title: Hemoglobin induces the expression and secretion of vascular endothelial growth factor from human malignant cells.
abstract: Vascular endothelial growth factor (VEGF) is an angiogenic hormone that increases the growth of many malignant tumors. Tissue factor (TF), the initiator of blood coagulation, is implicated in VEGF regulation. We recently reported that hemoglobin (Hb) upregulates TF on malignant cells. Therefore, to explore the role of Hb in angiogenesis, we examined its effect on VEGF production in A375 melanoma and J82 bladder carcinoma (TF+) and KG1 myeloid leukemia (TF-) cells. Hb (0.50 mg/ml) induced VEGF expression and secretion in TF+ malignant cells. VEGF secretion was inhibited by cycloheximide (85%) and the specific inhibitors of protein tyrosine kinase, genistein (71+/-0.74 and 55+/-4.90%) and mitogen-activated protein (MAP)-kinase, PD098059 (82+/-2.0 and 59+/-6.7%) in A375 and J82 cells respectively. In contrast, Hb (2.0 mg/ml) did not increase VEGF in KG1 cells. Hb-induced VEGF was purified from the culture medium of J82 cells using immunoaffinity chromatography and two isoforms (46 and 30 kd) identified. We conclude that Hb-induced synthesis of VEGF in TF-bearing malignant cells is mediated by protein tyrosine kinase and by MAP-kinase pathways.
authors.affiliation: Center for Hemostasis and Thrombosis, Clinical and Research Laboratories, Florida Hospital Cancer Institute, Orlando, Florida, USA. farooq.siddiqui@flhosp.org
authors.forename: Farooq A
authors.initials: FA
authors.lastname: Siddiqui
authors.forename: Hina
authors.initials: H
authors.lastname: Desai
authors.forename: Tazeen F
authors.initials: TF
authors.lastname: Siddiqui
authors.forename: John L
authors.initials: JL
authors.lastname: Francis
mesh_terms: D016228:Endothelial Growth Factors / Q000096:biosynthesis* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D006454:Hemoglobins / Q000494:pharmacology* / Q000502:physiology; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis* / Q000378:metabolism; D008222:Lymphokines / Q000096:biosynthesis* / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D009369:Neoplasms / Q000378:metabolism / Q000473:pathology*; D020033:Protein Isoforms / Q000302:isolation & purification; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D015398:Signal Transduction; D013925:Thromboplastin; D014407:Tumor Cells, Cultured; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
chemical_list: D016228:Endothelial Growth Factors; D004791:Enzyme Inhibitors; D006454:Hemoglobins; D036341:Intercellular Signaling Peptides and Proteins; D008222:Lymphokines; D020033:Protein Isoforms; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D013925:Thromboplastin; D011505:Protein-Tyrosine Kinases; D020928:Mitogen-Activated Protein Kinases