Involvement of the γ1 subunit of the large-conductance Ca2+-activated K+ channel in the proliferation of human somatostatinoma cells.

Pancreatic neuroendocrine tumors (pNETs) occur due to the abnormal growth of pancreatic islet cells and predominantly develop in the duodenal-pancreatic region. Somatostatinoma is one of the pNETs associated with tumors of pancreatic δ cells, which produce and secrete somatostatin. Limited information is currently available on the pathogenic mechanisms of somatostatinoma. The large-conductance Ca2+-activated K+ (BKCa) channel is expressed in several types of cancer cells and regulates cell proliferation, migration, invasion, and metastasis. In the present study, the functional expression of the BKCa channel was examined in a human somatostatinoma QGP-1 cell line. In QGP-1 cells, outward currents were elicited by membrane depolarization at pCa 6.5 (300 nM) in the pipette solution and inhibited by the specific BKCa channel blocker, paxilline. Paxilline-sensitive currents were detected, even at pCa 8.0 (10 nM) in the pipette solution, in QGP-1 cells. In addition to the α and ß2-4 subunits of the BKCa channel, the novel regulatory γ1 subunit (BKCaγ1) was co-localized with the α subunit in QGP-1 cells. Paxilline-sensitive currents at pCa 8.0 in the pipette solution were reduced by the siRNA knockdown of BKCaγ1. Store-operated Ca2+ entry was smaller in BKCaγ1 siRNA-treated QGP-1 cells. The proliferation of QGP-1 cells was attenuated by paxilline or the siRNA knockdown of BKCaγ1. These results strongly suggest that BKCaγ1 facilitates the proliferation of human somatostatinoma cells. Therefore, BKCaγ1 may be a novel therapeutic target for somatostatinoma.

Somatostatin-Immunoreactive Pancreaticoduodenal Neuroendocrine Neoplasms: Twenty-Three Cases Evaluated according to the WHO 2010 Classification.

BACKGROUND/OBJECTIVE: Neuroendocrine neoplasms of the pancreas and duodenum with predominant or exclusive immunoreactivity for somatostatin (pdSOMs) are rare, and knowledge about tumour biology, treatment, survival and prognostic factors is limited. This study aims to describe clinical, pathological and biochemical features as well as treatment and prognosis of pdSOMs. DESIGN: Twenty-three patients with pdSOM (9 duodenal, 12 pancreatic and 2 unknown primary tumours) were identified from our prospective neuroendocrine tumour database, and data according to the study aims were recorded. RESULTS: Among the 9 patients with duodenal SOM, the male/female ratio was 4/5. All males and 1 female had neurofibromatosis type 1. Seven patients had stage 1A/B and 2 had stage 2B disease. The Ki-67 index was 1-5% (median 2%). Plasma somatostatin was elevated in the patients with 2B disease. Of the 14 patients with pancreatic SOM or an unknown primary tumour, the male/female ratio was 2/12. One male had multiple endocrine neoplasia type 1. Five had stage 1A/2B and 9 had stage 4. The Ki-67 index was 1-40% (median 7%). Plasma somatostatin was elevated in 7 patients. Patients reported symptoms related to the somatostatinoma syndrome, but none fulfilled the criteria for a full syndrome. Primary tumour in the pancreas, metastatic disease at diagnosis and higher tumour grade were all associated with significantly poorer survival. CONCLUSION: None of the patients with pdSOM presented with the full somatostatinoma syndrome. Prognostic factors are localisation of the primary tumour, dissemination and tumour grade. A Ki-67 index of 5% may discriminate the course of the disease.

Novel HIF2A mutations disrupt oxygen sensing, leading to polycythemia, paragangliomas, and somatostatinomas.

Hypoxia-inducible factors (HIFs) control the cellular response to hypoxia and, when dysregulated, contribute to tumorigenesis. Previously, we identified 2 gain-of-function somatic mutations in patients presenting with multiple paragangliomas or somatostatinomas, and polycythemia. Here, we report 2 additional unique HIF2A mutations, which disrupt the hydroxylation domain recognized by prolyl hydroxylase domain-2 containing protein, leading to stabilization of HIF-2α and increased expression of hypoxia-related genes.

