ABSTRACT
BACKGROUND: ASCL1 role in pancreatic endocrine tumourigenesis has not been established. Recently it was suggested that ASCL1 negatively controls expression of the Wnt signalling antagonist DKK1. Notch signalling regulates expression of TPH1, the rate limiting enzyme in the biosynthesis of serotonin. Understanding the development and proliferation of pancreatic endocrine tumours (PETs) is essential for the development of new therapies. METHODS: ASCL1 target genes in the pancreatic endocrine tumour cell line BON1 were identified by RNA interference and microarray expression analysis. Protein expressions of selected target genes in PETs were evaluated by immunohistochemistry. RESULTS: 158 annotated ASCL1 target genes were identified in BON1 cells, among them DKK1 and TPH1 that were negatively regulated by ASCL1. An inverse relation of ASCL1 to DKK1 protein expression was observed for 15 out of 22 tumours (68%). Nine tumours displayed low ASCL1/high DKK1 and six tumours high ASCL1/low DKK1 expression. Remaining PETs showed high ASCL1/high DKK1 (n = 4) or low ASCL1/low DKK1 (n = 3) expression. Nine of twelve analysed PETs (75%) showed TPH1 expression with no relation to ASCL1. CONCLUSION: A number of genes with potential importance for PET tumourigenesis have been identified. ASCL1 negatively regulated the Wnt signalling antagonist DKK1, and TPH1 expression in BON1 cells. In concordance with these findings DKK1 showed an inverse relation to ASCL1 expression in a subset of PETs, which may affect growth control by the Wnt signalling pathway.
Subject(s)
Basic Helix-Loop-Helix Transcription Factors/metabolism , Down-Regulation , Intercellular Signaling Peptides and Proteins/genetics , Pancreatic Neoplasms/genetics , Tryptophan Hydroxylase/genetics , Adult , Aged , Aged, 80 and over , Basic Helix-Loop-Helix Transcription Factors/genetics , Cell Line, Tumor , Female , Gene Expression Regulation, Neoplastic , Humans , Intercellular Signaling Peptides and Proteins/metabolism , Male , Middle Aged , Pancreatic Neoplasms/metabolism , Tryptophan Hydroxylase/metabolism , Young AdultABSTRACT
OBJECTIVES: To investigate if transcription factors involved in pancreatic differentiation and regeneration are present in pancreatic endocrine tumors and if they are differentially expressed in normal pancreas compared with multiple endocrine neoplasia type 1 (MEN1) nontumorous pancreas. METHODS: The expression of neurogenin 3 (NEUROG3), neurogenic differentiation 1 (NEUROD1), POU class 3 homeobox 4 (POU3F4), pancreatic duodenal homeobox factor 1 (PDX1), ribosomal protein L10 (RPL10), delta-like 1 homolog (Drosophila; DLK1), and menin was analyzed by immunohistochemistry in normal pancreas and pancreatic endocrine tumors from 6 patients with MEN1 and 16 patients with sporadic tumors, as well as pancreatic specimens from Men1 heterozygous and wild type mice. Quantitative polymerase chain reaction was performed in a subset of human tumors. RESULTS: Tumors and MEN1 nontumorous endocrine cells showed a prominent cytoplasmatic NEUROG3 and NEUROD1 expression. These factors were significantly more expressed in the cytoplasm of Men1 heterozygous mouse islet cells compared with wild type islets; the latter showed an exclusively nuclear reactivity. The degree of Pou3f4, Rpl10, and Dlk1 immunoreactivities differed significantly between islets of heterozygous and wild type mice. The expressions of RPL10 and NEUROD1 were prominent in the MEN1 human and heterozygous mouse exocrine pancreas. Insulinomas had significantly higher PDX1 and DLK1 messenger RNA levels compared with other tumor types. CONCLUSIONS: Transcription factors involved in pancreatic development show altered expression and subcellular localization in MEN1 nontumorous pancreas and pancreatic endocrine tumors.
