Aberrant expression of human achaete-scute homologue gene 1 in the gastrointestinal neuroendocrine carcinomas.

PURPOSE Gastrointestinal neuroendocrine carcinoma (NEC) is extremely aggressive, but its pathophysiologic features remain poorly understood. There have been no biologically specific markers for this disease. In this study, distinctive up-regulation of human achaete-scute homologue 1 (hASH1) in gastrointestinal NECs was clarified. EXPERIMENTAL DESIGN Expression of hASH1 in NECs (n=10), carcinoid tumors (n = 10), other tumors (10 adenocarcinomas, 2 squamous cell carcinomas and 1 malignant lymphoma), and the corresponding normal mucosa were investigated by in situ hybridization, reverse transcription-PCR (RT-PCR), real-time RT-PCR, and immunohistochemistry. RESULTS By in situ hybridization, mild to intense signals of hASH1 mRNA were detected in 9 of 10 NECs, but not in other tumors or normal mucosa, except for focally weak signals in one carcinoid tumor. RT-PCR showed strong expression of hASH1 in a small cell NEC, followed by a moderately differentiated NEC, and a carcinoid tumor, whereas it is undetectable in adenocarcinomas or normal mucosa. By real-time RT-PCR, the amounts of hASH1 mRNA in a small cell NEC were 16,600 times higher than those in adenocarcinomas and 110 times higher than those in a carcinoid tumor. Immunohistochemically, mammalian homologue of hASH1 was positive in 7 of 10 NECs but was negative in the other tumors. Pan-endocrine markers chromogranin A and synaptophysin were positive in almost all carcinoid tumors, in 4 and 7 of the 10 NECs, respectively. CONCLUSIONS These findings revealed that hASH1 is distinctly up-regulated in gastrointestinal NECs. hASH1 may be used as a more sensitive and specific marker than conventional pan-endocrine markers for clinical diagnosis of gastrointestinal NECs.