Gastrointestinal hormones stimulate growth of Foregut Neuroendocrine Tumors by transactivating the EGF receptor.

Foregut neuroendocrine tumors [NETs] usually pursuit a benign course, but some show aggressive behavior. The treatment of patients with advanced NETs is marginally effective and new approaches are needed. In other tumors, transactivation of the EGF receptor (EGFR) by growth factors, gastrointestinal (GI) hormones and lipids can stimulate growth, which has led to new treatments. Recent studies show a direct correlation between NET malignancy and EGFR expression, EGFR inhibition decreases basal NET growth and an autocrine growth effect exerted by GI hormones, for some NETs. To determine if GI hormones can stimulate NET growth by inducing transactivation of EGFR, we examined the ability of EGF, TGFα and various GI hormones to stimulate growth of the human foregut carcinoid,BON, the somatostatinoma QGP-1 and the rat islet tumor,Rin-14B-cell lines. The EGFR tyrosine-kinase inhibitor, AG1478 strongly inhibited EGF and the GI hormones stimulated cell growth, both in BON and QGP-1 cells. In all the three neuroendocrine cell lines studied, we found EGF, TGFα and the other growth-stimulating GI hormones increased Tyr(1068) EGFR phosphorylation. In BON cells, both the GI hormones neurotensin and a bombesin analogue caused a time- and dose-dependent increase in EGFR phosphorylation, which was strongly inhibited by AG1478. Moreover, we found this stimulated phosphorylation was dependent on Src kinases, PKCs, matrix metalloproteinase activation and the generation of reactive oxygen species. These results raise the possibility that disruption of this signaling cascade by either EGFR inhibition alone or combined with receptor antagonists may be a novel therapeutic approach for treatment of foregut NETs/PETs.

Somatostatin-producing neuroendocrine tumors of the duodenum and pancreas: incidence, types, biological behavior, association with inherited syndromes, and functional activity.

Somatostatin-producing neuroendocrine tumors (SOM-NETs) of the duodenum and pancreas appear to be heterogeneous. To determine their clinicopathological profiles, respective data were analyzed on a series of 82 duodenal and 541 pancreatic NETs. In addition, the clinical records of 821 patients with duodenal or pancreatic NETs were reviewed for evidence of a somatostatinoma syndrome. Predominant or exclusive expression of somatostatin was found in 21 (26%) duodenal and 21 (4%) pancreatic NETs. They were classified as sporadic (n=31) or neurofibromatosis type 1 (NF1)-associated duodenal NETs (n=3), gangliocytic paragangliomas (GCPGs; n=6), or poorly differentiated neuroendocrine carcinomas (pdNECs; n=2). In addition, five duodenal and four pancreatic SOM-NETs were found in five patients with multiple endocrine neoplasia type 1 (MEN1). Metastases occurred in 13 (43%) patients with sporadic or NF1-associated SOM-NETs, but in none of the duodenal or pancreatic MEN1-associated SOM-NETs or GCPGs. Sporadic advanced (stage IV) SOM-NETs were more commonly detected in the pancreas than in the duodenum. None of the patients (including the 821 patients for whom only the clinical records were reviewed) fulfilled the criteria of a somatostatinoma syndrome. Our data show that somatostatin expression is not only seen in sporadic NETs but may also occur in GCPGs, pdNECs, and hereditary NETs. Surgical treatment is effective in most duodenal and many pancreatic SOM-NETs. MEN1-associated SOM-NETs and GCPGs follow a benign course, while somatostatin-producing pdNECs are aggressive neoplasms. The occurrence of the so-called somatostatinoma syndrome appears to be extremely uncommon.

Large somatostatin-producing endocrine carcinoma of the ampulla of vater in association with GIST in a patient with von Recklinghausen's disease. Case report and review of the literature.

