The Process of Angiogenesis & Inhibition of Angiogenesis and/or Lymphangiogenesis

The Process of Angiogenesis & Inhibition of Angiogenesis and/or Lymphangiogenesis Nam Deuk Kim, Ph.D. Pusan National University

Contents Part 1. The process of angiogenesis Part 2. The role of angiopoietins in tumor angiogenesis Part 3. The role of angiogenesis and lymphangiogenesis in tumorigenesis Part 4. Angiogenesis inhibition by BIBF 1120, an investigational triple angiokinase inhibitor 2

Part 1: The Process of Angiogenesis Endothelial cell proliferation and the survival of new blood vessels

Angiogenesis is essential for tumor growth and metastasis Tumor growth requires an increased supply of oxygen and nutrients for endothelial cell proliferation and survival of new blood vessels 1-3 Angiogenesis supplies additional oxygen and nutrients to tumors 4 4 References: 1. Pugh CW, Ratcliffe PJ. Nat Med. 2003;9:677-684. 2. Bergers G, Benjamin LE. Nat Rev Cancer. 2003;3:401-410. 3. Acker T, Plate KH. Cell Tissue Res. 2003;314:145-155. 4. Hanahan D, Weinberg RA. Cell. 2000;100:57-70.

Hypoxia & necrosis of cells in poorly vascularized sections of tumor tissues Tumor parenchyma with capillaries (green) and hypoxic area (red) 5

Angiogenesis requires multiple growth factors and receptors Hypoxia is the primary stimulus for angiogenesis 1 Under hypoxic conditions, tumors produce and release multiple growth factors, including 2-6 : VEGFs bfgf PDGF TGF- -1 PlGF Angiopoietin-2 These growth factors stimulate receptors to initiate and regulate angiogenesis 7 6 References: 1. Acker T, Plate KH. Cell Tissue Res. 2003;314:145-155. 2. Pugh CW, Ratcliffe PJ. Nat Med. 2003;9:677-684. 3. Cao Y et al. J Clin Invest. 1996;98:2507-2511. 4. Calvani M et al. Blood. 2006;107:2705-2712. 5. Jiang Y et al. Acta Biochim Biophys Sin (Shanghai). 2007;39:73-80. 6. Lewis CE, Hughes R. Microenvironmental factors regulating macrophage function in breast tumours: hypoxia and angiopoietin-2. Breast Cancer Res. 2007;9:209. Available at: http://breast-cancer-research.com/content/9/3/209. Accessed March 17, 2008. 7. Ferrara N et al. Nat Med. 2003;9:669-676.

7 Angiogenic factors

Endogenous inhibitors of angiogenesis 8

9 Balancing the angiogenic switch

VEGF and PDGF pathways initiate and regulate angiogenesis Growth factors bind to the extracellular portion of receptors to stimulate activity 1 The intracellular portion of these receptors then initiates a chain of chemical reactions, resulting in cellular activity 1,2 Both VEGF and PDGF signaling pathways play key roles in angiogenesis 3,4 10 References: 1. Ullrich A, Schlessinger J. Cell. 1990;61:203-212. 2. Schlessinger J. Cell. 2000;103:211-225. 3. Ferrara N et al. Nat Med. 2003;9:669-676. 4. Yu J et al. J Biochem Mol Bio. 2003;36:49-59.

VEGF receptors play a central role in endothelial cell proliferation, migration, and survival The VEGFR family consists of 3 known receptors 1 : VEGFR-1 VEGFR-2 VEGFR-3 VEGFR-2 is the predominant receptor for endothelial cell proliferation and migration 1 VEGFR-2 provides a survival signal for new endothelial cells and vessel buds 1 11 Reference: 1. Ferrara N et al. Nat Med. 2003;9:669-676.

