Preferential location of somatostatin receptors in germinal centers of human gut lymphoid tissue

Diagnostic and Therapeutic Management of Primary Orbital Neuroendocrine Tumors (NETs): Systematic Literature Review and Clinical Case Presentation

BACKGROUND

The ocular involvement of neuroendocrine neoplasms (NENs) is uncommon and mainly represented by metastases from gastrointestinal and lung neuroendocrine tumors. Primary orbital NENs are even less common and their diagnostic and therapeutic management is a challenge.

METHODS

A systematic review of the literature was conducted from 1966 to September 2023 on PubMed to identify articles on orbital NENs and to summarize their clinical-pathological features, diagnosis and therapeutic management. Furthermore, we presented a case of a locally advanced retro-orbital primary neuroendocrine tumor that was referred to the certified Center of Excellence of Sant'Andrea Hospital, La Sapienza University of Rome, Italy.

RESULTS

The final analysis included 63 records on orbital NENs and 11 records focused on primary orbital NENs. The localization was mostly unilateral and in the right orbit; proptosis or exophthalmos represented the initial symptoms. The diagnostic work-up and therapeutic management was discussed and a diagnostic algorithm for the suspicion of primary orbital NENs was proposed.

CONCLUSIONS

A multidisciplinary approach is required for the management of primary orbital NENs, emphasizing the importance of early referral to dedicated centers for prompt differential diagnosis, tailored treatment, and an improved quality of life and survival.

Physiological Biodistribution of 68Ga-DOTA-TATE in Normal Subjects

Objectives:

Somatostatin is an endocrine peptide hormone that regulates neurotransmission and cell proliferation by interacting with G protein-coupled somatostatin receptors (SSTRs). SSTRs are specific molecular targets of several radiotracers for neuroendocrine tumor (NET) imaging. Gallium-68 (⁶⁸Ga)-DOTA-TATE is widely used for positron emission tomography/computed tomography (PET/CT) imaging of SSTRs and has shown a higher affinity for SSTR2, the most common SSTR subtype found in NETs. We aimed to analyze the distribution pattern of ⁶⁸Ga-DOTA-TATE in normal subjects.

Methods:

A total of 617 consecutive ⁶⁸Ga-DOTA-TATE PET/CT whole-body scans performed in our department from May 2015 through April 2020 with known or suspected neuroendocrine malignancies, mostly to evaluate adrenal adenomas, were retrospectively analyzed by 2 nuclear medicine physicians. One hundred eighteen subjects without a diagnosis of NET, with no tracer avid lesion of NET on ⁶⁸Ga-DOTA-TATE PET/CT, and followed up for at least 6 months (average 2-3 years) without any biochemical, clinical, or imaging findings suggestive of NET were included in this study.

Results:

The highest uptake of ⁶⁸Ga-DOTA-TATE was noted in the spleen followed by the kidneys, adrenal glands, liver, stomach, small intestine, prostate gland, pancreas head, pancreas body, thyroid gland, and uterus, in descending order. Minimal to mild uptake was detected in the submandibular glands, parotid glands, thymus, muscles, bones, breast, lungs, and mediastinum.

Conclusion:

Our study shows the biodistribution pattern of ⁶⁸Ga-DOTA-TATE in normal subjects and the ranges of the maximum standard uptake value (SUV_max) and SUV_mean values of 68Ga-DOTA-TATE obtained in several tissues for reliably identifying malignancy in ⁶⁸Ga-DOTA-TATE PET/CT studies.

Current Role of 111In-DTPA-Octreotide Scintigraphy in Diagnosis of Thymic Masses

Aims and background

Thymic tumors (thymomas and thymic carcinomas) represent 50% of all mediastinal tumors. Thymomas usually express high levels of somatostatin receptors, which enable in vivo imaging with 111In-DTPA-octreotide (OctreoScan®). The aim of this study was to further investigate the role of radionuclide techniques in the diagnosis, staging and follow-up of these tumors.

Methods

Eight patients (5 women, 3 men, age range 35–79 years; mean ± SD 56.1 ± 15.8 years) entered the study. In 4 patients, myasthenia gravis was the presenting symptom. 111In-DTPA-octreotide scan was performed within 3 weeks after contrast enhanced CT and/or MRI. Planar and tomographic images were acquired within 24 hours of the injection of 111 MBq OctreoScan. The scintigraphic results were defined in correlation with the histological findings.

Results

Histology revealed thymoma in 3 patients, thymic carcinoma in 1, insular carcinoma of presumably thymic origin in 1, thymic carcinoid in 1, and thymic hyperplasia in 2 patients. Two thymomas were at stage I, 1 thymoma and 1 thymic carcinoma at stage II, 1 insular carcinoma of presumably thymic origin at stage IV, and 1 thymic carcinoid at stage IV. OctreoScan consistently accumulated in primary and/or metastatic sites of thymic tumors while no radiotracer uptake was detected in the 2 patients with benign thymic hyperplasia. In 1 patient with a very large mediastinal mass (13 cm in largest diameter) and multiple metastatic deposits in the lungs, OctreoScan scintigraphy showed a large area of pathological uptake in the anterior mediastinum and a small area of focal uptake in the cervical-dorsal region of the right lung corresponding to a lymph node expressing somatostatin receptors.

