Purpose: Tumor progression correlates with the induction of a dense supply of blood vessels and the formation of peritumoral lymphatics. Hemangiogenesis and lymphangiogenesis are potently regulated by members of the vascular endothelial growth factor (VEGF) family. Previous studies have indicated the upregulation of VEGF-A and -C in progressed neuroblastoma, however, quantification was performed using semiquantitative methods, or patients who had received radiotherapy or chemotherapy were studied.
Experimental design: We have analyzed primary neuroblastoma from 49 patients using real-time reverse transcription-PCR and quantified VEGF-A, -C, and -D and VEGF receptors (VEGFR)-1, 2, 3, as well as the soluble form of VEGFR2 (sVEGFR-2), which has recently been characterized as an endogenous inhibitor of lymphangiogenesis. None of the patients had received radiotherapy or chemotherapy before tumor resection.
Results: We did not observe upregulation of VEGF-A, -C, and -D in metastatic neuroblastoma, but found significant downregulation of the lymphangiogenesis inhibitor sVEGFR-2 in metastatic stages III, IV, and IVs. In stage IV neuroblastoma, there were tendencies for the upregulation of VEGF-A and -D and the downregulation of the hemangiogenesis/lymphangiogenesis inhibitors VEGFR-1 and sVEGFR-2 in MYCN-amplified tumors. Similarly, MYCN transfection of the neuroblastoma cell line SH-EP induced the upregulation of VEGF-A and -D and the switching-off of sVEGFR-2.
Conclusion: We provide evidence for the downregulation of the lymphangiogenesis inhibitor sVEGFR-2 in metastatic neuroblastoma stages, which may promote lymphogenic metastases. Downregulation of hemangiogenesis and lymphangiogenesis inhibitors VEGFR-1 and sVEGFR-2, and upregulation of angiogenic activators VEGF-A and VEGF-D in MYCN-amplified stage IV neuroblastoma supports the crucial effect of this oncogene on neuroblastoma progression.