Islet cell tumour with vacuolated lipid-rich cytoplasm: a new histological variant of islet cell tumour

AIMS

A previously unreported clear cell variant of islet cell tumour of the pancreas is described.

METHODS AND RESULTS

By light microscopy, the cytoplasm of the clear cells was finely reticulated and vacuolated. Immuno-histochemical and electron microscopy studies confirmed the endocrine nature of the tumour.

CONCLUSIONS

The clear cell morphology was due to the accumulation of lipid in the cytoplasm.

A growth hormone-releasing hormone-producing pancreatic islet cell tumor metastasized to the pituitary is associated with pituitary somatotroph hyperplasia and acromegaly

The functional and morphological changes in the pituitary gland caused by a GHRH-producing pancreatic islet cell tumor that metastasized to the pituitary and caused somatotroph hyperplasia are described. A 52-yr-old woman presented with loss of visual acuity, diabetes insipidus, and acromegaly caused by a GHRH-producing endocrine carcinoma metastasized to the pituitary. The serum GHRH, GH, and insulin-like growth factor I levels of the patient were elevated. Immunohistochemical and in situ hybridization study revealed GHRH immunoreactivity and GHRH messenger RNA (mRNA) in the metastatic tumor cells. The anterior pituitary showed hyperplasia of somatotroph cells with intact acinar structure that did not contain an adenoma, determined by light microscopy using silver impregnation. Electron microscopy revealed hyperplastic characteristics of densely granulated somatotrophs. In situ hybridization documented strong signals for GH mRNA and pituitary-specific transcriptional factor Pit-1 mRNA in the hyperplastic somatotrophs. A weak signal for GHRH receptor mRNA was detected in these somatotrophs. However, using in situ RT-PCR, GHRH receptor mRNA was more conclusively observed in most of the somatotrophs. The excessive production of GHRH by metastatic tumor may have resulted in somatotroph hyperplasia by the synergistic effects of Pit-1 and GHRH receptor. It can be concluded that the pathogenesis of pituitary adenoma formation is primarily mediated by other factors than hypothalamic hormone.

Expression of peptide receptors in human endocrine tumours of the pancreas

BACKGROUND

Gut peptides are known to influence hormone release and growth of endocrine tumours of the pancreas. Although information on somatostatin receptors has been provided recently, little is known on the receptor status of other gastrointestinal hormones in such tumours.

AIMS

To analyse the spectrum of gut hormone receptors on endocrine tumours of pancreas.

SUBJECTS

Four types of endocrine tumours from eight patientS.

METHODS

The receptors for bombesin, secretin, vasoactive intestinal peptide, cholecystokinin, and somatostatin have been visualised and quantified with storage phosphor autoradiography.

RESULTS

Bombesin receptors were present in all five gastrinomas and two primary VIPomas. Secretin receptors were expressed in four primary gastrinomas and one primary VIPoma from pancreas. Vasoactive intestinal peptide receptors were identified in four primary gastrinomas and all VIPomas. Furthermore, all VIPomas expressed cholecystokinin-B (gastrin) receptors, whereas, gastrinomas did not contain cholecystokinin-B receptors. The receptors for somatostatin were detected in all gastrinomas and VIPomas. Both somatostatinoma and glucagonoma were negative for all five types of peptide receptors studied.

CONCLUSIONS

Besides somatostatin receptors, most of gastrinomas and VIPomas also express receptors for bombesin, secretin, and vasoactive intestinal peptide.

TGF-beta1 triggers oxidative modifications and enhances apoptosis in HIT cells through accumulation of reactive oxygen species by suppression of catalase and glutathione peroxidase

Transforming growth factor-beta1 (TGF-beta1) is a multifunctional polypeptide that is related to the progression of chronic pancreatitis. However, the mechanism of beta-cell damage by TGF-beta1 is unknown. Treatment with TGF-beta1 enhanced internucleosomal DNA cleavage caused by exogenous hydrogen peroxide in a hamster pancreatic beta-cell line (HIT). TGF-beta1 also induced protein oxidation, assessed by measuring carbonyl groups in proteins, and was involved in reactions that lead to lipid peroxidation. This eventually destructs membrane lipids and forms malondialdehyde. We have investigated its effects on two major antioxidative enzymes, catalase and glutathione peroxidase (GPx). TGF-beta1 suppressed mRNA expression as well as reduced the activities of catalase and GPx. The decrease in the catalase and GPx activities in TGF-beta1-treated cells resulted in an increase in intracellular peroxides as judged by flow cytometric analysis using a peroxide-sensitive dye, 2',7'-dichlorofluorescin diacetate. These data suggest that the augmented production of reactive oxygen species by TGF-beta1 through suppression of antioxidative enzymes may cause cellular damage and consequent apoptosis and induce pancreatitis or diabetes.

Evaluation of somatostatin-receptor scintigraphy for detecting neuroendocrine tumors

BACKGROUND

Somatostatin-receptor scintigraphy (SRS) has gained attention as an imaging modality for neuroendocrine tumors (NETs). The purpose of this study was to present one of the first American series evaluating the ability of SRS to detect local and distant disease caused by NETs.

METHODS

Medical records were reviewed from 35 patients who underwent a total of 38 studies using 111In-pentetreotide between 1993 and 1995. Twenty-two patients had islet cell tumors, seven had carcinoid tumors, and six had other NETs.

RESULTS

The overall sensitivity of SRS was 74% for detecting local disease (primary tumor +/- regional lymph node metastases) in all NETs, excluding insulinoma, 75% in gastrinoma, 0% in insulinoma, 78% in other islet cell tumors, and 50% in carcinoids. For detecting distant disease, the overall sensitivity of SRS was 67% for all NETs, excluding insulinoma, 100% for gastrinoma, 50% for other islet cell tumors, and 80% for carcinoids. Specificity and positive predictive value were 100% for all tumors. Negative predictive value ranged from 33% to 100%.

