bims-pideca Biomed News
on Class IA PI3K signalling in development and cancer
Issue of 2020–07–05
nineteen papers selected by
Ralitsa Radostinova Madsen, University College London
  1. A substrate-specific mTORC1 pathway underlies Birt-Hogg-Dubé syndrome.
  2. PTEN Alterations and Their Role in Cancer Management: Are We Making Headway on Precision Medicine?
  3. Neutralization of HSF1 in cells from PIK3CA-related overgrowth spectrum patients blocks abnormal proliferation.
  4. Dual function of PI(4,5)P2 in insulin-regulated exocytic trafficking of GLUT4 in adipocytes.
  5. Fibroblast-tumor cell signaling limits HER2 kinase therapy response via activation of MTOR and antiapoptotic pathways.
  6. AIMTOR, a BRET biosensor for live imaging, reveals subcellular mTOR signaling and dysfunctions.
  7. The Splicing Factor SF2 Is Critical for Hyperproliferation and Survival in a TORC1-Dependent Model of Early Tumorigenesis in Drosophila.
  8. The Lysosome at the Intersection of Cellular Growth and Destruction.
  9. CRISPR gene editing in human embryos wreaks chromosomal mayhem.
  10. Reciprocal Regulation between Primary Cilia and mTORC1.
  11. Dermatologic adverse events related to the PI3Kα inhibitor alpelisib (BYL719) in patients with breast cancer.
  12. Metabolic Communication and Healthy Aging: Where Should We Focus Our Energy?
  13. Endocytic regulation of cellular ion homeostasis controls lysosome biogenesis.
  14. Potential of Tyrosine Kinase Receptor TIE-1 as Novel Therapeutic Target in High-PI3K-Expressing Ovarian Cancer.
  15. mTORC2 Is Involved in the Induction of RSK Phosphorylation by Serum or Nutrient Starvation.
  16. A Patient-Derived Xenograft Model for Venous Malformation.
  17. Clinical and genetic evaluation of six children with diffuse capillary malformation and undergrowth.
  18. Rethinking the Relationship between Insulin and Cancer.
  19. Cotargeting BET proteins overcomes resistance arising from PI3K/mTOR blockade-induced protumorigenic senescence in colorectal cancer.
  1. Nature. 2020 Jul 01.
    A substrate-specific mTORC1 pathway underlies Birt-Hogg-Dubé syndrome.
    Gennaro Napolitano, Chiara Di Malta, Alessandra Esposito, Mariana E G de Araujo, Salvatore Pece, Giovanni Bertalot, Maria Matarese, Valerio Benedetti, Angela Zampelli, Taras Stasyk, Diletta Siciliano, Alessandro Venuta, Marcella Cesana, Claudia Vilardo, Edoardo Nusco, Jlenia Monfregola, Alessia Calcagnì, Pier Paolo Di Fiore, Lukas A Huber, Andrea Ballabio.
      The mechanistic target of rapamycin complex 1 (mTORC1) is a key metabolic hub that controls the cellular response to environmental cues by exerting its kinase activity on multiple substrates1-3. However, whether mTORC1 responds to diverse stimuli by differentially phosphorylating specific substrates is poorly understood. Here we show that transcription factor EB (TFEB), a master regulator of lysosomal biogenesis and autophagy4,5, is phosphorylated by mTORC1 via a substrate-specific mechanism that is mediated by Rag GTPases. Owing to this mechanism, the phosphorylation of TFEB-unlike other substrates of mTORC1, such as S6K and 4E-BP1- is strictly dependent on the amino-acid-mediated activation of RagC and RagD GTPases, but is insensitive to RHEB activity induced by growth factors. This mechanism has a crucial role in Birt-Hogg-Dubé syndrome, a disorder that is caused by mutations in the RagC and RagD activator folliculin (FLCN) and is characterized by benign skin tumours, lung and kidney cysts and renal cell carcinoma6,7. We found that constitutive activation of TFEB is the main driver of the kidney abnormalities and mTORC1 hyperactivity in a mouse model of Birt-Hogg-Dubé syndrome. Accordingly, depletion of TFEB in kidneys of these mice fully rescued the disease phenotype and associated lethality, and normalized mTORC1 activity. Our findings identify a mechanism that enables differential phosphorylation of mTORC1 substrates, the dysregulation of which leads to kidney cysts and cancer.
