Measurements of chromogranin A, chromogranin B (secretogranin I), chromogranin C (secretogranin II) and pancreastatin in plasma and urine from patients with carcinoid tumours and endocrine pancreatic tumours

Ghrelin and obestatin in human neuroendocrine tumors: expression and effect on obestatin levels after food intake

BACKGROUND

Ghrelin and obestatin are derived from the same peptide hormone precursor and are mainly produced by the gastric mucosa. Ghrelin is involved in many biological processes, whereas the physiological function of obestatin needs further investigation. The aims of the present study were to establish the incidence of ghrelin- and obestatin-immunoreactive cells in a comprehensive panel of human neuroendocrine tumors (NETs) and to investigate if blood obestatin concentrations are influenced during a standardized meal stimulation test in healthy individuals and patients with NETs.

MATERIALS AND METHODS

The expression of ghrelin and obestatin was investigated in NETs (n = 149) and other endocrine-related disorders (n = 3) using immunohistochemistry with specific polyclonal antibodies. Coexpression of the peptides was evaluated by double immunofluorescence. Concentrations of obestatin in blood were measured during a meal test in 6 healthy individuals and 5 patients with pancreatic NETs.

RESULTS

Ghrelin and obestatin were expressed in 14/152 and 19/152 tumor tissues, respectively, mainly representing NETs of foregut origin and in pancreatic tissue from a nesidioblastosis patient. Double immunofluorescence staining showed colocalization of the peptides. During the meal test, obestatin levels in blood were unchanged in all patients but decreased significantly in the healthy individuals.

CONCLUSION

Only a minority of NETs express ghrelin and obestatin. However, analysis of patients with tumors originating from tissues that express the peptides in normal conditions could be of importance. The results from the meal test indicate that the hormone levels are affected by food intake in healthy individuals, whereas obestatin levels remained unchanged in pancreatic NET patients.

Altered levels of fecal chromogranins and secretogranins in IBS: relevance for pathophysiology and symptoms?

OBJECTIVES

Chromogranins (Cg) and secretogranins (Sg) are proteins ubiquitous in secretory cells of the enteric, endocrine, and immune systems, and may reflect activity of these systems. We therefore performed a hypothesis generating study to evaluate the association between fecal levels of CgA, CgB, SgII, and SgIII, with the clinical and pathophysiological phenotype of irritable bowel syndrome (IBS) patients.

METHODS

Analyses of CgA, CgB, SgII, SgIII, and calprotectin in fecal samples of 82 IBS patients and 29 healthy controls were performed. All IBS subjects completed validated questionnaires to assess gastrointestinal and psychological symptom severity, and underwent rectal barostat test and colonic transit time measurement.

RESULTS

IBS patients demonstrated higher levels of fecal CgA (P=0.009), SgII (P<0.001), and SgIII (P<0.001), but lower levels of CgB (P<0.001) compared with controls. SgII had good discriminative validity to positively identify IBS patients, with an area under the receiver operating characteristics (ROC) curve (AUROC) of 0.86 (95% confidence interval (CI): 0.78-0.94). SgIII and CgB both had fairly good discriminative validity to positively identify IBS patients, with an AUROC of 0.79 (95% CI: 0.71-0.87) and 0.78 (95% CI: 0.69-0.87), respectively. There were negative correlations between the colonic transit time and fecal levels of CgA (r=-0.53, P<0.001), SgII (r=-0.55, P<0.001), and SgIII (r=-0.28, P=0.03). Perceived abdominal pain was moderately associated with levels of CgA (r=0.32, P=0.004), SgII (r=0.31, P=0.006), and SgIII (r=0.24, P=0.04). Calprotectin levels were not associated with the levels of granins or with the clinical or pathophysiological phenotype of IBS patients.

CONCLUSIONS

Fecal levels of Cg and Sg may be related to the underlying pathophysiology of IBS and of potential importance for symptoms of the patients. Granins also show promise to serve as future biomarkers of IBS. Further studies are needed to explore the potential role of granins in IBS patients.

Ghrelin in neuroendocrine tumors

Ghrelin is a 28 amino acid peptide, primarily produced by the oxyntic mucosa X/A like neuroendocrine cells in the stomach. It is also found in the small intestine, hypothalamus, pituitary gland, pancreas, heart, adipose tissue, and immune system. In gastrointestinal neuroendocrine tumors (NETs) ghrelin release has been well documented. Ghrelin is a brain-gut circuit peptide with an important role in the physiological regulation of appetite, response to hunger and starvation, metabolic and endocrine functions as energy expenditure, gastric motility and acid secretion, insulin secretion and glucose homeostasis, as well as in the potential connection to the central nervous system. Recently, there has been a significant interest in the biological effects of ghrelin in NETs. In this article, we present a comprehensive review of ghrelin's expression and a brief summary of ghrelin's physiological role in NETs patients with carcinoids, type A chronic atrophic gastritis (CAG), with or without MEN-1, and with and without liver metastases. We hope, with the research reviewed here, to offer compelling evidence of the potential significance of ghrelin in NETs, as well as to provide a useful guide to the future work in this area.

Role of (68)Ga-DOTATOC PET-CT in the diagnosis and staging of pancreatic neuroendocrine tumours

OBJECTIVE

The objective of the present study was to evaluate the role of (68)Ga-DOTA(0)-Phe(1)-Tyr(3)-octreotide ((68)Ga-DOTATOC) positron emission tomography computed tomography (PET-CT) for detection and staging of pancreatic neuroendocrine tumours (NETs).

METHODS

Twenty patients with clinically suspected and/or histopathologically proven pancreatic NET underwent (68)Ga-DOTATOC PET-CT imaging for staging and /or localisation of primary lesion. They also underwent contrast enhanced CT (CECT) and 8 patients underwent (18)F-FDG PET-CT. SUVmax of primary and metastatic lesions were measured. Results were verified with histopathology for primary tumour and with clinical follow up/MRI and /or biopsy for metastatic disease. Results of (68)Ga-DOTATOC PET-CT were compared to CECT and (18)F-FDG PET-CT.

RESULTS

(68)Ga-DOTATOC PET-CT correctly localised primary in all 20, CECT in 15 and (18)F-FDG PET-CT in 2 patients. (68)Ga-DOTATOC PET-CT demonstrated metastases in 13 patients, CECT in 7 and (18)F-FDG PET-CT in 2. (68)Ga-DOTATOC PET-CT emerged as the best investigation with 100% sensitivity and PPV for detecting primary tumour and metastatic disease. The detection rate of CECT was lower than (68)Ga-DOTATOC PET-CT, both for primary tumour (20vs.15) or metastatic disease (13vs.7). (18)F-FDG PET-CT performed poorly for primary and metastasis.

CONCLUSION

Ga-DOTATOC PET-CT is a very useful imaging investigation for diagnosing and staging pancreatic NET.

The archaic distinction between functioning and nonfunctioning neuroendocrine neoplasms is no longer clinically relevant

BACKGROUND

Neuroendocrine neoplasms (NENs) are increasing in incidence and prevalence. This reflects greater clinical awareness, effective imaging, and increasing pathological diagnostic recognition. Although the identification and treatment of clinical neuroendocrine syndromes are established, there is confusion when a NEN has no discernible clinical symptoms.

DISCUSSION

Nonfunctional tumors are usually diagnosed incidentally and at a later stage largely because either they do not secrete a bioactive product or do so, but in a form that is either inactive or in quantities that have no discernible effect. Nevertheless, the histopathology is indistinguishable from functional NENs, and tumors exhibit somatostatin receptor expression, and positive immunohistochemistry for neuroendocrine cell markers (CgA, NSE/synaptophysin). Similarly, their rates of growth and metastatic behavior are, like other NENs, predictably based on staging and grading (mitotic rate and Ki67 expression). Both types are diagnosed biochemically (CgA) and by imaging in an identical fashion with computed tomography, magnetic resonance imaging, somatostatin receptor scintigraphy, and endoscopic ultrasound. NENs, irrespective of function or bioactive secretory profile, respond with equal efficacy to the same regimen of surgery or antitumor drugs (e.g., somatostatin analogs with or without tyrosine kinase inhibitors/antiangiogenics or cytotoxics) depending on grade. Given the efficacy of somatostatin analogs in increasing progression free survival, nonfunctional NENs should be managed identically to symptomatic NENs. The consideration of NENs as functional or nonfunctional is an archaic clinical concept that should be discarded since the tumors are indistinguishable at a cellular, biological, and morphological level. All current evidences indicate that their diagnosis and treatment should follow the same common principles.

