Table 4.

Summary of study results concerning MAPK signaling in GEP-NENs.

Study results	Reference
Ras is expressed in GEP-NENs but mutations are rare	21, 263-266
Raf mutations are rare events	263, 305-307
Rap1 and B-Raf are highly expressed in GEP-NEN	309
Raf inhibition triggers feedback activation of Akt	135, 310, 311
MAPK signaling triggers NE secretion and migration in vitro	312-314
Raf activation induces a paradox inhibition of proliferation and NE secretion	318-321
ERK activation is frequent in GEP-NENs	6, 263, 309, 361