Conclusions

OctreoScan is avidly taken up by thymic tumors, enabling the diagnosis of these tumors and a better evaluation of their extension. It does not accumulate in thymic hyperplasia, thus allowing the differential diagnosis between these 2 pathological conditions. In patients affected by myasthenia gravis, OctreoScan scintigraphy can play an important role in characterizing thymic masses.

Chylous Ascites: A Rare Adverse Effect of Methimazole Treatment for Grave's Disease-A Case Report and Review of the Literature

A 40-year-old woman was admitted due to an urticarial rash that was attributed to recent onset of methimazole treatment for a diagnosis of Grave's disease. The patient had no prior significant medical history and used no medications, including over-the-counter or herbal medications. Her sister had Grave's disease. On admission, the patient received corticosteroids with improvement in her rash. On the second day of the hospitalization, the patient complained of abdominal discomfort. Abdominal ultrasound revealed a large amount of new onset ascites. Peritoneal tap yielded a milky fluid with high triglyceride level (12.2 mmol/L or 1080 mg/dL), consistent with chylous ascites. After discontinuation of the methimazole, the ascites disappeared. The patient later underwent therapeutic thyroidectomy, after which all features of thyrotoxicosis had improved.

Neuroendocrine tumor imaging with 68Ga-DOTA-NOC: physiologic and benign variants

OBJECTIVE

Imaging with (68)Ga-labeled 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-octreotide analogs has become an important modality in patients with neuroendocrine tumors (NETs). In addition to high uptake in NET lesions, prominent physiologic radiotracer activity has been reported in the pituitary gland, pancreas, adrenal glands, liver, and spleen, and faint activity has been reported in the thyroid and gastrointestinal tract. This article describes previously unknown sites of 68Ga-DOTA-1-NaI3-octreotide (NOC) uptake unrelated to NETs.

MATERIALS AND METHODS

One hundred eighty-two patients (96 female and 86 male patients; age range, 4-89 years) with documented (n=156) or suspected (n=26) NETs underwent 207 68Ga-DOTA-NOC PET/CT studies. Studies were retrospectively reviewed for the presence, intensity, and localization of foci of increased uptake that were further correlated with findings on additional imaging studies and clinical follow-up for a period of 4-32 months.

RESULTS

Uptake of 68Ga-DOTA-NOC not identified as NET or known physiologic activity was detected in 297 sites with confirmation in 149 of 207 studies (72%). The most common location of non-NET-related 68Ga-DOTA-NOC-avid sites was in small lymph nodes, followed by prostate, uterus, breasts, lungs, brown fat, musculoskeletal system, and other sites, including oropharynx, pineal body, thymus, aortic plaque, genitalia, surgical bed, and subcutaneous granuloma. Intensity of uptake in non-NET-related 68Ga-DOTA-NOC-avid sites ranged in maximum standardized uptake value from 0.8 to 10.5.

CONCLUSION

Previously unreported benign sites of 68Ga-DOTA-NOC uptake were found in the majority of studies, suggesting the presence of somatostatin receptors in physiologic variants or processes with no evidence of tumor. Knowledge of increased tracer uptake in non-NET-related sites is important for accurate interpretation and for avoiding potential pitfalls of 68Ga-DOTA-NOC PET/CT.

[Efficacy of octreotide in the treatment of chyle fistulas associated with pancreatic disease]

INTRODUCTION

A chyle fistula is an uncommon complication following abdominal and pancreatic surgery, particularly in the retroperitoneal compartment. It can also appear as a complication of a severe acute pancreatitis. Medical treatment is the initial approach, but resolution is often slow. Somatostatin or octreotide can help in accelerating the resolution of fistulae.

PATIENTS AND METHODS

Patients developing a chyle fistula (output > 100ml/24h, normal amylase levels and triglyceride concentrations above 110mg/dl) associated with pancreatic disorders were treated with oral intake restriction and parenteral nutrition, followed by subcutaneous octreotide 0.1mg/8h.

RESULTS

Four female patients from 55 to 80 years old, underwent pancreatic surgery or presented with an acute pancreatitis, were treated. Chyle fistulae ranging from 100 to 2,000ml/24h were treated with octreotide, being resolved within five to seven days. No recurrence has been found in a 2 to 4 years follow up.

CONCLUSIONS

We have found that chyle fistula medical treatment is often related to a slow resolution, somatostatin or octreotide administration dramatically reduces its duration. Other previously reported studies have also shown that the quick onset of such treatment can accelerate the whole process, leading to a shorter recovery and lower hospital costs.

Somatostatin in inflammatory bowel disease

Intestinal inflammation is controlled by various immunomodulating cells, interacting by molecular mediators. Neuropeptides, released by enteric nerve cells and neuroendocrine mucosa cells, are able to affect several aspects of the general and intestinal immune system, with both pro- as well as anti-inflammatory activities. In inflammatory bowel disease (IBD) there is both morphological as well as experimental evidence for involvement of neuropeptides in the pathogenesis. Somatostatin is the main inhibitory peptide in inflammatory processes, and its possible role in IBD is discussed.