The clinical relevance of chromogranin A as a biomarker for gastroenteropancreatic neuroendocrine tumors

Chromogranin A, although it exhibits limitations, is currently the most useful general tumor biomarker available for use in the diagnosis and management of gastroenteropancreatic neuroendocrine tumors (NETs). The value of the chromogranin A lies in its universal cosecretion by the majority of neuroendocrine cells that persists after malignant transformation. Clinicians aware of the physiologic role of chromogranin A and its secretion in a variety of non-NET-related pathologic conditions can use this protein as a moderately effective tumor biomarker in the management of GEP-NETs.

Pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors (PNETs) are rare neoplasms representing <5% of all pancreatic malignancies with an estimated incidence of 1-1.5 cases/100,000. PNETs are broadly classified as either functional or nonfunctional. Functional PNETs include insulinomas, gastrinomas, vasoactive intestinal peptideomas, glucagonomas, and somatostatinomas. The clinical manifestations associated with these tumors are the result of excessive hormonal secretion and action. The functional nature of these tumors makes pancreatic hormone testing critical not only for initial diagnosis but also for follow-up, because they are important tumor markers. Nonfunctional PNETs typically remain clinically silent until a substantial mass effect occurs. Although the majority of PNETs occur sporadically, it is important to recognize that these tumors may be associated with a variety of familial syndromes and in many cases genetic testing of PNET patients is warranted. This article familiarizes the reader with the clinical presentation and the biochemical, radiologic, and genetic testing indicated for diagnosis and follow-up of patients with PNET.

Immunohistochemical and biochemical studies with region-specific antibodies to chromogranins A and B and secretogranins II and III in neuroendocrine tumors

This short review deals with our investigations in neuroendocrine tumors (NETs) with antibodies against defined epitopes of chromogranins (Cgs) A and B and secretogranins (Sgs) II and III. The immunohistochemical expression of different epitopes of the granin family of proteins varies in NE cells in normal human endocrine and non-endocrine organs and in NETs, suggesting post-translational processing. In most NETs one or more epitopes of the granins were lacking, but variations in the expression pattern occurred both in benign and malignant NETs. A few epitopes displayed patterns that may be valuable in differentiating between benign and malignant NET types, e.g., well-differentiated NET types expressed more CgA epitopes than the poorly differentiated ones and C-terminal secretoneurin visualized a cell type related to malignancy in pheochromocytomas. Plasma concentrations of different epitopes of CgA and CgB varied. In patients suffering from carcinoid tumors or endocrine pancreatic tumors the highest concentrations were found with epitopes from the mid-portion of CgA. For CgB the highest plasma concentrations were recorded for the epitope 439-451. Measurements of SgII showed that patients with endocrine pancreatic tumors had higher concentrations than patients with carcinoid tumors or pheochromocytomas. SgIII was not detectable in patients with NETs.

[177Lu-DOTA 0-Tyr 3]-octreotate treatment in patients with disseminated gastroenteropancreatic neuroendocrine tumors: the value of measuring absorbed dose to the kidney

BACKGROUND

Peptide receptor radiation therapy (PRRT) using [(177)Lu-DOTA(0)-Tyr(3)]-octreotate is a new, promising option for treatment of disseminated gastroenteropancreatic neuroendocrine tumors (GEPNETs).

METHODS

During 2006-2008, 26 patients with disseminated GEPNETs were treated with (177)Lu-octreotate. Radiologic response (RECIST), biochemical response [plasma chromogranin-A (P-CgA)], hematologic toxicity [Common Toxicity Criteria (CTC)], absorbed dose to the kidneys (conjugate view method), and glomerular filtration rate (GFR) were analyzed.

RESULTS

(177)Lu-octreotate (8 GBq) was given one to five times (median = 3) with a 6-week interval between each. Sixteen of the 26 patients were evaluated radiologically; 6 (38%) had partial response (PR), 8 (50%) had stable disease (SD), and 2 (13%) had progressive disease (PD). Seventeen of the 26 patients were evaluated biochemically; 6 (35%) showed a >or=30% decrease, 8 (47%) showed a >or=20% increase, and 3 (18%) showed neither a >or=30% decrease nor a >or=20% increase. The mean absorbed dose to the kidneys was 24 Gy. With a dose limit of 27 Gy to the kidneys, 10 patients did not receive the planned four treatments, while four patients had the potential to receive additional treatment. A significant reduction (p = 0.0013) of GFR was observed at follow-up. Three patients experienced CTC grade 3 hematologic toxicity.

CONCLUSIONS

By using the absorbed dose to the kidneys as a limiting factor, treatment with (177)Lu-octreotate can be individualized, e.g., overtreatment can be avoided and patients with the potential to receive additional treatment can be identified. Further studies are needed to define tolerance doses to the kidneys so that treatment can be optimized.

Chromogranin A--biological function and clinical utility in neuro endocrine tumor disease

BACKGROUND

Neuroendocrine tumors (NETs) are a form of cancer that differ from other neoplasia in that they synthesize, store, and secrete peptides, e.g., chromogranin A (CgA) and amines. A critical issue is late diagnosis due to failure to identify symptoms or to establish the biochemical diagnosis. We review here the utility of CgA measurement in NETs and describe its biological role and the clinical value of its measurement.

METHODS

Literature review and analysis of the utility of plasma/serum CgA measurements in NETs and other diseases.

RESULTS

CgA is a member of the chromogranin family; its transcription and peptide processing are well characterized, but its precise function remains unknown. Levels are detectable in the circulation but vary substantially (approximately 25%) depending on which assay is used. Serum and plasma measurements are concordant. CgA is elevated in approximately 90% of gut NETs and correlates with tumor burden and recurrence. Highest values are noted in ileal NETs and gastrointestinal NETs associated with multiple endocrine neoplasia type 1. Both functioning and nonfunctioning pancreatic NETs have elevated values. CgA is more frequently elevated in well-differentiated tumors compared to poorly differentiated NETs. Effective treatment is often associated with decrease in CgA levels. Proton pump inhibitors falsely increase CgA, but levels normalize with therapy cessation.

CONCLUSIONS

CgA is currently the best available biomarker for the diagnosis of NETs. It is critical to establish diagnosis and has some utility in predicting disease recurrence, outcome, and efficacy of therapy. Measurement of plasma CgA is mandatory for the effective diagnosis and management of NET disease.

Gastrointestinal neuroendocrine (carcinoid) tumours: current diagnosis and management

Neuroendocrine tumours (NETs) are increasing in both incidence and prevalence and, as a group, are more prevalent than either gastric, pancreatic, oesophageal or hepatobiliary adenocarcinomas, or any two of these cancers combined. Clinical awareness of the protean and intermittent symptoms of NETs (eg, sweating, flushing, diarrhoea, and bronchospasm) is critical for timely diagnosis; however, the classical carcinoid syndrome is relatively uncommon. The most useful diagnostic test for gastrointestinal NETs is measurement of plasma chromogranin A (CgA) levels. Disease extent is assessed by both anatomical imaging, and nuclear imaging with radiolabelled somatostatin analogues. Pathological evaluation comprises tumour-node-metastasis classification, a minimum pathological dataset, CgA and synaptophysin immunostaining, as well as mitotic count or Ki-67 index (a marker of cell proliferation) to define grading. Resection of the primary lesion and as much metastatic disease as possible increases the efficacy of medical therapy. Other management strategies include hepatic embolisation and peptide receptor radionuclide therapy. Patients with tumours expressing somatostatin receptors should be treated with somatostatin analogues. Depending on the tumour grade, other effective agents include cytotoxics, tyrosine kinase inhibitors, and antiangiogenics. The overarching requirement for best management of patients with NETs is to ensure that they have ready access to experienced multidisciplinary clinician groups located within centres of appropriate subspecialty expertise.

