CXCL12 and malignant peripheral nerve sheath tumor: In NF1-associated MPNST, CXCR4/CXCL12 signaling stimulates Cyclin D1 expression and promotes cell cycle progression by activating the AKT/serine–threonine kinase/glycogen synthase kinase 3 beta signaling pathway, ultimately increasing MPNST cell proliferation.