Immunohistochemical localization and quantitative expression of somatostatin receptors in normal human spleen and thymus: Implications for the in vivo visualization during somatostatin receptor scintigraphy

BACKGROUND

[111In-DTPA-D-Phe1]-octreotide scintigraphy allows the visualization of SRIF receptor (SSR)-expressing tumors, including thymic tumors, and normal tissues. While the spleen is clearly visualized, the thymus is not depicted, although both contain SSR.

AIM

We evaluated whether the heterogeneity, the type, and the amount of SSR might explain this contrasting finding.

MATERIALS, METHODS, AND RESULTS

By ligand-binding the number of [125I-Tyr11]-SRIF- 14 binding sites resulted comparable between the two tissues, whereas the number of [125I-Tyr3]-octreotide sites was significantly higher in the spleen (p<0.001). Quantitative RTPCR showed a significantly higher expression of sst2A mRNA in the spleen, whereas a significantly higher expression of SRIF and sst3 in the thymus. The highest density of sst2A in the spleen is in line with the in vivo uptake of [111In-DTPA-D-Phe1]- octreotide, which is considered a sst2-preferring ligand. The specificity is confirmed by the evidence that in vivo [111In-DTPA- D-Phe1]-octreotide uptake can be abolished during chronic administration of "cold" octreotide. Immunohistochemistry confirmed a preferential expression of sst2A on microenvironmental cells and of sst3 on lymphoid cells.

CONCLUSIONS

The heterogeneity of SSR expression and the higher SRIF content explain the lack of thymus visualization during scintigraphy, whereas thymic tumors, which do not express SRIF, are visualized. Apart from the affinity of the radioligand, also the efficacy of the internalization is crucial for the in vivo uptake, and both heterogeneity and SRIF content affect this process. These observations might have an important impact when interpretating in vivo visualization of SSR-positive lesions, and when treatment with novel SRIF analogs is considered.

Prevention and treatment of lymphorrhoea following surgery for gastric cancer

BACKGROUND

Lymphorrhoea is a rare complication of abdominal surgery. However, there have been a few reports of lymphorrhoea following radical gastrectomy. Here, we retrospectively review the clinical analysis and treatment of lymphorrhoea based on our experiences.

METHODS

We retrospectively reviewed a total of 1596 patients who underwent surgery for gastric cancer between January 1995 and January 2007. D1 and D2 lymphadenectomies were performed in 1104 patients, and D3 and D4 lymphadenectomies were performed in the other 492 patients. Disrupted lymph vessels were ligated in 545 patients, and electrically cauterized in 559 patients. Before December 31 2000, total parenteral nutrition (TPN) was administered to all the patients, and after 1 January 2001, TPN was supplemented with octreotide in all the post-operative patients.

RESULTS

The incidence of lymphorrhoea in patients with D3 and D4 lymphadenectomy was much higher than that in D1 and D2 lymphadenectomy patients (P < 0.05). In addition, the incidence of lymphorrhoea in patients in whom the electrotome cautery was significantly higher than that in patients who received ligation. The addition of octreotide to TPN can reduce the quantity and duration of lymphorrhoea (P < 0.05).

CONCLUSION

Ligating rather than cauterizing the disrupted lymph vessels can be done to minimize the incidence of lymphorrhoea. The combination of Octreotide and TPN appears to be an effective therapeutic modality for lymphorrhoea.

The effectiveness of the treatment of octreotide on chylous ascites after liver cirrhosis

Octreotide is a crucial drug used for treating patients with chylous ascites; however, there have been few reports related to octreotide that are being used in cirrhotic patients. Thus, this thesis is designed to determine the effects of octreotide on patients with chylous ascites after liver cirrhosis. Eight patients were diagnosed with chylous ascites, on the basis of laboratory findings on ascites samples, between January 2003 and May 2008. Octreotide was given to the six patients, while the remaining two were treated as a control. All patients had persistent peritoneal drainage with the quantity and quality of the drainage fluid observed once every other day. All the necessary care was individually given to the patients during the therapy. All patients properly received combined therapy including a low-fat and low-sodium diet, and diuretic and peritoneal drainage. The volume of the peritoneal drainage was reduced to zero in one of the six patients who received octreotide therapy, while the other five had the drainage volumes decreased from 2,000 to 50 ml with a clear appearance and negative qualitative analysis of chyle. For those two patients who did not receive octreotide therapy, the conditions of peritoneal drainage seldom changed both from the qualitative and quantitative aspects. In conclusion, Octreotide, along with combined therapy, can rapidly relieve portal hypertension and reduce triglyceride levels in ascites. It appears to be an effective therapy available for the treatment of chylous ascites caused by liver cirrhosis.