Subject(s)
Basic Helix-Loop-Helix Transcription Factors/metabolism , Insulinoma/metabolism , Multiple Endocrine Neoplasia Type 1/metabolism , Nerve Tissue Proteins/metabolism , Pancreatic Neoplasms/metabolism , Animals , Calcium-Binding Proteins , Cytoplasm/metabolism , Female , Heterozygote , Homeodomain Proteins/metabolism , Humans , Immunohistochemistry , Insulinoma/genetics , Intercellular Signaling Peptides and Proteins/metabolism , Male , Membrane Proteins/metabolism , Mice , Mice, Mutant Strains , Multiple Endocrine Neoplasia Type 1/genetics , POU Domain Factors/metabolism , Pancreas, Exocrine/metabolism , Pancreatic Neoplasms/genetics , Ribosomal Protein L10 , Ribosomal Proteins/metabolism , Trans-Activators/metabolismABSTRACT
OBJECTIVE: Expression of ghrelin has been reported in pancreatic endocrine tumours, but data on ghrelin receptor protein expression are lacking. The aim of this study was to examine the ghrelin receptor, as well as ghrelin, in a selected series of these tumours, including multiple endocrine neoplasia 1 (MEN1) associated tumours, and to correlate data with clinical features including body mass index. DESIGN: Immunohistochemical detection of ghrelin and its receptor was performed on frozen tissue from 31 tumours: 9 MEN1 and 22 sporadic. Twenty tumours were analysed by quantitative PCR. Plasma ghrelin was assessed in 26 patients. RESULTS: Twenty-one (68%) of 31 tumours showed immunoreactivity for ghrelin (8/9 MEN1) and 19/20 expressed ghrelin mRNA. Ghrelin receptor protein was detected in 21/30 (70%) tumours (4/8 MEN1), and mRNA was detected in all analysed tumours. Insulinomas had significantly higher levels of receptor mRNA than other tumours. Five patients had elevated plasma ghrelin (> 2 SD above the control group mean). No significant difference in mean plasma ghrelin levels was found between patients (908 +/- 569 ng/l) and controls (952 +/- 164 ng/l). Mean BMI was 24.3 kg/m(2). There was no association between ghrelin or receptor expression and survival. CONCLUSIONS: We report the first immunohistochemical data on expression of the ghrelin receptor in pancreatic endocrine tumours: 70% of tumours in our material. Concomitant ghrelin and receptor expression was seen in 50% of tumours, indicating an autocrine loop. Ghrelin was expressed in 68% of tumours (8/9 MEN1). Despite frequent ghrelin expression, elevated circulating ghrelin is rare in these patients.
Subject(s)
Adenoma, Islet Cell/metabolism , Pancreatic Neoplasms/metabolism , Peptide Hormones/genetics , Receptors, G-Protein-Coupled/genetics , Adenoma, Islet Cell/blood , Adenoma, Islet Cell/chemistry , Adult , Aged , Aged, 80 and over , Body Mass Index , Chi-Square Distribution , Female , Gene Expression , Ghrelin , Humans , Immunohistochemistry , Insulinoma/chemistry , Insulinoma/metabolism , Male , Middle Aged , Multiple Endocrine Neoplasia Type 1/chemistry , Multiple Endocrine Neoplasia Type 1/metabolism , Pancreatic Neoplasms/blood , Pancreatic Neoplasms/chemistry , Peptide Hormones/analysis , Peptide Hormones/blood , Receptors, G-Protein-Coupled/analysis , Receptors, Ghrelin , Survival RateABSTRACT
Expression of the neuroendocrine marker synaptic vesicle protein 2 (SV2) has been reported in a few cases of gastrointestinal stromal tumors (GISTs). The goal of the present study was to assess the relevance of this finding and identify a possible hormone production in these tumors. We chose to study the orexigen ghrelin and its receptor, since these patients are seldom cachexic, even in advanced disease stages. We investigated ghrelin expression by means of immunohistochemistry on frozen or paraffin-embedded sections from 22 GISTs from a well-characterized patient material. Expression of the growth hormone secretagogue receptor, the ghrelin receptor, was investigated in a subset of lesions. In six tumors, mRNA levels of ghrelin, the ghrelin receptor, and SV2 were analyzed by real-time quantitative PCR. Totally 17 out of 22 tumors showed immunoreactivity for ghrelin. Five out of ten tumors were immunoreactive for the ghrelin receptor, and all of these co-expressed ghrelin. All tumors expressed ghrelin, ghrelin receptor, and SV2 mRNA. GISTs frequently express SV2, ghrelin, and its receptor, indicating the presence of autocrine/paracrine loops.
