its neighboring genes on chromosome 17 occurs in approximately 25% of breast tumors and is associated with poor prognosis. While amplification of the 17q12-21 chromosomal region often correlates with an increase in the transcriptional rates of the locus, the molecular mechanisms and the factors involved in the coordinated expression of genes residing within the ERBB2 amplicon remain largely unknown. Here we demonstrate that estrogen-related receptor α (ERRα, NR3B1) and its coregulator PGC-1ß are key effectors in this process. Using a mouse model of ERBB2-initiated mammary tumorigenesis, we first show that ablation of ERRα significantly delays ERBB2-induced tumor development and lowers the levels of amplicon transcripts. Chromosome 17q-wide binding site location analyses in human breast cancer cells show preferential recruitment of ERRα to DNA segments associated with the ERBB2 amplicon. Furthermore, ERRα directs the co-recruitment of the coactivator PGC-1ß to segments in the 17q12 region and the recruitment of RNA polymerase II to the promoters of the ERBB2 and coamplified genes. ERRα and PGC-1ß also participate in the de-repression of ERBB2 expression through competitive genomic cross-talk with estrogen receptor α (ERα) and, as a consequence, influence tamoxifen sensitivity in breast cancer cells. Taken together, our results suggest that ERRα and PGC-1ß are key players in the etiology of malignant breast cancer by coordinating the transcriptional regulation of genes located in the 17q12 region, a process that also involves interference with the repressive function of ERα on ERBB2 expression.

miR-378(∗) mediates metabolic shift in breast cancer cells via the PGC-1ß/ERRγ transcriptional pathway.

Cancer cell metabolism is often characterized by a shift from an oxidative to a glycolytic bioenergetics pathway, a phenomenon known as the Warburg effect. miR-378(∗) is embedded within PPARGC1b which encodes PGC-1ß, a transcriptional regulator of oxidative energy metabolism. Here we show that miR-378(∗) expression is regulated by ERBB2 and induces a metabolic shift in breast cancer cells. miR-378(∗) performs this function by inhibiting the expression of two PGC-1ß partners, ERRγ and GABPA, leading to a reduction in tricarboxylic acid cycle gene expression and oxygen consumption as well as an increase in lactate production and in cell proliferation. In situ hybridization experiments show that miR-378(∗) expression correlates with progression of human breast cancer. These results identify miR-378(∗) as a molecular switch involved in the orchestration of the Warburg effect in breast cancer cells via interference with a well-integrated bioenergetics transcriptional pathway.

Genome-wide identification of direct target genes implicates estrogen-related receptor alpha as a determinant of breast cancer heterogeneity.

Estrogen-related receptor alpha (ERRalpha) is an orphan nuclear receptor, the expression of which correlates with negative prognosis in breast cancer. ERRalpha shares functional features with the estrogen receptor alpha (ERalpha) and its activity is modulated by the ERBB2 signaling pathway. Using genome-wide binding sites location analyses in ERalpha-positive and ERalpha-negative breast cancer cell lines, we show that ERRalpha and ERalpha display strict binding site specificity and maintain independent mechanisms of transcriptional activation. Nonetheless, ERRalpha and ERalpha coregulate a small subset of common target genes via binding either to a dual-specificity binding site or to distinct cognate binding sites located within the extended promoter region of the gene. Although ERRalpha signaling in breast cancer cells is mostly independent of ERalpha, the small fraction of common ERRalpha/ERalpha targets comprises genes with high relevance to breast tumor biology, including genes located within the ERBB2 amplicon and GATA3. Finally, unsupervised hierarchical clustering based on the expression profiling of ERRalpha direct target genes in human breast tumors revealed four main clusters that recapitulate established tumor subtypes. Taken together, the identification and functional characterization of the ERRalpha transcriptional network implicate ERRalpha signaling as a determinant of breast cancer heterogeneity.