CONCLUSIONS

A positive SRS study strongly predicts the presence of tumor (100% positive predictive value in our study). However, unlike the European reports of very high sensitivity (80% to 88%), we found that SRS had a lower sensitivity (67% for all NETs excluding insulinoma and 71% for noninsulinoma gastroenteropancreatic NETs). Thus negative SRS in patients with NETs must be viewed cautiously, because the false-negative rate is high, and this limits the use of this method in the most difficult patients.

mRNA profiling of rat islet tumors reveals nkx 6.1 as a beta-cell-specific homeodomain transcription factor

Development of a high capacity multiplex reverse transcriptase-polymerase chain reaction protocol has allowed us to screen lineage related rat islet tumors classified as alpha-, beta-, and delta-like as judged by their hormone profile for differential expression of more than 50 selected genes. We find that in addition to insulin the insulinoma express the normal beta-cell markers Pdx-1, IAPP, and Glut-2, and that these markers are absent from the glucagonoma: a reflection of the normal alpha-cell. Furthermore, this study suggests that the GLP-1, glucagon, GIP, IGF-1, and insulin receptors as well as E-cadherin, R-cadherin, Id-1, and Id-2 are differentially expressed within the islet of Langerhans. Importantly, insulinoma-specific expression of the recently cloned homeodomain protein Nkx 6.1 predicted beta-cell-specific expression in the normal islet. Immunohistochemistry using antibodies raised against recombinant Nkx 6.1 did indeed localize Nkx 6.1 expression exclusively to the nuclei of normal islet beta-cells. Apart from pancreatic islets only the antral part of the stomach contained Nkx 6.1 mRNA. We conclude that multiplex reverse transcriptase-polymerase chain reaction-based mRNA profiling is a powerful tool to identify differentially expressed genes within phenotypically related cells and propose that Nkx 6.1 is involved in specifying the unique characteristics of the beta-cell.

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.

DNA ploidy and proliferating cell nuclear antigen in islet cell tumors

It is often difficult for pathologists to differentiate between benign and malignant islet cell tumors solely by histopathological criteria. The unequivocal evidence of malignancy is still the presence of metastases since cellular morphology or pleomorphism does not often render the biological clues of malignancy. Recently, nuclear DNA patterns have been reported for islet cell tumors using flow cytometry and image analysis to differentiate between benign and malignant tumors, yet conclusions are still controversial. With 28 surgically resected islet cell tumors, including 20 primary and eight metastatic tumors, nuclear DNA ploidy was analyzed and compared for the S-phase by image analysis and immunocytochemical staining for proliferating cell nuclear antigen (PCNA). Five additional autopsy cases were included for image analysis study. Small insulinomas (< 5 cm) were all benign, whereas gastrinomas were more frequently malignant. One-half of all islet cell tumors (14 of 28) were diploid and S-phase values by image analysis did not correspond with the comparable data obtained by PCNA staining. With cumulative information on tumor size, hormone secretion, mitotic figures, and PCNA positivity, islet cell tumors can be classified as benign or malignant with confidence.

Vascular endothelial growth factor and its receptors, flt-1 and flk-1, are expressed in normal pancreatic islets and throughout islet cell tumorigenesis

Endocrine organs, such as the pancreatic islets of Langerhans, contain permeable, fenestrated endothelium that allows direct access of endocrine cells to the blood stream. Factors that control differentiation and maintenance of this highly specialized endothelium remain unknown. Vascular endothelial growth factor (VEGF) is a multifunctional growth factor that may be responsible for the homeostasis of endocrine endothelium; it is a selective mitogen for endothelial cells and is able to permeabilize endothelium. We have analyzed the expression of VEGF mRNA and protein in pancreatic islet cells of normal mice and during the different stages of tumor progression in a transgenic mouse model of beta-cell carcinogenesis. The 120-amino acid and the 164-amino acid isoforms of VEGF are expressed in normal islets of Langerhans and are moderately up-regulated during the stages of tumor development. Two high-affinity receptors for VEGF, flt-1 and flk-1, are expressed by endothelial cells both in normal islets and in the stages of tumorigenesis; these receptors are not up-regulated during this process. Our data raise the possibility that VEGF is involved in the maintenance of permeable endothelium in islets of Langerhans, an observation that may have implications for islet cell physiology and diabetes. While VEGF may also play an important role in the growth of new blood vessels during islet cell tumorigenesis, it cannot be the only factor required for the activation of tumor angiogenesis.

Role of surgery in management of adrenocorticotropic hormone-producing islet cell tumors of the pancreas

BACKGROUND

Ectopic adrenocorticotropic hormone-producing islet cell tumors of the pancreas (ACTH-ICT) are a rare cause of Cushing's syndrome with a severe and rapidly progressive clinical course.

METHODS

Charts were reviewed on all patients evaluated and treated for proven Cushing's syndrome caused by ACTH-ICT (n = 12), specifically for the role of surgery in the management of this disease.

RESULTS

Ten (83%) of twelve patients with ACTH-ICT had liver metastases at the time of diagnosis (eight of eight with Zollinger-Ellison syndrome, two of four without Zollinger-Ellison syndrome). Surgical management of the primary tumor included three patients who underwent distal pancreatectomy combined with hepatic resection and one patient who underwent laparoscopic enucleation of a tumor from the pancreatic tail. Eight of twelve patients underwent bilateral adrenalectomy to control symptoms of Cushing's syndrome, including three patients who underwent concurrent distal pancreatectomy and hepatic resection. Six of twelve patients died of the disease within 2 1/2 years of diagnosis, four are alive with progressive hepatic metastases, and one has biochemical evidence of disease.

CONCLUSIONS

ACTH-ICT of the pancreas is an aggressive tumor, particularly when there is coproduction of gastrin. The benefit of aggressive surgical resection of primary or metastatic ACTH-ICT has not been established. However, palliative bilateral adrenalectomy is justified, because no patients had biochemical cures after aggressive surgical resection in this series.

Ca2+ ion transport through patch-clamped cells exposed to magnetic fields

The total current of Ca2+ ions through patch-clamped cell membranes was measured while exposing clonal insulin-producing beta-cells (RINm5F) to a combination of DC and AC magnetic fields at so-called cyclotron resonance conditions. Previous experimental evidence supports the theory that a resonant interaction between magnetic fields and organisms can exist. This experiment was designed to test one possible site of interaction: channels in the cell membrane. The transport of Ca2+ ions through the protein channels of the plasma membrane did not show any resonant behavior in the frequency range studied.

Malignant islet cell tumor associated with hypercalcemia

BACKGROUND

Three cases of islet cell tumors of the pancreas with hypercalcemia were studied, and 16 similar cases have been found in a 25-year review of the English-language literature. The purpose of the study was to review the cause of the hypercalcemia and the clinical characteristics of the tumors.

METHODS

Tumor tissue retrieved from paraffin-embedded blocks was studied immunohistochemically for both parathyroid hormone (PTH) and PTH-related protein (PTHrP). PTH was measured in the serum in each patient and the serum PTHrP was measured by immunoassay in one patient.

RESULTS

One of our patients had a fatal serum calcium level of 26.4 mg/dl. PTHrP stains were positive in two of our tumors, and one patient had an elevated PTHrP serum level. Serum PTH levels were normal or low in each patient. All three tumors were malignant and extremely vascular. The total group of 19 patients have in common hypercalcemia associated with a normal or low serum PTH level. Although the cause of hypercalcemia has not been proved, the tumors apparently produce PTHrP, because seven of eight tumors stained positive for PTHrP and each of the four patients tested had an elevated PTHrP serum titer. The tumors are extremely vascular, are usually malignant (17 of 18), and become large, but they are compatible with a relatively long patient survival time.

