NRP1 and glioblastoma: Therefore, we determined the number of NRP1/Plexin-A1 dimers at the surface of the wild-type (WT) cells and in cells knocked down for NRP1. This assay was performed with cells of the glioblastoma U-118MG cell line previously shown to express NRP1 and Plexin-A1 [54], cells of the metastatic breast cancer cell line MDA-MB231, and cells with a knockdown of NRP1 expression that was confirmed by reverse transcription followed by quantitative polymerase chain reaction (RT-qPCR) analysis in both cell lines (Figure 3a,b).