title: Sorafenib (BAY 43-9006) inhibits tumor growth and vascularization and induces tumor apoptosis and hypoxia in RCC xenograft models.
abstract: OBJECTIVE
  New research findings have revealed a key role for vascular endothelial growth factor (VEGF) in the stimulation of angiogenesis in clear cell renal carcinoma (RCC) which is a highly vascularized and treatment-resistant tumor. Sorafenib (BAY 43-9006, Nexavar) is a multi-kinase inhibitor which targets receptor tyrosine and serine/threonine kinases involved in tumor progression and tumor angiogenesis. The effect of sorafenib on tumor growth and tumor histology was assessed in both ectopic and orthotopic mouse models of RCC.
  
  
  METHODS
  Sorafenib was administered orally to mice bearing subcutaneous (SC, ectopic) or sub-renal capsule (SRC, orthotopic) tumors of murine (Renca) or human (786-O) RCC. Treatment efficacy was determined by measurements of tumor volume and tumor growth delay. In mechanism of action studies, using the 786-O and Renca RCC tumor models, the effect of sorafenib was assessed after dosing for 3 or 5 days in the SC models and 21 days in the SRC models. Inhibition of tumor angiogenesis was assessed by measuring level of CD31 and alpha-smooth muscle actin (alphaSMA) staining by immunohistochemistry (IHC). The effect of sorafenib on MAPK signaling, cell cycle progression and cell proliferation was also assessed by IHC by measuring levels of phospho-ERK, phospho-histone H3 and Ki-67 staining, respectively. The extent of tumor apoptosis was measured by terminal deoxynucleotidyl transferase-mediated nick-end labeling (TUNEL) assays. Finally, the effects of sorafenib on tumor hypoxia was assessed in 786-O SC model by injecting mice intravenously with pimonidazole hydrochloride 1 h before tumor collection and tumor sections were stained with a FITC-conjugated Hypoxyprobe antibody.
  
  
  RESULTS
  Sorafenib produced significant tumor growth inhibition (TGI) and a reduction in tumor vasculature of both ectopic and orthotopic Renca and 786-O tumors, at a dose as low as 15 mg/kg when administered daily. Inhibition of tumor vasculature was observed as early as 3 days post-treatment, and this inhibition of angiogenesis correlated with increased level of tumor apoptosis (TUNEL-positive) and central necrosis. Consistent with these results, a significant increase in tumor hypoxia was also observed 3 days post-treatment in 786-O SC model. However, no significant effect of sorafenib on phospho-ERK, phospho-histone H3 or Ki-67 levels in either RCC tumor model was observed.
  
  
  CONCLUSIONS
  Our results show the ability of sorafenib to potently inhibit the growth of both ectopically- and orthotopically-implanted Renca and 786-O tumors. The observed tumor growth inhibition and tumor stasis or stabilization correlated strongly with decreased tumor angiogenesis, which was due, at least in part, to inhibition of VEGF and PDGF-mediated endothelial cell and pericyte survival. Finally, sorafenib-mediated inhibition of tumor growth and angiogenesis occurred at concentrations equivalent to those achieved in patients in the clinic.
authors.affiliation: Department of Protein Therapeutics, Bayer Research Center, Bayer HealthCare, Pharmaceuticals, 400 Morgan Lane, West Haven, CT 06516, USA. yong.chang.b@bayer.com
authors.forename: Yong S
authors.initials: YS
authors.lastname: Chang
authors.forename: Jalila
authors.initials: J
authors.lastname: Adnane
authors.forename: Pamela A
authors.initials: PA
authors.lastname: Trail
authors.forename: Joan
authors.initials: J
authors.lastname: Levy
authors.forename: Arris
authors.initials: A
authors.lastname: Henderson
authors.forename: Dahai
authors.initials: D
authors.lastname: Xue
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Bortolon
authors.forename: Marina
authors.initials: M
authors.lastname: Ichetovkin
authors.forename: Charles
authors.initials: C
authors.lastname: Chen
authors.forename: Angela
authors.initials: A
authors.lastname: McNabola
authors.forename: Dean
authors.initials: D
authors.lastname: Wilkie
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Carter
authors.forename: Ian C A
authors.initials: IC
authors.lastname: Taylor
authors.forename: Mark
authors.initials: M
authors.lastname: Lynch
authors.forename: Scott
authors.initials: S
authors.lastname: Wilhelm
mesh_terms: D000199:Actins / Q000378:metabolism; D018262:Adenocarcinoma, Clear Cell / Q000098:blood supply / Q000188:drug therapy* / Q000473:pathology*; D020533:Angiogenesis Inhibitors / Q000627:therapeutic use*; D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001557:Benzenesulfonates / Q000627:therapeutic use*; D002196:Capillaries / Q000473:pathology; D045744:Cell Line, Tumor; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000139:chemically induced* / Q000473:pathology; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D007680:Kidney Neoplasms / Q000098:blood supply / Q000188:drug therapy* / Q000473:pathology*; D051379:Mice; D008819:Mice, Nude; D009536:Niacinamide / Q000031:analogs & derivatives; D010671:Phenylurea Compounds; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000276:immunology; D011725:Pyridines / Q000627:therapeutic use*; D012039:Regional Blood Flow / Q000187:drug effects; D000077157:Sorafenib; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D000199:Actins; D020533:Angiogenesis Inhibitors; D000970:Antineoplastic Agents; D001557:Benzenesulfonates; D010671:Phenylurea Compounds; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D011725:Pyridines; D042461:Vascular Endothelial Growth Factor A; D009536:Niacinamide; D000077157:Sorafenib