Cathy Ng

Bevacizumab Suppresses Neuroblastoma Progression in the Setting of Minimal Disease

BACKGROUND We hypothesized that vascular endothelial growth factor (VEGF) contributes to autocrine stimulation of neuroblastoma and that inhibition of its signaling pathway contributes to the anticancer activity of bevacizumab, an anti-VEGF monoclonal antibody. METHODS For in vitro studies, 2 neuroblastoma cell lines, CHLA-255 and NB1691, were treated with VEGF+/-bevacizumab. For in vivo studies, disseminated neuroblastoma was established by intravenous administration of luciferase-expressing tumor cells in SCID mice prior to bevacizumab treatment. RESULTS Exogenous VEGF increased cell counts after 48 h (NB1691: 58,878 +/- 8279 vs 137,500 +/- 13,108 cells, P < .001; CHLA: 1.56 x 10(6) +/- 866 vs 1.81 x 10(6) +/- 2550 cells, P <.001); the addition of bevacizumab abrogated this stimulation. In vivo, mice with disseminated disease treated twice weekly with intraperitoneal bevacizumab had a decreased tumor burden at day 14 and prolonged survival (NB1691: 50 +/- 2 vs 43 +/- 2 days, P < .001; CHLA: 53 +/- 3 vs 42 +/- 1 days, P = .006). Interestingly, VEGF and basic fibroblast growth factor expression was increased in treated NB1691 tumors, which likely occurred in response to VEGF signaling inhibition. CONCLUSION Our results suggest that VEGF has a role in neuroblastoma autocrine signaling. Maintenance therapy with bevacizumab may be useful for disease suppression after maximal cytoreductive therapy; however, upregulation of proangiogenic factors may provide resistance to this approach, which suggests that maximal antitumor efficacy may require combination therapy.

2: Bortezomib inhibits angiogenesis and reduces tumor burden in a murine model of neuroblastoma

BACKGROUND Bortezomib is a proteasome inhibitor with pleiotropic antitumor activity. Here we investigate the antiangiogenic and antitumor efficacy of bortezomib against neuroblastoma both in vitro and in a murine model of localized and disseminated disease. METHODS In vitro activity of bortezomib was assessed by evaluating its effect on cell proliferation and cell cycle status. Localized tumor burden was followed with caliper measurements and total-body bioluminescence in mice with disseminated disease. The antiangiogenic activity was evaluated with immunohistochemistry and human vascular endothelial growth factor (VEGF) enzyme-linked immunosorbent assay on tumor protein extracts. RESULTS Bortezomib treatment resulted in dose and time-dependent decreases in cell proliferation and resulted in cell cycle arrest. In vivo, bortezomib restricted tumor growth in a model of localized disease and decreased bioluminescence in mice with disseminated disease. That decreased bioluminescence reflected decreased tumor burden was confirmed at necropsy by assessing disease in specific organs. In addition, treatment resulted in a decrease in intratumoral vessel counts and reduced tumor VEGF expression. CONCLUSION Bortezomib shows significant activity against neuroblastoma in vitro, and it inhibits tumor growth and angiogenesis in vivo. These results suggest that clinical studies of bortezomib are warranted for the treatment of this difficult disease.

711. Treatment of Acute Myeloid Leukemia by rAAV 8 Vector Mediated Human Interferon-|[beta]| Gene Transfer

Alpha-interferons are widely used in the treatment of hematological malignancies such as CML, multiple myeloma and hairy cell leukemia. However their efficacy in the management of acute myeloid leukemia (AML) has not been fully evaluated. Furthermore the antitumour effects of the related |[beta]|-interferon have also not been systematically investigated in AML. Treatment with recombinant interferon is limited by its short half-life and its side effects which frequently results in failure to achieve stable therapeutic levels. We have therefore adopted a gene therapy approach using rAAV type 8 vectors to deliver sustained systemic expression of human IFN-|[beta]| invivo and evaluated the subsequent effect on tumour development in murine xenograft models using both AML cell lines as well as primary cells.