bims-pideca 2019-12-01 papers

bims-pideca

Biomed News

on Class IA PI3K signalling in development and cancer

Issue of 2019–12–01
sixteen papers selected by
Ralitsa Radostinova Madsen, University College London

Phosphatidic acid drives mTORC1 lysosomal translocation in the absence of amino acids.
Adipose PTEN regulates adult adipose tissue homeostasis and redistribution via a PTEN-leptin-sympathetic loop.
Tsc1-mTORC1 signaling controls striatal dopamine release and cognitive flexibility.
Fbxw7 is a driver of uterine carcinosarcoma by promoting epithelial-mesenchymal transition.
Acute β-adrenoceptor mediated glucose clearance in brown adipose tissue; a distinct pathway independent of functional insulin signaling.
A high-throughput screen identifies that CDK7 activates glucose consumption in lung cancer cells.
The effects of growth hormone on adipose tissue: old observations, new mechanisms.
The human secretome.
A Phase Ib/II, open-label, multicenter study of INC280 (capmatinib) alone and in combination with buparlisib (BKM120) in adult patients with recurrent glioblastoma.
High glucose concentrations mask cellular phenotypes in a stem cell model of tuberous sclerosis complex.
Subcellular metabolic pathway kinetics are revealed by correcting for artifactual post harvest metabolism.
Loss of FoxOs in muscle reveals sex-based differences in insulin sensitivity but mitigates diet-induced obesity.
Deregulating MYC in a model of HER2+ breast cancer mimics human intertumoral heterogeneity.
The microcosmos of intratumor heterogeneity: the space-time of cancer evolution.
Brain Endothelial Cells Maintain Lactate Homeostasis and Control Adult Hippocampal Neurogenesis.
Topical rapamycin reduces markers of senescence and aging in human skin: an exploratory, prospective, randomized trial.

J Biol Chem. 2019 Nov 24. pii: jbc.RA119.010892. [Epub ahead of print]

Phosphatidic acid drives mTORC1 lysosomal translocation in the absence of amino acids.

Maria A Frias, Suman Mukhopadhyay, Elyssa Lehman, Aleksandra Walasek, Matthew Utter, Deepak Menon, David A Foster.

  mTOR Complex 1 (mTORC1) promotes cell growth and proliferation in response to nutrients and growth factors. Amino acids induce lysosomal translocation of mTORC1 via the Rag GTPases. Growth factors activate Ras homolog enriched in brain (Rheb), which in turn, activates mTORC1 at the lysosome. Amino acids and growth factors also induce the phospholipase D (PLD)-phosphatidic acid (PA) pathway, required for mTORC1 signaling through mechanisms that are not fully understood. Here, using human and murine cell lines, along with immunofluorescence, confocal microscopy, endocytosis, PLD activity, and cell viability assays, we show that exogenously supplied PA vesicles deliver mTORC1 to the lysosome in the absence of amino acids, Rag GTPases, growth factors, and Rheb. Of note, pharmacological or genetic inhibition of endogenous PLD prevented mTORC1 lysosomal translocation. We observed that precancerous cells with constitutive Rheb activation through loss of TSC complex subunit 2 (TSC2) exploit the PLD-PA pathway and thereby sustain mTORC1 activation at the lysosome in the absence of amino acids. Our findings indicate that sequential inputs from amino acids and growth factors trigger PA production required for mTORC1 translocation and activation at the lysosome.

Keywords:  Phospholipase D; amino acid; cancer biology; cancer therapy; growth factor; lysosome; mTOR complex (mTORC); phosphatidic acid; phospholipid vesicle

DOI:  https://doi.org/10.1074/jbc.RA119.010892
Mol Metab. 2019 Dec;pii: S2212-8778(19)30911-1. [Epub ahead of print]30 48-60

Adipose PTEN regulates adult adipose tissue homeostasis and redistribution via a PTEN-leptin-sympathetic loop.

Wei Huang, Nicholas J Queen, Travis B McMurphy, Seemaab Ali, Lei Cao.