Granins and their derived peptides in normal and tumoral chromaffin tissue: Implications for the diagnosis and prognosis of pheochromocytoma

Pheochromocytomas are rare catecholamine-secreting tumors that arise from chromaffin tissue within the adrenal medulla and extra-adrenal sites. Typical clinical manifestations are sustained or paroxysmal hypertension, severe headaches, palpitations and sweating resulting from hormone excess. However, their presentation is highly variable and can mimic many other diseases. The diagnosis of pheochromocytomas depends mainly upon the demonstration of catecholamine excess by 24-h urinary catecholamines and metanephrines or plasma metanephrines. Occurrence of malignant pheochromocytomas can only be asserted by imaging of metastatic lesions, which are associated with a poor survival rate. The characterization of tissue, circulating or genetic markers is therefore crucial for the management of these tumors. Proteins of the granin family and their derived peptides are present in dense-core secretory vesicles and secreted into the bloodstream, making them useful markers for the identification of neuroendocrine cells and neoplasms. In this context, we will focus here on reviewing the distribution and characterization of granins and their processing products in normal and tumoral chromaffin cells, and their clinical usefulness for the diagnosis and prognosis of pheochromocytomas. It appears that, except SgIII, all members of the granin family i.e. CgA, CgB, SgII, SgIV-SgVII and proSAAS, and most of their derived peptides are present in adrenomedullary chromaffin cells and in pheochromocytes. Moreover, besides the routinely used CgA test assays, other assays have been developed to measure concentrations of tissue and/or circulating granins or their derived peptides in order to detect the occurrence of pheochromocytomas. In most cases, elevated levels of these entities were found, in correlation with tumor occurrence, while rarely discriminating between benign and malignant neoplasms. Nevertheless, measurement of the levels of granins and derived peptides improves the diagnostic sensitivity and may therefore provide a complementary tool for the management of pheochromocytomas. However, the existing data need to be substantiated in larger groups of patients, particularly in the case of malignant disease.

Chromogranin B in heart failure: a putative cardiac biomarker expressed in the failing myocardium

BACKGROUND

Chromogranin B (CgB) is a member of the granin protein family. Because CgB is often colocalized with chromogranin A (CgA), a recently discovered cardiac biomarker, we hypothesized that CgB is regulated during heart failure (HF) development.

METHODS AND RESULTS

CgB regulation was investigated in patients with chronic HF and in a post-myocardial infarction HF mouse model. Animals were phenotypically characterized by echocardiography and euthanized 1 week after myocardial infarction. CgB mRNA levels were 5.2-fold increased in the noninfarcted part of the left ventricle of HF animals compared with sham-operated animals (P<0.001). CgB mRNA level in HF animals correlated closely with animal lung weight (r=0.74, P=0.04) but not with CgA mRNA levels (r=0.20, P=0.61). CgB protein levels were markedly increased in both the noninfarcted (110%) and the infarcted part of the left ventricle (70%) but unaltered in other tissues investigated. Myocardial CgB immunoreactivity was confined to cardiomyocytes. Norepinephrine, angiotensin II, and transforming growth factor-beta increased CgB gene expression in cardiomyocytes. Circulating CgB levels were increased in HF animals (median levels in HF animals versus sham, 1.23 [interquartile range, 1.03 to 1.93] versus 0.98 [0.90 to 1.04] nmol/L; P=0.003) and in HF patients (HF patients versus control, 1.66 [1.48 to 1.85] versus 1.47 [1.39 to 1.58] nmol/L; P=0.007), with levels increasing in proportion to New York Heart Association functional class (P=0.03 for trend). Circulating CgB levels were only modestly correlated with CgA (r=0.31, P=0.009) and B-type natriuretic peptide levels (r=0.27, P=0.014).

CONCLUSIONS

CgB production is increased and regulated in proportion to disease severity in the left ventricle and circulation during HF development.

Chromogranins A and B and secretogranin II as prohormones for regulatory peptides from the diffuse neuroendocrine system

Chromogranin A (CgA), chromogranin B (CgB), and secretogranin II (SgII) belong to a family of uniquely acidic secretory proteins in elements of the diffuse neuroendocrine system. These "granins" are characterized by numerous pairs of basic amino acids as potential sites for intra- and extragranular processing. In response to adequate stimuli, the granins are coreleased with neurotransmitters and hormones and appear in the circulation as potential modulators of homeostatic processes. This review is directed towards functional aspects of the secreted CgA, CgB, and SgII and their biologically active sequences. Widely different effects and targets have been reported for granin-derived peptides. So far, the CgA peptides vasostatin-I, pancreastatin, and catestatin, the CgB peptides CgB(1-41) and secretolytin, and the SgII peptide secretoneurin are the most likely candidates for granin-derived regulatory peptides. Most of their effects fit into patterns of direct or indirect modulations of major functions, in particular associated with inflammatory conditions.

Granin-derived peptides as diagnostic and prognostic markers for endocrine tumors

Chromogranin A-like immunoreactivity (CgA-LI) has been, and remains, the most widely used diagnostic and prognostic marker for endocrine tumors. The availability of assay kits combined with moderately high sensitivity and specificity has meant that there has been no great incentive to develop alternative markers. However, circulating concentrations of CgA-LI are elevated in several non-neoplastic diseases and in patients receiving acid-suppression therapy which may lead to false positive diagnosis. Additionally, certain endocrine tumors, such as rectal carcinoids, do not express the CgA gene so that there is a need for additional markers to complement CgA measurements. Plasma concentrations of the CgA-derived peptide, pancreastatin, measured with antisera of defined regional specificity, have a prognostic value in patients with metastatic midgut carcinoid tumors receiving somatostatin analog therapy or hepatic artery chemoembolization. Other CgA-derived peptides with potential as tumor markers are vasostatin-1, WE-14, catestatin, GE-25, and EL-35 but their value has yet to be fully assessed. Circulating concentrations of chromogranin B-like immunoreactivity (CgB-LI) are not elevated in non-neoplastic diseases and measurements of CCB, the COOH-terminal fragment of CgB, may be useful as a biochemical marker for neuroendocrine differentiation in lung tumors. Antisera to the secretogranin II-derived peptide, secretoneurin detects carcinoid tumors of the appendix with greater frequency than antisera to CgA and are of value in identifying therapy-resistant carcinoma of the prostate (clinical stage D3). Measurement of concentrations of a second secretogranin II-derived peptide, EM-66 in tumor tissue has been used to differentiate between benign and malignant pheochromocytoma. These examples point to a limited although potentially valuable role for granin-derived peptides as tumor markers.

Cytoskeleton mediates negative inotropism and lusitropism of chromogranin A-derived peptides (human vasostatin1-78 and rat CgA₁₋₆₄) in the rat heart

Cytoskeleton scaffold in cardiac myocytes provides structural support and compartmentalization of intracellular components. It is implicated in cardiac pathologies including hypertrophy and failure, playing a key role in the determinism of contractile and diastolic dysfunctions. Chromogranin A (CgA) and its derived peptides have revealed themselves as novel cardiovascular modulators. In humans, normal CgA levels considerably increase in several pathologies, including heart failure. Recent data have shown on the unstimulated rat heart that human recombinant Vasostatin-1 (hrVS-1) and rat chromogranin A 1-64 (rCgA₁₋₆₄) induce negative inotropic and lusitropic effects counteracting the β-adrenergic-dependent positive inotropism with a functional non-competitive antagonism. This study investigates, on the isolated Langendorff perfused rat heart, whether cardiac cytoskeleton is involved in the modulation of contractility and relaxation exerted by hrVS-1 and rCgA₁₋₆₄. Cytoskeleton impairment by either cytochalasin-D (actin polymerization inhibitor), BDM (myosin ATP-ase antagonist) or wortmannin (inhibitor of PI3-K/Akt transduction cascade), or W-7 (calcium-calmodulin antagonist) abolished hrVS-1 and rCgA₁₋₆₄-mediated inotropism and lusitropism. Using fluorescent phalloidin, we showed on rat cardiac H9C2 cells that hrVS-1 (10 nM÷10 µM) stimulates actin polymerization. Taken together these data indicate that in the rat heart, the actin cytoskeletal network strongly contributes to the cardiotropic action of CgA-derived peptides.