    DOI:  https://doi.org/10.1038/s41586-020-2444-0
  2. Genes (Basel). 2020 Jun 28. pii: E719. [Epub ahead of print]11(7):
    PTEN Alterations and Their Role in Cancer Management: Are We Making Headway on Precision Medicine?
    Nicola Fusco, Elham Sajjadi, Konstantinos Venetis, Gabriella Gaudioso, Gianluca Lopez, Chiara Corti, Elena Guerini Rocco, Carmen Criscitiello, Umberto Malapelle, Marco Invernizzi.
      Alterations in the tumor suppressor phosphatase and tensin homolog (PTEN) occur in a substantial proportion of solid tumors. These events drive tumorigenesis and tumor progression. Given its central role as a downregulator of the phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway, PTEN is deeply involved in cell growth, proliferation, and survival. This gene is also implicated in the modulation of the DNA damage response and in tumor immune microenvironment modeling. Despite the actionability of PTEN alterations, their role as biomarkers remains controversial in clinical practice. To date, there is still a substantial lack of validated guidelines and/or recommendations for PTEN testing. Here, we provide an update on the current state of knowledge on biologic and genetic alterations of PTEN across the most frequent solid tumors, as well as on their actual and/or possible clinical applications. We focus on possible tailored schemes for cancer patients' clinical management, including risk assessment, diagnosis, prognostication, and treatment.
    Keywords:  PI3K/Akt; PTEN; biomarker; cancer; precision medicine; solid tumors; tumor immune microenvironment; tumor suppressor
    DOI:  https://doi.org/10.3390/genes11070719
  3. Biochem Biophys Res Commun. 2020 Jun 30. pii: S0006-291X(20)30886-X. [Epub ahead of print]
    Neutralization of HSF1 in cells from PIK3CA-related overgrowth spectrum patients blocks abnormal proliferation.
    Romain Da Costa, Steven De Almeida, Martin Chevarin, Smail Hadj-Rabia, Stéphanie Leclerc-Mercier, Christel Thauvin-Robinet, Carmen Garrido, Laurence Faivre, Pierre Vabres, Laurence Duplomb, Gaëtan Jego.
      PIK3CA-related overgrowth spectrum is caused by mosaicism mutations in the PIK3CA gene. These mutations, which are also observed in various types of cancer, lead to a constitutive activation of the PI3K/AKT/mTOR pathway, increasing cell proliferation. Heat shock transcription factor 1 (HSF1) is the major stress-responsive transcription factor. Recent findings indicate that AKT phosphorylates and activates HSF1 independently of heat-shock in breast cancer cells. Here, we aimed to investigate the role of HSF1 in PIK3CA-related overgrowth spectrum. We observed a higher rate of proliferation and increased phosphorylation of AKT and p70S6K in mutant fibroblasts than in control cells. We also found elevated phosphorylation and activation of HSF1, which is directly correlated to AKT activation. Specific AKT inhibitors inhibit HSF1 phosphorylation as well as HSF1-dependent gene transcription. Finally, we demonstrated that targeting HSF1 with specific inhibitors reduced the proliferation of mutant cells. As there is currently no curative treatment for PIK3CA-related overgrowth spectrum, our results identify HSF1 as a new potential therapeutic target.
    Keywords:  HSF1; PI3K; Segmental overgrowth spectrum
    DOI:  https://doi.org/10.1016/j.bbrc.2020.04.146
  4. J Mol Biol. 2020 Jun 25. pii: S0022-2836(20)30417-4. [Epub ahead of print]
    Dual function of PI(4,5)P2 in insulin-regulated exocytic trafficking of GLUT4 in adipocytes.
    Hanbing Li, Ping Shentu, Mei Xiao, Xuqin Zhao, Jiannan Fan, Xuechun Liu, Yinyan Lin, Lei Wang, Hong Li, Xiaogang Guo, Olof Idevall-Hagren, Yingke Xu.
