Here, we demonstrate an inhibitory effect of NF1-GRD (GAP-related domain, residues 1198–1509) fused with RAS-CAAX motif on tumor cell growth and ERK signaling in NF1-MPNST and further prove the growth dependency of NF1-MPNST cells on CRAF and BRAF. The gene discussed is BRAF; the disease is malignant peripheral nerve sheath tumor.