Oncogenic BRAF regulates oxidative metabolism via PGC1? and MITF
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
SUBMITTER: WIDLUND Hans
PROVIDER: S-ECPF-GEOD-38007 | biostudies-other |
REPOSITORIES: biostudies-other
Similar Datasets
Project description:Activating mutations in BRAF are the most common genetic alterations in melanoma. Inhibition of BRAF by small molecules leads to cell-cycle arrest and apoptosis. We show here that BRAF inhibition also induces an oxidative phosphorylation gene program, mitochondrial biogenesis, and the increased expression of the mitochondrial master regulator, PGC1?. We further show that a target of BRAF, the melanocyte lineage factor MITF, directly regulates the expression of PGC1?. Melanomas with activation of the BRAF/MAPK pathway have suppressed levels of MITF and PGC1? and decreased oxidative metabolism. Conversely, treatment of BRAF-mutated melanomas with BRAF inhibitors renders them addicted to oxidative phosphorylation. Our data thus identify an adaptive metabolic program that limits the efficacy of BRAF inhibitors.
| S-EPMC3635826 | biostudies-literature
Project description:We evaluated two matched human cell lines derived from primary melanocytes, termed pmel+BRAF(V600E) and pmel+BRAF(V600E)+MITF. These cells are therefore isogenic with the exception of the expression of MITF. Gene Set Enrichment Analysis of microarray data identified a highly significant induction of oxidative phosphorylation gene set in MITF expressing cells compared to control cells.
2013-03-07 | E-GEOD-38007 | biostudies-arrayexpress
Project description:Gene expression signatures were measured in logarithmic growing cultures Affymetrix HG-U133AV2 expression arrays were performed according to the manufacturer's directions using RNA extracted by Qiagen RNeasy from engineered human melanoma cells
2013-03-07 | GSE38007 | GEO
Project description:The Microphthalmia-associated transcription factor (MITF) is an important regulator of cell-type specific functions in melanocytic cells. MITF is essential for the survival of pigmented cells, but whereas high levels of MITF drive melanocyte differentiation, lower levels are required to permit proliferation and survival of melanoma cells. MITF is phosphorylated by ERK, and this stimulates its activation, but also targets it for degradation through the ubiquitin-proteosome pathway, coupling MITF degradation to its activation. We have previously shown that because ERK is hyper-activated in melanoma cells in which BRAF is mutated, the MITF protein is constitutively down-regulated. Here we describe another intriguing aspect of MITF regulation by oncogenic BRAF in melanoma cells. We show oncogenic BRAF up-regulates MITF transcription through ERK and the transcription factor BRN2 (N-Oct3). In contrast, we show that in melanocytes this pathway does not exist because BRN2 is not expressed, demonstrating that MITF regulation is a newly acquired function of oncogenic BRAF that is not performed by the wild-type protein. Critically, in melanoma cells MITF is required downstream of oncogenic BRAF because it regulates expression of key cell cycle regulatory proteins such as CDK2 and CDK4. Wild-type BRAF does not regulate this pathway in melanocytes. Thus, we show that oncogenic BRAF exerts exquisite control over MITF on two levels. It downregulates the protein by stimulating its degradation, but then counteracts this by increasing transcription through BRN2. Our data suggest that oncogenic BRAF plays a critical role in regulating MITF expression to ensure that its protein levels are compatible with proliferation and survival of melanoma cells. We propose that its ability to appropriate the regulation of this critical factor explains in part why BRAF is such a potent oncogene in melanoma.