CONCLUSIONS

These neuroendocrine tumors associated with hypercalcemia share several characteristics, but a claim that they represent another type of "functioning islet cell tumor" should await a clearer delineation of the cause of the hypercalcemia.

ACTH-secreting islet cell tumor: appearances on dynamic gadolinium-enhanced MRI

Adrenocorticotropic hormone (ACTH) secreting islet cell tumors of the pancreas are extremely rare. A case of an ACTH producing islet cell tumor with multiple liver metastases is reported and the magnetic resonance imaging (MRI) findings are described.

Lipid composition of glucose-stimulated pancreatic islets and insulin-secreting tumor cells

The effect of glucose stimulation (25 mM for 5 min) on the phospholipid and neutral lipid composition of isolated pancreatic islets was studied to find out whether there is a change in the mass of potential lipid mediators or modulators of insulin secretion. For comparison, the lipid compositions of homogenates and subcellular fractions from RINm5F insulin-secreting tumor cells and of glucose-stimulated streptozotocin/nicotinamide-induced islet cell tumors were analyzed. After separation of the lipid extract into a neutral and an acidic fraction by anion-exchange chromatography, lipids were separated by high-performance thin-layer chromatography and quantitated by in situ densitometry of the cupric sulfate-charred bands. In glucose-stimulated islets, the molar percentages of phosphatidic acid (PA) and of phosphatidylinositol were significantly increased (3.1 vs. 4.7 mol% and 8.6 vs. 11.8 mol%), while those of all other phospholipids and neutral lipids, including 1,2-diacylglycerol, were not significantly changed. In stimulated islet cell tumors, an increase of PA was visible in the microsomal fraction, and there was an increase of lysophosphatidylcholine in the mitochondrial fraction. However, in both tumoral tissues, particularly in RINm5F cells, the lipid distribution pattern showed abnormalities which can be regarded as a loss of differentiation and which limit the usefulness of these tissues for the study of the physiological regulation of lipid metabolism during glucose stimulation. In conclusion, the data are in accordance with a role of PA early in stimulus-secretion coupling. The well-known stimulation of phospholipid synthesis in pancreatic islets during glucose-induced insulin secretion does not result in an increase in the total phospholipid mass.

Glucocorticoids regulate somatostatin peptide and steady state messenger ribonucleic acid levels in normal rat tissues and in a somatostatin-producing islet tumor cell line (1027B2)

Although a number of previous studies have suggested that glucocorticoids influence somatostatin (SS) function at the peptide level in some tissues and SS mRNA levels in thyroid tumor cells, there has been no systematic investigation of the effects of glucocorticoids on SS gene expression in normal tissues. In the present study, we have examined the effect of dexamethasone (DEX) on SS secretion and gene expression in rat tissues using as models DEX-treated rats in vivo, primary cultures of rat islet and cerebrocortical cells, and a SS-producing rat islet tumor cell line (1027B2). In vivo DEX administration (0.5 mg/kg) for 3 or 8 days augmented SS-mRNA 2- to 3-fold in peripheral tissues (stomach, pancreas, and jejunum), but reduced it by 50-60% in brain. The DEX effect was time dependent, being more pronounced after 8 days than after 3 days of treatment. In all tissues, SS mRNA levels returned to control values 2 weeks after cessation of DEX. Changes in tissue content of immunoreactive SS paralleled those in SS mRNA. In cultured rat islet cells, 18-h incubation with DEX induced dose-dependent biphasic effects on immunoreactive SS and SS mRNA; low doses (10(-10) M) were stimulatory, and high doses (10(-8)-10(-5) M) were inhibitory. Insulin secretion displayed dose-dependent stimulation by DEX, whereas glucagon release was inhibited. The effect of DEX on SS mRNA levels in primary cultures of brain cells was solely inhibitory. 1027B2 cells responded to DEX with augmented immunoreactive SS secretion and SS mRNA levels at low concentration (10(-10) M), followed by a dose-dependent inhibition of both parameters with increasing DEX concentrations. We conclude that glucocorticoids exert significant effects on SS peptide production and steady state mRNA levels in normal SS-producing tissues in vivo, in vitro, and in cultured 1027B2 cells. The glucocorticoid effect is time and dose dependent, tissue specific, and at least in part due to a direct action of the steroid hormone on SS-producing cells.

Effects of the microtubule depolymerizing and stabilizing agents Nocodazole and taxol on glucose-induced insulin secretion from hamster islet tumor (HIT) cells

Hamster islet tumor (HIT) cells retain much of the capacity of normal beta cells to act as glucose sensors. When stimulated with glucose or glucose plus forskolin, HIT cells release much more insulin than unstimulated cells. Ultrastructural analysis reveals that the secretory product of these cells is stored in membrane-bound granules that associate with microtubules under certain circumstances. Immunofluorescence studies using insulin antibody confirm the presence of insulin in granular structures in these cells. The microtubule inhibitor Nocodazole reduces the number of polymerized microtubules and inhibits the sustained phase of insulin secretion in HIT cells. Thus, the structural integrity of microtubules is important for the sustained phase of the insulin secretion to occur. The microtubule stabilizing drug taxol does not decrease insulin secretion. Since taxol blocks microtubule depolymerization, microtubule polymerization-depolymerization alone does not appear to be responsible for insulin granule transport. The increased use of these drugs in cancer research and therapy makes it important to understand their effects on insulin secretion.

[Localizing of Langerhans islets adenoma by transhepatic portal catheterization]

BACKGROUND

The procedures used to locate pancreatic endocrine tumors have only limited success in infants and children in whom the nodules may be small. Portal catheterization may therefore be useful.

CASE REPORT

A child aged 6 yrs 4 months was admitted because of several recent episodes of pallor and sweating associated with hypoglycemia. Further investigation showed moderate hyperinsulinemia and low blood levels of ketone bodies and branched amino-acids after a 15 hr fast. Celiac angiography was normal. The hypoglycemic episodes recurred despite treatment with diazoxide for 6 months. A transparietal portal catheterization was therefore performed. Selective pancreatic venous sampling showed high concentrations of insulin in two small veins draining one part of the head of the pancreas (117 and 89 microU/ml). The head of pancreas was removed 16 months later. Extemporaneous examination revealed an adenoma 0.8 cm in diameter. This patient has completely recovered, 8 months after surgery.

CONCLUSION

Transparietal portal catheterization can detect pancreatic areas with high insulin secretion. It may also help the interpretation of celiac angiographs in children, as diagnosis may be obscured by the normal rich vascularity of the pancreas in these patients.

