GNAS and gastrointestinal disease: Somatic variations of GNAS, a heterotrimeric G protein α subunit that activates adenylyl cyclase downstream of activated G protein–coupled receptors in response to hormones and a plethora of extracellular signals,24 have been identified in many gastrointestinal diseases, including neoplasms of the pancreas25,26,27,28 and stomach29 as well as adenomas of the colorectum.30,31 However, GNAS variation patterns in ACs remain incompletely understood.