   OBJECTIVE: Despite the large body of work describing the tumor suppressor functions of Phosphatase and tensin homologue deleted on chromosome ten (PTEN), its roles in adipose homeostasis of adult animals are not yet fully understood. Here, we sought to determine the role of PTEN in whole-body adipose homeostasis.
METHODS: We genetically manipulated PTEN in specific fat depots through recombinant adeno-associated viral vector (rAAV)-based gene transfer of Cre recombinase to adult PTENflox mice. Additionally, we used a denervation agent, 6OHDA, to assess the role of sympathetic signaling in PTEN-related adipose remodeling. Furthermore, we chemically manipulated AKT signaling via a pan-AKT inhibitor, MK-2206, to assess the role of AKT in PTEN-related adipose remodeling. Finally, to understand the role of leptin and central signaling on peripheral tissues, we knocked down hypothalamic leptin receptor with a microRNA delivered by a rAAV vector.
RESULTS: Knockdown PTEN in individual fat depot resulted in massive expansion of the affected fat depot through activation of AKT signaling associated with suppression of lipolysis and induction of leptin. This hypertrophic expansion of the affected fat depot led to upregulation of PTEN level, higher lipolysis, and induction of white fat browning in other fat depots, and the compensatory reduced fat mass to maintain a set point of whole-body adiposity. Administration of AKT inhibitor MK-2206 prevented the adipose PTEN knockdown-associated effects. 6OHDA-mediated denervation demonstrated that sympathetic innervation was required for the PTEN knockdown-induced adipose redistribution. Knockdown hypothalamic leptin receptor attenuated the adipose redistribution induced by PTEN deficiency in individual fat depot.
CONCLUSIONS: Our results demonstrate the essential role of PTEN in adipose homeostasis, including mass and distribution in adulthood, and reveal an "adipose PTEN-leptin-sympathetic nervous system" feedback loop to maintain a set point of adipose PTEN and whole-body adiposity.

Keywords:  Adipose; Homeostasis; Hypothalamus; Leptin; PTEN; Redistribution

DOI:  https://doi.org/10.1016/j.molmet.2019.09.008
Nat Commun. 2019 Nov 28. 10(1): 5426

Tsc1-mTORC1 signaling controls striatal dopamine release and cognitive flexibility.

Polina Kosillo, Natalie M Doig, Kamran M Ahmed, Alexander H C W Agopyan-Miu, Corinna D Wong, Lisa Conyers, Sarah Threlfell, Peter J Magill, Helen S Bateup.

Tuberous Sclerosis Complex (TSC) is a neurodevelopmental disorder caused by mutations in TSC1 or TSC2, which encode proteins that negatively regulate mTOR complex 1 (mTORC1). TSC is associated with significant cognitive, psychiatric, and behavioral problems, collectively termed TSC-Associated Neuropsychiatric Disorders (TAND), and the cell types responsible for these manifestations are largely unknown. Here we use cell type-specific Tsc1 deletion to test whether dopamine neurons, which modulate cognitive, motivational, and affective behaviors, are involved in TAND. We show that loss of Tsc1 and constitutive activation of mTORC1 in dopamine neurons causes somatodendritic hypertrophy, reduces intrinsic excitability, alters axon terminal structure, and impairs striatal dopamine release. These perturbations lead to a selective deficit in cognitive flexibility, preventable by genetic reduction of the mTOR-binding protein Raptor. Our results establish a critical role for Tsc1-mTORC1 signaling in setting the functional properties of dopamine neurons, and indicate that dopaminergic dysfunction may contribute to cognitive inflexibility in TSC.

DOI: https://doi.org/10.1038/s41467-019-13396-8
Proc Natl Acad Sci U S A. 2019 Nov 26. pii: 201911310. [Epub ahead of print]

Fbxw7 is a driver of uterine carcinosarcoma by promoting epithelial-mesenchymal transition.

Ileana C Cuevas, Subhransu S Sahoo, Ashwani Kumar, He Zhang, Jill Westcott, Mitzi Aguilar, Jeremy D Cortez, Stephanie A Sullivan, Chao Xing, D Neil Hayes, Rolf A Brekken, Victoria L Bae-Jump, Diego H Castrillon.