      Phosphoinositides are important signaling molecules involved in the regulation of vesicular trafficking. It has been implicated that phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] is involved in insulin-regulated GLUT4 translocation in adipocytes. However, it remains unclear where and how PI(4,5)P2 regulates discrete steps of GLUT4 vesicle translocation in adipocytes, especially on the exocytic arm of regulation. Here, we employed optogenetic tools to acutely control the PI(4,5)P2 metabolism in living cells. By combination of TIRFM imaging, we were able to monitor the temporal-spatial-dependent PI(4,5)P2 regulation on discrete steps of GLUT4 translocation in adipocytes. We found that the plasma membrane localized PI(4,5)P2 is crucial for proper insulin signaling propagation and for insulin-stimulated GLUT4 vesicle translocation in 3 T3-L1 adipocytes. Global depletion of PI(4,5)P2 on the cell surface blunted insulin-stimulated Akt phosphorylation and abolished insulin effects in promotion of the docking and fusion of GLUT4 vesicle with the plasma membrane. Furthermore, by development of a novel optogenetic module to selectively modulate PI(4,5)P2 levels on the GLUT4 vesicle docking site, we identified an important regulatory role of PI(4,5)P2 in controlling of vesicle docking process. Local depletion of PI(4,5)P2 at the vesicle docking site promoted GLUT4 vesicle undocking, diminished insulin-stimulated GLUT4 vesicle docking and fusion, but without perturbation of insulin signaling propagation in adipocytes. Our results provide strong evidence that cell surface PI(4,5)P2 plays two distinct functions on regulation of the exocytic trafficking of GLUT4 in adipocytes. PI(4,5)P2 not only regulates the proper activation of insulin signaling in general, but also controls GLUT4 vesicle docking process at the vesicle-membrane contact sites.
    Keywords:  Exocytosis; GLUT4; Optogenetics; Phosphoinositide; TIRFM
    DOI:  https://doi.org/10.1016/j.jmb.2020.06.019
  5. Proc Natl Acad Sci U S A. 2020 Jun 29. pii: 202000648. [Epub ahead of print]
    Fibroblast-tumor cell signaling limits HER2 kinase therapy response via activation of MTOR and antiapoptotic pathways.
    Ioannis K Zervantonakis, Matthew D Poskus, Alexis L Scott, Laura M Selfors, Jia-Ren Lin, Deborah A Dillon, Shailja Pathania, Peter K Sorger, Gordon B Mills, Joan S Brugge.
      Despite the implementation of multiple HER2-targeted therapies, patients with advanced HER2+ breast cancer ultimately develop drug resistance. Stromal fibroblasts represent an abundant cell type in the tumor microenvironment and have been linked to poor outcomes and drug resistance. Here, we show that fibroblasts counteract the cytotoxic effects of HER2 kinase-targeted therapy in a subset of HER2+ breast cancer cell lines and allow cancer cells to proliferate in the presence of the HER2 kinase inhibitor lapatinib. Fibroblasts from primary breast tumors, normal breast tissue, and lung tissue have similar protective effects on tumor cells via paracrine factors. This fibroblast-mediated reduction in drug sensitivity involves increased expression of antiapoptotic proteins and sustained activation of the PI3K/AKT/MTOR pathway, despite inhibition of the HER2 and the RAS-ERK pathways in tumor cells. HER2 therapy sensitivity is restored in the fibroblast cocultures by combination treatment with inhibitors of MTOR or the antiapoptotic proteins BCL-XL and MCL-1. Expression of activated AKT in tumor cells recapitulates the effects of fibroblasts resulting in sustained MTOR signaling and poor lapatinib response. Lapatinib sensitivity was not altered by fibroblasts in tumor cells that exhibited sustained MTOR signaling due to a strong gain-of-function PI3KCA mutation. These findings indicate that in addition to tumor cell-intrinsic mechanisms that cause constitutive PI3K/AKT/MTOR pathway activation, secreted factors from fibroblasts can maintain this pathway in the context of HER2 inhibition. Our integrated proteomic-phenotypic approach presents a strategy for the discovery of protective mechanisms in fibroblast-rich tumors and the design of rational combination therapies to restore drug sensitivity.
    Keywords:  breast cancer; cell–cell interactions; drug resistance; fibroblasts; tumor microenvironment
    DOI:  https://doi.org/10.1073/pnas.2000648117
  6. BMC Biol. 2020 Jul 03. 18(1): 81
    AIMTOR, a BRET biosensor for live imaging, reveals subcellular mTOR signaling and dysfunctions.
