title: Regulation of the pro-angiogenic microenvironment by carboxyamido-triazole.
abstract: Anti-angiogenic agents regulate tumor growth by inhibiting endothelial cell proliferation and invasion. Carboxyamido-triazole (CAI), an inhibitor of non-voltage-operated calcium entry and calcium influx-mediated pathways, has angiogenesis and invasion inhibitory activity. We hypothesized that CAI may express its anti-angiogenic effects through negative regulation of pro-angiogenic cytokine production and/or function. In vivo, orally administered CAI prevented A2058 human melanoma xenograft growth and concomitantly resulted in a marked reduction in circulating vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8). In vitro, A2058 cell secretion of VEGF was inhibited by CAI treatment under limiting micronutrient conditions that approximate the tumor microenvironment, media restriction, and acidification to pH 6.8 (P=0.0003 and P=0.0006, respectively). VEGF and HIF-1alpha message and protein were also reduced by CAI treatment. Oral CAI treatment reduced vascular ingrowth in vivo into VEGF-containing Matrigel plugs. Commensurate with those findings, human umbilical vein endothelial cell (HUVEC) migration towards VEGF was reduced below background by exposure to CAI in the migration chamber (P<0.0001). An 88% reduction in circulating IL-8 concentration was measured in CAI-treated animals. However, IL-8 protein secretion and gene expression were increased by CAI treatment in culture (P< or =0.01), where CAI caused a dose-dependent acidification of the culture milieu (P< or =0.005). This paradox suggests that IL-8 production in vitro may be more sensitive to ambient pH than cytosolic calcium. These observations suggest that CAI inhibition of tumor cell VEGF production and endothelial cell response to VEGF results in disruption of signaling between the tumor and its microenvironment, causing a net anti-angiogenic effect.
authors.affiliation: Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892-1500, USA.
authors.forename: Vyta Kulpa
authors.initials: VK
authors.lastname: Oliver
authors.forename: Angela M
authors.initials: AM
authors.lastname: Patton
authors.forename: Sudhen
authors.initials: S
authors.lastname: Desai
authors.forename: Dominique
authors.initials: D
authors.lastname: Lorang
authors.forename: Steven K
authors.initials: SK
authors.lastname: Libutti
authors.forename: Elise C
authors.initials: EC
authors.lastname: Kohn
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D002465:Cell Movement / Q000187:drug effects; D017690:Cell Transplantation; D003470:Culture Media / Q000737:chemistry; D016228:Endothelial Growth Factors / Q000032:analysis / Q000097:blood; D004730:Endothelium, Vascular; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D015151:Immunoblotting; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins / Q000032:analysis / Q000097:blood; D016209:Interleukin-8 / Q000032:analysis / Q000097:blood; D008222:Lymphokines / Q000032:analysis / Q000097:blood / Q000187:drug effects*; D008545:Melanoma / Q000378:metabolism; D051379:Mice; D009389:Neovascularization, Pathologic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000187:drug effects / Q000378:metabolism; D014183:Transplantation, Heterologous; D014230:Triazoles / Q000008:administration & dosage / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D014471:Umbilical Veins / Q000166:cytology; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
chemical_list: D000970:Antineoplastic Agents; D003470:Culture Media; D016228:Endothelial Growth Factors; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D036341:Intercellular Signaling Peptides and Proteins; D016209:Interleukin-8; D008222:Lymphokines; D014157:Transcription Factors; D014230:Triazoles; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; C062058:carboxyamido-triazole