Pancreatic beta cells cultured from individual preneoplastic foci in a multistage tumorigenesis pathway: a potentially general technique for isolating physiologically representative cell lines

Culturing and comparing the discrete stages of tumorigenesis provide a route to defining important components of the cancer phenotype and, in addition, present the opportunity to establish cell cultures more representative of normal cells than the ultimate malignant cancer cells. Herein we report that preneoplastic foci in one multistep tumorigenesis pathway can be cultured in vitro and show that they preserve distinctive characteristics of the normal cells from which they arose, pancreatic beta cells. In the RIP1-Tag2 line of transgenic mice, which express the simian virus 40 T antigen in insulin-producing beta cells, pancreatic islets develop into vascularized tumors in a multistage pathway. We established conditions for reproducible derivation of beta-cell lines from individual hyperplastic islets that have not yet developed into solid tumors. Most of these cell lines, designated beta HC, release insulin at physiological concentrations of glucose. In contrast to tumor-derived lines (beta TC), which are not properly regulated, the ability of the beta HC lines to respond correctly to glucose correlated with maintenance of normally depressed levels of low-Km hexokinases. Glutamic acid decarboxylase (GAD), an early autoantigen in type I diabetes, was detected in most of the beta HC lines. The relative levels of the two forms of this enzyme (GAD65 and GAD67) varied significantly between the different cell lines, suggesting independent regulation. Class I major histocompatibility complex antigens were detected on the beta HC cells, and the levels of surface major histocompatibility complex expression correlated with their capacity to serve as targets in a cytotoxic T-cell killing assay. The beta HC lines will be of value for studies of beta-cell physiology, autoantigenicity, and tumor development. This work suggests the possibility of culturing preneoplastic stages of other cancers, both to address the mechanisms of transformation and to provide a source of cells that maintain important qualities of their normal progenitors.

Use of isotope-labeled somatostatin analogs for visualization of islet cell tumors

The results of visualization of the islet cell tumors of 25 patients after intravenous administration of two isotope-labeled somatostatin analogs (123I-Tyr3-octreotide and 111In-octreotide) are described. The primary tumors, as well as previously often unrecognized distant metastases were visualized in 20 of the 25 patients (80%). Parallel in vitro detection of somatostatin receptors on those tumors that had also been visualized in vivo indicates that the ligand binding to the tumor in vivo indeed represents binding to specific somatostatin receptors. The detection of somatostatin receptors on these tumors in vivo predicted a good suppressive effect of octreotide on hormonal hypersecretion by these tumors. It is an easy, quick, harmless procedure that is valuable for localization of primary endocrine pancreatic tumors and their often radiologically and clinically not yet recognized metastases.

Octreotide as an antineoplastic agent in the treatment of functional and nonfunctional neuroendocrine tumors

BACKGROUND

Although patients with neuroendocrine tumors typically exhibit an indolent clinical course, the pace of disease accelerates and the prognosis deteriorates once objective progression of disease begins. Thirty-four patients with advanced neuroendocrine tumors were treated with octreotide as antineoplastic therapy. This treatment was begun only after documentation of clear objective progression of disease.

METHODS

A Phase II trial was performed at a tertiary comprehensive cancer center.

RESULTS

The median survival for this patient population from the start of octreotide therapy has not been reached, with a median follow-up of 29 months (range, 1-47 months). No major objective tumor regressions were seen. Seventeen patients (50%) experienced a computed tomography-documented stabilization of disease that was maintainable for a minimum of 2 months (median, 5 months; range, 0-27 months). Of the 34 patients, 20 patients received octreotide as their first antineoplastic therapy. The median survival for these 20 patients has not been reached, with a median follow-up also of 29 months (range, 12-41 months).

CONCLUSIONS

Octreotide may influence the natural history of neuroendocrine tumors. The survival in patients treated with octreotide, as measured from the time of progression of disease, compares favorably with that of historical controls. Proof of a survival advantage for patients treated with octreotide would require a multicenter, randomized trial.

Parallel secretion of pancreastatin and somatostatin from human pancreastatin producing cell line (QGP-1N)

In this investigation we studied pancreastatin (PST) secretion from a human PST producing cell line (QGP-1N) in response to various secretagogues. Immunocytochemical study revealed the immunoreactivity of PST and somatostatin (SMT) in the same cells of a monolayer culture. Ki-ras DNA point mutation on codon 12 was found. Carbachol stimulated secretion of PST and SMT and intracellular Ca2+ mobilization in the range of 10(-6)-10(-4) M. The secretion and Ca2+ mobilization were inhibited by atropine, a muscarinic receptor antagonist. Phorbol ester and calcium ionophore (A23187) stimulated secretion of PST and SMT. The removal of extracellular calcium suppressed both secretions throughout stimulation with 10(-5) M carbachol. Fluoride, a well-known activator of guanine nucleotide binding (G) protein, stimulated intracellular Ca2+ mobilization and secretion of PST and SMT in a dose-dependent manner in the range of 5-40 mM. Also, 10(-5) M carbachol and 20 mM fluoride stimulated inositol 1,4,5-triphosphate production. However, cholecystokinin and gastrin-releasing peptide did not stimulate Ca2+ mobilization or secretion of the two peptides. These results suggest that secretion of PST and SMT from QGP-1N cells is regulated mainly by acetylcholine in a parallel fashion through muscarinic receptors coupled to the activation of polyphosphoinositide breakdown by a G-protein and that increases in intracellular Ca2+ and protein kinase C play an important role in stimulus-secretion coupling.

Positron emission tomography (PET) in neuroendocrine gastrointestinal tumors

Positron emission tomography (PET) makes it possible to study effects of medical treatment in vivo. Carcinoid tumors with liver metastases, especially those of midgut origin, produce serotonin via the precursors tryptophan and 5-hydroxytryptophan (5-HTP) and this overproduction contributes to the clinical symptoms of the carcinoid syndrome. Seven patients with histopathologically verified neuroendocrine tumors and liver metastases, five of whom with ileal carcinoids, one a lung carcinoid and one an endocrine pancreatic tumor, were included in the study. All patients had elevation of urinary 5-HIAA with the exception of one patient with a solitary liver metastasis of midgut origin. After an intravenous injection of 11C-5-HTP, PET was performed and the uptake of radioactivity in tumor tissue, normal liver and plasma were compared. All patients with elevated urinary 5-HIAA and also the patient with a solitary liver metastasis and normal urinary 5-HIAA had high accumulation and signs of a high rate of binding of 5-HTP in the liver metastases. The uptake was relatively homogeneous in midgut carcinoid liver metastases but in large necrotic metastases the radioactivity was localized to the periphery. In three patients PET examination was repeated after 3 months of interferon treatment and in agreement with circulating tumor markers and ultrasonography the uptake of 5-HTP was unchanged. Another patient who received the somatostatin analog somatuline progressed on treatment and accordingly the uptake of 5-HTP also increased. The experience with PET in neuroendocrine gastrointestinal tumors is very limited. Our results so far indicate that 5-HTP can be used to visualize serotonin-producing neuroendocrine tumors and furthermore it might prove to be of value to monitor the effects of treatment, possibly also as an early predictive test of the outcome of treatment.

