VEGF Regulation of Hepatic Erythropoietin Synthesis

Summary

Principal Investigator: Calvin Kuo
Affiliation: Stanford University
Country: USA
Abstract: 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

Top Publications

  1. ncbi Vascular endothelial growth factor: biology and therapeutic applications
    Quoc 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
  2. ncbi VEGF modulates erythropoiesis through regulation of adult hepatic erythropoietin synthesis
    Betty 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
  3. ncbi Recombinant adenovirus as a methodology for exploration of physiologic functions of growth factor pathways
    Kevin 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
  4. ncbi Soluble receptor-mediated selective inhibition of VEGFR and PDGFRbeta signaling during physiologic and tumor angiogenesis
    Frank Kuhnert
    Division of Hematology, Stanford University School of Medicine, Stanford, CA 94305, USA
    Proc Natl Acad Sci U S A 105:10185-90. 2008
  5. ncbi Attribution of vascular phenotypes of the murine Egfl7 locus to the microRNA miR-126
    Frank 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
  6. ncbi Endochondral ossification is required for haematopoietic stem-cell niche formation
    Charles 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
  7. ncbi Increased hemoglobin associated with VEGF inhibitors in advanced renal cell carcinoma
    Lauren C Harshman
    Stanford University School of Medicine, California 94305, USA
    Cancer Invest 27:851-6. 2009

Scientific Experts

  • Charles K F Chan
  • Calvin J Kuo
  • Frank Kuhnert
  • Kevin Wei
  • Betty Y Y Tam
  • Lauren C Harshman
  • Richard C Mulligan
  • Nihar R Nayak
  • Jenny Yuan
  • Quoc T Ho
  • Bryan Y Wong
  • Nicholas J Vogelzang
  • Sandy Srinivas
  • John T Gray
  • Jessica Hampton
  • Michael R Mancuso
  • Chang Zheng Chen
  • Tomoichiro Asano
  • Kryn Stankunas
  • Donald M McDonald
  • Barbara Sennino
  • Angeline Jocson
  • Grace Wu
  • Cecile Chartier
  • Jeng Shin Lee
  • Randall S Johnson
  • George D Yancopoulos
  • Colleen Hefner
  • Sang-Ki Park
  • Lisa Ma
  • Stanley L Schrier
  • Jana Hoffman
  • John S Rudge
  • Nihar R Niyak
  • Jeng-Shin Lee
  • Joseph A Garcia
  • Sang Ki Park
  • Shelly Jiang
  • Joceyln Holash
  • Jacquelyn J Maher
  • Frans A Kuypers
  • Uma Sundram

Detail Information

Publications7

  1. ncbi Vascular endothelial growth factor: biology and therapeutic applications
    Quoc 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
    ....
  2. ncbi VEGF modulates erythropoiesis through regulation of adult hepatic erythropoietin synthesis
    Betty 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
    ....
  3. ncbi Recombinant adenovirus as a methodology for exploration of physiologic functions of growth factor pathways
    Kevin 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...
  4. ncbi Soluble receptor-mediated selective inhibition of VEGFR and PDGFRbeta signaling during physiologic and tumor angiogenesis
    Frank 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...
  5. ncbi Attribution of vascular phenotypes of the murine Egfl7 locus to the microRNA miR-126
    Frank 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
    ....
  6. ncbi Endochondral ossification is required for haematopoietic stem-cell niche formation
    Charles 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...
  7. ncbi Increased hemoglobin associated with VEGF inhibitors in advanced renal cell carcinoma
    Lauren 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...