NF1 and neoplasm: Exploiting this unique mutation, we employed a combination of human-induced pluripotent stem cell (hiPSC) and Nf1-mutant mouse lines to demonstrate that central (retinal ganglion cells; RGCs) and peripheral (sensory neurons and dorsal root ganglion cells; DRGs) nervous system neurons support tumor growth by secreting paracrine factors necessary for tumor progression in an Nf1 mutation- and neuronal activity-dependent manner.