title: Downregulation of VEGF-A, STAT5 and AKT in acute myeloid leukemia blasts of patients treated with SU5416.
abstract: In acute myeloid leukemia (AML), autocrine or paracrine activation of receptor tyrosine kinases such as c-kit and FLT3 contributes to proliferation and apoptosis resistance of leukemic blasts. This provided the rationale for a multicenter clinical trial in patients with refractory AML with SU5416, a small molecule kinase inhibitor which blocks phosphorylation of c-kit, FLT3, VEGFR-1, VEGFR-2 (KDR) and VEGFR-3. The levels of VEGF mRNA expression were investigated in peripheral blood leukemic blasts taken from AML patients before and during treatment with SU5416. Rapid down regulation of VEGF was observed in AML blasts from 72% (13 of 18) of patients analysed. Patients initially expressing high VEGF-levels had a stronger downregulation and a higher clinical response rate (mean 865-fold, n = 10, P = 0,01) than patients initially expressing low VEGF-levels (mean four-fold, n = 8). These results suggest that abnormal high VEGF expression is downregulated by SU5416 treatment, and furthermore that decreases in VEGF mRNA levels may provide an early marker of therapeutic response with anti-angiogenic therapy. Additionally, protein expression of STAT5 and AKT was assessed by western blotting in these patient samples, as well as in the leukemia cell line, M-07e, treated in vitro with SU5416 as a model system. In the AML patient samples, parallel downregulation of both STAT5 and AKT was observed in several cases (STAT5 in four of 15; AKT in three of six examined patients). These effects were confirmed with the cell line M-07e after incubation with SU5416 in vitro using concentrations that are achievable in patients. In summary, our data show suppression of the expression of VEGF and key signal transduction intermediates in AML blasts during treatment with SU5416.
authors.affiliation: Department of Medicine II, Cellular Signal Transduction, University Hospital Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Sonja
authors.initials: S
authors.lastname: Loges
authors.forename: Heike
authors.initials: H
authors.lastname: Tinnefeld
authors.forename: Anja
authors.initials: A
authors.lastname: Metzner
authors.forename: Manfred
authors.initials: M
authors.lastname: Jücker
authors.forename: Martin
authors.initials: M
authors.lastname: Butzal
authors.forename: Melanie
authors.initials: M
authors.lastname: Bruweleit
authors.forename: Uta
authors.initials: U
authors.lastname: Fischer
authors.forename: Elena
authors.initials: E
authors.lastname: Draab
authors.forename: Gunter
authors.initials: G
authors.lastname: Schuch
authors.forename: Anne Marie
authors.initials: AM
authors.lastname: O'-Farrel
authors.forename: Dieter Kurt
authors.initials: DK
authors.lastname: Hossfeld
authors.forename: Carsten
authors.initials: C
authors.lastname: Bokemeyer
authors.forename: Walter
authors.initials: W
authors.lastname: Fiedler
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology; D045744:Cell Line, Tumor; D002469:Cell Separation; D017931:DNA Primers / Q000737:chemistry; D018450:Disease Progression; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000096:biosynthesis* / Q000235:genetics*; D011758:Pyrroles / Q000494:pharmacology*; D050799:STAT5 Transcription Factor / Q000096:biosynthesis* / Q000235:genetics*; D015398:Signal Transduction; D016896:Treatment Outcome; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis* / Q000235:genetics*
chemical_list: D020533:Angiogenesis Inhibitors; D017931:DNA Primers; D007211:Indoles; D047428:Protein Kinase Inhibitors; D011758:Pyrroles; D050799:STAT5 Transcription Factor; D042461:Vascular Endothelial Growth Factor A; C116890:Semaxinib; D051057:Proto-Oncogene Proteins c-akt