Abstract
Objective: To investigate the effects of tyrosine-kinase inhibitors of vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF)-receptors on non-malignant tissue and whether they depend upon the stage of vascular maturation.
Materials and methods: PTK787/ZK222584 and CGP53716 (VEGF- and PDGF-receptor inhibitor respectively), both alone and combined, were applied on chicken chorioallantoic membrane (CAM).
Results: On embryonic day of CAM development (E)8, only immature microvessels, which lack coverage of pericytes, are present; whereas the microvessels on E12 have pericytic coverage. This development was reflected in the expression levels of pericytic markers (α -smooth muscle actin, PDGF-receptor ß and desmin), which were found by immunoblotting to progressively increase between E8 and E12. Monotherapy with 2 μ g of PTK787/ZK222584 induced significant vasodegeneration on E8, but not on E12. Monotherapy with CGP53716 affected only pericytes. When CGP53716 was applied prior to treatment with 2 μ g of PTK787/ZK222584, vasodegeneration occurred also on E12. The combined treatment increased the apoptotic rate, as evidenced by the cDNA levels of caspase-9 and the TUNEL-assay.
Conclusion: Anti-angiogenic treatment strategies for non-neoplastic disorders should aim to interfere with the maturation stage of the target vessels: monotherapy with VEGF-receptor inhibitor for immature vessels, and combined anti-angiogenic treatment for well developed mature vasculature.