title: Analysis of molecular pathways in sporadic neuroendocrine tumors of the gastro-entero-pancreatic system.
abstract: Little is known about the molecular pathogenesis of neuroendocrine tumors (NET) of the gastro-entero-pancreatic (GEP) system. We analyzed genetic and epigenetic alterations as well as the CpG island methylator phenotype (CIMP). The study comprised 118 well-differentiated fore- and mid-gut GEP-NET from 71 patients. In addition to loss of heterozygosity (LOH), microsatellite instability (MSI) and the methylation status of various tumor associated genes were examined. The expression profile of p16, APC and MENIN was investigated by immunohistochemistry. None of the tumors was highly microsatellite unstable, LOH was found in 22.2%. Significant differences in promoter hypermethylation were identified in the RUNX3 and the O(6)-MGMT genes. We found a significant loss of p16 expression in insulinomas (p = 0.05) and functional NET (p = 0.01), respectively. APC was expressed less in gastrinomas (p = 0.01) and functional GEP-NET (p = 0.05) vs. nonfunctional tumors. MENIN expression was reduced in pancreatic vs. extrapancreatic NET (p = 0.008) and in insulinomas vs. nonfunctional GEP-NET (p = 0.019) and NET associated with the carcinoid syndrome (p = 0.029). Further CIMP and a Ki-67 index >10% showed a close correlation. Outcome analysis of 19 patients showed a better survival for CIMP-negative patients. The analyses identified significant genetic and epigenetic alterations in well-differentiated fore- and mid-gut NET. CIMP, similar to Ki-67, might turn out to be of prognostic relevance.
authors.affiliation: Department of Internal Medicine, University of Freiburg, Hugstetterstrasse 55, D-79106 Freiburg, Germany. arnold@med1.ukl-uni-freiburg.de
authors.forename: Christian N
authors.initials: CN
authors.lastname: Arnold
authors.forename: Andrea
authors.initials: A
authors.lastname: Sosnowski
authors.forename: Annette
authors.initials: A
authors.lastname: Schmitt-Gräff
authors.forename: Rudolf
authors.initials: R
authors.lastname: Arnold
authors.forename: Hubert E
authors.initials: HE
authors.lastname: Blum
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics; D025601:Adenomatous Polyposis Coli Protein / Q000096:biosynthesis / Q000235:genetics; D018899:CpG Islands; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000096:biosynthesis / Q000235:genetics; D019175:DNA Methylation; D005770:Gastrointestinal Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D017491:Genes, APC; D016147:Genes, Tumor Suppressor; D019942:Genes, p16; D006801:Humans; D019656:Loss of Heterozygosity; D053842:Microsatellite Instability; D000070957:MutL Protein Homolog 1; D018358:Neuroendocrine Tumors / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D009687:Nuclear Proteins / Q000235:genetics; D010190:Pancreatic Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D025601:Adenomatous Polyposis Coli Protein; D019941:Cyclin-Dependent Kinase Inhibitor p16; C105373:MEN1 protein, human; C501486:MLH1 protein, human; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D000070957:MutL Protein Homolog 1