Distribution and elimination of the somatostatin analogue (111In-DTPA-D-Phe1)-Octreotide (OctreoScan111)

The distribution and elimination characteristics of the 111In-labelled somatostatin analogue OctreoScan111 were studied in 23 patients with malignant tumours. The substance exhibited a rapid blood elimination following a bi-phasic pattern. The initial part of the elimination curves showed a t1/2a of between 0.27 and 3.6 h. The patients investigated had creatinine clearance rates ranging from 33 to 124 ml/min. However, within this range, no apparent correlation was found between the OctreoScan111 elimination rate and kidney function. Also no correlation was observed between the amount of administered activity and the elimination rate of OctreoScan111. The serum radioactivity of 6 patients was analyzed with respect to molecular size. These experiments showed that OctreoScan111 circulated unbound in serum. About 3% of the radioactivity, most probably representing 111In-chloride of DTPA-111In-chloride, circulated protein-bound. The elimination of OctreoScan111 radioactivity in urine displayed a bi-phasic pattern. Size separation of the radioactivity appearing in the urine after 24 h showed a higher molecular weight when compared with OctreoScan111, indicating the existence of a metabolite of the injected substance. The results obtained are discussed in the light of a potential role for the substance in systemic radiotherapy.

Expression of growth factor peptides and their receptors in neuroendocrine tumors of the digestive system

Neuroendocrine tumors of the digestive system are slow growing neoplasms which often present with pronounced fibrosis around tumor cells and in the peritoneal cavity. In this report 30 midgut carcinoids and endocrine pancreatic tumors were examined for the expression of peptide growth factors and their receptors, both by immunohistochemistry and in situ hybridization. Our data indicate that multiple peptide growth factors, PDGF, TGF-beta, and bFGF are expressed by these tumors. PDGF was expressed on tumor cells and stroma in 70% of tissues examined. PDGF alpha-receptor was seen on clusters of tumor cells and occasionally on adjacent stroma, whereas PDGF beta-receptor was seen only in the stroma. Our data suggest that PDGF may be involved in the autocrine stimulation of tumor cells and stimulation of stromal cell growth through paracrine and possibly autocrine mechanism. In addition, tumor tissues express all three isoforms of TGF-beta in more than half of the tissues examined. Tumor cells produce small latent complexes causing an escape from potent inhibitory effect of TGF-beta and stimulation of stromal cell growth and matrix deposition through paracrine mechanism. bFGF, a potent stimulant of endothelial cell growth, was expressed by all tumor tissues examined. Our data suggest that multiple peptide growth factors may have an important role in tumor progression and desmoplastic reaction accompanying these tumors.

Production of immunoreactive corticotropin-releasing hormone in various neuroendocrine tumors

The concentrations of immunoreactive (IR) corticotropin-releasing hormone (CRH) in 218 neuroendocrine tumors were determined by CRH radioimmunoassay. The tumors examined were 86 pancreatic endocrine tumors (PET), 22 neuroblastic tumors (NBT), 26 carcinoid tumors (CA), 24 pheochromocytomas (PHEO), 40 small cell lung carcinomas (SCLC) and 20 medullary thyroid carcinomas (MTC). IR-CRH was detectable in 21 neuroendocrine tumors (10 PET, four NBT, three CA, two PHEO and two SCLC) at levels of 10-2,700 ng/g wet weight (9.6%). The 21 patients with these CRH-producing tumors showed no clinical symptoms suggestive of Cushing's syndrome. The levels of plasma IR-CRH extracted by immunoaffinity chromatography were < 7.5 pg/ml in five normal subjects and a patient with a neuroblastic tumor containing 55 ng/g wet weight IR-CRH, but in a patient with a thymic carcinoid tumor containing 1,000 ng/g wet weight IR-CRH, the plasma level was elevated to 180 pg/ml. This patient did not have Cushing's syndrome nor an elevated plasma adrenocorticotropic hormone (ACTH) level. The concentrations of nine peptides (growth hormone-releasing hormone, somatostatin, ACTH, calcitonin, gastrin-releasing peptide, glucagon, vasoactive intestinal peptide, neuropeptide tyrosine and pancreatic polypeptide) were determined in extracts of the 21 IR-CRH-producing tumors. Some of these peptides were frequently found to be produced concomitantly with CRH. The results indicate IR-CRH to be produced by various neuroendocrine tumors, but Cushing's syndrome, due to the CRH, to be very rare. The results also show that CRH-producing tumors produce multiple hormones.

Islet amyloid polypeptide-producing pancreatic islet cell tumor. A clinical and biochemical characterization

Islet amyloid peptide (IAPP) or amylin is a recently discovered polypeptide without settled physiology in man. We present a patient with an endocrine pancreatic tumor secreting huge amounts of IAPP-like immunoreactivity (20,000 mol/l) and a concomitant development of diabetes mellitus. The release of insulin and pancreatic polypeptide (PP) was totally absent after an oral glucose load and a mixed meal, respectively. Tumor secretion of IAPP-like immunoreactivity seemed to be influenced by cholinergic mechanisms and by nutrients. The observed effects on insulin and PP secretion by high circulating levels of IAPP-like immunoreactivity may be of beneficial value for further studies of the physiology of IAPP in man.

Mucin-producing pancreatic tumor: CT findings and histopathologic correlation

Twenty patients with mucin-producing pancreatic tumor and 60 with other pancreatic diseases underwent computed tomography (CT) to establish the CT characteristics of mucin-producing pancreatic tumor. Scans were obtained with thin sections by administering a large volume of contrast material (200 mL). Mucin-producing pancreatic tumors were divided into three subgroups, and the CT characteristics were as follows: Main duct type tumors consisted of a cystic mass in or communicating with the dilated main pancreatic duct (MPD). Excrescent nodules and/or septa were found in the cyst. The MPD was markedly dilated over its entire length. Branch duct type tumors consisted of clustered small cysts that were all approximately the same size in diameter (1-2 cm). Excrescent nodules or septa were not always seen. The MPD near the lesion was often slightly dilated. Peripheral type tumors consisted of a well-defined cystic mass with excrescent nodules and/or septa. Even if the cyst was multilocular, a large main cyst was in it. The MPD usually was not dilated. The CT findings corresponded to macroscopic findings. Mucin-producing pancreatic tumor can be differentiated from other pancreatic diseases with these criteria.

