NF1 and neoplasm: Furthermore, these engineered models of NF1 were crucial to confirming the role of RAS hyperactivation in the development of OPG, providing the biological rationale to test a series of compounds able to counteract the effectors downstream to RAS: the RAS-MEK-ERK and the PI3K-AKT-mTOR signaling pathways are up-regulated in tumor cells [91,92,93], whereas the adenylyl cyclase-mediated cyclic AMP is associated with decreased levels of cAMP [94].