  Uterine carcinosarcoma is an aggressive variant of endometrial carcinoma characterized by unusual histologic features including discrete malignant epithelial and mesenchymal components (carcinoma and sarcoma). Recent studies have confirmed a monoclonal origin, and comprehensive genomic characterizations have identified mutations such as Tp53 and Pten However, the biological origins and specific combination of driver events underpinning uterine carcinosarcoma have remained mysterious. Here, we explored the role of the tumor suppressor Fbxw7 in endometrial cancer through defined genetic model systems. Inactivation of Fbxw7 and Pten resulted in the formation of precancerous lesions (endometrioid intraepithelial neoplasia) and well-differentiated endometrioid adenocarcinomas. Surprisingly, all adenocarcinomas eventually developed into definitive uterine carcinosarcomas with carcinomatous and sarcomatous elements including heterologous differentiation, yielding a faithful genetically engineered model of this cancer type. Genomic analysis showed that most tumors spontaneously acquired Trp53 mutations, pointing to a triad of pathways (p53, PI3K, and Fbxw7) as the critical combination underpinning uterine carcinosarcoma, and to Fbxw7 as a key driver of this enigmatic endometrial cancer type. Lineage tracing provided formal genetic proof that the uterine carcinosarcoma cell of origin is an endometrial epithelial cell that subsequently undergoes a prominent epithelial-mesenchymal transition underlying the attainment of a highly invasive phenotype specifically driven by Fbxw7.

Keywords:  Fbxw7; Pten; Tp53; epithelial-mesenchymal transition; uterine carcinosarcoma

DOI:  https://doi.org/10.1073/pnas.1911310116
Mol Metab. 2019 Dec;pii: S2212-8778(19)30925-1. [Epub ahead of print]30 240-249

Acute β-adrenoceptor mediated glucose clearance in brown adipose tissue; a distinct pathway independent of functional insulin signaling.

Jessica M Olsen, Alice Åslund, Muhammad Hamza Bokhari, Dana S Hutchinson, Tore Bengtsson.

   OBJECTIVE: β-adrenoceptor mediated activation of brown adipose tissue (BAT) has been associated with improvements in metabolic health in models of type 2 diabetes and obesity due to its unique ability to increase whole body energy expenditure, and rate of glucose and free fatty acid disposal. While the thermogenic arm of this phenomenon has been studied in great detail, the underlying mechanisms involved in β-adrenoceptor mediated glucose uptake in BAT are relatively understudied. As β-adrenoceptor agonist administration results in increased hepatic gluconeogenesis that can consequently result in secondary pancreatic insulin release, there is uncertainty regarding the importance of insulin and the subsequent activation of its downstream effectors in mediating β-adrenoceptor stimulated glucose uptake in BAT. Therefore, in this study, we made an effort to discriminate between the two pathways and address whether the insulin signaling pathway is dispensable for the effects of β-adrenoceptor activation on glucose uptake in BAT.
METHODS: Using a specific inhibitor of phosphoinositide 3-kinase α (PI3Kα), which effectively inhibits the insulin signaling pathway, we examined the effects of various β-adrenoceptor agonists, including the physiological endogenous agonist norepinephrine on glucose uptake and respiration in mouse brown adipocytes in vitro and on glucose clearance in mice in vivo.
RESULTS: PI3Kα inhibition in mouse primary brown adipocytes in vitro, did not inhibit β-adrenoceptor stimulated glucose uptake, GLUT1 synthesis, GLUT1 translocation or respiration. Furthermore, β-adrenoceptor mediated glucose clearance in vivo did not require insulin or Akt activation but was attenuated upon administration of a β3-adrenoceptor antagonist.
CONCLUSIONS: We conclude that the β-adrenergic pathway is still functionally intact upon the inhibition of PI3Kα, showing that the activation of downstream insulin effectors is not required for the acute effects of β-adrenoceptor agonists on glucose homeostasis or thermogenesis.

Keywords:  Akt; Brown adipose tissue; GLUT1; Glucose clearance; Insulin; PI3Kα; Thermogenesis

DOI:  https://doi.org/10.1016/j.molmet.2019.10.004
Nat Commun. 2019 Nov 29. 10(1): 5444

A high-throughput screen identifies that CDK7 activates glucose consumption in lung cancer cells.

Chiara Ghezzi, Alicia Wong, Bao Ying Chen, Bernard Ribalet, Robert Damoiseaux, Peter M Clark.

