Intestinal CART is a regulator of GIP and GLP-1 secretion and expression

Impaired incretin effect is a culprit in Type 2 Diabetes. Cocaine- and amphetamine-regulated transcript (CART) is a regulatory peptide controlling pancreatic islet hormone secretion and beta-cell survival. Here we studied the potential expression of CART in enteroendocrine cells and examined the role of CART as a regulator of incretin secretion and expression. CART expression was found in glucose-dependent insulinotropic polypeptide (GIP)-producing K-cells and glucagon-like peptide-1 (GLP-1)-producing L-cells in human duodenum and jejunum and circulating CART levels were increased 60 min after a meal in humans. CART expression was increased by fatty acids and GIP, but unaffected by glucose in GLUTag and STC-1 cells. Exogenous CART had no effect on GIP and GLP-1 expression and secretion in GLUTag or STC-1 cells, but siRNA-mediated silencing of CART reduced GLP-1 expression and secretion. Furthermore, acute intravenous administration of CART increased GIP and GLP-1 secretion during an oral glucose-tolerance test in mice. We conclude that CART is a novel constituent of human K- and L-cells with stimulatory actions on incretin secretion and that interfering with the CART system may be a therapeutic avenue for T2D.

Histidine decarboxylase and urinary methylimidazoleacetic acid in gastric neuroendocrine cells and tumours

AIM: To study histidine decarboxylase (HDC) expression in normal and neoplastic gastric neuroendocrine cells in relationship to the main histamine metabolite.

METHODS: Control tissues from fundus (n = 3) and corpus (n = 3) mucosa of six patients undergoing operations for gastric adenocarcinoma, biopsy and/or gastric surgical specimens from 64 patients with primary gastric neuroendocrine tumours (GNETs), as well as metastases from 22 of these patients, were investigated using conventional immunohistochemistry and double immunofluorescence with commercial antibodies vs vesicular monoamine transporter 2 (VMAT-2), HDC and ghrelin. The urinary excretion of the main histamine metabolite methylimidazoleacetic acid (U-MeImAA) was determined using high-performance liquid chromatography in 27 of the 64 patients.

RESULTS: In the gastric mucosa of the control tissues, co-localization studies identified neuroendocrine cells that showed immunoreactivity only to VMAT-2 and others with reactivity only to HDC. A third cell population co-expressed both antigens. There was no co-expression of HDC and ghrelin. Similar results were obtained in the foci of neuroendocrine cell hyperplasia associated with chronic atrophic gastritis type A and also in the tumours. The relative incidence of the three aforementioned markers varied in the tumours that were examined using conventional immunohistochemistry. All of these GNETs revealed both VMAT-2 and HDC immunoreactivity, and their metastases showed an immunohistochemical pattern and frequency similar to that of their primary tumours. In four patients, increased U-MeImAA excretion was detected, but only two of the patients exhibited related endocrine symptoms.

CONCLUSION: Human enterochromaffin-like cells appear to partially co-express VMAT-2 and HDC. Co-expression of VMAT-2 and HDC might be required for increased histamine production in patients with GNETs.

Ki-67 Index and Solid Growth Pattern as Prognostic Markers in Small Intestinal Neuroendocrine Tumors

BACKGROUND/AIMS

The prognostic value of histopathological grading and the growth pattern of small intestinal neuroendocrine tumors (SI-NET) is unclear. In particular, the cutoff level between grades G1 and G2 at Ki-67 index above 2% is an open issue, and both lower and higher cutoffs have been proposed. The morphological solid growth pattern (SGP) in SI-NET has been reported to be associated with worse survival. The present study investigates whether a Ki-67 index cutoff of 1% has a higher predictive power than one of 2% for disease-specific survival in SI-NET, and whether an SGP is associated with survival.

PATIENTS AND METHODS

From a population-based cohort, 127 SI-NET patients with available tumor specimens were included. Medical records and pathology reports were reviewed. Tumor specimens were reexamined to confirm the diagnosis, recalculate the Ki-67 index, and assess the presence of an SGP, introducing an SGP score from 0 to 3+.

RESULTS

The current grading system with a G1/G2 cutoff of 2% was more discriminative (HR 2.30; 95% CI 1.20-4.38, p = 0.012) than one with a lower cutoff of 1% (HR 1.65; 95% CI 0.95-2.87, p = 0.078) after adjustment for patient age and clinical stage. SGP score was strongly associated with clinical stage (p = 0.004) and histopathological grade (p < 0.001) but was not an independent prognostic factor for disease-specific survival in SI-NET (p = 0.122) after adjusting for age, stage, and grade.

