title: A mechanistic role for the chromatin modulator, NAP1L1, in pancreatic neuroendocrine neoplasm proliferation and metastases.
abstract: BACKGROUND
  The chromatin remodeler NAP1L1, which is upregulated in small intestinal neuroendocrine neoplasms (NENs), has been implicated in cell cycle progression. As p57(Kip2) (CDKN1C), a negative regulator of proliferation and a tumor suppressor, is controlled by members of the NAP1 family, we tested the hypothesis that NAP1L1 may have a mechanistic role in regulating pancreatic NEN proliferation through regulation of p57(Kip2).
  
  
  RESULTS
  NAP1L1 silencing (siRNA and shRNA/lipofectamine approach) decreased proliferation through inhibition of mechanistic (mammalian) target of rapamycin pathway proteins and their phosphorylation (p < 0.05) in the pancreatic neuroendocrine neoplasm cell line BON in vitro (p < 0.0001) and resulted in significantly smaller (p < 0.05) and lighter (p < 0.05) tumors in the orthotopic pancreatic NEN mouse model. Methylation of the p57 (Kip2) promoter was decreased by NAP1L1 silencing (p < 0.05), and expression of p57(Kip2) (transcript and protein) was upregulated. For methylation of the p57 (Kip2) promoter, NAP1L1 bound directly to the promoter (-164 to +21, chromatin immunoprecipitation). In 43 pancreatic NEN samples (38 primaries and 5 metastasis), NAP1L1 was over-expressed in metastasis (p < 0.001), expression which was inversely correlated with p57(Kip2) (p < 0.01) on mRNA and protein levels. Menin was not differentially expressed.
  
  
  CONCLUSIONS
  NAP1L1 is over-expressed in pancreatic neuroendocrine neoplasm metastases and epigenetically promotes cell proliferation through regulation of p57 (Kip2) promoter methylation.
authors: Gastrointestinal Pathobiology Research Group, Yale University School of Medicine, PO Box 208602, New Haven, CT 06510, USA ; Department of General, Visceral and Transplantation Surgery, University Hospital Heidelberg, Im Neuenheimer Feld 110, Heidelberg 69120, Germany.
authors: Simon
authors: S
authors: Schimmack
authors: Gastrointestinal Pathobiology Research Group, Yale University School of Medicine, PO Box 208602, New Haven, CT 06510, USA.
authors: Andrew
authors: A
authors: Taylor
authors: Gastrointestinal Pathobiology Research Group, Yale University School of Medicine, PO Box 208602, New Haven, CT 06510, USA.
authors: Ben
authors: B
authors: Lawrence
authors: Gastrointestinal Pathobiology Research Group, Yale University School of Medicine, PO Box 208602, New Haven, CT 06510, USA.
authors: Daniele
authors: D
authors: Alaimo
authors: Department of General, Visceral and Transplantation Surgery, University Hospital Heidelberg, Im Neuenheimer Feld 110, Heidelberg 69120, Germany.
authors: Hubertus
authors: H
authors: Schmitz-Winnenthal
authors: Department of General, Visceral and Transplantation Surgery, University Hospital Heidelberg, Im Neuenheimer Feld 110, Heidelberg 69120, Germany.
authors: Markus W
authors: MW
authors: Büchler
authors: Gastrointestinal Pathobiology Research Group, Yale University School of Medicine, PO Box 208602, New Haven, CT 06510, USA.
authors: Irvin M
authors: IM
authors: Modlin
authors: Gastrointestinal Pathobiology Research Group, Yale University School of Medicine, PO Box 208602, New Haven, CT 06510, USA.
authors: Mark
authors: M
authors: Kidd
keywords: NAP1L1; Pancreatic neuroendocrine neoplasms; Proliferation; Promoter methylation; p57; pNETs