These opposite roles are related to dual functions of p75NTR in tumor cells, inducing either apoptosis in colorectal and in rat C6 glioma cell lines [7, 27] or cell activation in human breast, glioblastoma and melanoma cancer cells, depending on the cell type and the pro- or mature neurotrophin binding [26, 28, 33]. This evidence concerns the gene NGFR and central nervous system cancer.