Elevated glucose consumption is fundamental to cancer, but selectively targeting this pathway is challenging. We develop a high-throughput assay for measuring glucose consumption and use it to screen non-small-cell lung cancer cell lines against bioactive small molecules. We identify Milciclib that blocks glucose consumption in H460 and H1975, but not in HCC827 or A549 cells, by decreasing SLC2A1 (GLUT1) mRNA and protein levels and by inhibiting glucose transport. Milciclib blocks glucose consumption by targeting cyclin-dependent kinase 7 (CDK7) similar to other CDK7 inhibitors including THZ1 and LDC4297. Enhanced PIK3CA signaling leads to CDK7 phosphorylation, which promotes RNA Polymerase II phosphorylation and transcription. Milciclib, THZ1, and LDC4297 lead to a reduction in RNA Polymerase II phosphorylation on the SLC2A1 promoter. These data indicate that our high-throughput assay can identify compounds that regulate glucose consumption and that CDK7 is a key regulator of glucose consumption in cells with an activated PI3K pathway.

DOI: https://doi.org/10.1038/s41467-019-13334-8
Nat Rev Endocrinol. 2019 Nov 28.

The effects of growth hormone on adipose tissue: old observations, new mechanisms.

John J Kopchick, Darlene E Berryman, Vishwajeet Puri, Kevin Y Lee, Jens O L Jorgensen.

The ability of growth hormone (GH) to induce adipose tissue lipolysis has been known for over five decades; however, the molecular mechanisms that mediate this effect and the ability of GH to inhibit insulin-stimulated glucose uptake have scarcely been documented. In this same time frame, our understanding of adipose tissue has evolved to reveal a complex structure with distinct types of adipocyte, depot-specific differences, a biologically significant extracellular matrix and important endocrine properties mediated by adipokines. All these aforementioned features, in turn, can influence lipolysis. In this Review, we provide a historical and current overview of the lipolytic effect of GH in humans, mice and cultured cells. More globally, we explain lipolysis in terms of GH-induced intracellular signalling and its effect on obesity, insulin resistance and lipotoxicity. In this regard, findings that define molecular mechanisms by which GH induces lipolysis are described. Finally, data are presented for the differential effect of GH on specific adipose tissue depots and on distinct classes of metabolically active adipocytes. Together, these cellular, animal and human studies reveal novel cellular phenotypes and molecular pathways regulating the metabolic effects of GH on adipose tissue.

DOI: https://doi.org/10.1038/s41574-019-0280-9
Sci Signal. 2019 Nov 26. pii: eaaz0274. [Epub ahead of print]12(609):

The human secretome.

Mathias Uhlén, Max J Karlsson, Andreas Hober, Anne-Sophie Svensson, Julia Scheffel, David Kotol, Wen Zhong, Abdellah Tebani, Linnéa Strandberg, Fredrik Edfors, Evelina Sjöstedt, Jan Mulder, Adil Mardinoglu, Anna Berling, Siri Ekblad, Melanie Dannemeyer, Sara Kanje, Johan Rockberg, Magnus Lundqvist, Magdalena Malm, Anna-Luisa Volk, Peter Nilsson, Anna Månberg, Tea Dodig-Crnkovic, Elisa Pin, Martin Zwahlen, Per Oksvold, Kalle von Feilitzen, Ragna S Häussler, Mun-Gwan Hong, Cecilia Lindskog, Fredrik Ponten, Borbala Katona, Jimmy Vuu, Emil Lindström, Jens Nielsen, Jonathan Robinson, Burcu Ayoglu, Diana Mahdessian, Devin Sullivan, Peter Thul, Frida Danielsson, Charlotte Stadler, Emma Lundberg, Göran Bergström, Anders Gummesson, Bjørn G Voldborg, Hanna Tegel, Sophia Hober, Björn Forsström, Jochen M Schwenk, Linn Fagerberg, Åsa Sivertsson.

The proteins secreted by human cells (collectively referred to as the secretome) are important not only for the basic understanding of human biology but also for the identification of potential targets for future diagnostics and therapies. Here, we present a comprehensive analysis of proteins predicted to be secreted in human cells, which provides information about their final localization in the human body, including the proteins actively secreted to peripheral blood. The analysis suggests that a large number of the proteins of the secretome are not secreted out of the cell, but instead are retained intracellularly, whereas another large group of proteins were identified that are predicted to be retained locally at the tissue of expression and not secreted into the blood. Proteins detected in the human blood by mass spectrometry-based proteomics and antibody-based immunoassays are also presented with estimates of their concentrations in the blood. The results are presented in an updated version 19 of the Human Protein Atlas in which each gene encoding a secretome protein is annotated to provide an open-access knowledge resource of the human secretome, including body-wide expression data, spatial localization data down to the single-cell and subcellular levels, and data about the presence of proteins that are detectable in the blood.