CONCLUSIONS

The present grading system of SI-NET is supported by our results. The SGP is not an independent prognostic factor for disease-specific survival in SI-NET.

Malignant presacral ghrelinoma with long-standing hyperghrelinaemia

BACKGROUND

A 57-year old man with low-back pain was found to have a 3 × 3 × 3 cm presacral neuroendocrine tumour (NET) with widespread metastases, mainly to the skeleton. His neoplastic disease responded well to peptide receptor radionuclide therapy (PRRT) with the radiotagged somatostatin agonist (177)Lu-DOTATATE. During almost 10 years he was fit for a normal life. He succumbed to an intraspinal dissemination.

PROCEDURES

A resection of the rectum, with a non-radical excision of the adjacent NET, was made. In addition to computerized tomography (CT), receptor positron emission tomography (PET) with (68)Ga-labelled somatostatin analogues was used.

OBSERVATIONS

The NET showed the growth pattern and immunoprofile of a G2 carcinoid. A majority cell population displayed immunoreactivity to ghrelin, exceptionally with co-immunoreactivity to motilin. Somatostatin receptor scintigraphy and (68)Ga-DOTATATE PET-CT demonstrated uptake in the metastatic lesions. High serum concentrations of total (desacyl-)ghrelin were found with fluctuations reflecting the severity of the symptoms. In contrast, the concentrations of active (acyl-)ghrelin were consistently low, as were those of chromogranin A (CgA).

CONCLUSIONS

Neoplastically transformed ghrelin cells can release large amounts of desacyl-ghrelin, evoking an array of non-specific clinical symptoms. Despite an early dissemination to the skeleton, a ghrelinoma can be compatible with longevity after adequate radiotherapy.

Survival and prognostic factors in patients with small bowel carcinoid tumour

BACKGROUND

Previous studies of small bowel carcinoid tumours usually presented overall or relative survival. This study, in addition, evaluated disease-specific survival in a cohort of patients in a geographically defined population.

METHODS

Patients diagnosed with carcinoid of the jejunum or ileum in Jönköping County between 1960 and 2005 were eligible for inclusion. Available tumour specimens were re-examined to confirm the diagnosis. Medical records and pathology reports were reviewed in detail.

RESULTS

A total of 145 patients were included in the study. One hundred and thirty-five patients underwent surgery in connection with the diagnosis. Resection was considered complete (R0) in 74 patients (54·8 per cent). Only two localized tumours recurred, whereas no patient with distant metastases was cured. Patients with regional metastases who underwent R0 resection had a better survival than patients with incomplete resection (P = 0·005), and a majority of patients remained recurrence-free. Median overall survival was 7·2 years and median disease-specific survival 12·3 years. In multivariable analysis, age 61-74 years (hazard ratio (HR) 3·78, 95 per cent confidence interval 1·86 to 7·68), age 75 years or more (HR 3·96, 1·79 to 8·74), distant metastases (HR 14·44, 1·59 to 131·36) and incomplete tumour resection (HR 2·71, 1·11 to 6·61) were associated with worse disease-specific survival. Later time period of diagnosis (HR 0·45, 0·24 to 0·84) was associated with better disease-specific survival.

CONCLUSION

Age, disease stage and complete resection were identified as independent prognostic factors for survival in patients with small bowel carcinoid tumours. The importance of achieving R0 resection is therefore emphasized.

Expression of connective tissue growth factor and IGF1 in normal and neoplastic gastrointestinal neuroendocrine cells and their clinico-pathological significance

Connective tissue growth factor (CTGF) and IGF1 are both expressed in a variety of tumours and are involved in tumourigenesis. However, information about their expression in the gastrointestinal (GI) neuroendocrine (NE) cells and tumours is mainly limited, with the exception of midgut carcinoids where abundant CTGF expression has been demonstrated. Normal mucosa specimens from stomach and ileum, as well as tumour tissue specimens from gastric NE tumours (GNETs; n=58) and midgut NETs (n=38) were included. Immunohistochemical techniques were used to investigate the possible expression of CTGF and IGF1 in GI NE cells and tumours. The latter results were correlated with various clinico-biochemical and histopathological variables. CTGF was expressed in a proportion of NE cells of the normal GI mucosa but not in enterochromaffin-like (ECL) cells, whereas IGF1 was undetectable. CTGF was absent in the foci of ECL cell hyperplasia, and in most of the poorly differentiated carcinomas, but present in some GNETs (mainly in type III ECL cell carcinoids (ECL-CCs)) and in all but one midgut NETs. CTGF correlated with tumour stage in well-differentiated GNETs and with size larger than 1  cm but only in the subgroup of type I ECL-CCs. IGF1 was detected in the foci of ECL cell hyperplasia and in all GI NETs. These findings suggest that both CTGF and IGF1 may be involved in the neoplastic transformation of GI NE cells, whereas IGF1 may play an important role even at early stage.