CONTEXT: Somatostatin-producing endocrine tumors of the duodenum are very rare neoplasms of the gastrointestinal tract. These tumors may be associated with von Recklinghausen's disease. CASE REPORT: We present the case of a 49-year-old female patient with von Recklinghausen's disease and an incidentally diagnosed ampullary neoplasm. The patient was treated with a classical pancreaticoduodenectomy. At surgery, a mass was found in the greater curve of the stomach which was resected using the classic Whipple procedure. Histology and immunohistochemistry showed that the duodenal tumor was an ampullary somatostatin-producing endocrine carcinoma while the gastric tumor was a gastrointestinal stromal tumor (GIST). The postoperative course was uneventful and the patient is alive, without tumor recurrence, six years after surgery. CONCLUSION: Somatostatin-producing endocrine tumors of the duodenum are rare tumors, often associated with von Recklinghausen's disease; these neoplasms should be treated aggressively using radical surgical resection. Although local resection may be appropriate for small duodenal somatostatin-producing tumors, a pancreaticoduodenectomy is usually required for larger tumors.

Neuroendocrine tumors of the pancreas.

The neuroendocrine tumors (NET) of the pancreas are very rare lesions with frequency of about 3 to 10 per 1 000 000 inhabitants. The neuroendocrine tumors composes a heterogeneous group of tumors. The gastro-entero-pancreatic tumors (GEP) constitute 70% of all NET and 2% of all digestive system tumors. There have been several attempts to classify those lesions and since 2000 exists WHO classification which divides NET according to malignancy and histologic structure. The most often NET of the pancreas are insulinoma, gastrinoma, glucagonoma, somatostatinoma, VIPoma. There is a recommendation to assay hormonal activity, measure concentration of specific peptides, biogenic amines and hormones produced by NET cells to establish diagnosis. Those tests are useful in monitoring treatment and in prognostication course of the disease. Imaging methods especially useful in localization GEP-NET are: ultrasound (US), endoscopic ultrasound (EUS), somatostatin receptor scintigraphy (SRS), computer tomography (CT), magnetic resonance (MR) and angiography. The most sensitive method in preoperative diagnosis seems to be EUS or less accessible intra ductal ultrasonography (IDUS). Surgical treatment depends on progression of disease as well as on localization of tumor and consists in both radical methods and palliative operations. The gold standard in pharmacological treatment are somatostatin analogs which can induce long-term remission even in inoperable lesions. Although NET of pancreas are very rare. they are still important diagnostic and therapeutic problem and requires interdisciplinary co-operation. The neuroendocrine tumors should be treated in centers with highest rank of references.

Src family kinase activity regulates adhesion, spreading and migration of pancreatic endocrine tumour cells.

Pancreatic endocrine tumours (PETs) are rare and 'indolent' neoplasms that usually develop metastatic lesions and exhibit poor response to standard medical treatments. Few studies have investigated pathways responsible for PET cell growth and invasion and no alternative therapeutic strategies have been proposed. In a recent microarray analysis for genes up-regulated in PETs, we have described the up-regulation of soluble Src family tyrosine kinases in this neoplasia, which may represent potentially promising candidates for therapy. Herein, we have investigated the expression and function of Src family kinases in PETS and PET cell lines. Western blot analysis indicated that Src is highly abundant in the PET cell lines CM and QGP-1. Immunohistochemistry and Western blot analyses showed that Src is up-regulated also in human PET lesions. Pharmacological inhibition of Src family kinases by the specific inhibitor PP2 strongly interfered with adhesion, spreading and migration of PET cell lines. Accordingly, the actin cytoskeleton was profoundly altered after inhibition of Src kinases, whereas even prolonged incubation with PP2 exerted no effect on cell cycle progression and/or apoptosis of PET cells. A transient increase in tyrosine phosphorylation of a subset of proteins was observed in QGP-1 cells adhering to the plate, with a peak at 75 min after seeding, when approximately 80% of cells were attached. Inhibition of Src kinases caused a dramatic reduction in the phosphorylation of proteins with different molecular weight that were isolated from the cell extracts by anti-phosphotyrosine immunoprecipitation or pull-down with the SH2 domain of Src. Among them, the docking protein p130Cas interacted with Src and is a major substrate of the Src kinases in QGP-1 cells undergoing adhesion. Our results suggest that Src kinases play a specific role during adhesion, spreading and migration of PET cells and may indicate therapeutical approaches directed to limiting the metastatic potential of these cells.

Characterization of the functional and growth properties of long-term cell cultures established from a human somatostatinoma.