DOI: https://doi.org/10.1126/scisignal.aaz0274
J Neurooncol. 2019 Nov 27.

A Phase Ib/II, open-label, multicenter study of INC280 (capmatinib) alone and in combination with buparlisib (BKM120) in adult patients with recurrent glioblastoma.

Martin van den Bent, Analia Azaro, Filip De Vos, Juan Sepulveda, W K Alfred Yung, Patrick Y Wen, Andrew B Lassman, Markus Joerger, Ghazaleh Tabatabai, Jordi Rodon, Ralph Tiedt, Sylvia Zhao, Tiina Kirsilae, Yi Cheng, Sergio Vicente, O Alejandro Balbin, Hefei Zhang, Wolfgang Wick.

   PURPOSE: To estimate the maximum tolerated dose (MTD) and/or identify the recommended Phase II dose (RP2D) for combined INC280 and buparlisib in patients with recurrent glioblastoma with homozygous phosphatase and tensin homolog (PTEN) deletion, mutation or protein loss.
METHODS: This multicenter, open-label, Phase Ib/II study included adult patients with glioblastoma with mesenchymal-epithelial transcription factor (c-Met) amplification. In Phase Ib, patients received INC280 as capsules or tablets in combination with buparlisib. In Phase II, patients received INC280 only. Response was assessed centrally using Response Assessment in Neuro-Oncology response criteria for high-grade gliomas. All adverse events (AEs) were recorded and graded.
RESULTS: 33 patients entered Phase Ib, 32 with altered PTEN. RP2D was not declared due to potential drug-drug interactions, which may have resulted in lack of efficacy; thus, Phase II, including 10 patients, was continued with INC280 monotherapy only. Best response was stable disease in 30% of patients. In the selected patient population, enrollment was halted due to limited activity with INC280 monotherapy. In Phase Ib, the most common treatment-related AEs were fatigue (36.4%), nausea (30.3%) and increased alanine aminotransferase (30.3%). MTD was identified at INC280 Tab 300 mg twice daily + buparlisib 80 mg once daily. In Phase II, the most common AEs were headache (40.0%), constipation (30.0%), fatigue (30.0%) and increased lipase (30.0%).
CONCLUSION: The combination of INC280/buparlisib resulted in no clear activity in patients with recurrent PTEN-deficient glioblastoma. More stringent molecular selection strategies might produce better outcomes.
TRIAL REGISTRATION: NCT01870726.

Keywords:  Buparlisib; Capmatinib; Glioblastoma; INC280; PTEN; c-Met

DOI:  https://doi.org/10.1007/s11060-019-03337-2
Epilepsy Behav. 2019 Nov 21. pii: S1525-5050(19)30573-6. [Epub ahead of print] 106581

High glucose concentrations mask cellular phenotypes in a stem cell model of tuberous sclerosis complex.

Paula Rocktäschel, Arjune Sen, M Zameel Cader.

  Tuberous sclerosis complex (TSC) is a neurodevelopmental disorder caused by deletions in the TSC1 or TSC2 genes that is associated with epilepsy in up to 90% of patients. Seizures are suggested to start in benign brain tumors, cortical tubers, or in the perituberal tissue making these tubers an interesting target for further research into mechanisms underlying epileptogenesis in TSC. Animal models of TSC insufficiently capture the neurodevelopmental biology of cortical tubers, and hence, human stem cell-based in vitro models of TSC are being increasingly explored in attempts to recapitulate tuber development and epileptogenesis in TSC. However, in vitro culture conditions for stem cell-derived neurons do not necessarily mimic physiological conditions. For example, very high glucose concentrations of up to 25 mM are common in culture media formulations. As TSC is potentially caused by a disruption of the mechanistic target of rapamycin (mTOR) pathway, a main integrator of metabolic information and intracellular signaling, we aimed to examine the impact of different glucose concentrations in the culture media on cellular phenotypes implicated in tuber characteristics. Here, we present preliminary data from a pilot study exploring cortical neuronal differentiation on human embryonic stem cells (hES) harboring a TSC2 knockout mutation (TSC2-/-) and an isogenic control line (TSC2+/+). We show that the commonly used high glucose media profoundly mask cellular phenotypes in TSC2-/- cultures during neuronal differentiation. These phenotypes only become apparent when differentiating TSC2+/+ and TSC2-/- cultures in more physiologically relevant conditions of 5 mM glucose suggesting that the careful consideration of culture conditions is vital to ensuring biological relevance and translatability of stem cell models for neurological disorders such as TSC. This article is part of the Special Issue "Proceedings of the 7th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures".