Cocaine- and amphetamine-regulated transcript in neuroendocrine tumors

BACKGROUND/AIMS

Cocaine- and amphetamine-regulated transcript (CART) is an anorexigenic regulatory peptide highly expressed in the brain's appetite control centers, but also in peripheral neurons and in endocrine cells in the adrenal medulla, thyroid, pancreatic islets, and in the gastrointestinal tract. Plasma levels of CART were recently shown to be elevated in patients with neuroendocrine tumors (NETs), but the cellular sources of CART in NETs have remained unknown. The aim of the study was to establish whether CART is expressed in various types of NETs and, if so, to examine the frequency, distribution and phenotype of CART-expressing cells.

METHODS

Tumor specimens from 133 NETs originating in the stomach, ileum, rectum, pancreas and thyroid were examined with immunohistochemistry and in situ hybridization. The expression of CART was quantified and the CART-expressing cells were phenotyped by double staining for established markers and hormones.

RESULTS

CART-expressing tumor cells were found in the majority of the examined NETs. The expression pattern of CART was highly heterogeneous not only between tumors, but also within individual tumors. In 14% of the NETs, CART was found in a major population of the tumor cells.

CONCLUSION

CART is produced in the majority of NETs, regardless of tumor origin. This likely explains the elevated levels of circulating CART in certain NETs patients, as recently described. CART could therefore prove to be a useful tool in the diagnostics of NETs not only in blood samples, but also in histopathological specimens.

Obestatin/ghrelin cells in normal mucosa and endocrine tumours of the stomach

OBJECTIVE

Obestatin and ghrelin are derived from the same gene and co-expressed in the same endocrine cells. Vesicular monoamine transporter-2 (VMAT-2), a marker for enterochromaffin-like (ECL) cells, is considered to be expressed in ghrelin cells. The aim was to establish if the two peptides and the transporter are co-expressed, both in normal gastric mucosa and in gastric endocrine tumours.

DESIGN

An immunohistochemical study was performed on gastric biopsy material and on surgical specimens from 63 patients with gastric endocrine tumours and from individuals with normal gastric mucosa. Cells displaying obestatin immunoreactivity were examined regarding co-localization with ghrelin and VMAT-2. Both single- and double-immunostaining techniques were applied. Obestatin concentration in blood was measured in a subgroup of these patients. The results were correlated to various clinico-pathological parameters.

RESULTS

In the normal mucosa, obestatin/ghrelin-immunoreactive cells rarely co-expressed VMAT-2. In most tumour tissue specimens, only a fraction of neoplastic cells displayed immunoreactivity to obestatin, and these cells always co-expressed ghrelin. Neoplastic obestatin-/ghrelin-IR cells invariably expressed VMAT-2, except for two ghrelinomas. The obestatin concentrations in blood were consistently low and did not correlate to clinico-pathological data.

CONCLUSIONS

Obestatin and ghrelin immunoreactivity always occurred in the same endocrine cells in the gastric mucosa but these cells only occasionally co-expressed VMAT-2, opposite to the findings in tumours. These results indicate that endocrine cells expressing obestatin and ghrelin mainly differ from VMAT-2 expressing cells (ECL-cells) and can develop into pure ghrelinomas. Plasma concentrations of obestatin did not correlate to cellular expression.

Neuroendocrine cells in pancreatic duct adenocarcinoma: an immunohistochemical study