Immunohistochemical characterization of an amphicrine mucinous islet-cell carcinoma of the pancreas. Case report

Immunohistochemical characteristics of a mucinous islet-cell carcinoma of the pancreas are described. The tumour presented with jaundice in a 59-year-old male. It consisted of polygonal atypical cells forming a reticular pattern, and invaded the common bile duct. In DNA flow cytometry, the tumour cells showed a clear-cut aneuploid peak. Intercellular mucin was abundant. A panel of antisera and monoclonal markers was applied in the immunohistochemical analysis. In addition to general epithelial and endocrine markers, the tumour cells showed a focal positive immunoreaction with anti-glucagon, anti-insulin, anti-vasoactive intestinal polypeptide, anti-pancreatic secretory trypsin inhibitor and anti-phospholipase A2 antigen. At the ultrastructural level, mucous and neuroendocrine granules were demonstrated in the same tumour cells.

Malignant pancreatic oncocytoma. An unusual cause of organic hypoglycemia

A case of malignant islet-cell tumor with oncocytic features occurring in a 54-year-old woman with symptoms of organic hypoglycemia is reported. The tumor was composed of ribbons of cells arranged in an endocrine pattern. The cytoplasm of these cells was eosinophilic and finely granular. Ultrastructurally, the cells contained numerous mitochondria and dense-core neurosecretory granules. Tumor cells were focally immunoreactive for neuron-specific enolase, insulin, glucagon and VIP. Capillaries invasion and metastases to lymph nodes argued in favor of malignancy but there was no subsequent malignant involvement during a 3-year follow-up after surgery. Such insulinomas with oncocytic features have not been previously described. Endocrine features in oncocytomas of the pancreas and of other locations are discussed.

Pancreatic mixed ductal-islet tumors. Is this an entity?

Thirty-eight human pancreatic cancer specimens were studied for the reactivity of cancer cells with monoclonal antibodies against insulin, glucagon, somatostatin, pancreatic polypeptide (PP), vasoactive intestinal peptide (VIP), gastrin, calcitonin, and with argyrophilic reactivity. Immunoreactivity with one or several antibodies or argyrophilic reactivity were found in 30 (79%) cases. In 17 cases, the number of endocrine cells was excessive and morphologically consistent with the mixed ductal-islet tumor. Although most immunoreactive cells were located at the base of the malignant glands, some had intraepithelial location and were also present in the invasive portion of cancers, indicating their malignant nature. Endocrine cell proliferation were found in the pancreatic tissue adjacent to the carcinoma in 8 out of 12 specimens examined. In these cases, the immunoreactive cells were either distributed among the acinar cells or ductal cells. More endocrine cells were found in the hyperplastic ducts; however, no correlation was found between the degree of hyperplasia and the occurrence of any type of immunoreactive cells. Although several types of endocrine cells occurred in different pancreatic regions (head, body, and tail), PP cells were restricted to tissues taken from the head of the pancreas. Experimental data and similar observations by other investigators led us to conclude that participation of endocrine cells in ductal-type carcinomas is a general phenomenon and does not justify the classification of these lesions to mixed ductal-islet entity. However, because immunoreactive cells were more common and numerous in well-differentiated carcinomas, they may have some prognostic values.

Immunohistochemical study of the distribution of pancreastatin in endocrine tumors of the pancreas and in normal pancreatic tissue: analysis of autopsy cases

Using sixteen cases (sixteen lesions) of endocrine tumor of the pancreas, found in 1,300 consecutive autopsy cases (661 men and 639 women; mean age, 79.0 years), we examined distribution patterns of pancreastatin (PST) in these endocrine tumors and in normal tissues around them, using immunohistochemical staining. In addition, the distribution patterns of PST was compared with those of insulin (INS), glucagon (GLU), somatostatin (SOM), and pancreatic polypeptide (PP), in these tissues. Normal islets of Langerhans were stained completely and evenly for PST. Two endocrine tumors did not stain for PST at all, six were partially stained, and eight were stained as densely as normal islets, or even more densely. Acinar cells were only partially stained for PST in 11 cases and showed scattered staining in three cases. Epithelial cells of ducts or ductuli were partially stained for PST in 10 cases and showed scattered staining in three cases. Distribution patterns of PST coincided with that of INS in 56% (9/16) of cases, GLU in 81% (13/16), SOM in 31% (5/16), and PP in 31% (5/16). In the eight tumors that were stained at least as densely for PST as normal islets, the staining pattern did not coincide with that of INS in any case (0%), coincided with that of GLU in all 8 cases (100%), and coincided with those of SOM and PP in one case each (13%). Therefore, the distribution of GLU-producing cells (A cells) coincided most closely with that of PST. It is concluded that most PST is secreted from A cells in human pancreas.

Acetylcholine regulates pancreastatin secretion from the human pancreastatin-producing cell line (QGP-1N)

Studies were made of pancreastatin (PST) secretion from a human PST-producing cell line (QGP-1N) in response to various secretagogues. Cells with immunoreactivity for PST were observed in monolayer cultures of QGP-1N cells. Carbachol stimulated PST secretion and the intracellular Ca2+ mobilization concentration dependently in the range of 10(-6)-10(-4) M. The PST secretion and Ca2+ mobilization induced by carbachol were inhibited by atropine. The calcium ionophore (A23187) stimulated PST secretion. However, cholecystokinin and gastrin-releasing peptide did not stimulate either PST secretion or Ca2+ mobilization. Secretin also did not stimulate PST secretion. The glucose concentration in the culture medium had no effect on PST secretion. These results suggest that PST secretion is mainly regulated by acetylcholine through a muscarinic receptor, and that an increase in intracellular Ca2+ plays an important role in stimulus-secretion coupling in QGP-1N cells.

Parathyroid hormone-related peptide mediates hypercalcemia in an islet cell tumor of the pancreas

Hypercalcemia occurring in a patient with an islet cell carcinoma of the pancreas suggests the diagnosis of Multiple Endocrine Neoplasia Type I and associated hyperparathyroidism. We describe a patient with an islet cell carcinoma and hypercalcemia in whom low concentrations of PTH, the absence of skeletal metastases, hypophosphatemia, and elevated nephrogenous cAMP alternatively suggested the syndrome of humoral hypercalcemia of malignancy. The peptide PTHrP was measured in the patient's serum during the course of therapy by an immunoradiometric assay directed toward the midportion of the molecule. Hypercalcemia was treated with an investigational aminobisphosphonate. The concentration of PTHrP[56-86] increased over time and fell after the patient received chemotherapy directed toward the islet cell tumor.