    Nathalie Bouquier, Enora Moutin, Lionel A Tintignac, Amandine Reverbel, Elodie Jublanc, Michael Sinnreich, Yan Chastagnier, Julien Averous, Pierre Fafournoux, Chiara Verpelli, Tobias Boeckers, Gilles Carnac, Julie Perroy, Vincent Ollendorff.
       BACKGROUND: mTOR signaling is an essential nutrient and energetic sensing pathway. Here we describe AIMTOR, a sensitive genetically encoded BRET (Bioluminescent Resonance Energy Transfer) biosensor to study mTOR activity in living cells.
    RESULTS: As a proof of principle, we show in both cell lines and primary cell cultures that AIMTOR BRET intensities are modified by mTOR activity changes induced by specific inhibitors and activators of mTORC1 including amino acids and insulin. We further engineered several versions of AIMTOR enabling subcellular-specific assessment of mTOR activities. We then used AIMTOR to decipher mTOR signaling in physio-pathological conditions. First, we show that mTORC1 activity increases during muscle cell differentiation and in response to leucine stimulation in different subcellular compartments such as the cytosol and at the surface of the lysosome, the nucleus, and near the mitochondria. Second, in hippocampal neurons, we found that the enhancement of neuronal activity increases mTOR signaling. AIMTOR further reveals mTOR-signaling dysfunctions in neurons from mouse models of autism spectrum disorder.
    CONCLUSIONS: Altogether, our results demonstrate that AIMTOR is a sensitive and specific tool to investigate mTOR-signaling dynamics in living cells and phenotype mTORopathies.
    Keywords:  Autism spectrum disorder; BRET; Muscle differentiation; Neuronal activity; mTORC1 Biosensor; mTor signaling; mToropathies
    DOI:  https://doi.org/10.1186/s12915-020-00790-8
  7. Int J Mol Sci. 2020 Jun 24. pii: E4465. [Epub ahead of print]21(12):
    The Splicing Factor SF2 Is Critical for Hyperproliferation and Survival in a TORC1-Dependent Model of Early Tumorigenesis in Drosophila.
    Malgorzata Maria Parniewska, Hugo Stocker.
      The Target of Rapamycin complex 1 (TORC1) is an evolutionarily conserved kinase complex coordinating cellular growth with nutritional conditions and growth factor signaling, and its activity is elevated in many cancer types. The use of TORC1 inhibitors as anticancer drugs is, however, limited by unwanted side-effects and development of resistance. We therefore attempted to identify limiting modulators or downstream effectors of TORC1 that could serve as therapeutic targets. Drosophila epithelial tissues that lack the tumor suppressor Pten hyperproliferate upon nutrient restriction in a TORC1-dependent manner. We probed candidates of the TORC1 signaling network for factors limiting the overgrowth of Pten mutant tissues. The serine/arginine-rich splicing factor 2 (SF2) was identified as the most limiting factor: SF2 knockdown drives Pten mutant cells into apoptosis, while not affecting control tissue. SF2 acts downstream of or in parallel to TORC1 but is not required for the activation of the TORC1 target S6K. Transcriptomics analysis revealed transcripts with alternatively used exons regulated by SF2 in the tumor context, including p53. SF2 may therefore represent a highly specific therapeutic target for tumors with hyperactive TORC1 signaling.
    Keywords:  Drosophila melanogaster; Pten; SF2; TORC1; cancer; tumor suppression
    DOI:  https://doi.org/10.3390/ijms21124465
  8. Dev Cell. 2020 Jun 30. pii: S1534-5807(20)30460-3. [Epub ahead of print]
    The Lysosome at the Intersection of Cellular Growth and Destruction.
    Hijai R Shin, Roberto Zoncu.
      The lysosome is an essential catabolic organelle that consumes cellular biomass to regenerate basic building blocks that can fuel anabolic reactions. This simple view has evolved more recently to integrate novel functions of the lysosome as a key signaling center, which can steer the metabolic trajectory of cells in response to changes in nutrients, growth factors, and stress. Master protein kinases and transcription factors mediate the growth-promoting and catabolic activities of the lysosome and undergo a complex interplay that enables cellular adaptation to ever-changing metabolic conditions. Understanding how this coordination occurs will shed light on the fundamental logic of how the lysosome functions to control growth in the context of development, tissue homeostasis, and cancer.
