Differential dependency of human glioblastoma cells on vascular endothelial growth factor­A signaling via neuropilin­1.

Despite the high expression of neuropilin­1 (NRP­1) in human glioblastoma (GB), the understanding of its function as a co­receptor of vascular endothelial growth factor receptors (VEGFRs) in angiogenesis is currently limited. Therefore, the aim of the present study was to elucidate the non­classical function of NRP­1 expression in human GB. Expression patterns of NRP­1 and VEGF­A were determined by sandwich ELISA, western blot analysis, or immunohistochemistry. Differential dependency of GB cells following ablation of VEGF­A signaling was validated in vitro and in vivo. Cellular mechanism responsible for distinct response to VEGF­A signaling was evaluated by western blotting and immunoprecipitation analysis. Prognostic implications were assessed using IHC analysis. GB cells exhibited differing sensitivity to silencing of vascular endothelial growth factor (VEGF)­A signaling, which resulted in a distinct expression pattern of wild­type or chondroitin­sulfated NRP­1. VEGF­A­sensitive GB exhibited the physical interaction between wild­type NRP­1 and FMS related receptor tyrosine kinase 1 (Flt­1) whereas VEGF­A­resistant GB exhibited chondroitin­sulfated NRP­1 without interaction with Flt­1. Eliminating the chondroitin sulfate modification in NRP­1 led to re­sensitization to VEGF­A signaling, and chondroitin sulfate modification was found to be associated with an adverse prognosis in patients with GB. The present study identified the distinct functions of NRP­1 in VEGF­A signaling in accordance with its unique expression type and interaction with Flt­1. The present research is expected to provide a strong basis for targeting VEGF­A signaling in patients with GB, with variable responses.