The role(s) of somatostatin, structurally related peptides and somatostatin receptors in the gastrointestinal tract: a review

Extensive functional and morphological research has demonstrated the pivotal role of somatostatin (SOM) in the regulation of a wide variety of gastrointestinal activities. In addition to its profound inhibitory effects on gastrointestinal motility and exocrine and endocrine secretion processes along the entire gastrointestinal tract, SOM modulates several organ-specific activities. In contrast to these well-known SOM-dependent effects, knowledge on the SOM receptors (SSTR) involved in these effects is much less conclusive. Experimental data on the identities of the SSTRs, although species- and tissue-dependent, point towards the involvement of multiple receptor subtypes in the vast majority of gastrointestinal SOM-mediated effects. Recent evidence demonstrating the role of SOM in intestinal pathologies has extended the interest of gastrointestinal research in this peptide even further. More specifically, SOM is supposed to suppress intestinal inflammatory responses by interfering with the extensive bidirectional communication between mucosal mast cells and neurons. This way, SOM not only acts as a powerful inhibitor of the inflammatory cascade at the site of inflammation, but exerts a profound antinociceptive effect through the modulation of extrinsic afferent nerve fibres. The combination of these physiological and pathological activities opens up new opportunities to explore the potential of stable SOM analogues in the treatment of GI inflammatory pathologies.

Treatment and prevention of lymphorrhea after radical gastrectomy of gastric cancer

PURPOSE

Lymphorrhea is an uncommon complication of abdominal surgery. Here, we retrospectively investigate the treatment and prevention of lymphorrhea after radical gastrectomy.

METHODS

From January 1995 to January 2007, a total of 1,596 patients who underwent surgery for gastric cancer were investigated. According to the AJCC cancer stage manual, tumor stages of 693 (43.4%) cases were T1 or T2 and 903 (56.6%) cases were T3 or T4. A total of 1,104 (69.2%) patients received grade D1 lymphadenectomy or grade D2, and 492 (30.8%) patients received grade D3 or D4. Ligation was used during the lymphadenectomy in 829 (51.9%) patients, and the electrotome cautery was used in 767 (48.1%) patients. Patients diagnosed of lymphorrhea were treated with total parenteral nutrition (TPN) alone before 2001, and with TPN plus octreotide after 2001.

RESULTS

The incidence of lymphorrhea of patients with D1-2 lymphadenectomy was much lower than those with D3-4 lymphadenectomy (P < 0.01). For patients whose lymphatic vessels were ligated during the operation, the incidence of lymphorrhea was much lower than those lymphatic vessels were electrically cauterized (P < 0.01). No significant difference of incidence of lymphorrhea could be found between patients with T1-2 and T3-4 tumor stages (P > 0.05). Octreotide or TPN administration can reduce the quantity and duration of lymphorrhea,and the combination of Octreotide and TPN has a more significant effect on lymphorrhea than TPN alone (P < 0.01).

CONCLUSION

The major cause of lymphorrhea following radical gastrectomy was the inappropriate management of lymphadenectomy. Avoiding an extensive lymphadenectomy at surgery and ligating the disrupted lymph vessels would reduce the incidence of lymphorrhea. The combination of Octreotide and TPN is an effective therapeutic modality for lymphorrhea.

The role of cortistatin in the human immune system

Cortistatin (CST) is a recently described neuropeptide that shares high homology with somatostatin (somatotropin release-inhibiting factor, SRIF) and binds with high affinity to all somatostatin (sst) receptor subtypes. CST is currently known to have a widespread distribution in many human organs including the immune system. The activities specific to CST may be partially attributable to its binding to the growth hormone secretagogue (GHS)-receptor (GHS-R) and the orphan G-protein-coupled receptor MrgX2. Human immune cells produce CST, whereas macrophage lineage and activated endothelium express sst2, and human lymphocytes express sst3. The human thymus expresses sst1, 2, 3, MrgX2 and almost all immune cells express GHS-R. Moreover, at this very moment promising research with CST in experimental animal models is being performed. On the basis of these promising results, studies aiming to further evaluate the possibilities of CST as a therapeutic agent in human immune-mediated inflammatory diseases are warranted.

Chylous ascites secondary to pancreatitis: management of an uncommon entity using parenteral nutrition and octreotide

Malignancy, surgical trauma, cirrhosis and tuberculosis account for more than 95% of causes for chylous ascites. We report a case of persistent chylous ascites following acute pancreatitis that responded to parenteral nutrition and octreotide. A 50 year-old male was diagnosed with acute alcoholic pancreatitis after presenting with typical abdominal pain, and elevated amylase and lipase. The acute symptoms resolved within one week. Four weeks later he started developing increased abdominal girth. Examination revealed the presence of shifting dullness and paracentesis confirmed diagnosis of chylous ascites. Investigations for the common causes of chylous ascites were negative. Laparoscopy confirmed the presence of fat necrosis within mesenteric lymph nodes linking the chylous ascites to the episode of pancreatitis. The Chylous ascites was resistant to the usual medical therapy, but responded only to the combination of octreotide and total parenteral nutrition with complete resolution of ascites in 8 weeks. This case of chylous ascites secondary to pancreatitis represents an uncommon presentation with effective management resulting in a dramatic response.

Cortistatin as a therapeutic target in inflammation

Cortistatin (CST) is a recently discovered neuropeptide from the somatostatin gene family, named after its predominantly cortical expression and ability to depress cortical activity. CST shows many remarkable structural and functional similarities to its related neuropeptide somatostatin, or somatotropin release-inhibiting factor. However, the many physiological differences between CST and somatostatin are just as remarkable as the similarities. CST-29 has recently been shown to prevent inflammation in rodent models for human diseases, raising novel therapeutic properties to this neuropeptide. In this review, the authors address a new possible role for CST in the immune system and evaluate the possible therapeutic use of CST to treat disorders associated with inflammation.