In somatostatinoma, a rare malignant somatostatin (SST)-secreting neoplasia, tumour regression is rarely observed, implying the need for novel antiproliferative strategies. Here, we characterized a long-term culture (SST-secreting cancer (SS-C cells)) established from a human somatostatinoma. High concentrations of SST and chromogranin A were released by SS-C cells and SST release was stimulated by depolarizing stimuli and inhibited by the SST analogue, octreotide. SS-C cells expressed mRNA for SST receptor (SSTR) subtypes 1, 2 and 4, being also able to bind native SST. Moreover, SS-C cells were positively stained with an antibody to SSTR2. SS-C cells also expressed interferon-gamma (IFN-gamma) receptor mRNA and measurable telomerase activity. Our findings indicate that in vitro exposure of SS-C cells to native SST-28, to octreotide, to IFN-gamma, or to 3'-azido-3'deoxythymidine (AZT), a telomerase inhibitor, results in inhibition of SS-C cell proliferation. Concomitant with growth inhibition, apoptosis was detected in SST-, octreotide-, IFN-gamma- or AZT-treated SS-C cell cultures. Taken together our results characterized native SST, SST analogues, IFN-gamma and a telomerase inhibitor as growth-inhibiting and proapoptotic stimuli in cultured human somatostatinoma cells. Based on these findings, the potential of SST analogues, IFN-gamma and AZT, alone or in combination, should be further explored in the medical treatment of somatostatinoma.

Neuroendocrine tumors of the pancreas, excluding gastrinoma.

In summary, neuroendocrine tumors of the pancreas comprise a unique and relatively rare group of tumors, of which gastrinoma and insulinoma are the most common types. Insulinomas tend to be small, solitary and benign, with surgical resection curable in most cases. The remainder of the neuroendocrine tumors are usually large, and unlikely to be cured with surgery; their slow-growing nature, however, mandates aggressive surgical therapy; even in cases where metastatic disease is present. Somatostatin analogs such as octreotide, are used to control the symptoms of hormone secretion; they are generally less effective in patients with insulinoma than in those with the other neuroendocrine tumors. Streptozocin, 5-fluorouracil, and doxorubicin are the most widely used chemotherapeutic agents in metastatic neuroendocrine tumors; their efficacy is limited, and significant side effects limit their use. Finally, liver transplantation in very select patients may prolong survival and alleviate debilitating symptoms.

A somatostatin-secreting cell line established from a human pancreatic islet cell carcinoma (somatostatinoma): release experiment and immunohistochemical study.

Production and secretion of somatostatin (SRIF) were studied using a carcinoembryonic antigen (CEA)-producing cell line (QGP-1) established from a human pancreatic islet cell carcinoma. High concentrations of SRIF (274 +/- 51 ng/mg of protein, mean +/- SD, n = 5) and CEA (3083 +/- 347 ng/mg of protein, mean +/- SD, n = 5) were present in QGP-1 cells, and the basal secretion rates of SRIF and CEA by the cells (n = 5) were 46.4 +/- 4.8 and 1690 +/- 78 pg/10(5) cells/h, respectively. Immunohistochemical studies revealed the presence of SRIF in xenografts of QGP-1 cells and colocalization of SRIF and CEA. Secretion of SRIF by QGP-1 cells was stimulated in the presence of high K+ (50 mmol) and theophylline (10 mmol), but arginine (10 mmol) and glucose (300 mg/dl) had no effect on the SRIF secretion. The QGP-1 cell line may be useful for studying the regulation mechanism of SRIF secretion.

Duodenal somatostatinoma associated with diabetic ketoacidosis presumably caused by somatostatin-28 hypersecretion.

CONTEXT: Extrapancreatic somatostatinoma is very rare and clinically distinguished from its pancreatic counterpart because somatostatinoma syndrome with mild diabetes is rare in extrapancreatic somatostatinoma because of poor secretion of somatostatin. Moreover, because somatostatin inhibits the secretion of insulin and glucagon simultaneously, true diabetic ketoacidosis (DKA) seldom ensues. PATIENT: A 23-yr-old woman presented with DKA and an abdominal mass. A computed tomography scan showed a huge, encapsulated mass in a duodenal submucous portion. A high circulating level of somatostatin was detected (67.2 pmol/liter; reference range, 0.6-7.3 pmol/liter). INTERVENTION: The tumor mass was successfully removed with Whipple's procedure, and the patient gradually recovered both clinically and biochemically. RESULTS: Immunohistochemical staining of the tumor tissue exhibited diffusely positive for somatostatin and somatostatin-28 but negative for insulin, glucagon, calcitonin, serotonin, and S-100. CONCLUSION: As far as we know, this is the first case report of gastrointestinal somatostatinoma associated with DKA.