Keywords:  Model reliability; Stem cell models; Tuberous sclerosis complex

DOI:  https://doi.org/10.1016/j.yebeh.2019.106581
Mol Metab. 2019 Dec;pii: S2212-8778(19)30907-X. [Epub ahead of print]30 61-71

Subcellular metabolic pathway kinetics are revealed by correcting for artifactual post harvest metabolism.

Sophie Trefely, Joyce Liu, Katharina Huber, Mary T Doan, Helen Jiang, Jay Singh, Eliana von Krusenstiern, Anna Bostwick, Peining Xu, Juliane G Bogner-Strauss, Kathryn E Wellen, Nathaniel W Snyder.

   OBJECTIVE: The dynamic regulation of metabolic pathways can be monitored by stable isotope tracing. Yet, many metabolites are part of distinct processes within different subcellular compartments. Standard isotope tracing experiments relying on analyses in whole cells may not accurately reflect compartmentalized metabolic processes. Analysis of compartmentalized metabolism and the dynamic interplay between compartments can potentially be achieved by stable isotope tracing followed by subcellular fractionation. Although it is recognized that metabolism can take place during biochemical fractionation of cells, a clear understanding of how such post-harvest metabolism impacts the interpretation of subcellular isotope tracing data and methods to correct for this are lacking. We set out to directly assess artifactual metabolism, enabling us to develop and test strategies to correct for it. We apply these techniques to examine the compartment-specific metabolic kinetics of 13C-labeled substrates targeting central metabolic pathways.
METHODS: We designed a stable isotope tracing strategy to interrogate post-harvest metabolic activity during subcellular fractionation using liquid chromatography-mass spectrometry (LC-MS).
RESULTS: We show that post-harvest metabolic activity occurs rapidly (within seconds) upon cell harvest. With further characterization we reveal that this post-harvest metabolism is enzymatic and reflects the metabolic capacity of the sub-cellular compartment analyzed, but it is limited in the extent of its propagation into downstream metabolites in metabolic pathways. We also propose and test a post-labeling strategy to assess the amount of post-harvest metabolism occurring in an experiment and then to adjust data to account for this. We validate this approach for both mitochondrial and cytosolic metabolic analyses.
CONCLUSIONS: Our data indicate that isotope tracing coupled with sub-cellular fractionation can reveal distinct and dynamic metabolic features of cellular compartments, and that confidence in such data can be improved by applying a post-labeling correction strategy. We examine compartmentalized metabolism of acetate and glutamine and show that acetyl-CoA is turned over rapidly in the cytosol and acts as a pacemaker of anabolic metabolism in this compartment.

Keywords:  Acetyl-CoA; Compartmentalization; Mevalonate pathway; Organelle; Stable isotope tracing; Sub-cellular metabolism

DOI:  https://doi.org/10.1016/j.molmet.2019.09.004
Mol Metab. 2019 Dec;pii: S2212-8778(19)30920-2. [Epub ahead of print]30 203-220

Loss of FoxOs in muscle reveals sex-based differences in insulin sensitivity but mitigates diet-induced obesity.

Christie M Penniman, Pablo A Suarez Beltran, Gourav Bhardwaj, Taylor L Junck, Jayashree Jena, Kennedy Poro, Michael F Hirshman, Laurie J Goodyear, Brian T O'Neill.

   OBJECTIVE: Gender influences obesity-related complications, including diabetes. Females are more protected from insulin resistance after diet-induced obesity, which may be related to fat accumulation and muscle insulin sensitivity. FoxOs regulate muscle atrophy and are targets of insulin action, but their role in muscle insulin sensitivity and mitochondrial metabolism is unknown.
METHODS: We measured muscle insulin signaling, mitochondrial energetics, and metabolic responses to a high-fat diet (HFD) in male and female muscle-specific FoxO1/3/4 triple knock-out (TKO) mice.
RESULTS: In male TKO muscle, insulin-stimulated AKT activation was decreased. AKT2 protein and mRNA levels were reduced and insulin receptor protein and IRS-2 mRNA decreased. These changes contributed to decreased insulin-stimulated glucose uptake in glycolytic muscle in males. In contrast, female TKOs maintain normal insulin-mediated AKT phosphorylation, normal AKT2 levels, and normal glucose uptake in glycolytic muscle. When challenged with a HFD, fat gain was attenuated in both male and female TKO mice, and associated with decreased glucose levels, improved glucose homeostasis, and reduced muscle triglyceride accumulation. Furthermore, female TKO mice showed increased energy expenditure, relative to controls, due to increased lean mass and maintenance of mitochondrial function in muscle.
CONCLUSIONS: FoxO deletion in muscle uncovers sexually dimorphic regulation of AKT2, which impairs insulin signaling in male mice, but not females. However, loss of FoxOs in muscle from both males and females also leads to muscle hypertrophy and increases in metabolic rate. These factors mitigate fat gain and attenuate metabolic abnormalities in response to a HFD.