Nuclear medicine imaging and therapy of neuroendocrine tumours

Radiolabelled peptides are used for specific targeting of receptors (over-)expressed by tumour cells. Dependent on the kind of labelling and the radionuclide used, these compounds may be utilised for imaging or for therapy. A concise overview is provided on basic principles of designing and developing radiopeptides for these applications. Furthermore, clinical application of these compounds for imaging and therapy is described. Advantages of the method compared to other techniques (such as the use of radiolabelled antibodies or antibody fragments) are discussed as well as pitfalls and limitations.

Somatostatin receptors and autoimmune-mediated diabetes

Somatostatin (SST) peptide is produced by various SST-secreting cells throughout the body and acts as a neurotransmitter or paracrine/autocrine regulator in response to ions, nutrients, peptides hormones and neurotransmitters. SST is also widely distributed in the periphery to regulate the inflammatory and immune cells in response to hormones, growth factors, cytokines and other secretive molecules. SST peptides are considered the most important physiologic regulator of the islet cell, gastrointestinal cell and immune cell functions, and the importance of SST production levels has been implicated in several diseases including diabetes. The expression of SST receptors has also been found in T lymphocytes and primary immunologic organs. Interaction of SST and its receptors is also involved in T-cell proliferation and thymocyte selection. SSTR gene-ablated mice developed diabetes with morphologic, physiologic and immunologic alterations in the endocrine pancreas. Increased levels of mononuclear cell infiltration of the islets are associated with the increased levels of antigen-presenting cells located in the islets and peripancreatic lymph nodes. Increased levels of SST were also found in antigen-presenting cells and are associated with a significant increase of CD8 expression levels on CD4(+)/CD8(+) immature thymocytes. These findings highlight the crucial role of this neuroendocrine peptide and its receptors in regulating autoimmune functions.

Somatostatin receptors

In 1972, Brazeau et al. isolated somatostatin (somatotropin release-inhibiting factor, SRIF), a cyclic polypeptide with two biologically active isoforms (SRIF-14 and SRIF-28). This event prompted the successful quest for SRIF receptors. Then, nearly a quarter of a century later, it was announced that a neuropeptide, to be named cortistatin (CST), had been cloned, bearing strong resemblance to SRIF. Evidence of special CST receptors never emerged, however. CST rather competed with both SRIF isoforms for specific receptor binding. And binding to the known subtypes with affinities in the nanomolar range, it has therefore been acknowledged to be a third endogenous ligand at SRIF receptors. This review goes through mechanisms of signal transduction, pharmacology, and anatomical distribution of SRIF receptors. Structurally, SRIF receptors belong to the superfamily of G protein-coupled (GPC) receptors, sharing the characteristic seven-transmembrane-segment (STMS) topography. Years of intensive research have resulted in cloning of five receptor subtypes (sst(1)-sst(5)), one of which is represented by two splice variants (sst(2A) and sst(2B)). The individual subtypes, functionally coupled to the effectors of signal transduction, are differentially expressed throughout the mammalian organism, with corresponding differences in physiological impact. It is evident that receptor function, from a physiological point of view, cannot simply be reduced to the accumulated operations of individual receptors. Far from being isolated functional units, receptors co-operate. The total receptor apparatus of individual cell types is composed of different-ligand receptors (e.g. SRIF and non-SRIF receptors) and co-expressed receptor subtypes (e.g. sst(2) and sst(5) receptors) in characteristic proportions. In other words, levels of individual receptor subtypes are highly cell-specific and vary with the co-expression of different-ligand receptors. However, the question is how to quantify the relative contributions of individual receptor subtypes to the integration of transduced signals, ultimately the result of collective receptor activity. The generation of knock-out (KO) mice, intended as a means to define the contributions made by individual receptor subtypes, necessarily marks but an approximation. Furthermore, we must now take into account the stunning complexity of receptor co-operation indicated by the observation of receptor homo- and heterodimerisation, let alone oligomerisation. Theoretically, this phenomenon adds a novel series of functional megareceptors/super-receptors, with varied pharmacological profiles, to the catalogue of monomeric receptor subtypes isolated and cloned in the past. SRIF analogues include both peptides and non-peptides, receptor agonists and antagonists. Relatively long half lives, as compared to those of the endogenous ligands, have been paramount from the outset. Motivated by theoretical puzzles or the shortcomings of present-day diagnostics and therapy, investigators have also aimed to produce subtype-selective analogues. Several have become available.

Imaging Lung Tumors with Peptide-Based Radioligands

The somatostatin analogue octreotide was the first radiopeptide to be used for the scintigraphic diagnosis of tumors. Somatostatin receptor scintigraphy (SRS) has proven its value, especially in the detection of gut neuroendocrine tumors. In some tumor types, it is considered the diagnostic gold standard. In carcinoid tumors of the lung, SRS is of major importance in diagnostic workup. Furthermore, the combination of computed tomography scanning and SRS is a reliable and cost-effective approach for the evaluation of single pulmonary nodules. Despite these favorable properties, SRS fails in the detection of metastases of lung cancer. The problem of false-positive results in SRS resulting from inflammatory disease might be overcome by the use of new radiopeptides such as cholecystokinin-B receptor-binding gastrin analogues. This article focuses on the current status of peptide-receptor scintigraphy in the diagnosis of lung tumors and on future developments in this field.