    Keywords:  TFEB; anabolism; autophagy; catabolism; lysosome; mTORC1; nutrient sensing
    DOI:  https://doi.org/10.1016/j.devcel.2020.06.010
  9. Nature. 2020 07;583(7814): 17-18
    CRISPR gene editing in human embryos wreaks chromosomal mayhem.
    Heidi Ledford.
      
    Keywords:  Biological techniques; CRISPR-Cas9 genome editing; Genetics
    DOI:  https://doi.org/10.1038/d41586-020-01906-4
  10. Genes (Basel). 2020 Jun 26. pii: E711. [Epub ahead of print]11(6):
    Reciprocal Regulation between Primary Cilia and mTORC1.
    Yandong Lai, Yu Jiang.
      In quiescent cells, primary cilia function as a mechanosensor that converts mechanic signals into chemical activities. This unique organelle plays a critical role in restricting mechanistic target of rapamycin complex 1 (mTORC1) signaling, which is essential for quiescent cells to maintain their quiescence. Multiple mechanisms have been identified that mediate the inhibitory effect of primary cilia on mTORC1 signaling. These mechanisms depend on several tumor suppressor proteins localized within the ciliary compartment, including liver kinase B1 (LKB1), AMP-activated protein kinase (AMPK), polycystin-1, and polycystin-2. Conversely, changes in mTORC1 activity are able to affect ciliogenesis and stability indirectly through autophagy. In this review, we summarize recent advances in our understanding of the reciprocal regulation of mTORC1 and primary cilia.
    Keywords:  AMPK; LKB1; Tsc2; autophagy; ciliogenesis; mTOR; mTORC1; polycystin-1; primary cilia
    DOI:  https://doi.org/10.3390/genes11060711
  11. Breast Cancer Res Treat. 2020 Jun 29.
    Dermatologic adverse events related to the PI3Kα inhibitor alpelisib (BYL719) in patients with breast cancer.
    Diana G Wang, Dulce M Barrios, Victoria S Blinder, Jacqueline F Bromberg, Pamela R Drullinsky, Samuel A Funt, Komal L Jhaveri, Diana E Lake, Tomas Lyons, Shanu Modi, Pedram Razavi, Michelle Sidel, Tiffany A Traina, Linda T Vahdat, Mario E Lacouture.
       PURPOSE: Rash develops in approximately 50% of patients receiving alpelisib for breast cancer, often requiring dose modifications. Here, we describe the clinicopathologic, laboratory, and management characteristics of alpelisib-related dermatologic adverse events (dAEs).
    METHODS: A single center-retrospective analysis was conducted. Data were abstracted from electronic medical records.
    RESULTS: A total of 102 patients (mean age 56 years, range 27-83) receiving alpelisib most frequently in combination with endocrine therapy (79, 77.5%) were included. We identified 41 (40.2%) patients with all-grade rash distributed primarily along the trunk (78%) and extremities (70%) that developed approximately within two weeks of treatment initiation (mean 12.8 ± 1.5 days) and lasted one-week (mean duration 7.1 ± 0.8 days). Of 29 patients with documented morphology of alpelisib-related dAEs, 26 (89.7%) had maculopapular rash. Histology showed perivascular and interface lymphocytic dermatitis. All-grade rash correlated with an increase in serum eosinophils from 2.7 to 4.4%, p < 0.05, and prophylaxis with non-sedating antihistamines (n = 43) was correlated with a reduction of grade 1/2 rash (OR 0.39, p = 0.09). Sixteen (84.2%) of 19 patients with grade 3 dAEs resulted in interruption of alpelisib, which were managed with antihistamines, topical and systemic corticosteroids. We did not observe rash recurrence in 12 (75%) patients who were re-challenged.
    CONCLUSIONS: A maculopapular rash associated with increased blood eosinophils occurs frequently with alpelisib. While grade 3 rash leads to alpelisib therapy interruption, dermatologic improvement is evident with systemic corticosteroids; and most patients can continue oncologic treatment at a maintained or reduced dose upon re-challenge with alpelisib.
    Keywords:  Adverse event; Alpelisib; BYL719; PI3K; PIK3CA; Rash
    DOI:  https://doi.org/10.1007/s10549-020-05726-y
  12. Dev Cell. 2020 Jun 26. pii: S1534-5807(20)30461-5. [Epub ahead of print]
    Metabolic Communication and Healthy Aging: Where Should We Focus Our Energy?
