Genomes and Genes
VEGF Regulation of Hepatic Erythropoietin Synthesis
Principal Investigator: Calvin Kuo
Affiliation: Stanford University
Abstract: DESCRIPTION (provided by applicant): Erythropolesis, the production of red blood cells (RBCs), is regulated by an intricate network of signals involving the hormone erythropoietin (Epo), and sensing of hypoxia through inhibition of both HIF-1alpha proline hydroxylation and its subsequent interaction with the Von Hippel-Lindau (VHL) protein. Either insufficient or excess erythropoiesis produces disease in humans, with too few RBCs resulting in anemia, and too many RBCs resulting in polycythemia vera. The treatment of anemia alone consumes significant economic resources, with the necessity for either blood transfusions or Epo treatment. We have developed adenoviruses which express soluble ectodomains of the Flkl and Fltl receptors for Vascular Endothelial Growth Factor (VEGF). Single injections in mice of these adenoviruses produce high levels of circulating soluble Flk1 and Flt1 ectodomains which persist for >3-4 weeks, potently suppressing tumor growth and angiogenesis, and producing stringent conditional inactivation of-VEGF in adult animals. Surprisingly, adenoviral expression of Flk1 or Flt1 ectodomains (soluble VEGF receptors, or sVEGFRs) in normal mice strongly stimulates erythropoiesis, with increase in hematocrit increasing from baseline 45% to new levels of 55-75 %. Circulating erythropoietin levels are elevated in parallel;however, the Epo originates from the liver as in embryonic development, not the usual site of synthesis in the kidney. This data implicates VEGF as an unsuspected repressor of hepatic Epo synthesis, and this grant application is focused on determining the underlying moIecular mechanisms. In Aim 1, experiments will expand upon preliminary data implicating perturbation of hepatocyte--endothelial cross-talk in the sVEGFR induction of hepatic Epo. Adenoviral and transgenic expression of Cre recombinase will be used to test the effects of specific inhibition of hepatocyte-produced VEGF on hepatocyte Epo expression. Conversely, co-culture experiments manipulating VEGF will be used to test the effects of endothelial cells on hepatocyte Epo production. Aim 2 will define the specific factors mediating the transcriptional regulation of Epo by VEGF and VEGF blockade. Candidate factors (HIF proteins, HNF4, RXRalpha, GATA factors) will be directly tested by chromatin immunoprecipitation assays and functionally by adenoviral and transgenic expression of Cre to delete floxed alleles of relevant candidates. Additionally, novel factors will be sought by unbiased approaches of DNAse1 footprinting and hypersensitivity assays. The therapeutic implications of the ability to reactivate hepatic Epo synthesis are substantial. These studies should also yield significant insight into the action of VEGF as an unsuspected upstream regulator of RBC homeostasis, into the regulation of hepatic Epo production which is strongly repressed post-natally, and indicate the potential utility of alterations in erythropoiesis as surrogate markers for or a desirable consequence of stringent VEGF blockade.
Funding Period: 2009-07-01 - 2011-06-30
more information: NIH RePORT
- Vascular endothelial growth factor: biology and therapeutic applicationsQuoc T Ho
Division of Hematology, Stanford University School of Medicine, 269 Campus Drive, Stanford, CA 94305, USA
Int J Biochem Cell Biol 39:1349-57. 2007....
- A liver Hif-2α-Irs2 pathway sensitizes hepatic insulin signaling and is modulated by Vegf inhibitionKevin Wei
1 Division of Hematology, Stanford University School of Medicine, Stanford, California, USA 2
Nat Med 19:1331-7. 2013..These studies also indicate distinct roles in hepatic metabolism for Hif-1α, which promotes glycolysis, and Hif-2α, which suppresses gluconeogenesis, and suggest new treatment approaches for type 2 diabetes mellitus. ..
- Cross-talk between hypoxia and insulin signaling through Phd3 regulates hepatic glucose and lipid metabolism and ameliorates diabetesCullen M Taniguchi
Division of Radiation and Cancer Biology, Department of Radiation Oncology, Center for Clinical Sciences Research, Stanford, California, USA
Nat Med 19:1325-30. 2013..Thus, isoform-specific inhibition of Phd3 could be exploited to treat type 2 diabetes without the toxicity that could occur with chronic inhibition of multiple Phd isoforms. ..