Keywords:  Diet-induced obesity; FoxO; Gender differences; Glucose uptake; High-fat diet; Insulin resistance; Muscle hypertrophy; Sexual dimorphism

DOI:  https://doi.org/10.1016/j.molmet.2019.10.001
J Clin Invest. 2019 Nov 25. pii: 126390. [Epub ahead of print]

Deregulating MYC in a model of HER2+ breast cancer mimics human intertumoral heterogeneity.

Tyler Risom, Xiaoyan Wang, Juan Liang, Xiaoli Zhang, Carl Pelz, Lydia G Campbell, Jenny Eng, Koei Chin, Caroline Farrington, Goutham Narla, Ellen M Langer, Xiao-Xin Sun, Yulong Su, Colin J Daniel, Mu-Shui Dai, Christiane V Löhr, Rosalie C Sears.

  The c-MYC (MYC) oncoprotein is often overexpressed in human breast cancer; however, its role in driving disease phenotypes is poorly understood. Here, we investigate the role of MYC in HER2+ disease, examining the relationship between HER2 expression and MYC phosphorylation in HER2+ patient tumors and characterizing the functional effects of deregulating MYC expression in the murine NeuNT model of amplified-HER2 breast cancer. Deregulated MYC alone was not tumorigenic, but coexpression with NeuNT resulted in increased MYC Ser62 phosphorylation and accelerated tumorigenesis. The resulting tumors were metastatic and associated with decreased survival compared with NeuNT alone. MYC;NeuNT tumors had increased intertumoral heterogeneity including a subtype of tumors not observed in NeuNT tumors, which showed distinct metaplastic histology and worse survival. The distinct subtypes of MYC;NeuNT tumors match existing subtypes of amplified-HER2, estrogen receptor-negative human tumors by molecular expression, identifying the preclinical utility of this murine model to interrogate subtype-specific differences in amplified-HER2 breast cancer. We show that these subtypes have differential sensitivity to clinical HER2/EGFR-targeted therapeutics, but small-molecule activators of PP2A, the phosphatase that regulates MYC Ser62 phosphorylation, circumvents these subtype-specific differences and ubiquitously suppresses tumor growth, demonstrating the therapeutic utility of this approach in targeting deregulated MYC breast cancers.

Keywords:  Breast cancer; Cell Biology; Mouse models; Oncogenes; Oncology

DOI:  https://doi.org/10.1172/JCI126390
Oncogene. 2019 Nov 29.

The microcosmos of intratumor heterogeneity: the space-time of cancer evolution.

Michalina Janiszewska.

The Cancer Genome Atlas consortium brought us terabytes of information about genetic alterations in different types of human tumors. While many cancer-driver genes have been identified through these efforts, interrogating cancer genomes has also shed new light on tumor complexity. Mutations were found to vary tremendously in their allelic frequencies within the same tumor. Based on those variant allelic frequencies grouping, an estimate of genetically distinct "clones" of cancer cells can be determined for each tumor. It was estimated that 4-8 clones are present in every human tumor. Presence of distinct clones, cells that differ in their genotype and/or phenotype, is one of the roots for the major challenge of effectively curing cancer patients. Any given treatment applied to a heterogeneous mixture of cancer cells will yield distinct responses in different cells and may be ineffective in killing particular clones. Moreover, in highly heterogeneous tumors, stochastically, there is a higher chance of presence of traits, such as point mutations in key receptor tyrosine kinases, that drive drug resistance. Thus, intratumor heterogeneity is like an arsenal, providing a variety of weapons for self-defense against cancer-targeted therapy. However, in this arsenal the supplies are constantly changing, as cancer cells are accumulating new mutations. What is also changing is the battlefield-the tumor microenvironment including all noncancerous cells within the tumor and surrounding tissue, which also contribute to the diversification of cancer's forces. In order to design more effective therapies that would target this ever-changing landscape, we need to learn more about the two elusive variables that shape the tumor ecosystem: the space-how could we exploit the organization of tumor microenvironment? and the time-how could we predict the changes in heterogeneous tumors?