Duodenal somatostatinoma: clinical and immunohistochemical patterns--difficult differential diagnosis in regard to gangliocytic paraganglioma: report of a case.

The authors report a large duodenal somatostatinoma, a very rare tumor entity. A 8.5 cm globular mass in the area of the unicate process of the pancreas was detected in a 45 year old caucasian female by computerized tomography. The patient had only mild complaints. Initial treatment consisted of right pancreatectomy with preservation of the pylorus. Histological evaluation rendered a diagnosis of low-grade malignant neuroendocrine carcinoma with expression of somatostatin, respectively of somatostatinoma arising in the duodenum and infiltrating into the pancreas. 26 months after the initial surgery liver and lymph node metastases were detected and surgically removed. This case confirms that duodenal somatostatinomas are very difficult to diagnose preoperatively because of unspecific symptoms. Most duodenal somatostatinomas are found incidentally. Treatment of choice is radical surgical resection with a possible cure in early stages of the disease. Even a large tumor as ours is resectable with negative surgical margins. Management of recurrent or metastatic disease is also surgical. Additional chemotherapy and supportive care may be beneficial for the patient.

In vivo phosphorylation of the somatostatin 2A receptor in human tumors.

Hormone-stimulated receptor internalization and desensitization occur widely in the G protein-coupled receptor (GPCR) family. A critical first step in both these processes is thought to be receptor phosphorylation, a reaction which has been extensively characterized in cell culture. However, little is known about GPCR phosphorylation in vivo. The somatostatin (SS) receptor subtype (sst)2A is widely distributed in human neuroendocrine tumors, and SS analogs are commonly used to target this receptor for both therapy and diagnosis. In cultured pituitary cells sst2A is rapidly phosphorylated and internalized after hormone binding. The aim of the present study was to go one crucial step further and characterize the phosphorylation state of this receptor in human neuroendocrine tumors using a newly developed gel-shift assay. The receptor from a somatostatinoma was completely phosphorylated. In contrast, only unphosphorylated sst2A was present in human tumors that were not exposed to autocrine stimulation. Both in vivo and in cultured cells, the phosphorylation state of the sst2A receptor was correlated with its subcellular localization: phosphorylated receptor was mostly intracellular, whereas unphosphorylated receptor was localized at the cell surface. These results are the first to demonstrate ligand-stimulated GPCR phosphorylation in human tissue in situ, providing a crucial step toward a better understanding of receptor regulation in vivo. Analysis of sst2A phosphorylation promises to provide a sensitive indicator of the effectiveness of SS analogs in diagnostic and therapeutic situations in tumor patients.

Somatostatin-secreting islet cell tumor (somatostatinoma): suppression of growth hormone (GH) release induced by GH-releasing hormone.

A patient with a somatostatin (SRIH)-secreting islet cell tumor, whose only symptoms were dyspepsia and anemia, is described. The diagnosis of somatostatinoma was based on high plasma SRIH concentrations and immunocytochemical findings. The pancreatic exocrine response to secretin was decreased, whereas the insulin and/or glucagon responses to glucose and arginine were normal. Although the basal plasma GH concentration was normal, the plasma GH response to GHRH was subnormal. Gel permeation chromatography studies indicated that SRIH-14 was the predominant form of SRIH in plasma as well as in tumor tissue.

Somatostatin-producing neuroendocrine tumor of the ampulla (ampullary somatostatinoma). Evidence of prosomatostatin production.

Two cases of somatostatin-producing ampullary neuroendocrine tumors (somatostatinoma) are reported. The authors have characterized their immunoreactivity using antibodies specific for the amino- and carboxyl-terminal portions of prosomatostatin, the precursor of somatostatin in the normal synthetic pathway. Cytoplasmic staining was found using each of these two antibodies in the tumor cells of both ampullary somatostatinomas as well as in the cytoplasm of cells in the hypothalamus, crypt cells of the duodenal mucosa, mucosal cells of the biliary tract, D cells of the pancreatic islets, and parafollicular cells of fetal thyroid. These studies suggest that the synthesis of somatostatin in ampullary somatostatinomas occurs through the normal pathway from the precursor prosomatostatin.

