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.

New syndrome of paraganglioma and somatostatinoma associated with polycythemia.

PURPOSE: The occurrence of ≥ two distinct types of tumors, one of them paraganglioma (PGL), is unusual in an individual patient, except in hereditary cancer syndromes. PATIENTS AND METHODS: Four unrelated patients were investigated, with thorough clinical evaluation. Plasma and tissue catecholamines and metanephrines were measured by high-performance liquid chromatography. Anatomic and functional imaging were performed for tumor visualization. Germline and tumor tissue DNA were analyzed for hypoxia-inducible factor 2 alpha (HIF2A) mutations. The prolyl hydroxylation and stability of the mutant HIF2α protein, transcriptional activity of mutant HIF2A, and expression of hypoxia-related genes were also investigated. Immunohistochemical staining for HIF1/2α was performed on formalin-fixed, paraffin-embedded tumor tissue. RESULTS: Patients were found to have polycythemia, multiple PGLs, and duodenal somatostatinomas by imaging or biochemistry with somatic gain-of-function HIF2A mutations. Each patient carried an identical unique mutation in both types of tumors but not in germline DNA. The HIF2A mutations in these patients were clustered adjacent to an oxygen-sensing proline residue, affecting HIF2α interaction with the prolyl hydroxylase domain 2-containing protein, decreasing the hydroxylation of HIF2α, and reducing HIF2α affinity for the von Hippel-Lindau protein and its degradation. An increase in the half-life of HIF2α was associated with upregulation of the hypoxia-related genes EPO, VEGFA, GLUT1, and END1 in tumors. CONCLUSION: Our findings indicate the existence of a new syndrome with multiple PGLs and somatostatinomas associated with polycythemia. This new syndrome results from somatic gain-of-function HIF2A mutations, which cause an upregulation of hypoxia-related genes, including EPO and genes important in cancer biology.

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.

Diarrhea caused by circulating agents.

Circulating agents cause intestinal secretion or changes in motility with decreased intestinal transit time, resulting in secretory-type diarrhea. Secretory diarrhea as opposed to osmotic diarrhea is characterized by large-volume, watery stools, often more than 1 L per day; by persistence of diarrhea when patients fast; and by the fact that on analysis of stool-water, measured osmolarity is identical to that calculated from the electrolytes present. Although sodium plays the main role in water and electrolyte absorption, chloride is the major ion involved in secretion.

The immunohistochemistry aspects in two cases of neurofibromatosis-associated abdominal tumors.

Type 1 neurofibromatosis associates various abdominal tumors as gastrointestinal stromal tumors, duodenal or pancreatic carcinoid, and adrenal tumors like pheochromocytoma. We present the immunohistochemistry report in two cases with different profile regarding the evolution. One case is a 7th decade women diagnosed with unilateral pheochromocytoma and GISTs, with a good prognosis after surgery. The other case is a 41-year-old male diagnosed with duodenal metastatic somatostatinoma after an intestinal occlusive syndrome and later the hormonal profile leaded to the diagnosis of pheochromocytoma. The patient had a fulminate evolution within six months from diagnosis.

Hypercalcitonemia revealing a somatostatinoma.

Somatostatinoma are rare well-differentiated endocrine tumors with malignant behavior arising from the pancreas and duodenum. They are defined by somatostatin positive immunostaining of the majority of tumor cells. The main clinical features are diabetes, diarrhea and biliary lithiasis related to somatostatin production. Somatostatinoma secreting both calcitonin and somatostatin may be unrecognized as a small number of such observations have been published. We report the case of a 57- year-old woman referred for weight loss, diarrhea and worsening diabetes. Computer tomography scan revealed multiple hypervascular liver lesions suggestive of metastases. High plasma calcitonin level was evidenced, with normal chromogranin-A value, and high plasma somatostatin results lately communicated. Calcitonin secretion of extra-thyroidal origin was suspected leading to the identification of a pancreatic mass by further multiphase CT. The patient underwent left pancreatectomy with surgical hepatic resection. Histological and immunostaining studies confirmed definitive diagnosis of somatostatinoma secreting both somatostatin and calcitonin. Plasma calcitonin should be measured in the assessment of duodeno-pancreatic endocrine neoplasm. Calcitonin determination is available, more reproducible than other specific pancreatic endocrine markers and could be effective for diagnosis and follow-up of such foregut-derived endocrine neoplasia.

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.

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.

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.

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.

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.

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.

Somatostatin-producing pancreatic endocrine carcinoma presented as relapsing cholangitis -- a case report.

Somatostatin-producing endocrine tumors are rare neoplasms usually arising in the pancreas and duodenum and they account for less than 1% of all gastrointestinal endocrine tumors. Besides somatostatinoma syndrome, which is characterized by diabetes mellitus, steatorrhea and cholelithiasis, patients with somatostatin-producing endocrine tumors commonly complain of nonspecific symptoms such as vague abdominal pain, weight loss or changes in bowel habits. Tumor behavior cannot be predicted by histological features alone, and malignancy is determined by the presence of metastases. We report here a case of malignant pancreatic endocrine tumor producing somatostatin presented as relapsing cholangitis who was treated with Whipple pancreatoduodenectomy.

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.

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.