| S-EPMC2444043 | biostudies-literature
Project description:The energetic burden of continuously concentrating solutes against gradients along the tubule may render the kidney especially vulnerable to ischaemia. Acute kidney injury (AKI) affects 3% of all hospitalized patients. Here we show that the mitochondrial biogenesis regulator, PGC1?, is a pivotal determinant of renal recovery from injury by regulating nicotinamide adenine dinucleotide (NAD) biosynthesis. Following renal ischaemia, Pgc1?(-/-) (also known as Ppargc1a(-/-)) mice develop local deficiency of the NAD precursor niacinamide (NAM, also known as nicotinamide), marked fat accumulation, and failure to re-establish normal function. Notably, exogenous NAM improves local NAD levels, fat accumulation, and renal function in post-ischaemic Pgc1?(-/-) mice. Inducible tubular transgenic mice (iNephPGC1?) recapitulate the effects of NAM supplementation, including more local NAD and less fat accumulation with better renal function after ischaemia. PGC1? coordinately upregulates the enzymes that synthesize NAD de novo from amino acids whereas PGC1? deficiency or AKI attenuates the de novo pathway. NAM enhances NAD via the enzyme NAMPT and augments production of the fat breakdown product ?-hydroxybutyrate, leading to increased production of prostaglandin PGE2 (ref. 5), a secreted autacoid that maintains renal function. NAM treatment reverses established ischaemic AKI and also prevented AKI in an unrelated toxic model. Inhibition of ?-hydroxybutyrate signalling or prostaglandin production similarly abolishes PGC1?-dependent renoprotection. Given the importance of mitochondrial health in ageing and the function of metabolically active organs, the results implicate NAM and NAD as key effectors for achieving PGC1?-dependent stress resistance.
| S-EPMC4909121 | biostudies-literature
Project description:Multiple myeloma (MM) is an incurable hematologic malignancy due to inevitable relapse and chemoresistance development. Our preliminary data show that MM cells express high levels of PGC1? and LDHA. In this study, we investigated the mechanism behind PGC1?-mediated LDHA expression and its contribution to tumorigenesis, to aid in the development of novel therapeutic approaches for MM. Real-time PCR and western blotting were first used to evaluate gene expression of PGC1? and LDHA in different MM cells, and then, luciferase reporter assay, chromatin immunoprecipitation, LDHA deletion report vectors, and siRNA techniques were used to investigate the mechanism underlying PGC1?-induced LDHA expression. Furthermore, knockdown cell lines and lines stably overexpressing PGC1? or LDHA lentivirus were established to evaluate in vitro glycolysis metabolism, mitochondrial function, reactive oxygen species (ROS) formation, and cell proliferation. In addition, in vivo xenograft tumor development studies were performed to investigate the effect of PGC1? or LDHA expression on tumor growth and mouse survival. We found that PGC1? and LDHA are highly expressed in different MM cells and LDHA is upregulated by PGC1? through the PGC1?/RXR? axis acting on the LDHA promoter. Overexpression of PGC1? or LDHA significantly potentiated glycolysis metabolism with increased cell proliferation and tumor growth. On the other hand, knockdown of PGC1? or LDHA largely suppressed glycolysis metabolism with increased ROS formation and apoptosis rate, in addition to suppressing tumor growth and enhancing mouse survival. This is the first time the mechanism underlying PGC1?-mediated LDHA expression in multiple myeloma has been identified. We conclude that PGC1? regulates multiple myeloma tumor growth through LDHA-mediated glycolytic metabolism. Targeting the PGC1?/LDHA pathway may be a novel therapeutic strategy for multiple myeloma treatment.
| S-EPMC6120252 | biostudies-literature
Project description:Osteoporosis is a metabolic bone disorder associated with compromised bone strength and an increased risk of fracture. Inhibition of the differentiation of bone-resorbing osteoclasts is an effective strategy for the treatment of osteoporosis. Prior work by our laboratory and others has shown that MYC promotes osteoclastogenesis in vitro, but the underlying mechanisms are not well understood. In addition, the in vivo importance of osteoclast-expressed MYC in physiological and pathological bone loss is not known. Here, we have demonstrated that deletion of Myc in osteoclasts increases bone mass and protects mice from ovariectomy-induced (OVX-induced) osteoporosis. Transcriptomic analysis revealed that MYC drives metabolic reprogramming during osteoclast differentiation and functions as a metabolic switch to an oxidative state. We identified a role for MYC action in the transcriptional induction of estrogen receptor-related receptor α (ERRα), a nuclear receptor that cooperates with the transcription factor nuclear factor of activated T cells, c1 (NFATc1) to drive osteoclastogenesis. Accordingly, pharmacological inhibition of ERRα attenuated OVX-induced bone loss in mice. Our findings highlight a MYC/ERRα pathway that contributes to physiological and pathological bone loss by integrating the MYC/ERRα axis to drive metabolic reprogramming during osteoclast differentiation.