Angiogenesis involves multiple VEGF receptors VEGFR-1 and VEGFR-3 also play roles in angiogenesis and tumor metastasis 1-3 VEGFR-1 is expressed on multiple cell types 1,2,4,5 Endothelial cells (angiogenesis) Macrophages (metastasis) Tumor cells (survival) VEGFR-3 signaling induces the proliferation and growth of lymphatics, which may enhance metastasis 3 12 References: 1. Ferrara N et al. Nat Med. 2003;9:669-676. 2. Hiratsuka S et al. Cancer Cell. 2002;2:289-300. 3. Su JL et al. Br J Cancer. 2007;96:541-545. 4. Tsuchiya N et al. Tohoku J Exp Med. 2001;195:101-113. 5. Drescher D et al. World J Gastroenterol. 2007;13:3605-3609.

PDGFR- activity in pericytes plays a key role in established tumor vasculature PDGFR- signaling in pericytes is important for maturation, maintenance, and survival of established vessels 1,2 PDGFR- initiates pericyte proliferation and migration to newly formed endothelial cell buds 3 Pericytes contribute to the survival of new endothelial cell tubes through direct cell-to-cell contact and paracrine signaling 2,4 Blocking of pericyte migration to new blood vessels enhances endothelial cell apoptosis in response to VEGF pathway inhibition 5 13 References: 1. Bergers G et al. J Clin Invest. 2003;111:1287-1295. 2. Saharinen P, Alitalo K. J Clin Invest. 2003;111:1277-1280. 3. Benjamin LE et al. Development. 1998;125:1591-1598. 4. Pietras K et al. Cancer Cell. 2003;3:439-443. 5. Erber R et al. FASEB J. Available at: http://www.fasebj.org/cgi/reprint/03-0271fjev1. Accessed March 17, 2008.

In animal models, Simultaneous blockade of VEGFR and PDGFR- produced significant tumor regression Inhibition of VEGFR survival signaling inhibited tumor growth 1 Blocking PDGFR- and VEGFRs enhanced regression of tumor vasculature and tumors, compared with blocking VEGFRs alone 1,2 14 References: 1. Bergers G et al. J Clin Invest. 2003;111:1287-1295. 2. Potapova O et al. Mol Cancer Ther. 2006;5:1280-1289.

Current approaches to angiogenesis inhibition Signaling may be inhibited from outside or inside the cell 1 Monoclonal antibodies bind to growth factors or the extracellular portion of receptors 1 Receptor tyrosine kinase (RTK) inhibitors can bind to the intracellular portion of the receptor 1 As multiple growth factors may bind to a single receptor, intracellular blockade may be an effective anti-angiogenic approach 2 15 References: 1. Segota E, Bukowski RM. Cleve Clin J Med. 2004;71:551-560. 2. Ferrara N, Kerbel RS. Nature. 2005;438:967-974.

16 Heterotypic interactions as targets for therapeutic intervention

17 Angiogenesis inhibitors and their development & use in clinical trials

Angiogenesis: a complex process essential for tumor growth and metastasis Angiogenesis is essential for the growth and metastasis of most solid tumors 1,2 VEGFRs and PDGFR- initiate and regulate angiogenesis 3,4 VEGFRs play a central role in endothelial cell proliferation, migration, and survival 3 Intracellular blockade of VEGFR-1, -2, and -3 may be an effective approach to angiogenesis inhibition 5 PDGFR- signaling in pericytes is important for maturation, maintenance, and survival of established vessels 6,7 In animal models, blocking PDGFR- and VEGFRs enhanced regression of tumor vasculature and tumors compared with blocking VEGFRs alone 6,8 Current approaches to blocking growth factor regulation of angiogenesis include monoclonal antibody and RTK inhibitors 9 18 References: 1. Hicklin DJ, Ellis LM. J Clin Oncol. 2005;23:1011-1027. 2. Hanahan D, Weinberg RA. Cell. 2000;100:57-70. 3. Ferrara N et al. Nat Med. 2003;9:669-676. 4. Yu J et al. J Biochem Mol Biol. 2003;36:49-59. 5. Ferrara N, Kerbel RS. Nature. 2005;438:967-974. 6. Bergers G et al. J Clin Invest. 2003;111:1287-1295. 7. Saharinen P, Alitalo K. J Clin Invest. 2003;111:1277-1280. 8. Potapova O et al. Mol Cancer Ther. 2006;5:1280-1289. 9. Segota E, Bukowski RM. Cleve Clin J Med. 2004;71:551-560.

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