Application of a New Logic to Old Drugs: Angiogenesis Inhibition in Neuroblastoma

Sammanfattning: Neuroblastoma is one of the most common solid cancers of early childhood. In Sweden, approximately 10-15 cases occur annually. The overall five-year neuroblastoma survival in Europe is approximately 45%. Since cancer treatment involves drugs with risks of side effects in the growing child, there is a need for more effective and less toxic drugs. One new approach in cancer treatment is inhibition of tumor angiogenesis, i.e., of new blood vessel growth into the tumor. An angiogenesis inhibitor may be combined with cytostatic drugs to enhance the efficacy. The aim of this study was to investigate how drugs could be used to inhibit angiogenesis and tumor growth in a xenograft model of human neuroblastoma in nude mice. The tumors express the angiogenesis stimulator vascular endothelial growth factor (VEGF) on both protein and mRNA levels. The angiogenesis inhibitors SU5416 (an inhibitor of VEGF signalling) and TNP-470 (an inhibitor of endothelial cell proliferation) inhibited angiogenesis in our model. TNP-470, however, inhibited angiogenesis without significant reduction of the tumor growth, in contrast to SU5416. We also discovered that the cytostatic drug CHS 828 could cause regression of neuroblastoma tumors in the model when given orally at a low daily dose, alone or in combination with the angiogenesis inhibitor SU5416 or TNP-470. Furthermore, a new use of the cardiac glycoside digoxin was found. Digoxin inhibited FGF-2 -stimulated bovine capillary endothelial cell growth in vitro, and inhibited angiogenesis in vivo in the chick chorioallantoic membrane assay (CAM). It also inhibited neuroblastoma growth by approximately 50% in our neuroblastoma model. In conclusion, CHS 828 and digoxin represent two classes of drugs with potent antitumor effects that may be valuable in treatment of neuroblastoma, either alone or in combination with angiogenesis inhibitors.