    Hannah J Smith, Arpit Sharma, William B Mair.
      Aging is associated with a loss of metabolic homeostasis and plasticity, which is causally linked to multiple age-onset pathologies. The majority of the interventions-genetic, dietary, and pharmacological-that have been found to slow aging and protect against age-related disease in various organisms do so by targeting central metabolic pathways. However, targeting metabolic pathways chronically and ubiquitously makes it difficult to define the downstream effects responsible for lifespan extension and often results in negative effects on growth and health, limiting therapeutic potential. Insight into how metabolic signals are relayed between tissues, cells, and organelles opens up new avenues to target metabolic regulators locally rather than globally for healthy aging. In this review, we discuss the pro-longevity effects of targeting metabolic pathways in specific tissues and how these interventions communicate with distal cells to modulate aging. These studies may be crucial in designing interventions that promote longevity without negative health consequences.
    Keywords:  AMPK; NAD+; aging; extracellular vesicles; insulin signaling; mTOR; metabolism; microRNA; sirtuins; tissue-specificity
    DOI:  https://doi.org/10.1016/j.devcel.2020.06.011
  13. Nat Cell Biol. 2020 Jun 29.
    Endocytic regulation of cellular ion homeostasis controls lysosome biogenesis.
    Tania López-Hernández, Dmytro Puchkov, Eberhard Krause, Tanja Maritzen, Volker Haucke.
      Lysosomes serve as cellular degradation and signalling centres that coordinate metabolism in response to intracellular cues and extracellular signals. Lysosomal capacity is adapted to cellular needs by transcription factors, such as TFEB and TFE3, which activate the expression of lysosomal and autophagy genes. Nuclear translocation and activation of TFEB are induced by a variety of conditions such as starvation, lysosome stress and lysosomal storage disorders. How these various cues are integrated remains incompletely understood. Here, we describe a pathway initiated at the plasma membrane that controls lysosome biogenesis via the endocytic regulation of intracellular ion homeostasis. This pathway is based on the exo-endocytosis of NHE7, a Na+/H+ exchanger mutated in X-linked intellectual disability, and serves to control intracellular ion homeostasis and thereby Ca2+/calcineurin-mediated activation of TFEB and downstream lysosome biogenesis in response to osmotic stress to promote the turnover of toxic proteins and cell survival.
    DOI:  https://doi.org/10.1038/s41556-020-0535-7
  14. Cancers (Basel). 2020 Jun 26. pii: E1705. [Epub ahead of print]12(6):
    Potential of Tyrosine Kinase Receptor TIE-1 as Novel Therapeutic Target in High-PI3K-Expressing Ovarian Cancer.
    Xuewei Zhang, Masumi Ishibashi, Kazuyuki Kitatani, Shogo Shigeta, Hideki Tokunaga, Masafumi Toyoshima, Muneaki Shimada, Nobuo Yaegashi.
      Tyrosine kinase receptor TIE-1 plays a critical role in angiogenesis and blood-vessel stability. In recent years, increased TIE-1 expression has been observed in many types of cancers; however, the biological significance and underlying mechanisms remain unknown. Thus, in the present study, we investigated the tumor biological functions of TIE-1 in ovarian cancer. The treatment of SKOV3 ovarian-cancer cells with siRNA against TIE-1 decreased the expression of key molecules in the PI3K/Akt signaling pathway, such as p110α and phospho-Akt, suggesting that TIE-1 is related to the PI3K/Akt pathway. Furthermore, the knockdown of TIE-1 significantly decreased cell proliferation in high-PI3K-expressing cell lines (SKOV3, CAOV3) but not low-PI3K-expressing cell lines (TOV112D, A2780). These results suggested that inhibition of TIE-1 decreases cell growth in high-PI3K-expressing cells. Moreover, in low-PI3K-expressing TOV112D ovarian-cancer cells, TIE-1 overexpression induced PI3K upregulation and promoted a PI3K-mediated cell proliferative phenotype. Mechanistically, TIE-1 participates in cell growth and proliferation by regulating the PI3K/Akt signaling pathway. Taken together, our findings strongly implicate TIE-1 as a novel therapeutic target in high-PI3K-expressing ovarian-cancer cells.