Interactions between the enteric nervous system and the immune system: role of neuropeptides and nutrition

Neuropeptidergic synthesis occurs in enteric nerves and immune cells of the gut-associated lymphoid tissue. Lymphocytes, macrophages, mast cells, and intestinal epithelial cells are capable of responding to these neuropeptides. Neuropeptides generate proliferative or antiproliferative responses of mucosal lymphocytes and intestinal epithelial cells, affect cytokine production and immunoglobulin synthesis by immune cells, and control secretion of water and electrolytes. Some neuropeptides, particularly cholecystokinin, gastrin-releasing peptide, and neurotensin, appear promising to maintain mucosal immunity in patients who cannot receive enteral feeding during critical illness or after GI tract loss. Exogenous administration of neuropeptides to preserve normal immune defenses represents a potential new field of pharmacotherapeutics against bacterial invasion.

Effects of Schistosoma mansoni infection on somatostatin and somatostatin receptor 2A expression in mouse ileum

Intestinal schistosomiasis is accompanied by motility-related dysfunctions but the underlying mechanisms are not well-known. Therefore, the presence and effects on intestinal contractility of somatostatin (SOM) and its receptor, SSTR2A, were investigated in the ileum of normal and infected mice. The distribution of SOM and SSTR2A was visualized using immunocytochemistry. Radioimmunoassay combined with oogram studies was performed to determine SOM levels and contractility measurements were determined in organ bath experiments. Schistosomiasis resulted in a significant decrease in somatostatin-positive endocrine cells, whereas the number of somatostatin-immunoreactive (IR) neuronal cell bodies did not change. From 8 weeks postinfection onwards, an increase was noted in somatostatin-IR nerve fibres in both villi and granulomas. The staining intensity for SSTR2A, expressed in somatostatin-negative myenteric cholinergic neurones, increased during infection suggesting an upregulation of this receptor. SOM levels were negatively correlated with the number of eggs during the acute phase, and were elevated during the chronic phase. Pharmacological experiments revealed that schistosomiasis diminished the inhibitory effect of SOM on neurogenic contractions. We can conclude that schistosomiasis influences the distribution and expression levels of SOM and SSTR2A in the murine ileum, which might explain the changed motility pattern.

Signal transduction of somatostatin in human B lymphoblasts

Somatostatin (SST) and somatostatin receptors (SSTR) are widely distributed in lymphoid tissues. Here, we report on the stimulatory effects of SST in Epstein-Barr virus-immortalized B lymphoblasts. By RT-PCR, we demonstrated the exclusive expression of the somatostatin receptor isoform 2A (SSTR2A) in B lymphoblasts. Addition of SST rapidly increased the cytosolic free calcium concentration [Ca(2+)](i) maximally by about 200 nM, with an EC(50) of 1.3 nM, and stimulated the formation of inositol phosphates. Furthermore, SST increased binding of guanosine 5'-O-(3-thiotriphosphate) by 50% above basal. These effects were partly inhibited by pertussis toxin (PTX), which indicates the involvement of PTX-sensitive G proteins. We provide further evidence that Galpha(16,) a PTX-insensitive G protein confined to lymphohematopoietic cells, is involved in the otherwise unusual coupling of SSTR2A to phospholipase C activation. In addition, SST activated extracellular regulated kinases and induced a 3.5-fold stimulation of DNA synthesis and a 4.4-fold stimulation of B lymphoblast proliferation, which was accompanied by an enhanced immunoglobulin formation. Thus SST exerts a growth factor-like activity on human B lymphoblasts.

Tissue distribution of octreotide binding receptors in normal mice and strains prone to autoimmunity

Somatostatin has diverse functions, including immunomodulatory functions. In humans, sites of active inflammation can be visualized by the administration of 111In-DTPA(0)-octreotide, a radiolabelled somatostatin analogue. We wished to establish an animal model for preclinical evaluation of the effects of somatostatin analogues on the immune system. However, most animal models for immunological diseases are murine. This report is a preliminary study of the distribution of somatostatin receptors in mouse tissues, with emphasis on the immune system. Tissue distribution of octreotide binding receptors in normal (BALB/c) mice was determined in vivo by receptor binding of 111In-DTPA(0)-octreotide and in vitro and ex vivo by receptor autoradiography. Additionally, we investigated the tissue distribution of octreotide binding receptors in inflammatory lesions in a murine model of immune mediated disease, i.e. pre-diabetic pancreatic infiltration in the non-obese diabetic mouse strain. High specific uptake of radioactivity was seen in the thymus (range 1-1.7% ID/g) and the pituitary (1-1.6% ID/g) in all mouse strains. Specific uptake was also found in the stomach (0.1-0.7% ID/g), in the adrenal glands (0.1-0.3% ID/g) and in the pancreas (0.1-0.3% ID/g). However, we did not detect increased uptake of radiolabelled octreotide in the pancreas of pre-diabetic NOD mice. Autoradiography on tissue sections confirmed the presence of octreotide binding sites in the tissues that showed specific uptake. Moreover, by using autoradiography we could localize the cortex of the thymus and the anterior part of the pituitary as the localization of specific and high affinity, octreotide binding sites. A high, but not a receptor mediated, uptake of radioactivity was seen in the kidneys and was significantly higher in females than in males (12-19% vs 4% ID/g, respectively). Our results point to profound species differences in the tissue distribution of octreotide binding receptors. Of particular interest is the high uptake of 111In-DTPA(0)-octreotide in the cortex of the mouse thymus. This offers perspectives for the use of this animal in studies concerning the effect of somatostatin analogues on the immune system. To our knowledge, this is the first report on the tissue distribution of octreotide binding receptors in mice.

