NF1 and cancer: Based on prior studies demonstrating that Ccl5 is necessary for murine Nf1 OPG growth in vivo11,12 and operates to control glioblastoma cell growth by inhibiting apoptosis, we next sought to determine whether Ccl5 increases the survival of cancer stem cells from murine Nf1 optic gliomas (optic glioma stem cells; o-GSCs).