    Keywords:  PI3K; TIE-1; molecular targeted therapy; ovarian cancer
    DOI:  https://doi.org/10.3390/cancers12061705
  15. Cells. 2020 Jun 27. pii: E1567. [Epub ahead of print]9(7):
    mTORC2 Is Involved in the Induction of RSK Phosphorylation by Serum or Nutrient Starvation.
    Po-Chien Chou, Swati Rajput, Xiaoyun Zhao, Chadni Patel, Danielle Albaciete, Won Jun Oh, Heineken Queen Daguplo, Nikhil Patel, Bing Su, Guy Werlen, Estela Jacinto.
      Cells adjust to nutrient fluctuations to restore metabolic homeostasis. The mechanistic target of rapamycin (mTOR) complex 2 responds to nutrient levels and growth signals to phosphorylate protein kinases belonging to the AGC (Protein Kinases A,G,C) family such as Akt and PKC. Phosphorylation of these AGC kinases at their conserved hydrophobic motif (HM) site by mTORC2 enhances their activation and mediates the functions of mTORC2 in cell growth and metabolism. Another AGC kinase family member that is known to undergo increased phosphorylation at the homologous HM site (Ser380) is the p90 ribosomal S6 kinase (RSK). Phosphorylation at Ser380 is facilitated by the activation of the mitogen-activated protein kinase/extracellular signal regulated kinase (MAPK/ERK) in response to growth factor stimulation. Here, we demonstrate that optimal phosphorylation of RSK at this site requires an intact mTORC2. We also found that RSK is robustly phosphorylated at Ser380 upon nutrient withdrawal or inhibition of glycolysis, conditions that increase mTORC2 activation. However, pharmacological inhibition of mTOR did not abolish RSK phosphorylation at Ser380, indicating that mTOR catalytic activity is not required for this phosphorylation. Since RSK and SIN1β colocalize at the membrane during serum restimulation and acute glutamine withdrawal, mTORC2 could act as a scaffold to enhance RSK HM site phosphorylation. Among the known RSK substrates, the CCTβ subunit of the chaperonin containing TCP-1 (CCT) complex had defective phosphorylation in the absence of mTORC2. Our findings indicate that the mTORC2-mediated phosphorylation of the RSK HM site could confer RSK substrate specificity and reveal that RSK responds to nutrient fluctuations.
    Keywords:  AGC kinases; CCT/TRiC; CCTβ; MAPK/ERK; RSK; chaperonin; mTORC2; metabolism; nutrients; p90 ribosomal s6 kinase; starvation
    DOI:  https://doi.org/10.3390/cells9071567
  16. J Vis Exp. 2020 Jun 15.
    A Patient-Derived Xenograft Model for Venous Malformation.
    Sandra Schrenk, Jillian Goines, Elisa Boscolo.
      Venous malformation (VM) is a vascular anomaly that arises from impaired development of the venous network resulting in dilated and often dysfunctional veins. The purpose of this article is to carefully describe the establishment of a murine xenograft model that mimics human VM and is able to reflect patient heterogeneity. Hyper-activating non-inherited (somatic) TEK (TIE2) and PIK3CA mutations in endothelial cells (EC) have been identified as the main drivers of pathological vessel enlargement in VM. The following protocol describes the isolation, purification and expansion of patient-derived EC expressing mutant TIE2 and/or PIK3CA. These EC are injected subcutaneously into the back of immunodeficient athymic mice to generate ectatic vascular channels. Lesions generated with TIE2 or PIK3CA-mutant EC are visibly vascularized within 7‒9 days of injection and recapitulate histopathological features of VM patient tissue. This VM xenograft model provides a reliable platform to investigate the cellular and molecular mechanisms driving VM formation and expansion. In addition, this model will be instrumental for translational studies testing the efficacy of novel drug candidates in preventing the abnormal vessel enlargement seen in human VM.
    DOI:  https://doi.org/10.3791/61501
  17. Pediatr Dermatol. 2020 Jul 01.
    Clinical and genetic evaluation of six children with diffuse capillary malformation and undergrowth.
    Xavier Cubiró, Eduardo Rozas-Muñoz, Pau Castel, Esther Roé Crespo, Cristina Garcia-Melendo, Lluis Puig, Eulalia Baselga.
       BACKGROUND: Diffuse capillary malformation with overgrowth (DCMO) has been well described. However, capillary malformation with undergrowth (CMU) has been less reported in the literature.
