interleukin-8 and carboxyamido-triazole

The Bcr/Abl kinase has been targeted for the treatment of chronic myelogenous leukaemia (CML) by imatinib mesylate. While imatinib has been extremely effective for chronic phase CML, blast crisis CML are often resistant. New therapeutic options are therefore needed for this fatal disease. Although more common in solid tumors, increased microvessel density was also reported in chronic myelogenous leukaemia and was associated with a significant increase of angiogenic factors, suggesting that vascularity in hematologic malignancies is a controlled process and may play a role in the leukaemogenic process thus representing an alternative therapeutic target. Carboxyamidotriazole-orotate (CTO) is the orotate salt form of carboxyamidotriazole (CAI), an orally bioavailable signal transduction inhibitor that in vitro has been shown to possess antileukaemic activities. CTO, which has a reduced toxicity, increased oral bioavailability and stronger efficacy when compared to the parental compound, was tested in this study for its ability to affect imatinib-resistant CML tumor growth in a xenograft model. The active cross talk between endothelial cells and leukemic cells in the bone marrow involving exosomes plays an important role in modulating the process of neovascularization in CML. We have thus investigated the effects of CTO on exosome-stimulated angiogenesis. Our results indicate that CTO may be effective in targeting both cancer cell growth and the tumor microenvironment, thus suggesting a potential therapeutic utility for CTO in leukaemia patients.

Topics: Animals; Antineoplastic Agents; Benzamides; Cell Adhesion; Cell Adhesion Molecules; Cell Line, Tumor; Cell Movement; Cell Proliferation; Drug Resistance, Neoplasm; Exosomes; Extracellular Signal-Regulated MAP Kinases; Fusion Proteins, bcr-abl; Gene Expression Regulation, Leukemic; Human Umbilical Vein Endothelial Cells; Humans; Imatinib Mesylate; Interleukin-8; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Male; Mice; Neovascularization, Pathologic; Orotic Acid; Phosphorylation; Phosphotyrosine; Piperazines; Proto-Oncogene Proteins c-akt; Pyrimidines; RNA, Messenger; Triazoles; Xenograft Model Antitumor Assays

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.

Topics: Animals; Antineoplastic Agents; Cell Movement; Cell Transplantation; Culture Media; Endothelial Growth Factors; Endothelium, Vascular; Enzyme-Linked Immunosorbent Assay; Female; Humans; Hydrogen-Ion Concentration; Hypoxia-Inducible Factor 1, alpha Subunit; Immunoblotting; Immunohistochemistry; Intercellular Signaling Peptides and Proteins; Interleukin-8; Lymphokines; Melanoma; Mice; Neovascularization, Pathologic; Reverse Transcriptase Polymerase Chain Reaction; Transcription Factors; Transplantation, Heterologous; Triazoles; Tumor Cells, Cultured; Umbilical Veins; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors