Silencing of UCHL1 by CpG Promoter Hyper-methylation is Associated with Metastatic Gastroenteropancreatic Well-Differentiated Neuroendocrine (Carcinoid) Tumors

Well-differentiated gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are rare tumors with varying metastatic potential. The underlying molecular basis for metastasis by GEP-NETs remains undefined. Quantitative PCR and immunohistochemistry (IHC) staining for ubiquitin carboxyl-terminal esterase L1 (UCHL1) gene and protein expression was performed on a group of localized and metastatic well-differentiated GEP-NET samples acquired from a prospectively maintained tissue bank. The ability of extent of UCHL1 IHC staining to differentiate localized and metastatic tumors was compared with Ki-67 index. Among 46 total samples, UCHL1 expression at both the gene and protein level was significantly greater among localized GEP-NETs compared with metastatic tumors and metastases (p