DOI: https://doi.org/10.1038/s41388-019-1127-5
Cell Stem Cell. 2019 Nov 11. pii: S1934-5909(19)30420-5. [Epub ahead of print]

Brain Endothelial Cells Maintain Lactate Homeostasis and Control Adult Hippocampal Neurogenesis.

Jun Wang, Yaxiong Cui, Zhenyang Yu, Wenjing Wang, Xuan Cheng, Wenliang Ji, Shuyue Guo, Qing Zhou, Ning Wu, Yan Chen, Ying Chen, Xiaopeng Song, Hui Jiang, Yanxiao Wang, Yu Lan, Bin Zhou, Lanqun Mao, Jin Li, Huanming Yang, Weixiang Guo, Xiao Yang.

  Increased understanding of the functions of lactate has suggested a close relationship between lactate homeostasis and normal brain activity because of its importance as an energy source and signaling molecule. Here we show that lactate levels affect adult hippocampal neurogenesis. Cerebrovascular-specific deletion of PTEN causes learning and memory deficits and disrupts adult neurogenesis with accompanying lactate accumulation. Consistently, administering lactate to wild-type animals impairs adult hippocampal neurogenesis. The endothelial PTEN/Akt pathway increases monocarboxylic acid transporter 1 (MCT1) expression to enhance lactate transport across the brain endothelium. Moreover, cerebrovascular overexpression of MCT1 or deletion of Akt1 restores MCT1 expression, decreases lactate levels, and normalizes hippocampal neurogenesis and cognitive function in PTEN mutant mice. Together, these findings delineate how the brain endothelium maintains lactate homeostasis and contributes to adult hippocampal neurogenesis and cognitive functions.

Keywords:  CRISPR-Cas9; PTEN/Akt signaling; adult neurogenesis; cerebrovascular endothelial cell; cognition; lactate; monocarboxylic acid transporter 1

DOI:  https://doi.org/10.1016/j.stem.2019.09.009
Geroscience. 2019 Nov 25.

Topical rapamycin reduces markers of senescence and aging in human skin: an exploratory, prospective, randomized trial.

Christina Lee Chung, Ibiyonu Lawrence, Melissa Hoffman, Dareen Elgindi, Kumar Nadhan, Manali Potnis, Annie Jin, Catlin Sershon, Rhonda Binnebose, Antonello Lorenzini, Christian Sell.

  Aging is a major risk factor for the majority of human diseases, and the development of interventions to reduce the intrinsic rate of aging is expected to reduce the risk for age-related diseases including cardiovascular disease, cancer, and dementia. In the skin, aging manifests itself in photodamage and dermal atrophy, with underlying tissue reduction and impaired barrier function. To determine whether rapamycin, an FDA-approved drug targeting the mechanistic target of rapamycin (mTOR) complex, can reduce senescence and markers of aging in human skin, an exploratory, placebo-controlled, interventional trial was conducted in a clinical dermatology setting. Participants were greater than 40 years of age with evidence of age-related photoaging and dermal volume loss and no major morbidities. Thirty-six participants were enrolled in the study, and nineteen discontinued or were lost to follow-up. A significant (P = 0.008) reduction in p16INK4A protein levels and an increase in collagen VII protein levels (P = 0.0077) were observed among participants at the end of the study. Clinical improvement in skin appearance was noted in multiple participants, and immunohistochemical analysis revealed improvement in histological appearance of skin tissue. Topical rapamycin reduced the expression of the p16INK4A protein consistent with a reduction in cellular senescence. This change was accompanied by relative improvement in clinical appearance of the skin and histological markers of aging and by an increase in collagen VII, which is critical to the integrity of the basement membrane. These results indicate that rapamycin treatment is a potential anti-aging therapy with efficacy in humans.Trial registration ClinicalTrials.gov Identifier: NCT03103893.

Keywords:  aging; keratoses; mTOR; photoaging; rapamycin; senescence

DOI:  https://doi.org/10.1007/s11357-019-00113-y