New insights into granin-derived peptides: evolution and endocrine roles

The granin protein family is composed of two chromogranin and five secretogranin members that are acidic, heat-stable proteins in secretory granules in cells of the nervous and endocrine systems. We report that there is little evidence for evolutionary relationships among the granins except for the chromogranin group. The main granin members, including chromogranin A and B, and secretogranin II are moderately conserved in the vertebrates. Several small bioactive peptides can be generated by proteolysis from those homologous domains existing within the granin precursors, reflecting the conservation of biological activities in different vertebrates. In this context, we focus on reviewing the distribution and function of the major granin-derived peptides, including vasostatin, bovine CgB(1-41) and secretoneurin in vertebrate endocrine systems, especially those associated with growth, glucose metabolism and reproduction.

Chromogranin A regulates renal function by triggering Weibel-Palade body exocytosis

Chromogranin A (CHGA), a protein released from secretory granules of chromaffin cells and sympathetic nerves, triggers endothelin-1 release from endothelial cells. CHGA polymorphisms associate with an increased risk for ESRD, but whether altered CHGA-endothelium interactions may explain this association is unknown. Here, CHGA led to the release of endothelin-1 and Weibel-Palade body exocytosis in cultured human umbilical vein endothelial cells. In addition, CHGA triggered secretion of endothelin-1 from glomerular endothelial cells and TGF-beta1 from mesangial cells cocultured with glomerular endothelial cells. In humans, plasma CHGA correlated positively with endothelin-1 and negatively with GFR. GFR was highly heritable in twin pairs, and common promoter haplotypes of CHGA predicted GFR. In patients with progressive hypertensive renal disease, a CHGA haplotype predicted rate of GFR decline. In conclusion, these data suggest that CHGA acts through the glomerular endothelium to regulate renal function.

Cloning and expression analysis of a murine novel gene, Ayu17-449

We used gene trapping vector PU8 to search some interesting genes which play important roles in mouse development from murine ES cells. One positive ES colony termed Ayu17-449 was trapped. Its partial cDNA was obtained by using 5' RACE method. It is homologous to a 5,523 bp cDNA fragment (GI: 20879412) in EST database. Further analysis of the 5,523 bp cDNA sequence in Celera mouse gene database showed that it overlaps two genes. We designed serials of DNA primers according to the mRNAs of these two genes for RT-PCR and Northern blotting analysis, and identified a novel RNA about 9 kb (we named it as Ayu17-449) encoding 1,920 aa. This gene is expressed highly in the brain, kidney, heart, lung, muscle and stomach. The expressed protein contains a Granin motif on its N-terminus, showing that this gene may be involved in hormone secretion.

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.

Circulating markers for endocrine tumours of the gastroenteropancreatic tract

The diffuse endocrine system (DES) includes a wide range of secretory cells that may be the source of tumours. Gastroenteropancreatic endocrine (GEP) tumours arising within the DES secrete a variety of peptides and amines that are found in the circulation and are responsible for the syndromes associated with these tumours. In this review, the most common tumours of the GEP tract are outlined and the circulating products of these tumours identified. Where differential diagnosis is difficult these points are addressed. The peptides most commonly secreted by GEP neuroendocrine tumours are identified and described and their biological activities are discussed. Current methods available for measurement of these peptides are described. Attention is drawn towards molecular specificity where appropriate, as many pancreatic and gut peptides fall within families which show considerable homology, such as the tachykinin family or the glucagon family. Other peptides such as gastrin circulate in multiple molecular forms. This homology and diversity may cause difficulty in the interpretation of peptide measurements in the clinical situation if assays are not specific.

Principal component analysis, hierarchical clustering, and decision tree assessment of plasma mRNA and hormone levels as an early detection strategy for small intestinal neuroendocrine (carcinoid) tumors

Incidence of neuroendocrine tumors (NETs) is increasing (approximately 6%/year), but clinical presentation is nonspecific, resulting in delays in diagnosis (5-7 years; approximately 70% have metastases). This reflects absence of a sensitive plasma marker. The aim of this study is to investigate whether detection of circulating messenger RNA (mRNA) alone or in combination with circulating NET-related hormones and growth factors can detect gastrointestinal NET disease. The small intestinal (SI) NET cell line KRJ-I was used to define the sensitivity of real-time polymerase chain reaction (PCR) for mRNA detection in blood. NSE, Tph-1, and VMAT ( 2 ) transcripts were identified from one KRJ-I cell/ml blood. mRNA from the tissue and plasma of SI-NETs (n = 12) and gastric NETs (n = 7), and plasma from healthy controls (n = 9) was isolated and real-time PCR performed. Tph-1 was a specific marker of SI-NETs (58%, p < 0.03) whereas CgA transcripts did not differentiate tumors from controls. Patients with metastatic disease expressed more marker transcripts than localized tumors (75% versus 18%, p < 0.02). Plasma 5-hydroxytryptamine (5-HT), chromogranin A (CgA), ghrelin, and connective tissue growth factor (CTGF) fragments were measured, combined with mRNA levels, and a predictive mathematical model for NET diagnosis developed using decision trees. The sensitivity and specificity to diagnose SI-NETs and gastric NETs were 81.2% and 100%, and 71.4% and 55.6%, respectively. We conclude that mRNA from one NET cell/ml blood can be detected. Circulating plasma Tph-1 is a promising marker gene for SI-NET disease (specificity 100%) while an increased number of marker transcripts (>2) correlated with disease spread. Including NET-related circulating hormones and growth factors in the algorithm increased the sensitivity of detection of SI-NETs from 58 to 82%.

Naturally occurring human genetic variation in the 3'-untranslated region of the secretory protein chromogranin A is associated with autonomic blood pressure regulation and hypertension in a sex-dependent fashion

OBJECTIVES

We aimed to determine whether the common variation at the chromogranin A (CHGA) locus increases susceptibility to hypertension.

BACKGROUND

CHGA regulates catecholamine storage and release. Previously we systematically identified genetic variants across CHGA.

METHODS

We carried out dense genotyping across the CHGA locus in >1,000 individuals with the most extreme blood pressures (BPs) in the population, as well as twin pairs with autonomic phenotypes. We also characterized the function of a trait-associated 3'-untranslated region (3'-UTR) variant with transfected CHGA 3'-UTR/luciferase reporter plasmids.

RESULTS

CHGA was overexpressed in patients with hypertension, especially hypertensive men, and CHGA predicted catecholamines. In individuals with extreme BPs, CHGA genetic variants predicted BP, especially in men, with a peak association occurring in the 3'-UTR at C+87T, accounting for up to approximately 12/ approximately 9 mm Hg. The C+87T genotype predicted CHGA secretion in vivo, with the +87T allele (associated with lower BP) also diminishing plasma CHGA by approximately 10%. The C+87T 3'-UTR variant also predicted the BP response to environmental (cold) stress; the same allele (+87T) that diminished basal BP in the population also decreased the systolic BP response to stress by approximately 12 mm Hg, and the response was smaller in women (by approximately 6 mm Hg). In a chromaffin cell-transfected CHGA 3'-UTR/luciferase reporter plasmid, the +87T allele associated with lower BP also decreased reporter expression by approximately 30%. In cultured chromaffin cells, reducing endogenous CHGA expression by small interfering ribonucleic acid caused approximately two-thirds depletion of catecholamine storage vesicles.