Islet amyloid polypeptide in proliferating pancreatic B cells during development, hyperplasia, and neoplasia in humans and mice

The occurrence of islet amyloid polypeptide (IAPP) immunoreactivity was investigated in fetal pancreas, islet cell hyperplasia, and tumors in humans and mice. Transgenic mice heritably developing endocrine tumors of the pancreas (AVP/SV40, Rip 1 Tag2/Rip2PyST1 and Glu2-Tag strains) were used as murine models of islet cells proliferative disease. In the mouse, IAPP immunoreactivity was found in B cells at embryonic day 12 (E12), paralleling the onset of insulin immunoreactivity. In hyperplastic/dysplastic islets and in B-cell tumors of transgenic mice (n = 16), IAPP immunoreactivity was localized consistently to insulin-immunoreactive cells. Ultrastructural single- and double-immunogold labeling of transgenic mice B-cell tumors (n = 3) showed insulin and IAPP to be colocalized in beta granules. In human fetuses, IAPP immunoreactivity was found in insulin-immunoreactive B cells, but at a later gestational age than the onset of insulin immunoreactivity. In pancreatic specimens of infantile/neonatal persistent hyperinsulinemic hypoglycemia (11 cases) and in pancreatic endocrine tumors (21 cases, 10 of which were functioning insulinomas), IAPP immunoreactivity was found consistently in insulin-immunoreactive B cells. Congo-red-positive amyloid deposits present in tumors also were IAPP immunoreactive. Ultrastructural single and double immunogold labeling of infantile/neonatal persistent hyperinsulinemic hypoglycemia cases (n = 3) and functioning insulinomas (n = 2) showed IAPP and insulin to be colocalized in beta granules. In addition, IAPP immunoreactivity was observed in amyloidlike fibrils. These findings indicate that IAPP is a constitutive component of B cells. Possible relationships between IAPP and insulin expression and interspecies differences are suggested and discussed.

Regulation of islet somatostatin secretion and gene expression: selective effects of adenosine 3',5'-monophosphate and phorbol esters in normal islets of Langerhans and in a somatostatin-producing rat islet clonal cell line 1027 B2

To investigate cAMP-dependent regulation of somatostatin secretion and gene expression in the islets of Langerhans, we have correlated the effects of forskolin, theophylline, and (Bu)2cAMP (dbcAMP) on the secretion of somatostatin-like immunoreactivity (SLI), cAMP generation, and somatosatin mRNA (S-mRNA) accumulation by cultured rat islet cells and a rat somatostatin-producing islet tumor cell line (1027 B2). Additionally, we have compared these effects with those of phorbol esters. Forskolin induced large acute increases in cAMP levels in islet cells, whereas theophylline produced modest sustained elevations in cAMP. During 4-h exposure to islets cells, forskolin, theophylline, and dbcAMP produced time- and dose-related increases of up to 14-fold in SLI release and up to 5-fold in S-mRNA levels. The rate of increase in S-mRNA paralleled secretion and occurred with the following order of potency: forskolin greater than dbcAMP greater than theophylline. The analog 1,9-dideoxyforskolin, which is unable to activate adenylyl cyclase, produced a small increase in SLI release without affecting S-mRNA. The effects of short term increases in islet cAMP levels and SLI release on long term changes in S-mRNA accumulation were investigated in a 48-h study with forskolin. Pretreatment of islet cells for 30 min with forskolin evoked large acute increases in cAMP levels and SLI release. S-mRNA rose in a biphasic pattern, with an acute increase at 30 min followed by a secondary increase at 12-48 h. In 1027B2 cells, forskolin and theophylline generated large increases in cAMP levels. Despite this, the two agents as well as dbcAMP produced only slight (20-35%) stimulation of SLI release and S-mRNA accumulation. Phorbol 12-myristate 13-acetate and phorbol 12,13-dibutyrate evoked dose-dependent stimulation of SLI secretion of up to 4-fold from islet cells without altering S-mRNA. Both secretion and S-mRNA were unresponsive to phorbol esters in 1027 B2 cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Endocrine pancreatic carcinoma

Endocrine carcinomas of the pancreas are rare, but they should be treated aggressively because they threaten the patient's life by both malignant growth and hormone excess. Resection for cure should be attempted, but is hardly ever possible. Debulking should be performed primarily in hormone-active tumours so that symptoms can be controlled by subsequent medical treatment; this can be directed against tumour growth and/or hormone production, and it can reduce stomach acid secretion in the gastrinoma syndrome. Surgery should be undertaken whenever possible since the patient's life can be considerably prolonged in most cases. Palliative surgery can reduce the patient's symptoms that may be caused by excessive hormone production and/or obstruction of the bile duct or the duodenum.

Differential glucocorticoid regulation of glucagon gene expression in cell lines derived from rat and hamster islet cell tumors

Glucocorticoid regulation of peptide hormone gene expression was studied in two cell lines derived from rodent islet cell tumors. In rat RIN1056A cells, dexamethasone reduced the levels of glucagon mRNA transcripts while markedly inducing the expression of the angiotensinogen gene. In contrast, dexamethasone had no effect on the regulation of glucagon gene expression in hamster InR1-G9 cells. Wild type InR1-G9 cells did not support the induction of the murine mammary tumor virus promoter by glucocorticoids, suggesting that these cells lacked the necessary cellular factor(s) for glucocorticoid responsiveness. Introduction of the glucocorticoid receptor into wild type InR1-G9 cells restored glucocorticoid induction of the murine mammary tumor virus promoter, but not glucocorticoid regulation of glucagon gene expression. Dexamethasone treatment of Sprague-Dawley rats had no effect on the levels of pancreatic glucagon mRNA transcripts. The results of these studies demonstrate that glucocorticoid regulation of glucagon gene expression is restricted to the immortalized RIN1056A cell line, providing additional evidence for cell-specific diversity in the regulation of peptide hormone gene expression in neuroendocrine tumors.

Malignant islet cell tumor of the pancreas with multiple hormone production and expression of CEA and CA19-9. Report of an autopsy case

An autopsy case of malignant islet cell tumor of the pancreas is presented. The patient, a 64-year-old woman showed severe hypoglycemia as the initial symptom, and hyperinsulinemia was demonstrated by laboratory examinations. Metastatic tumors in the liver were found by abdominal computed tomography. Autopsy revealed a tumor measuring 6.5 x 3 x 2 cm occupying the pancreas from the body to the tail. From the results of histological and immunohistochemical studies, this was diagnosed as a malignant islet cell tumor producing multiple hormones such as insulin, glucagon, somatostatin and pancreatic polypeptide, as well as expressing the tumor-related antigens CEA and CA19-9. These findings suggested that the tumor cells showed differentiation to both endocrine cells and pancreatic duct cells.