| S-EPMC5490751 | biostudies-literature
Project description:The uncontrolled growth of tumors provides metabolic dependencies that can be harnessed for therapeutic benefit. Although tumor cells exhibit these increased metabolic demands due to their rapid proliferation, these metabolic processes are general to all cells, and furthermore, targeted therapeutic intervention can provoke compensatory adaptation that alters tumors' characteristics. As an example, a subset of melanomas depends on the transcriptional coactivator PGC1? function to sustain their mitochondrial energy-dependent survival. However, selective outgrowth of resistant PGC1?-independent tumor cells becomes endowed with an augmented metastatic phenotype. To find PGC1?-dependent components that would not affect metastasis in melanomas, an unbiased proteomic analyses was performed and uncovered the orphan nuclear receptor ERR?, which supports PGC1?'s control of mitochondrial energetic metabolism, but does not affect the antioxidant nor antimetastatic regulatory roles. Specifically, genetic or pharmacologic inhibition of ERR? reduces the inherent bioenergetic capacity and decreases melanoma cell growth, but without altering the invasive characteristics. Thus, within this particularly aggressive subset of melanomas, which is characterized by heighted expression of PGC1?, ERR? specifically mediates prosurvival functions and represents a tangible therapeutic target.Implications: ERR?, a druggable protein, mediates the bioenergetic effects in melanomas defined by high PGC1? expression, suggesting a rational means for therapeutic targeting of this particularly aggressive melanoma subtype. Mol Cancer Res; 15(10); 1366-75. ©2017 AACR.
| S-EPMC5954239 | biostudies-literature
Project description:The Fbw7 (F-box/WD repeat-containing protein 7) ubiquitin ligase targets multiple oncoproteins for degradation and is commonly mutated in cancers. Like other pleiotropic tumor suppressors, Fbw7's complex biology has impeded our understanding of how Fbw7 mutations promote tumorigenesis and hindered the development of targeted therapies. To address these needs, we employed a transfer learning approach to derive gene-expression signatures from The Cancer Gene Atlas datasets that predict Fbw7 mutational status across tumor types and identified the pathways enriched within these signatures. Genes involved in mitochondrial function were highly enriched in pan-cancer signatures that predict Fbw7 mutations. Studies in isogenic colorectal cancer cell lines that differed in Fbw7 mutational status confirmed that Fbw7 mutations increase mitochondrial gene expression. Surprisingly, Fbw7 mutations shifted cellular metabolism toward oxidative phosphorylation and caused context-specific metabolic vulnerabilities. Our approach revealed unexpected metabolic reprogramming and possible therapeutic targets in Fbw7-mutant cancers and provides a framework to study other complex, oncogenic mutations.
| S-EPMC6003503 | biostudies-literature
Project description:Thyroid cancer is common, yet the sequence of alterations that promote tumor formation are incompletely understood. Here, we describe a novel model of thyroid carcinoma in zebrafish that reveals temporal changes due to BRAFV600E. Through the use of real-time in vivo imaging, we observe disruption in thyroid follicle structure that occurs early in thyroid development. Combinatorial treatment using BRAF and MEK inhibitors reversed the developmental effects induced by BRAFV600E. Adult zebrafish expressing BRAFV600E in thyrocytes developed invasive carcinoma. We identified a gene expression signature from zebrafish thyroid cancer that is predictive of disease-free survival in patients with papillary thyroid cancer. Gene expression studies nominated TWIST2 as a key effector downstream of BRAF. Using CRISPR/Cas9 to genetically inactivate a TWIST2 orthologue, we suppressed the effects of BRAFV600E and restored thyroid morphology and hormone synthesis. These data suggest that expression of TWIST2 plays a role in an early step of BRAFV600E-mediated transformation.
| S-EPMC5389860 | biostudies-literature