Subject(s)
Fatty Liver/genetics , Nuclear Proteins/genetics , Obesity/genetics , Transcription Factors/genetics , Tumor Suppressor Proteins/genetics , Up-Regulation , Adult , Animals , Fatty Liver/metabolism , Female , Humans , Liver/metabolism , Male , Mice , Nuclear Proteins/metabolism , Obesity/metabolism , Promyelocytic Leukemia Protein , RNA, Messenger/metabolism , Transcription Factors/metabolism , Tumor Suppressor Proteins/metabolismABSTRACT
Cancer cells exhibit an aberrant metabolism that facilitates more efficient production of biomass and hence tumor growth and progression. However, the genetic cues modulating this metabolic switch remain largely undetermined. We identified a metabolic function for the promyelocytic leukemia (PML) gene, uncovering an unexpected role for this bona fide tumor suppressor in breast cancer cell survival. We found that PML acted as both a negative regulator of PPARγ coactivator 1A (PGC1A) acetylation and a potent activator of PPAR signaling and fatty acid oxidation. We further showed that PML promoted ATP production and inhibited anoikis. Importantly, PML expression allowed luminal filling in 3D basement membrane breast culture models, an effect that was reverted by the pharmacological inhibition of fatty acid oxidation. Additionally, immunohistochemical analysis of breast cancer biopsies revealed that PML was overexpressed in a subset of breast cancers and enriched in triple-negative cases. Indeed, PML expression in breast cancer correlated strikingly with reduced time to recurrence, a gene signature of poor prognosis, and activated PPAR signaling. These findings have important therapeutic implications, as PML and its key role in fatty acid oxidation metabolism are amenable to pharmacological suppression, a potential future mode of cancer prevention and treatment.
Subject(s)
Breast Neoplasms/metabolism , Breast Neoplasms/mortality , Nuclear Proteins/metabolism , Transcription Factors/metabolism , Tumor Suppressor Proteins/metabolism , Acetylation , Animals , Breast Neoplasms/pathology , Cell Line, Tumor , Cell Survival/genetics , Diet, High-Fat/adverse effects , Disease-Free Survival , Fatty Acids/metabolism , Female , Humans , Kaplan-Meier Estimate , Liver/metabolism , Mice , Mice, 129 Strain , Mice, Inbred C57BL , Mice, Knockout , Mice, Obese , Nuclear Proteins/genetics , Obesity/etiology , Obesity/metabolism , Oligonucleotide Array Sequence Analysis , Oxidation-Reduction , Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha , Peroxisome Proliferator-Activated Receptors/metabolism , Promyelocytic Leukemia Protein , Protein Processing, Post-Translational , Signal Transduction , Trans-Activators/metabolism , Transcription Factors/genetics , Transcription, Genetic , Transcriptome , Tumor Suppressor Proteins/geneticsABSTRACT
Stem-cell function is an exquisitely regulated process. Thus far, the contribution of metabolic cues to stem-cell function has not been well understood. Here we identify a previously unknown promyelocytic leukemia (PML)peroxisome proliferator-activated receptor δ (PPAR-δ)fatty-acid oxidation (FAO) pathway for the maintenance of hematopoietic stem cells (HSCs). We have found that loss of PPAR-δ or inhibition of mitochondrial FAO induces loss of HSC maintenance, whereas treatment with PPAR-δ agonists improved HSC maintenance. PML exerts its essential role in HSC maintenance through regulation of PPAR signaling and FAO. Mechanistically, the PMLPPAR-δFAO pathway controls the asymmetric division of HSCs. Deletion of Ppard or Pml as well as inhibition of FAO results in the symmetric commitment of HSC daughter cells, whereas PPAR-δ activation increased asymmetric cell division. Thus, our findings identify a metabolic switch for the control of HSC cell fate with potential therapeutic implications.
Subject(s)
Cell Division/physiology , Fatty Acids/metabolism , Hematopoietic Stem Cells/physiology , Metabolic Networks and Pathways/physiology , Models, Biological , Nuclear Proteins/metabolism , PPAR delta/metabolism , Transcription Factors/metabolism , Tumor Suppressor Proteins/metabolism , Animals , Blotting, Western , Colony-Forming Units Assay , Epoxy Compounds/pharmacology , Flow Cytometry , Fluorescent Antibody Technique , Hematopoietic Stem Cells/metabolism , Immunoprecipitation , Metabolic Networks and Pathways/drug effects , Mice , Mice, Inbred C57BL , Mice, Transgenic , Mitochondria/metabolism , Oxidation-Reduction/drug effects , PPAR delta/agonists , PPAR delta/deficiency , Promyelocytic Leukemia Protein , Real-Time Polymerase Chain Reaction , Thiazoles/pharmacologyABSTRACT
Here, we demonstrate that protein-coding RNA transcripts can crosstalk by competing for common microRNAs, with microRNA response elements as the foundation of this interaction. We have termed such RNA transcripts as competing endogenous RNAs (ceRNAs). We tested this hypothesis in the context of PTEN, a key tumor suppressor whose abundance determines critical outcomes in tumorigenesis. By a combined computational and experimental approach, we identified and validated endogenous protein-coding transcripts that regulate PTEN, antagonize PI3K/AKT signaling, and possess growth- and tumor-suppressive properties. Notably, we also show that these genes display concordant expression patterns with PTEN and copy number loss in cancers. Our study presents a road map for the prediction and validation of ceRNA activity and networks and thus imparts a trans-regulatory function to protein-coding mRNAs.
Subject(s)
Gene Expression Regulation , PTEN Phosphohydrolase/genetics , RNA, Messenger/metabolism , RNA, Untranslated/metabolism , Regulatory Sequences, Ribonucleic Acid , Animals , Humans , Mice , MicroRNAs/metabolism , PTEN Phosphohydrolase/metabolism , Phosphatidylinositol 3-Kinases/metabolism , RNA, Messenger/genetics , RNA, Untranslated/geneticsABSTRACT
We recently proposed that competitive endogenous RNAs (ceRNAs) sequester microRNAs to regulate mRNA transcripts containing common microRNA recognition elements (MREs). However, the functional role of ceRNAs in cancer remains unknown. Loss of PTEN, a tumor suppressor regulated by ceRNA activity, frequently occurs in melanoma. Here, we report the discovery of significant enrichment of putative PTEN ceRNAs among genes whose loss accelerates tumorigenesis following Sleeping Beauty insertional mutagenesis in a mouse model of melanoma. We validated several putative PTEN ceRNAs and further characterized one, the ZEB2 transcript. We show that ZEB2 modulates PTEN protein levels in a microRNA-dependent, protein coding-independent manner. Attenuation of ZEB2 expression activates the PI3K/AKT pathway, enhances cell transformation, and commonly occurs in human melanomas and other cancers expressing low PTEN levels. Our study genetically identifies multiple putative microRNA decoys for PTEN, validates ZEB2 mRNA as a bona fide PTEN ceRNA, and demonstrates that abrogated ZEB2 expression cooperates with BRAF(V600E) to promote melanomagenesis.