CONCLUSIONS

Common variant C+87T in the CHGA 3'-UTR is a functional polymorphism causally associated with hypertension especially in men of the population, and we propose steps ("intermediate phenotypes") whereby in a sex-dependent fashion this genetic variant influences the ultimate disease trait. These observations suggest new molecular strategies to probe the pathophysiology, risk, and rational treatment of hypertension.

The antihypertensive chromogranin a peptide catestatin acts as a novel endocrine/paracrine modulator of cardiac inotropism and lusitropism

Circulating levels of catestatin (Cts; human chromogranin A352-372) decrease in the plasma of patients with essential hypertension. Genetic ablation of the chromogranin A (Chga) gene in mice increases blood pressure and pretreatment of Chga-null mice with Cts prevents blood pressure elevation, indicating a direct role of Cts in preventing hypertension. This notable vasoreactivity prompted us to test the direct cardiovascular effects and mechanisms of action of wild-type (WT) Cts and naturally occurring human variants (G364S-Cts and P370L-Cts) on myocardial and coronary functions. The direct cardiovascular actions of WT-Cts and human variants were determined using the Langendorff-perfused rat heart. WT-Cts dose-dependently increased heart rate and coronary pressure and decreased left ventricular pressure, rate pressure product and both positive and negative LVdP/dt. WT-Cts not only inhibited phospholamban phosphorylation, but also the inotropic and lusitropic effects of WT-Cts were abolished by chemical inhibition of beta2-adrenergic receptors, Gi/o protein, nitric oxide or cGMP, indicating involvement of beta2-adrenergic receptors-Gi/o protein-nitric oxide-cGMP signaling mechanisms. In contrast, G364S-Cts did not affect basal cardiac performance but abolished isoproterenol-induced positive inotropism and lusitropism. P370L-Cts decreased rate pressure product and inhibited only isoproterenol-induced positive inotropism and lusitropism by 70%. Cts also inhibited endothelin-1-induced positive inotropism and coronary constriction. Taken together, the cardioinhibitory influence exerted on basal mechanical performance and the counterregulatory action against beta-adrenergic and endothelin-1 stimulations point to Cts as a novel cardiac modulator, able to protect the heart against excessive sympathochromaffin overactivation, e.g. hypertensive cardiomyopathy.

The homologous rat chromogranin A1-64 (rCGA1-64) modulates myocardial and coronary function in rat heart to counteract adrenergic stimulation indirectly via endothelium-derived nitric oxide

Chromogranin A (CGA), produced by human and rat myocardium, generates several biologically active peptides processed at specific proteolytic cleavage sites. A highly conserved cleavage N-terminal site is the bond 64-65 that reproduces the native rat CGA sequence (rCGA1-64), corresponding to human N-terminal CGA-derived vasostatin-1. rCGA1-64 cardiotropic activity has been explored in rat cardiac preparations. In Langendorff perfused rat heart, rCGA1-64 (from 33 nM) induced negative inotropism and lusitropism as well as coronary dilation, counteracting isoproterenol (Iso) - and endothelin-1 (ET-1) -induced positive inotropic effects and ET-1-dependent coronary constriction. rCGA1-64 also depressed basal and Iso-induced contractility on rat papillary muscles, without affecting calcium transients on isolated ventricular cells. Structure-function analysis using three modified peptides on both rat heart and papillary muscles revealed the disulfide bridge requirement for the cardiotropic action. A decline in Iso intrinsic activity in the presence of the peptides indicates a noncompetitive antagonistic action. Experiments on rat isolated cardiomyocytes and bovine aortic endothelial cells indicate that the negative inotropism observed in rat papillary muscle is probably due to an endothelial phosphatidylinositol 3-kinase-dependent nitric oxide release, rather than to a direct action on cardiomyocytes. Taken together, our data strongly suggest that in the rat heart the homologous rCGA1-64 fragment exerts an autocrine/paracrine modulation of myocardial and coronary performance acting as stabilizer against intense excitatory stimuli.

Correlation of chromogranin A levels and somatostatin receptor scintigraphy findings in the evaluation of metastases in carcinoid tumors

OBJECTIVE

Chromogranin A (CgA) has been gaining acceptance as a helpful tumor marker in patients with neuroendocrine tumors, with respect to both diagnosis and prognosis. The objective of this study was to correlate serum CgA levels and somatostatin receptor scintigraphy (SRS) findings in the evaluation of metastases in carcinoid tumors.

MATERIALS AND METHODS

A total of 125 patients(61 men and 64 women, aged from 23 to 84 years) with histologically diagnosed carcinoid tumor underwent serum CgA assay and SRS for detecting metastasis or disease recurrence. The quantitative determination of CgA was performed in serum using an enzyme immunoassay with a cut-off value fixed at 39 U/l. Scintigraphies were performed with 200-220 MBq of In-111-DTPA-Phel-octreotide including whole-body images as well as single-photon emission computed tomography and computed tomography scans of the chest and abdomen.

RESULTS

The primary tumors originated from the gastrointestinal tract in 115 of 125 patients (92.0%), the lung in 7 of 125 patients (5.6%), the kidney in 2 of 125 patients (1.6%), and the breast in 1 of 125 patients (0.8%). The primary tumors originated from the foregut, midgut, and hindgut in 13.6%, 71.2%, and 12.8%, respectively. Correlation of SRS with other imaging modalities and clinical follow-up findings revealed a sensitivity, a specificity, and an accuracy of 82.9%, 97.7%, and 88.0%, respectively, and for CgA 62.2%, 83.7%, and 69.6%, respectively. There was 1 false-positive and 14 false-negative SRS results and 7 false-positive and 31 false-negative CgA analyses. SRS demonstrated higher sensitivity, specificity, and accuracy than CgA for the evaluation of metastatic carcinoid tumors. The concordance between SRS and CgA results was 67.2%. Discrepancies, such as positive SRS with normal CgA levels, were noted in 26 (20.8%) cases, whereas negative SRS with high CgA levels was seen in 15 (12.0%) cases. Combining the results of CgA and SRS increased the sensitivity (92.7%) but decreased the specificity (81.4%) of tumor detection.

CONCLUSIONS

In our study, SRS proved to be more sensitive, more specific, and more accurate than CgA for metastatic evaluation of carcinoid tumors. Positive SRS correlated with elevation of serum CgA levels. Serum CgA might have some diagnostic utility in patients with negative SRS studies. Nevertheless, both SRS and CgA should be considered useful tools in the evaluation of metastases in carcinoid patients.

Measurements of secretogranins II, III, V and proconvertases 1/3 and 2 in plasma from patients with neuroendocrine tumours

INTRODUCTION

Chromogranin (Cg) and secretogranin (Sg) are members of the granin family of proteins, which are expressed in neuroendocrine and nervous tissue. In recent publications we have presented generation of region-specific antibodies against CgA and CgB and also development of several region-specific radioimmunoassays for measurements of specific parts of the Cgs. In this study we describe generation of antibodies against SgII, SgIII, SgV and the proconvertases PC1/3 and PC2 and development of radioimmunoassays for measurements of these proteins.

MATERIALS AND METHODS

Peptides homologous to defined parts of the secretogranin and proconvertase molecules were selected and synthesised. Antibodies were raised, radioimmunoassays were developed and circulating levels of the proteins in plasma samples from 22 patients with neuroendocrine tumours were measured in the assays.

RESULTS

Increased plasma concentrations were recorded in 11, 4 and 3 of the patients with the SgII 154-165 (N-terminal secretoneurin), the SgII 172-186 (C-terminal Secretoneurin) and the SgII 225-242 assays respectively. The SgIII, SgV, PC1/3 and PC2 assays failed to detect increased concentrations in any of the patients.

CONCLUSION

Increased concentrations of SgII, especially the N-terminal part of secretoneurin could be measured in plasma from patients with endocrine pancreatic tumours and in this case this assay was quite comparable to measurements of CgA and CgB. Even though secretoneurin was not as frequently increased as CgA and CgB in patients with carcinoid tumours or pheochromocytoma it may be a useful marker for endocrine pancreatic tumours.

