Angiopoietin-2 inhibition using siRNA or the peptide antagonist L1-10 results in antitumor activity in human neuroblastoma.

PURPOSE: The angiopoietin/Tie-2 system has been identified as a key role player in tumor angiogenesis. We investigated whether angiopoietin-2 could be a promising target in human neuroblastoma.
METHODS: Angiopoietin-2 down-regulation by siRNA or shRNA was evaluated in vitro in Kelly cells. Angiopoietin-2 shRNA-transfected Kelly cells were tested in a chorioallantoic membrane (CAM) assay to evaluate tumor growth and microvessel density. The effects of L1-10, a peptide-Fc fusion molecule blocking angiopoietin-2/Tie-2 interaction, administered 3 times/week were assessed in a murine neuroblastoma xenograft model.
RESULTS: Angiopoietin-2 down-regulation by siRNA or shRNA in Kelly cells inhibited cell proliferation and migration. In vivo growth and microvessel density of angiopoietin-2 shRNA-transfected Kelly cells in the CAM assay were reduced. Therapy of advanced tumors with L1-10 did not stop tumor progression. However, starting L1-10 treatment at the same time as neuroblastoma cell injection significantly inhibited tumor growth (vehicule: 903 ± 160 mm(3); L1-10: 270 ± 152 mm(3) after 26 days; P < 0.05). Microvessel density was reduced in both L1-10-treated tumors, whereas expression of angiopoietin-2 and VEGF-A did not change.
CONCLUSION: This first demonstration of beneficial angiopoietin-2 inhibition in neuroblastoma offers an additional approach for future therapy strategies, especially by using L1-10 in the setting of minimal residual disease.