No abstract

Vascular endothelial growth factor (VEGF) and its cellular receptor VEGFR-2 have been implicated as the main endothelial pathway required for tumor neovascularization. However, the importance of the VEGF/VEGFR-2 system for angiogenesis in hematologic malignancies such as AML remains to be elucidated. In 32 patients with newly diagnosed untreated AML, we observed by immunohistochemical analysis of bone marrow biopsies significantly higher levels of VEGF and VEGFR-2 expression than in 10 control patients (P Ͻ0.001). In contrast, VEGFR-1 staining levels in AML patients were in the same range as in the controls. Expression of VEGF and VEGFR-2 was significantly higher in patients with a high degree of microvessel density compared to those with a low degree (VEGF: P ‫;420.0؍‬ VEGFR-2: P ‫)040.0؍‬ and correlated well with bone marrow microvessel density (r s ‫665.0؍‬ and 0.609, respectively; P Ͻ0.001). Furthermore, in patients who achieved a complete remission following induction chemotherapy VEGFR-2 staining levels decreased into the normal range. In conclusion, our results provide evidence for increased expression of VEGF/VEGFR-2 of leukemic blasts and correlation with angiogenesis in the bone marrow of AML patients. Thus, VEGF/VEGFR-2 might constitute promising targets for antiangiogenic and antileukemic treatment strategies in AML.

Recurrent respiratory papillomatosis (RRP) is a primary benign disease, which is characterized by papillomatous growth in the respiratory tract. Malignant transformation occurs in only 3–5% of cases, however, local growth of the benign papillomas is interpreted as clinically malignant in a markedly higher proportion of patients. Local surgical or endoscopic interventional debulking or excision is currently the commonly selected treatment method and antiviral therapy is a potential adjuvant approach. However, the long-term management of RRP patients, who commonly require multiple procedures over numerous years, is challenging and the overall therapeutic armamentarium remains unsatisfactory. The administration of systemic bevacizumab treatment in a series of five patients with long histories of RRP, who required repeated local interventions to control papilloma growth is evaluated. Treatment with the anti-vascular endothelial growth factor (VEGF) antibody bevacizumab was administered at a dose of 5 mg/kg (n=1), 10 mg/kg (n=3) or 15 mg/kg (n=1) intravenously to the five RRP patients, who were clinically classified as exhibiting progressive disease. Endoscopic evaluations were performed prior to the first infusion of bevacizumab and intermittently at variable time points during the course of therapy. Histopathological analyses were performed using pre- and post-treatment papilloma biopsies, including immunohistochemical analyses of VEGF and phosphorylated VEGF receptor (VEGFR)-2 expression. The patients received between three and 16 courses of bevacizumab (median, six courses). The first course was initiated when progression following the previous intervention was observed. An immediate response to bevacizumab treatment was demonstrated in all five RRP patients. While the cumulative number of interventions in the five patients was 18 throughout the 12 months prior to the initiation of bevacizumab treatment, only one patient required interventional treatment due to a malignant transformation during the 12 months following treatment with bevacizumab (18 vs. 1 interventions, P=0.042). Histopathological analyses revealed regressive perivascular edema and normalization of the vascular structure, however, immunohistochemical analyses of the VEGF and phosphorylated VEGFR-2 expression did not demonstrate any changes following therapy. Due to the limited number of alternative treatments, VEGF-targeted therapies may represent a promising novel strategy in the treatment of RRP, which may have the potential to modify the current treatment standards, particularly in patients with poorly accessible papilloma lesions, however, this requires further investigation in clinical trials.

Matrix metalloproteinase 2 (MMP2) can associate with integrin ␣v␤3 on the surface of endothelial cells, thereby promoting vascular invasion. Here, we describe an organic molecule (TSRI265) selected for its ability to bind to integrin ␣v␤3 and block ␣v␤3 interaction with MMP2. Although disrupting ␣v␤3͞MMP2 complex formation, TSRI265 has no effect on ␣v␤3 binding to its extracellular matrix ligand vitronectin and does not influence MMP2 activation or catalytic activity directly. However, TSRI265 acts as a potent antiangiogenic agent and thereby blocks tumor growth in vivo. These findings suggest that activated MMP2 does not facilitate vascular invasion during angiogenesis unless it forms a complex with ␣v␤3 on the endothelial cell surface. By disrupting endothelial cell invasion without broadly suppressing cell adhesion or MMP function, the use of compounds such as TSRI265 may provide a novel therapeutic approach for diseases associated with uncontrolled angiogenesis.

Modulation of the balance between pro-and antiangiogenic factors holds great promise for the treatment of a broad spectrum of human disease ranging from ischemic heart disease to cancer. This requires both the identification of angiogenic regulators and their efficient delivery to target organs. Here, we demonstrate the use of a noncatalytic fragment of matrix metalloproteinase 2 (termed PEX) delivered by lentiviral vectors in different angiogenesis models. Transduction of human endothelial cells with PEX virus suppressed endothelial invasion and formation of capillary-like structures without affecting chemotaxis in vitro. Lentiviral delivery of PEX blocked basic fibroblast growth factor-induced matrix metalloproteinase 2 activation and angiogenesis on chicken chorioallantoic membranes. PEX expression also inhibited tumor-induced angiogenesis and tumor growth in a nude mouse model. Thus, our study shows that lentiviral vectors can deliver sufficient quantities of antiangiogenic substances to achieve therapeutic effects in vivo.