Project description:PTEN is implicated in a wide variety of pathophysiological conditions and traditionally studied in the context of the PIK3-AKT-mTOR axis. Recent studies from our group and others have reported a novel role of PTEN in the regulation of transcription at the genome-wide scale. This emerging role of PTEN on global transcriptional regulation is providing a better understanding of various diseases, including cancer. Since cancer progression is an energy-demanding process and PTEN is known to regulate metabolic processes, we sought to understand the role of PTEN in transcriptional regulation under metabolic stress, a condition often developing in the tumor microenvironment. In the present study, we demonstrate that PTEN modulates genome-wide RNA Polymerase II (Pol II) occupancy in cells undergoing glucose deprivation. The glucose-deprived PTEN null cells were found to continue global gene transcription, which may activate a survival mode. However, cells with constitutive PTEN expression slow transcription, an evolutionary mechanism that may save cellular energy and activate programmed cell death pathways, in the absence of glucose. Interestingly, alternative exon usage by PTEN null cells is increased under metabolic stress compared to PTEN expressing cells. Overall, our study comprehensively demonstrates distinct mechanisms involved in PTEN-dependent genome-wide transcriptional control under metabolic stress. Our findings provide a new insight in understanding the tumor microenvironment and how PTEN loss of function, whether by genetic or non-genetic mechanisms, can contribute to a favorable transcriptional program employed by tumor cells to escape apoptosis, hence developing more aggressive and metastatic phenotypes.
Project description:PTEN is implicated in a wide variety of pathophysiological conditions and traditionally studied in the context of the PIK3-AKT-mTOR axis. Recent studies from our group and others have reported a novel role of PTEN in the regulation of transcription at the genome-wide scale. This emerging role of PTEN on global transcriptional regulation is providing a better understanding of various diseases, including cancer. Since cancer progression is an energy-demanding process and PTEN is known to regulate metabolic processes, we sought to understand the role of PTEN in transcriptional regulation under metabolic stress, a condition often developing in the tumor microenvironment. In the present study, we demonstrate that PTEN modulates genome-wide RNA Polymerase II (Pol II) occupancy in cells undergoing glucose deprivation. The glucose-deprived PTEN null cells were found to continue global gene transcription, which may activate a survival mode. However, cells with constitutive PTEN expression slow transcription, an evolutionary mechanism that may save cellular energy and activate programmed cell death pathways, in the absence of glucose. Interestingly, alternative exon usage by PTEN null cells is increased under metabolic stress compared to PTEN expressing cells. Overall, our study comprehensively demonstrates distinct mechanisms involved in PTEN-dependent genome-wide transcriptional control under metabolic stress. Our findings provide a new insight in understanding the tumor microenvironment and how PTEN loss of function, whether by genetic or non-genetic mechanisms, can contribute to a favorable transcriptional program employed by tumor cells to escape apoptosis, hence developing more aggressive and metastatic phenotypes.
Project description:Decremental loss of PTEN results in cancer susceptibility and tumor progression. In turn this raises the possibility that PTEN elevation might be an attractive option for cancer prevention and therapy. We have generated several transgenic mouse lines with variably elevated PTEN expression levels, taking advantage of BAC (Bacterial Artificial Chromosome)-mediated transgenesis. Super-PTEN mutants are viable and show reduced body size due to decreased cell number, with no effect on cell size. Unexpectedly, PTEN elevation at the organism level results in healthy metabolism characterized by increased energy expenditure and reduced body fat accumulation. Cells derived from these mice show reduced glucose and glutamine uptake, increased mitochondrial oxidative phosphorylation, and are resistant to oncogenic transformation. Mechanistically we find that PTEN elevation orchestrates this metabolic switch by regulating PI3K-dependent and independent pathways, and negatively impacts two of the most pronounced metabolic features of tumor cells: glutaminolysis and the Warburg effect. In order to elucidate the pathophysiological impact of PTEN elevation, we generated transgenic mice carrying additional copies of this critical tumor suppressor gene (referred to as Super-PTEN mice). In order to maintain the regulation properties of the endogenous Pten gene, we made use of large genomic fragments containing the entire Pten locus carried by BACs (Bacterial Artificial Chromosomes). We next generated mouse embryonic fibroblasts (MEFs) and confirmed successful overexpression of PTEN by the BAC transgenic system. Primary cells derived from Super-PTEN mice represent a powerful tool to elucidate the molecular mechanisms underlying dose-dependent PTEN actions. We therefore performed microarray analysis in primary cells (MEFs) derived from day 13.5 embryos obtained by crossing Super-PTEN mice with C57BL6 mice. Three independent embryos from each genotype were analyzed (background: >98%C57BL6 / CBA). Gene expression profile analysis in these cells will reveal target genes and pathways differentially regulated upon PTEN elevation.
Project description:Decremental loss of PTEN results in cancer susceptibility and tumor progression. In turn this raises the possibility that PTEN elevation might be an attractive option for cancer prevention and therapy. We have generated several transgenic mouse lines with variably elevated PTEN expression levels, taking advantage of BAC (Bacterial Artificial Chromosome)-mediated transgenesis. Super-PTEN mutants are viable and show reduced body size due to decreased cell number, with no effect on cell size. Unexpectedly, PTEN elevation at the organism level results in healthy metabolism characterized by increased energy expenditure and reduced body fat accumulation. Cells derived from these mice show reduced glucose and glutamine uptake, increased mitochondrial oxidative phosphorylation, and are resistant to oncogenic transformation. Mechanistically we find that PTEN elevation orchestrates this metabolic switch by regulating PI3K-dependent and independent pathways, and negatively impacts two of the most pronounced metabolic features of tumor cells: glutaminolysis and the Warburg effect.
Project description:Developmental and metabolic signaling networks underpinning type-17 cell fate decisions and functional effects at coordination of PTEN-dependent tissue homeostasis
Project description:Developmental and metabolic signaling networks underpinning type-17 cell fate decisions and functional effects at coordination of PTEN-dependent tissue homeostasis
Project description:PTEN is a tumor suppressor that is often inactivated in cancer and possesses both lipid and protein phosphatase activities. We report the metabolic regulator PDHK1 (pyruvate dehydrogenase kinase1) is a synthetic-essential gene in PTEN-deficient cancer and normal cells. The predominant mechanism of PDHK1 regulation and dependency is the PTEN protein phosphatase dephosphorylates NFkB activating protein (NKAP) and limits NFkB activation to suppress expression of PDHK1, a NFkB target gene. Loss of the PTEN protein phosphatase upregulates PDHK1 to drive aerobic glycolysis and induce PDHK1 cellular dependence. PTEN-deficient human tumors harbor increased PDHK1, which is a biomarker of decreased patient survival, establishing clinical relevance. This study uncovers a PTEN-regulated signaling pathway and reveals PDHK1 as a potential target in PTEN-deficient cancers.