The ETS oncogene family transcription factor FEV identifies serotonin-producing cells in normal and neoplastic small intestine

Neuroendocrine (NE) or carcinoid tumors of the small intestine (SI) frequently metastasize and produce the hormone serotonin, causing significant morbidity and mortality. A member of the ETS oncogene family of transcription factors, Fev, acts with the homeodomain transcription factor Nkx2.2 in the development of serotonin neurons in mice. In this study, we investigated the role of Fev in normal and neoplastic SI. In NE tumors (NETs) of the SI, serotonin stimulates tumor growth and causes debilitating symptoms, such as diarrhea, flushing, wheezing, and right-sided valvular heart disease (i.e. carcinoid syndrome). Compared with those in the matched normal human SI, FEV expression levels were significantly elevated in primary NETs (20-fold, P