Immunohistochemical staining of human islet cells with region-specific antibodies against secretogranins II and III

Chromogranins and secretogranins belong to the granin family of proteins, which are expressed in neuroendocrine and nervous tissue. In earlier publications we have described the development of region-specific antibodies against CgA and CgB. In this study we describe antibodies to SgII and SgIII and their usefulness for immunohistochemical staining. Peptides homologous to defined parts of secretogranins II and III were selected and synthesized. Antibodies were raised and immunostainings were performed on normal human pancreas. The SgII 154-165 (N-terminal secretoneurin), SgII 172-186 (C-terminal secretoneurin) and SgIII antibodies immunostained all insulin-immunoreactive cells, most of the glucagon cells and some of the pancreatic polypeptide cells. The SgII 225-242 antibody immunostained only the insulin-containing cells. None of the antibodies immunostained the somatostatin cells. This study is the first observation of the expression of SgIII in human tissues, where we show expression of SgIII in three of the four major islet cell types in human pancreas.

Gastroenteropancreatic neuroendocrine tumours

Gastroenteropancreatic (GEP) neuroendocrine tumours (NETs) are fairly rare neoplasms that present many clinical challenges. They secrete peptides and neuroamines that cause distinct clinical syndromes, including carcinoid syndrome. However, many are clinically silent until late presentation with mass effects. Investigation and management should be highly individualised for a patient, taking into consideration the likely natural history of the tumour and general health of the patient. Management strategies include surgery for cure (which is achieved rarely) or for cytoreduction, radiological intervention (by chemoembolisation and radiofrequency ablation), chemotherapy, and somatostatin analogues to control symptoms that result from release of peptides and neuroamines. New biological agents and somatostatin-tagged radionuclides are under investigation. The complexity, heterogeneity, and rarity of GEP NETs have contributed to a paucity of relevant randomised trials and little or no survival increase over the past 30 years. To improve outcome from GEP NETs, a better understanding of their biology is needed, with emphasis on molecular genetics and disease modeling. More-reliable serum markers, better tumour localisation and identification of small lesions, and histological grading systems and classifications with prognostic application are needed. Comparison between treatments is currently very difficult. Progress is unlikely to occur without development of centers of excellence, with dedicated combined clinical teams to coordinate multicentre studies, maintain clinical and tissue databases, and refine molecularly targeted therapeutics.

[Effective treatment of a hormonally inactive carcinoid tumour with somatostatin analogues: application of serum chromogranin-A for clinical follow-up]

INTRODUCTION

Hormonally inactive carcinoids represent a significant proportion of all carcinoids tumours. Classical biochemical and hormonal parameters are not suitable for the diagnosis and follow-up of these tumours. However, the tumour marker chromogranin A that is characteristic for several neuroendocrine tumours and secreted by the majority of these tumours as well, may offer a better means of diagnosis and follow-up. Somatostatin receptors are expressed by hormonally inactive carcinoids and the presence of these receptors has important diagnostic and therapeutic consequences.

CASE REPORT

The authors present the history of a patient with a hormonally inactive bronchial carcinoid tumour. After surgical removal of the bronchial carcinoid, liver metastases developed which were found to be somatostatin receptor positive. Somatostatin analogue treatment was introduced, followed by Yttrium-isotope labelled somatostatin analogue therapy. Serum chromogranin A was elevated before somatostatin treatment, and gradually decreased in parallel with therapy. The size of liver metastases remained unchanged during treatment.

CONCLUSIONS

Chromogranin A can be efficiently applied for the clinical follow-up of hormonally inactive carcinoid tumours. Somatostatin analogues may be effective for preventing tumour progression not only in hormone-secreting but also in hormonally inactive carcinoid tumours.

Repeat transarterial chemoembolization (TACE) for progressive hepatic carcinoid metastases provides results similar to first TACE

BACKGROUND

Transarterial chemoembolization (TACE) is commonly used to treat metastatic carcinoid tumors; however, the management of progressive disease is less clear. We sought to determine if patients with disease progression after TACE would benefit from repeat TACE.

METHODS

The records of 27 patients undergoing repeat TACE for radiologic or symptomatic progression after TACE for metastatic carcinoid were reviewed and compared to 122 undergoing first TACE. Overall and progression-free survivals were estimated by the Kaplan-Meier method.

RESULTS

Mean disease-free interval after first TACE was 11.8 months. Radiologic response was observed in 61% compared to 82% after first TACE (p=0.058); hormone response in 64% compared to 80% (p=0.159); and symptomatic response in 77% compared to 92% (p=0.053). The complication rate after repeat TACE was lower than after first TACE (p=0.03). Median overall survival was similar after repeat (28.1 months) and first TACE (33.3 months) (p=0.53). Progression-free survival was shorter after repeat TACE but not significantly so. No factor examined could predict survival after repeat TACE.

CONCLUSION

Repeat TACE for patients with hepatic carcinoid metastases failing first TACE or having evidence of disease progression is safe and offers a viable treatment option.

Cardiotoxicity of histone deacetylase inhibitor depsipeptide in patients with metastatic neuroendocrine tumors

PURPOSE

This phase II study was undertaken to assess objective response and toxicity of histone deacetylase inhibitor depsipeptide in patients with neuroendocrine tumors.

EXPERIMENTAL DESIGN

A total of 15 patients with metastatic neuroendocrine tumors received a 4-hour i.v. infusion of depsipeptide at 14 mg/m2 on days 1, 8, and 15 every 28 days. Tumor response was assessed at 8-week intervals using Response Evaluation Criteria in Solid Tumors. Most patients were chemo-naïve (n = 12) but receiving long-acting octreotide for carcinoid syndrome (n = 11). All patients had Eastern Cooperative Oncology Group performance status of 0 to 1.

RESULTS

The study was terminated prematurely due to an unexpected high number of serious cardiac adverse events so the objective response rate could not be determined. A total of 77 doses of depsipeptide with a median of four doses (range, 2-13) per patient were administered. The most common adverse events included nausea (86%), anorexia (73%), vomiting (66%), and fatigue (73%). A sudden death attributed to possible fatal ventricular arrhythmia occurred within 24 hours after the fifth dose of depsipeptide. Furthermore, asymptomatic grade 2 ventricular tachycardia (n = 2) and prolonged QTc (n = 3) probably related to depsipeptide were observed. Plasma depsipeptide levels measured in a subset of patients failed to reveal differences among patients with or without cardiac adverse events.

CONCLUSIONS

Depsipeptide was associated with a high number of potentially serious cardiac adverse events in patients with metastatic neuroendocrine tumor. As sudden death possibly associated with depsipeptide was observed in this trial, the risks for potentially life-threatening arrhythmia associated with this agent need to be comprehensively evaluated.

Cerebrospinal fluid concentrations of peptides derived from chromogranin B and secretogranin II are decreased in multiple sclerosis

Novel biomarkers for multiple sclerosis (MS) could improve diagnosis and provide clues to pathogenesis. In this study surface-enhanced laser desorption/ionization time-of-flight mass spectrometry was used to analyze protein expression in CSF from 46 MS patients, 46 healthy siblings to the patients, and 50 unrelated healthy controls. Twenty-four proteins in the mass range 2-10 kDa were expressed at significantly different levels (p < 0.01) in a robust manner when comparing the three groups. Identities of three proteins were determined using biochemical purification followed by tandem mass spectrometric analysis. Immunoprecipitation experiments confirmed the identities for two peptides derived from chromogranin B (m/z 6252) and from secretogranin II (m/z 3679). These peptides were all decreased in MS when compared with siblings or controls. Radioimmunoassays specific for each peptide confirmed these differences. The lowered concentrations did not correlate to the axonal damage marker neurofilament light protein and may thus reflect functional changes rather than neurodegeneration. Further studies will investigate the involvement of these peptides in MS pathogenesis.