Galanin inhibits somatostatin release by the rat islet cell tumor in culture, Rin-m

Using a rat islet cell tumor in culture, Rin-m, we studied the effects of the neuropeptide, galanin, on somatostatin release. Galanin applied to the incubation medium inhibited pancreatic hormone release rapidly and dose dependently with an IC50 at 4 nM and the maximal effect (40% inhibition) was elicited by 100 nM peptide. Pretreatment of Rin-m cells with pertussis toxin abolished the inhibitory effect of galanin on somatostatin release. The results suggest that galanin probably controls the function of the pancreatic delta cell through a pertussis toxin-sensitive pathway.

Necrolytic migratory erythema: association with neuroendocrine tumour with predominant insulin secretion

We report a case of necrolytic migratory erythema in association with a neuroendocrine tumour producing predominantly insulin. As far as we know this has not been observed before.

Dexamethasone inhibits insulin biosynthesis by destabilizing insulin messenger ribonucleic acid in hamster insulinoma cells

Glucocorticoid effects on insulin biosynthesis and secretion have been controversial. To define whether glucocorticoids affect insulin biosynthesis in vitro, the actions of dexamethasone on insulin gene expression were examined using the HIT cell line, a transformed clonal line of hamster beta-cells. Dexamethasone induced a dose-dependent decrease in steady-state insulin messenger RNA (mRNA) levels, which was prevented by adding an excess of RU 486, a competitive inhibitor for the binding to the glucocorticoid receptor. Inhibition was not observed before 6 h of dexamethasone treatment and was maximal at 24 h. To further assess the molecular mechanisms of the dexamethasone-induced decreases in insulin mRNA levels, we investigated whether transcription of the insulin gene was affected. Run-on assays revealed that transcription rates were not changed by glucocorticoids. Inhibition of RNA and protein synthesis by actinomycin D and cycloheximide, respectively, completely abolished the dexamethasone effects, whereas actinomycin D added 9 h after dexamethasone had no effect on insulin mRNA levels. The present results demonstrate that glucocorticoids can acutely inhibit insulin biosynthesis by destabilizing insulin mRNA; this effect requires the transcriptional activation of a gene encoding a protein responsible for the accelerated disappearance of insulin mRNA.

Increased amino acid clearance and urea synthesis in a patient with glucagonoma

Fasting concentrations, clearance of exogenous infused amino acids, and lean body mass were studied in a patient with glucagonoma syndrome (fasting glucagon = 380 pmol/l, normal range 15-45 pmol). The fasting concentrations of all amino acids were reduced. The clearances of alanine, arginine, glycine, isoleucine, leucine, lysine, methionine, proline, serine, threonine, and tyrosine were increased. The urea synthesis rate during amino acid infusion was 27 mumols/kg per minute (normal range 20-24 mumols/kg per minute). The lean body mass of the patients was reduced to 59% of the expected value. It is suggested that the weight loss of patients with glucagonoma syndrome is partly due to increased hepatic conversion of amino acid nitrogen to urea nitrogen, resulting in decreased blood amino acid concentration, and secondary to this, organ protein catabolism, as shown by the decreased lean body mass.

Neuroendocrine pancreatic tumours: clinical presentation, biochemical and histopathological findings in 84 patients

A prospective study has been performed on 84 patients with endocrine pancreatic tumours evaluated at the Medical Department in Uppsala. Available information concerning the patients' presenting symptoms, age at diagnosis, clinical syndrome, tumour location, location of metastases, diagnostic radiology, biochemical and histopathological findings has been analysed. Our results indicate that most patients initially show rather vague and non-specific symptoms, with dyspepsia and pain being the most frequent presenting features. The median delay between appearance of the first symptom and diagnosis was 2 years; the delay was 35 months in sporadic cases and 14.5 months in familial cases. In spite of improvements in diagnostic methods, the median age at diagnosis (53 years) has not been reduced, and most patients are encountered when the tumour has reached an advanced stage. There is a need for a method of screening patients with still uncharacteristic abdominal symptoms for a neuroendocrine tumour. The presence of elevated levels of plasma chromogranin in all patients with a proven tumour suggests that such possibilities exist, and the use of this biochemical marker in the future might reduce the age at diagnosis and thus improve the likelihood of cure and survival of patients with endocrine pancreatic tumours.

Isolation and characterization of a tumor-derived human protein related to chromogranin A and its in vitro conversion to human pancreastatin-48

A protein with pancreastatin-like immunoreactivity has been isolated and purified from liver metastasis of a patient with insulinoma. NH2-terminal residue analysis, in conjunction with the use of antibodies that are specific for the C-terminal amide peptide of porcine pancreastatin, identified this protein as a 186-amino-acid protein corresponding to human chromogranin A-116-301 (the fragment corresponding to the positions from 116 to 301 of human chromogranin A). Digestion of this protein with trypsin yielded a 48-amino-acid peptide with the retention of full pancreastatin activity. Serum from patient with insulinoma contains a peptide specie(s) that comigrates with the 48-amino-acid pancreastatin, suggesting that this peptide might be a physiologically important circulation form of pancreastatin in humans. A sensitive radioimmunoassay was established using antibody developed against a synthetic 29-amino-acid peptide amide of pancreastatin. Immunocytochemical staining revealed that a major population of human pancreatic islet cells were immunoreactive to the antiserum but with varying intensity of staining. Pancreastatin-like immunoreactivity was not observed in exocrine acinar cells.

Serotonin-producing pancreatic endocrine tumour. Histological, ultrastructural and immunohistochemical study of a case

Serotonin-producing pancreatic endocrine tumours are rare neoplasms which in most cases exhibit malignant biological behaviour. These tumours, in the majority of the well-documented cases, are composed of argyrophil- and argentaffin-positive cells which contain large pleomorphic neurosecretory granules. In contrast, argyrophilic non-argentaffin pancreatic endocrine tumours with tumour cells containing round neurosecretory granules are exceptional. In this study we describe such a tumour not associated with clinical evidence of carcinoid syndrome in a 60-year-old woman. Histological examination revealed tumour extension in pancreatic lymphatic vessels and veins but no evidence of locoregional or distant metastases. Ten months after surgery the patient showed no recurrence of the disease. Immunohistochemistry revealed cytoplasmic serotonin production in the tumour cells which were negative for anti-gastrin, insulin, glucagon, somatostatin, pancreatic polypeptide (PP), vasoactive intestinal peptide (VIP) and ACTH. This study emphasizes the usefulness of combined ultrastructural and immunohistochemical investigations in order to identify and characterize the rare pancreatic endocrine tumours with serotonin production.

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.