NRP1 and central nervous system cancer: In vitro analysis of the secretome of the U87MG cell line showed significant elevations in the amount of Nrp1 secreted by the cells relative to the less invasive lines [93] In the U373MG human glioma cell line, it was shown that siRNA-mediated knockdown of Nrp1 reduced proliferation and increased apoptosis of the cells, associated with reductions in Bcl-2 expression and ERK, JNK, and MAPK activation [94].