Carcinoid heart disease

Progress in the medical and surgical management of patients with carcinoid disease has resulted in improved symptoms and survival. Carcinoid heart disease remains a major cause of morbidity and mortality among patients with malignant carcinoid syndrome. Limited medical treatment options are available for patients with symptomatic carcinoid heart disease. At the Mayo Clinic (Rochester, MN), we have taken an aggressive approach to severe valvular dysfunction from carcinoid heart disease. Patients with severe carcinoid heart disease currently are referred for cardiac operation when they develop cardiac symptoms, ventricular dysfunction, or (rarely) in anticipation of hepatic surgery. Surgical outcome depends on patient age and functional class at the time of cardiac surgery. Despite metastatic disease that limits longevity, cardiac surgical survivors usually demonstrate dramatic improvement in functional capacity. Cardiac surgery should be considered early for patients with symptomatic carcinoid heart disease and controlled carcinoid symptoms. An experienced medical, surgical, and anesthetic team approach to the patient with carcinoid heart disease is critical in order to provide state of the art management.

Prohormone convertases 1/3, 2, furin and protein 7B2 (Secretogranin V) in endocrine cells of the human pancreas

Prohormone convertases (PCs) are proteinases that cleave inactive prohormones to biologically active peptides. Seven PCs have been identified; two of them, PC1/3 and PC2, have only been localized in neuroendocrine (NE) tissues; a third, furin, in both endocrine and exocrine tissues. We have studied the immunoreactivity of PC1/3, PC2 and furin in the four major NE cell types of the human pancreas by using double immunofluorescence techniques. The study also included the expression of NE secretory protein 7B2 (secretogranin V), a member of the granin family, which influences the function of PC2. The results showed that the three PCs and 7B2 were expressed only in endocrine pancreas, furin also in exocrine cells. Insulin (B) cells harboured PC1/3 and PC2, but not furin. Glucagon (A) cells were immunoreactive to all three PCs; all glucagon cells expressed PC2, but one subpopulation showed PC1/3 immunoreactivity and another furin. Only a few somatostatin (D) cells contained PC2, but no other proconvertase. Pancreatic polypeptide (PP) cells were non-reactive to all three PCs. 7B2 occurred only in insulin and glucagon cells. A varying co-localization pattern was observed between PCs and between PCs and 7B2, with the exception of PC1/3 and furin which were not co-localized. In conclusion, our study shows that PCs are localized in insulin and glucagon cells and do seem to be important in these cell types for processing of hormone and other protein precursors, especially chromogranins, but for the two other major cell types probably other enzymes are of importance.

Chromogranin A in patients with acid hypersecretion and/or hypergastrinaemia

BACKGROUND

Chromogranin has been proposed as a marker for gastrin-dependent enterochromaffin-like cell proliferation.

AIM

To examine this question in three populations: acid hypersecretors with gastrinoma (Zollinger-Ellison), or without gastrinoma (non-Zollinger-Ellison), and also in pernicious anaemia with achlorhydria-caused hypergastrinaemia.

METHODS

We measured serum chromogranin, gastrin, gastric secretion and counted and quantified hyperplasia of enterochromaffin-like cells in gastric biopsies from 38 Zollinger-Ellison and 13 non-Zollinger-Ellison patients being treated with lansoprazole, for 5 years (median) and again 2.5 years later. We also studied 12 patients with pernicious anaemia, half with gastric enterochromaffin-like cell carcinoids.

RESULTS

Serum chromogranin was elevated in patients with gastrinoma, even without any enterochromaffin-like cell proliferation, but not in non-Zollinger-Ellison acid hypersecretors with normal gastrin (P < 0.001). In the hypersecretors chromogranin correlated well with serum gastrin (r = 0.82), but not with enterochromaffin-like cell proliferation. Moreover, chromogranin was normal or near normal (<75 ng/mL) despite very high serum gastrin in five of six patients with pernicious anaemia and enterochromaffin-like cell carcinoids.

CONCLUSIONS

Chromogranin is not a reliable marker for enterochromaffin-like cell activity or proliferation up to and including carcinoid; chromogranin originates in the gastrinoma and, like gastrin, is a marker for gastrinoma in acid hypersecretors.

Chromogranin A: Is It a Useful Marker of Neuroendocrine Tumors?

Purpose

We evaluated the pattern of chromogranin A (CgA) plasma levels in a large number of patients with neuroendocrine tumors (NETs), in a series of patients with chronic atrophic gastritis (CAG) with and without enterochromaffin-like (ECL) cell hyperplasia, and in healthy participants (HPs).

Patients and Methods

Two hundred thirty-eight patients with NETs, 42 patients with CAG with or without ECL cell hyperplasia, and 48 HPs were studied. All patients underwent a baseline visit, biochemical routine check-up, imaging techniques, endoscopy, and histologic determination.

Results

CgA plasma levels were higher in patients with NETs compared with CAG patients or HPs (P < .001). In the NET group, we observed higher CgA levels in patients with diffuse disease compared with patients with local or hepatic disease (P < .001). CgA plasma levels were significantly higher in patients with Zollinger-Ellison syndrome compared with other types of endocrine tumors (P < .001). We found the best cutoff range between HPs and NET patients to be 18 to 19 U/L (sensitivity, 85.3%; specificity, 95.8%). Comparing all participants without neoplasia (HPs, CAG patients, and disease-free patients) and patients with endocrine tumors, the best cutoff range was 31 to 32 U/L (sensitivity, 75.3%; specificity, 84.2%). Setting the specificity at 95%, the cutoff range was 84 to 87 U/L (sensitivity, 55%).

Conclusion

Our study confirms the high specificity and sensitivity of CgA in diagnosing an endocrine tumor. It is necessary to use a cutoff range of 84 to 87 U/L to obtain a high specificity in diagnosing NETs, with the aim of excluding patients in whom the CgA was elevated as a result of other non-neoplastic diseases.

Hepatic artery chemoembolization in 122 patients with metastatic carcinoid tumor: lessons learned

BACKGROUND

Hepatic artery chemoembolization (HACE) is a treatment option in the management of metastatic carcinoid. We reviewed our experience to identify potential factors that influence survival.

METHODS

The records of 122 patients with metastatic carcinoid tumor undergoing HACE were reviewed. Log-rank analysis and Cox proportional hazards were applied to identify factors predictive of decreased survival.

RESULTS

Median follow-up after HACE was 21.5 months. Complications occurred in 23% with periprocedural mortality of 5%. Radiographic tumor regression was seen in 82%, with stabilization of disease in 12%. Median duration of CT response was 19 months. Improvement in symptoms occurred in 92% for median duration of 13 months. HACE resulted in complete normalization of serum pancreastatin in 14%, with greater than 20% reduction in another 66%. Median overall survival was 33.3 months after HACE. Only pancreastatin level > or =5,000 pg/ml was associated with decreased survival by multivariate analysis.

CONCLUSION

HACE offers symptom palliation and long-term survival in patients with incurable carcinoid metastases. Although safe, it should be approached cautiously in patients with significant tumor burden as evidenced by pancreastatin levels > or =5,000 pg/ml. We do not recommend whole-liver embolization in these patients but prefer a staged approach to each lobe of the liver.

Orthotopic liver or multivisceral transplantation as treatment of metastatic neuroendocrine tumors

Liver transplantation can be a therapeutic option for individual patients with neuroendocrine tumors metastatic only to the liver. In this consecutive series of 15 patients (5 multivisceral and 10 orthotopic liver transplantations) with well-differentiated carcinoids, or endocrine pancreatic tumors, we allowed higher proliferation rate (Ki67 <10%), large tumor burden, and higher age than previous studies. Liver transplantation offered good relief of symptoms, long disease-free intervals, and potential cure in individual patients. The survival of grafts and patients compared well with transplantation for benign disease. The overall 5-year survival was 90%. The recurrence-free survival of both multivisceral and liver transplantation related to the time after transplantation (about 20% at 5 years) despite inclusion of patients with higher risk. In conclusion, the critical prognosticators for long-term outcome still remain to be defined. The experience with multivisceral transplantation for patients with endocrine tumors of the pancreatic head is still limited.