Primary intestinal and thoracic lymphangiectasia: a response to antiplasmin therapy

Lymphangiectasia is a congenital or acquired disorder characterized by abnormal, dilated lymphatics with a variable age of presentation. We describe a case of lymphangiectasia with intestinal and pulmonary involvement in an adolescent female, who presented with many of the classic features including chylous pleural effusions, lymphopenia, hypogammaglobinemia, and a protein-losing enteropathy. She also presented with recurrent lower gastrointestinal bleeding, which is infrequently described. The patient did not improve with bowel rest and a low-fat medium-chain triglyceride diet and had little improvement with octreotide acetate therapy. However, she had a clinical response to antiplasmin therapy, trans-4-aminothylcyclohexamine carboxylic acid (tranexamic acid) in terms of serum albumin and gastrointestinal bleeding. She continues to have exacerbations of her condition, as well as persistent lymphopenia and chronic pleural effusions.

Somatostatin receptor imaging

[(111)In-DTPA(0)]octreotide is a radiopharmaceutical with a great potential for the visualization of somatostatin receptor-positive tumors. The overall sensitivity of Somatostatin Receptor Imaging (SRI) to localize neuroendocrine tumors is high. In a number of neuroendocrine tumor types, as well as in Hodgkin's disease, inclusion of SRI in the localization or staging procedure may be very rewarding, either in terms of cost-effectiveness, patient management, or quality of life. The value of SRI in patients with other tumors, like breast cancer, or in patients with granulomatous diseases, has to be established. The development of Peptide Receptor Radionuclide Therapy (PRRT) is expected to stimulate peptide receptor imaging.

Octreotide in patients with active ulcerative colitis treated with high dose corticosteroids (OPUS 1)

BACKGROUND

In ulcerative colitis the intestinal somatostatin content is reduced. Somatostatin has several immune-inhibitory effects. In vitro it diminishes activity of intestinal lymphocytes and peripheral blood monocytes. Its long-acting analogue octreotide has beneficial effects on mucosal damage in acute experimental acetic acid colitis in rats.

AIMS

To determine the potential benefits of octreotide as a treatment for patients with severe ulcerative colitis treated with high dose corticosteroids.

PATIENTS

Forty-two patients with severe ulcerative colitis (more than 10 points on the Powell-Tuck scoring system and mucosal disease Heatly grade III or IV).

METHODS

In a multi-centre, double blind, placebo-controlled trial all patients were treated with oral 5-ASA (1.6-2.4 g daily) and high dose corticosteroids (tapering off from 60 to 80 mg daily). They were randomly assigned to receive subcutaneous placebo (n = 22) or octreotide 500 microg (n = 20) thrice daily during 21 days. Clinical and endoscopic disease activity, histology and laboratory parameters were obtained during the study period.

RESULTS

Clinical disease activity for both octreotide and placebo were not significantly different at baseline and after 21 days of treatment. Endoscopic disease activities (mean +/- SD) changed from 12.5 +/- 4.7 to 7.2 +/- 5.3 for octreotide, and from 11.5 +/- 5.0 to 5.0 +/- 3.4 for placebo (NS). Seven patients from both groups received additional treatment (colectomy (n = 6), cyclosporin (n = 1)). Adverse events occurred equally in both groups.

CONCLUSIONS

Subcutaneous administration of octreotide 500 microg thrice daily is not of additional benefit as adjuvant therapy to high dose corticosteroids in severe ulcerative colitis.

Octreotide therapy: a new horizon in treatment of iatrogenic chyloperitoneum

Chyloperitoneum is a rare and challenging complication of abdominal surgery. We report a case of iatrogenic chyloperitoneum. Infusion of octreotide, a somatostatin analogue, together with total parenteral nutrition followed by medium chain triglyceride diet resulted in rapid resolution of chyloperitoneum. We believe this to be the first report of successful use of octreotide in iatrogenic chyloperitoneum in a child.