Pancreatic ductal adenocarcinomas can display disseminated neuroendocrine (NE) cells. Controversies exist as to their relative incidence, histogenesis, hormone production, and the prognostic implications of their presence. These issues were elucidated by means of a broad immunohistochemical (IHC) investigation of the resected specimens from 47 patients. Chromogranin A (CgA) was chosen as the major NE marker. In addition, the sensitivity of the conventional IHC procedure was increased by means of the TSA (Tyramide Signal Amplification) technique. In tumours with CgA immunoreactive (IR) cells, detected by the conventional or the TSA methods, these NE cells were further IHC analyzed, using antisera raised against a broad spectrum of neurohormonal peptides, serotonin, and IGF-1. The IHC observations were correlated with clinical and histopathological data, the nuclear IR for the Ki67 antigen (proliferation) of the neoplastic cells, and their IR against the p53 protein. Distinct CgA IR cells were found in 5 out of 47 (11%) tumours when studied by the conventional method, and in 9 out of 47 (19%) when examined by the TSA technique. Corresponding figures, if tumours with only questionable IR against CgA were also included, were 14 (30%) and 23 (50%), respectively. Out of the 9 cases with unequivocal CgA IR, only 3 displayed an IR to an additional hormone or growth factor; this hormone turned out to be somatostatin (only minimal foci). Insulin and glucagon cells also appeared exceptionally. The NE differentiation was found to be unrelated to proliferation, p53 protein expression, and to the survival of the patients. It occurred mainly (7 out of 9) in poorly differentiated adenocarcinomas. Thus, the plain NE immunoprofile of the CgA IR cells, together with the increased IR observed when the TSA technique was used, indicates that the NE cells in these adenocarcinomas are only poorly differentiated. When the CgA IR cells exceptionally become highly differentiated, they can express islet hormones. Using strict structural and IHC criteria, a NE differentiation occurs in less than 20 % of cases; its clinico-pathological significance seems to be non relevant.

Guidelines for the management of gastroenteropancreatic neuroendocrine tumours (including bronchopulmonary and thymic neoplasms). Part II-specific NE tumour types

Part II of the guidelines contains a description of epidemiology, histopathology, clinical presentation, diagnostic procedure, treatment, and survival for each type of neuroendocrine tumour. We are not only including gastroenteropancreatic tumours but also bronchopulmonary and thymic neuroendocrine tumours. These guidelines essentially cover basic knowledge in the diagnosis and management of the different forms of neuroendocrine tumour. We have, however, tried to give more updated information about the epidemiology and histopathology, which is essential for the clinical management of these tumours.

Guidelines for the management of gastroenteropancreatic neuroendocrine tumours (including bronchopulmonary and thymic neoplasms). Part I-general overview

The incidence of neuroendocrine tumours of the gastroenteropancreatic system seems to have increased during the past decade. New diagnostic and therapeutic procedures have aroused the interest of physicians, though most see very few cases of such diseases. A group of members of the Nordic Neuroendocrine Tumour Group decided to compile some guidelines to facilitate the diagnosis and treatment of patients with these tumours. Part I of these guidelines discusses the principles of histopathology, biochemical and radiological diagnosis as well as therapeutic options.

Treatment of ECL cell carcinoids with octreotide LAR

BACKGROUND

Patients with chronic atrophic gastritis (CAG) and hypergastrinaemia are at risk of developing hyperplasia of the enterochromaffin-like (ECL) cells and ECL-cell-derived tumours. The effect of the somatostatin analogue octreotide on ECL cell carcinoids is examined.

METHODS

Five patients with hypergastrinaemia and ECL cell carcinoids were enrolled in a 1-year study of octreotide LAR (long-acting release) 20 mg given at monthly intervals. Biopsies from tumours and from flat oxyntic mucosa were done at the start and 3, 6 and 12 months thereafter. Sections were stained with haematoxylin-erythrosin, immunostained with chromogranin A (CgA) and doublestained with CgA and Ki-67. Serum gastrin and CgA were measured.

RESULTS

The number of visible tumours was reduced by more than 50 %. Sections from both tumours and flat mucosa showed a reduced number of CgA immunoreactive cells. Mean serum gastrin decreased from 421 to 186 pM (normal <40 pM); P > 0.05, and serum CgA from 73 to 25 ng/ml (normal < 30 ng/ml); P < 0.001.

CONCLUSIONS

During treatment the patients were still markedly hypergastrinaemic, whereas the serum CgA showed normalization. A diminished tumour load and reduced ECL cell density were found, indicating an antiproliferative effect of octreotide directly on the ECL cells.

Guidelines for the management of gastroenteropancreatic neuroendocrine tumours (including bronchopulmonary and thymic neoplasms). Part I-general overview

The incidence of neuroendocrine tumours of the gastroenteropancreatic system seems to have increased during the past decade. New diagnostic and therapeutic procedures have aroused the interest of physicians, though most see very few cases of such diseases. A group of members of the Nordic Neuroendocrine Tumour Group decided to compile some guidelines to facilitate the diagnosis and treatment of patients with these tumours. Part I of these guidelines discusses the principles of histopathology, biochemical and radiological diagnosis as well as therapeutic options.