title: Minichromosome Maintenance Expression Defines Slow-Growing Gastroenteropancreatic Neuroendocrine Neoplasms.
abstract: BACKGROUND
  Small intestinal neuroendocrine neoplasm (SI-NEN) proliferation is quantified by Ki67 measurements which capture G1-G2M phases of the cell cycle. G0and early G1phases, typical of slow-growing cells, can be detected by minichromosome maintenance protein (MCM) expression. We hypothesized that these replication licensing markers may provide clinically relevant information to augment Ki67 in low-grade neuroendocrine neoplasia.
  
  
  METHODS
  Immunohistochemical staining (IHC), Western blot analysis, quantitative polymerase chain reaction, and copy number variations of MCM2, MCM3, and Ki67 were undertaken in SI-NENs (n = 22). MCM and Ki67 expression was compared by Kaplan-Meier survival analysis (tissue microarray, independent set [n = 55]). Forty-three pancreatic NENs and 14 normal tissues were included as controls.
  
  
  RESULTS
  In SI-NENs, MCM2 (mean: 21.2%: range: 16%-25%) and MCM3 (28.7%: 22%-34%) were detected in significantly more cells than Ki67 (2.3%: 0%-7%, P < .01). MCM2 mRNA correlated with Ki67 IHC (P < .05). MCM3 protein expression was higher in metastases (38-fold) than in normal small intestine (P = .06) and was largely absent in normal neuroendocrine cells. There was considerable variation at the MCM copy number level (0-4 copies). MCM3 expression in proliferating cells significantly predicted overall survival (P < .002). Combinations of Ki67 and MCM2/3 in algorithms differentiated low and higher proliferative lesions (overall survival: 12 vs 6.1 years, P = .06). MCM expression was not informative in pancreatic NENs.
  
  
  CONCLUSIONS
  MCMs are expressed in a higher proportion of NEN cells than Ki67 in slow-growing small intestinal lesions and correlate with survival. Assessment can be used to augment Ki67 to improve prognostic classification in these low-grade tumors.
authors.affiliation: Gastrointestinal Pathobiology Research Group, Department of Gastrointestinal Surgery, Yale University School of Medicine, PO Box 208602, New Haven, CT, USA; University Hospital of General, Visceral and Transplantation-Surgery of Heidelberg, Im Neuenheimer Feld 110, 69120, Heidelberg, Germany. Electronic address: simon.schimmack@med.uni-heidelberg.de.
authors.forename: Simon
authors.initials: S
authors.lastname: Schimmack
authors.affiliation: Gastrointestinal Pathobiology Research Group, Department of Gastrointestinal Surgery, Yale University School of Medicine, PO Box 208602, New Haven, CT, USA. Electronic address: b.lawrence@auckland.ac.nz.
authors.forename: Ben
authors.initials: B
authors.lastname: Lawrence
authors.affiliation: Department of Pathology, Division of Gastrointestinal and Hepatic Pathology, Yale University School of Medicine, PO Box 208023, New Haven, CT, USA. Electronic address: barton.kenney@yale.edu.
authors.forename: Barton
authors.initials: B
authors.lastname: Kenney
authors.affiliation: University Hospital of General, Visceral and Transplantation-Surgery of Heidelberg, Im Neuenheimer Feld 110, 69120, Heidelberg, Germany. Electronic address: winnenthal@gmail.com.
authors.forename: Hubertus
authors.initials: H
authors.lastname: Schmitz-Winnenthal
authors.affiliation: Gastrointestinal Pathobiology Research Group, Department of Gastrointestinal Surgery, Yale University School of Medicine, PO Box 208602, New Haven, CT, USA. Electronic address: imodlin@optonline.net.
authors.forename: Irvin M
authors.initials: IM
authors.lastname: Modlin
authors.affiliation: Gastrointestinal Pathobiology Research Group, Department of Gastrointestinal Surgery, Yale University School of Medicine, PO Box 208602, New Haven, CT, USA. Electronic address: mkidd01@snet.net.
authors.forename: Mark
authors.initials: M
authors.lastname: Kidd