Clinical features of duodenal somatostatinomas.

BACKGROUND: Duodenal somatostatinomas are rare tumors that are often asymptomatic or present with local symptoms rather than with evidence of excess somatostatin production. To characterize the clinical presentation and management of these neoplasms we reviewed the course of four patients. METHODS: The records of three men and one woman with duodenal somatostatinomas, who were treated between 1988 and 1992, are reviewed. RESULTS: Three of the patients presented with vague gastrointestinal complaints, and one was free of symptoms. No patient had symptoms of somatostatinoma syndrome, nor did any have associated neurofibromatosis. Three patients were diagnosed after biopsy of a submucosal mass during upper endoscopy. Three patients with tumors that measured less than 2 x 2 cm underwent local resection. One patient with a large tumor and liver metastases underwent a Whipple's operation and resection of the liver lesions. Immunohistochemically all tumors predominantly contained somatostatin, although each had traces of other neuropeptides. All tumors contained psammoma bodies. Follow-up periods ranged from 1 to 4 years. CONCLUSIONS: Duodenal somatostatinomas often appear with only local symptoms or are completely asymptomatic. Small tumors may be locally excised. Intraarterial methylene blue injection may help localize very small tumors during operation. Larger tumors, including those with localized metastases, should also be resected when possible.

Lack of p53 immunoreactivity in pancreatic endocrine tumors.

Abnormal expression of the p53 tumor suppressor gene has been implicated in many human epithelial tumors. However recent evidence has revealed the absence of p53 gene abnormalities or overexpression in some human endocrine cancers. This study examines the immunohistological expression of the p53 gene product using the monoclonal antibody DO-7, an antibody directed against both wild and mutant forms of p53 protein, and a streptavidin-biotin-peroxidase method, in pancreatic endocrine tumors (n = 16). None of the cases of pancreatic endocrine tumors showed evidence of p53 immunostaining. This finding is in contrast to that in pancreatic adenocarcinomas in which increased p53 immunoreactivity has been previously observed. These observations suggest that the p53 gene may not be important in the development of endocrine tumors of the pancreas.

Duodenal somatostatinoma with psammoma bodies.

A duodenal somatostatinoma was found incidentally in a 60-year-old woman undergoing cholecystectomy. Microscopically, the tumor had a glandular architecture with abundant psammoma bodies. Electron microscopy revealed tumor cells resembling D-cells of the pancreatic islets. Immunohistochemically, there was staining for neuron-specific enolase, chromogranin, and diffuse cytoplasmic positivity for somatostatin only. By immunoelectron microscopy, somatostatin was identified predominantly in lucent membrane-bound secretory granules. X-ray-dispersive microanalysis showed the psammoma bodies contained calcium apatite crystals. This case is compared with other reported cases with a description of cellular localization of somatostatin and development of psammomatous calcification.

Concurrent gastrinoma and somatostatinoma in a 10-year-old Portuguese water dog.

Severe hypergastrinaemia in the dog is considered a strong indicator for a gastrin-producing pancreatic islet cell tumour. In human medicine, gastrinomas are described as enteropancreatic neuroendocrine tumours that cause the Zollinger-Ellison syndrome. However, in contrast to the supposed origin of canine gastrinomas in pancreatic islets, gastrinomas in human beings arise predominantly in the duodenum and gastric antrum, and are often a component of the syndrome of multiple endocrine neoplasia type I. This report is of a canine case of multiple endocrine neoplasms, consisting of a pancreatic islet cell somatostatinoma, and a gastrinoma in the mesenteric lymph nodes and liver. From the literature and the authors' findings, it is concluded that the clinical diagnosis of hypergastrinaemia is not pathognomonic for a gastrin-producing islet cell tumour. Furthermore, the presence of an islet cell tumour in the face of hypergastrinaemia does not warrant a diagnosis of an islet cell gastrinoma. Immunohistochemistry is necessary to confirm the diagnosis of a pancreatic islet cell gastrinoma.