Biochemistry of neuroendocrine tumours

Several circulating or urinary tumour markers can be used for the diagnosis and follow-up of functioning and clinically non-functioning neuroendocrine tumours of the pancreatic islet cells and intestinal tract. Among the specific tumour markers are serotonin and its metabolites--e.g. 5-hydroxyindoleacetic acid (5-HIAA)--in carcinoid tumours and the carcinoid syndrome, insulin and its precursors or breakdown products in insulinoma, and gastrin in gastrinoma. Plasma vasointestinal polypeptide (VIP) determinations have been used in the diagnosis of VIPoma, plasma glucagon for glucagonoma, and serum somatostatin for somatostatinoma. Among the tumour-non-specific markers are: chromogranins, neuron-specific enolase (NSE), alpha-subunits of the glycoprotein hormones, catecholamines, pancreatic polypeptide (PP), ghrelin and adrenomedullin.

Processing-independent quantitation of chromogranin a in plasma from patients with neuroendocrine tumors and small-cell lung carcinomas

BACKGROUND

Most neuroendocrine tumors express chromogranin A (CgA). The posttranslational processing of neuroendocrine proteins such as CgA is often specific for the individual tumor. To cope with this variability and improve tumor diagnosis, we developed a processing-independent analysis (PIA) method to measure the total CgA product.

METHODS

For PIA, samples underwent trypsin treatment followed by measurement of CgA by the "CgA(340-->)" assay, in which the antiserum binds an epitope starting at amino acid 340 of CgA and including amino acid residues located in the C-terminal direction. The diagnostic accuracy of the CgA PIA and 3 sequence-specific assays for CgA were evaluated on plasma samples from patients with neuroendocrine tumors and small-cell lung carcinomas. Furthermore, we investigated whether the CgA plasma concentrations correlated with the tumor burden.

RESULTS

Size-exclusion chromatography of plasma showed that CgA immunoreactivity mainly consisted of high-molecular-weight forms, indicating that neuroendocrine tumors may secrete large amounts of poorly processed CgA. Accordingly, trypsination of plasma from 54 patients with neuroendocrine tumors or small-cell lung carcinomas increased the CgA(340-->) immunoreactivity up to 500-fold. Both the CgA(340-->) assay and the PIA measured significantly higher plasma concentrations in patients with very extensive disease than in patients with less widespread disease. The diagnostic sensitivity was 0.91 when using the CgA(340-->) assay and 0.82 using the CgA PIA.

CONCLUSION

The CgA(340-->) assay and CgA PIA are both useful for diagnosis of neuroendocrine tumors and small-cell lung carcinomas and both assays correlate with tumor burden.

Recommedition for Apllication and Determination Tumor Markers of Neuroendocrine System

Neuroendokrini tumori vode poreklo iz neuroendokrinih ćelija, koji pod uslovima specifične stimulacije sekretuju hormone, regulišući niz različitih funkcija u organizmu. U radu je opisana grupa neuroendokrinih tumora koja se sastoji od: karcinoida endokrinih tumora pankreasa, neuroblastoma, medularnog karcinoma tiroidee i feohromocitoma. Biće diskutovani tumori koji potiču iz endokrinih žlezda, kao i oni koji vode poreklo iz takozvanog »difuznog« neuroendokrinog ćelijskog sistema gastrointestinalnog trakta. Radi se o najvećem endokrinom organu u organizmu. Oko 50 različitih neuroendokrinih ćelijskih tipova gastrointestinalnog trakta je indentifikovano. Važan dijagnostički segment u tretmanu ovih tumora, je određivanje biogenih amina i peptida, čija je aktivnost izmenjena kod pojave neoplazmi. Širok je spektar kliničkih simptoma kod pojave ove vrste tumora, a svi su posledica sposobnosti tumora da sekretuju povećane količine peptinih hormona i biogenih amina. Glavni ciljevi ovog teksta su procena važnosti ove grupe tumorskih markera, kao i predlozi za njihovo koriŠćenje u našim uslovima.

Serum chromogranin A concentration and intradialytic hypotension in chronic haemodialysis patients

AIM

The aim of this study was to investigate the influence of haemodialysis on plasma chromogranin A (CgA) concentration and to assess the relationship between CgA, blood pressure, occurrence of intradialytic hypotension episodes and residual renal function, respectively.

METHODS

The study included 38 chronic haemodialysis patients (24 M, 14 F; mean age 56.2+/-13.6 years). Plasma CgA and blood pressure were measured before and after a mid-week dialysis. Control group included 10 age- and sex-matched healthy subjects.

RESULTS

Plasma CgA levels were on average 50-fold higher in HD patients than in the controls (699+/-138 vs. 14+/-6 U/L). In HD patients plasma CgA corrected for ultrafiltration rates significantly increased (to 836+/-214 U/L, P<0.001) at the end of dialysis procedure. In patients with (n=8) and without frequent symptomatic intradialytic hypotension episodes predialysis values of CgA were similar (701+/-169 vs. 698+/-132 U/L) but post-dialysis were significantly lower in the former group (746+/-312 vs. 860+/-177 U/L; P=0.03) despite a similar rate of ultrafiltration (2675+/-1009 and 2583+/-1311 ml, respectively). Accordingly, in patients with intradialytic hypotension an increase of plasma CgA during dialysis was also much lower than in patients without hypotension (45+/-81 vs. 163+/-144 U/L; P=0.001).

CONCLUSIONS

CgA undergoes marked accumulation in renal failure. The increase of plasma CgA during dialysis is impaired in subjects with intradialytic hypotension episodes, which confirms the role of autonomic dysfunction in the pathogenesis of this complication.

Measurements of chromogranin B can serve as a complement to chromogranin A

OBJECTIVE

CgA has been shown to be an excellent marker for neuroendocrine tumours. However, there are two major drawbacks with CgA measurements; elevated levels are common in patients with decreased renal function and in patients on treatment with proton pump inhibitors. These problems are not seen with CgB measurements. We have recently presented the development of 13 region-specific radioimmunoassays for measurements of CgB. A region-specific assay was identified, which measured higher concentrations of CgB than the other assays and seemed to be very useful as a marker for neuroendocrine tumours. The aim of the present study was therefore to further explore the diagnostic potential of this assay in the clinical management of patients with neuroendocrine tumours.

METHODS

Measurements of CgB with two methods were compared with CgA in plasma samples from patients investigated for neuroendocrine tumours (N=86), patients with decreased renal function (N=35) and patients on treatment with proton pump inhibitors (N=29).

RESULTS

The diagnostic sensitivity for the new CgB assay was almost as good as that for CgA. Furthermore, with CgB measurements we could avoid the falsely elevated levels of CgA found in patients with decreased renal function and treatment with proton pump inhibitors.

CONCLUSIONS

We conclude that the new CgB assay can serve as a complement to CgA measurements as an important tumour marker for neuroendocrine tumours.

Gastrointestinal carcinoids: the evolution of diagnostic strategies

Carcinoid tumors are rare, often insidious neoplasms arising from neuroendocrine cells. The majority arise in the gastrointestinal system, and are often incidentally found during investigation, although some may present as an emergency bleed or perforation. The prosaic symptoms of flushing, diarrhea, and sweating are often overlooked; thus, the diagnosis is usually much delayed and the tumor is advanced at presentation. This diagnostic delay renders effective management difficult and adversely affects outcome. This overview provides a current assessment of the evolution of the diagnostic techniques available to establish an accurate biochemical (5-hydroxyindole-3-acetic acid and chromogranin A) and topographic diagnosis (octreoscan, radio-labeled metaidobenzylguanidine, computerized tomography, magnetic resonance imaging, positron emission tomography, enteroclysis, endoscopic ultrasound, enteroscopy, capsule endoscopy, and angiography) of carcinoid tumors. The utility and shortcomings of the respective modalities available are evaluated. Although considerable advances have been made in establishing the diagnosis of carcinoid tumors and in defining the topography of metastatic disease, the major limitation is the inability to establish an early and timely diagnosis before the advent of metastatic disease.