    OBJECTIVES: We sought to describe the clinical features and determine associated somatic mutations in patients with CMU.
    METHODS: We searched our multidisciplinary vascular anomalies clinic database for patients with CMU. Girth and length limb measurements were performed. In case of discrepancies in length, long leg radiograph studies were obtained. Whole-exome sequencing of blood and involved tissue DNA was carried out.
    RESULTS: We included six patients with CM and soft-tissue and bone undergrowth. CMs were patchy, reticulated, segmental, poorly demarcated, pink-red stains affecting the lower limb (five patients) or the whole hemibody (one patient). In five patients, the stain was diffuse, affecting more than one anatomic region. Prominent superficial veins were observed in three patients. Five patients presented with lower limb girth discrepancy; in three of them, there was also lower limb length discrepancy. In the remaining patient, only lower limb length discrepancy was found. Whole-exome sequencing from DNA tissue/blood detected previously described pathogenic somatic mutations on DDR2 (c.314G > A; p.Arg105His), GRHL2 (c.791A > G; p.Glu264Gly), and PIK3CA (c.2740G > A; p.Gly914Arg) genes.
    CONCLUSION: We propose the term "diffuse capillary malformation with undergrowth" for extensive reticular CMs associated with proportionate undergrowth. All our patients had a favorable outcome, and no genotype-phenotype association was found.
    Keywords:  PIK3CA; capillary malformation; hypoplasia; hypotrophy; undergrowth
    DOI:  https://doi.org/10.1111/pde.14252
  18. Trends Endocrinol Metab. 2020 Jun 26. pii: S1043-2760(20)30116-8. [Epub ahead of print]
    Rethinking the Relationship between Insulin and Cancer.
    R Vigneri, L Sciacca, P Vigneri.
      In addition to being a major metabolic hormone, insulin is also a growth factor with a mitogenic effect on all cells, more marked in malignant cells that often overexpress the insulin receptor. In patients with metabolic diseases characterized by hyperinsulinemia (obesity, type 2 diabetes, and metabolic syndrome), the incidence of several types of cancer is increased, as is cancer-related mortality. Because of the worldwide growing prevalence of metabolic diseases and the diffuse use of insulin and its analogs for treating diabetes, the relationship between insulin and cancer has become a clinically relevant issue. Clinical studies have not clarified the degree to which hyperinsulinemia can influence cancer occurrence and prognosis. To better understand this issue, an improved scientific approach is required, with more careful consideration of the mechanisms related to hyperinsulinemia and carcinogenesis.
    Keywords:  carcinogenesis; diabetes and cancer; hyperinsulinemia; insulin; insulin-dependent cancer; obesity and cancer
    DOI:  https://doi.org/10.1016/j.tem.2020.05.004
  19. Int J Cancer. 2020 Jun 29.
    Cotargeting BET proteins overcomes resistance arising from PI3K/mTOR blockade-induced protumorigenic senescence in colorectal cancer.
    Ho-Sung Lee, Soobeom Lee, Kwang-Hyun Cho.
      Therapeutics targeting the phosphatidylinositol 3-kinase/mammalian target of rapamycin (PI3K/mTOR) pathway initially produce potent antitumor effects, but resistance frequently occurs. Using a phosphoproteome analysis, we found that colorectal cancer (CRC) cells exhibit resistance against PI3K/mTOR inhibition through feedback activation of multiple receptor tyrosine kinases, and their downstream focal adhesion kinase, Src and extracellular signal-regulated kinases signaling. Unexpectedly, PI3K/mTOR blockade causes senescence, mediated by the activation of the stress kinase p38. The senescent cancer cells induce the secretion of various cytokines and this senescence-associated secretome increases migration and invasion capabilities of CRC cells. We found that cotargeting PI3K/mTOR and bromodomain and extra-terminal domain can suppress activation of many oncogenic kinases involved in resistance to the PI3K/mTOR inhibition, induce cell death in vitro and tumor regression in vivo, and further prolong the survival of xenograft models. Our findings provide a rationale for a novel therapeutic strategy to overcome resistance to the PI3K/mTOR inhibitors in CRC.
    Keywords:  cellular signaling pathways; colorectal cancer; combinatorial drug therapy; drug resistance mechanism; systems biology
    DOI:  https://doi.org/10.1002/ijc.33047
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