- Maintenance bevacizumab is associated with increased hemoglobin in patients with advanced, nonsquamous, non-small cell lung cancerJonathan W Riess
Division of Hematology, Department of Medicine, Stanford University School of Medicine, CA, USA
Cancer Invest 30:231-5. 2012..268 days, p =.38.) Maintenance bevacizumab is associated with increased hemoglobin in advanced, nonsquamous, NSCLC patients...
- Targeting endothelium-pericyte cross talk by inhibiting VEGF receptor signaling attenuates kidney microvascular rarefaction and fibrosisShuei Liong Lin
Renal Division, Department of Medicine, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan
Am J Pathol 178:911-23. 2011..These findings link fibrogenesis inextricably with microvascular rarefaction for the first time, add new significance to fibrogenesis, and identify novel therapeutic targets...
- Essential regulation of CNS angiogenesis by the orphan G protein-coupled receptor GPR124Frank Kuhnert
Department of Medicine, Hematology Division, Stanford University, Stanford, CA 94305, USA
Science 330:985-9. 2010..Further, the functional tropism of GPR124 marks this receptor as a therapeutic target for CNS-related vascular pathologies...
- VEGF signaling has distinct spatiotemporal roles during heart valve developmentKryn Stankunas
Division of Cardiovascular Medicine, Department of Medicine, Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
Dev Biol 347:325-36. 2010..Thus, VEGF roles in the developing valves are dynamic, transitioning from a differentiation role directed by VEGFR1 in the OFT to a morphogenetic role through VEGFR2 primarily in the AVC-derived valves...
- Angiopoietin/Tie2 signaling transforms capillaries into venules primed for leukocyte trafficking in airway inflammationJonas Fuxe
Department of Anatomy, University of California San Francisco, San Francisco, CA 94143 0452, USA
Am J Pathol 176:2009-18. 2010..pulmonis-infected mouse airways. Together, these findings suggest that blockade of the Ang/Tie2 pathway may represent a therapeutic approach in airway inflammation...
- Increased hemoglobin associated with VEGF inhibitors in advanced renal cell carcinomaLauren C Harshman
Stanford University School of Medicine, California 94305, USA
Cancer Invest 27:851-6. 2009..2 months with rises > 15%. This study identifies increased hemoglobin as a possible consequence of VEGF inhibitors. The correlation with longer PFS suggests that rise in hemoglobin may be a surrogate biomarker of efficacy...
- Endochondral ossification is required for haematopoietic stem-cell niche formationCharles K F Chan
Department of Pathology, Developmental Biology and Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, California, USA
Nature 457:490-4. 2009..Collectively, our data implicate endochondral ossification, bone formation that proceeds through a cartilage intermediate, as a requirement for adult HSC niche formation...
- Attribution of vascular phenotypes of the murine Egfl7 locus to the microRNA miR-126Frank Kuhnert
Division of Hematology, Department of Medicine, Stanford University School of Medicine, CCSR 1155, 269 Campus Drive, Stanford, CA 94305, USA
Development 135:3989-93. 2008....
- Soluble receptor-mediated selective inhibition of VEGFR and PDGFRbeta signaling during physiologic and tumor angiogenesisFrank Kuhnert
Division of Hematology, Stanford University School of Medicine, Stanford, CA 94305, USA
Proc Natl Acad Sci U S A 105:10185-90. 2008..These studies using highly specific soluble receptors suggest that additivity between VEGFR and PDGFRbeta inhibition depends on the strength of VEGF blockade and appears minimal under conditions of maximal VEGF antagonism...
- Recombinant adenovirus as a methodology for exploration of physiologic functions of growth factor pathwaysKevin Wei
Division of Hematology, Stanford University School of Medicine, 269 Campus Dr, CCSR 1155, Stanford, CA 94305, USA
J Mol Med (Berl) 86:161-9. 2008..Finally, we discuss the potential physiological and therapeutic relevance of our findings...
- VEGF modulates erythropoiesis through regulation of adult hepatic erythropoietin synthesisBetty Y Y Tam
Division of Hematology, Stanford University School of Medicine, 269 Campus Drive, CCSR 1155, Stanford, California, 94305, USA
Nat Med 12:793-800. 2006....