Somatostatin induces migration of acute myeloid leukemia cells via activation of somatostatin receptor subtype 2

Somatostatin, a neuropeptide with multiple activities, exerts its function via G-coupled membrane receptors. Five somatostatin receptor subtypes, sst1-5, have been identified. We have recently established that somatostatin acts as a chemoattractant on normal hematopoietic progenitor cells. Here, we studied the expression of somatostatin receptors (sst) on leukemic cells from 16 AML patients. Using fluorescent somatostatin (Fluo-SS) in flow cytometry, we found that sst are expressed in variable amounts on primary AML cells. Reverse transcriptase polymerase chain reaction (RT-PCR) analysis and immunochemistry revealed that only sst subtype 2 is expressed by AML cells. Using a two-chamber in vitro migration assay, we show that AML cells migrated towards a gradient of octreotide, a stable synthetic analogue of somatostatin. The degree of migration correlated with the cell surface density of sst2 as measured by Fluo-SS binding. These findings indicate that somatostatin influences trafficking of AML cells, which may have implications for the distribution of AML cells in the body and for clinical applications of somatostatin and analogues thereof in the context of AML.

Effects of octreotide on responses to colorectal distension in the rat

BACKGROUND AND AIMS

It has been suggested that the analgesic effect of the somatostatin analogue octreotide in visceral pain involves peripheral mechanisms. We evaluated the effect of octreotide on responses to noxious colorectal distension in rats.

METHODS

In a behavioural study, pressor and electromyographic responses to colorectal distension were evaluated before and after intravenous or intrathecal administration of octreotide. In pelvic nerve afferent fibre recordings, responses of mechanosensitive fibres innervating the colon to noxious colorectal distension (80 mm Hg, 30 seconds) were tested before and after octreotide.

RESULTS

Octreotide was ineffective in attenuating responses to colorectal distension in either normal or acetic acid inflamed colon when administered intravenously but attenuated responses when given intrathecally. Administration of octreotide over a broad dose range (0.5 microg/kg to 2.4 mg/kg) did not alter responses of afferent fibres to noxious colorectal distension in untreated, or acetic acid or zymosan treated colons.

CONCLUSIONS

In the rat, octreotide has no peripheral (pelvic nerve) modulatory action in visceral nociception. The antinociceptive effect of octreotide in this model of visceral nociception is mediated by an action at central sites.

Protein-Losing Enteropathy and Gastropathy

The diagnosis of protein-losing enteropathy (PLE) should be considered in all patients with hypoalbuminemia and edema without other known causes, and established by plasma alpha(1)-antitrypsin (alpha(1)-AT) clearance or nuclear studies. The therapy for PLE should focus principally on the treatment of the underlying disease after it has been identified. Therapeutic goals should include improvement of hypoalbuminemia, edema, and lymphopenia. The existing primary literature for therapy of PLE syndromes consists mainly of case reports and expert opinions, subject to substantial reporting bias and unknown rates of spontaneous remission; the rarity of and the diversity among this set of diseases make future large randomized trials unlikely. Therapeutic choices, therefore, must involve clinical acumen, empiricism, and understanding of the pathophysiology of the underlying disease process, and must be tailored to each individual patient's syndrome. Dietary interventions including hypolipidic, high-protein regimens, supplemented by medium-chain triglycerides (MCTs), are extremely useful, particularly in protein loss due to increased lymphatic pressure. Corticosteroids can be very useful in certain cases of PLE (though not without substantial long-term toxicity) when clinical serologic or histologic markers of inflammatory disease are present. Octreotide is a well tolerated drug that has been demonstrated to improve PLE in some patients, and is worth consideration. Octreotide is a well tolerated drug that has been demonstrated to improve PLE in some patients, and is worth consideration. Surgery finds its best role in treating gastrointestinal protein loss from neoplasia, inflammatory bowel disease, and hypertrophic gastritis. Most other PLEs are distributed too widely for surgical intervention. Protein-losing gastropathy (PLG) behaves somewhat differently from the general group of PLE, marked by excellent responses to elimination of Helicobacter pylori, antisecretory therapy, and surgical resection. Protein-losing enteropathy stemming from cardiovascular disease is best treated by medical or surgical cardiovascular interventions; however, some patients may respond to mucosa-directed therapy.

Peptides as regulators of the immune system: emphasis on somatostatin

Study of the communication between nervous and immune systems culminated in the understanding that cytokines, formerly considered exclusively as immune system-derived peptides, are endogenous to the brain and display central actions. More recently, immune cells have been recognized as a peripheral source of "brain-specific" peptides with immunomodulatory actions. This article reviews studies concerning reciprocal effects of selected cytokines and neuropeptides in the nervous and immune systems, respectively. The functional equivalence of these two categories of communicators is discussed with reference to the example of the actions of neuropeptide somatostatin in the immune system.

Expression of somatostatin receptor subtypes on guinea pig gastric and colonic smooth muscle cells

In vivo and in vitro studies have demonstrated that somatostatin can influence motility and smooth muscle contractility of the stomach and colon. Recent studies have proposed that some of these effects may be mediated by somatostatin receptors (sst) directly on the smooth muscle cells. If this is correct, the sst receptor subtypes that are present are unknown. This study aimed to resolve these points. Because nucleotide sequences of guinea pig sst genes are unknown, we used sst subtype-specific primers based on comparisons of human and rat sst subtypes and performed RT-PCR of DNase I-treated total RNA from guinea pig total brain. PCR products were cloned in pCR II and sequenced and showed 87% (sst(1)), 90% (sst(2)), 90% (sst(3)), 99% (sst(4)), and 80% (sst(5)), respectively, nucleotide homology to the same region (transmembrane 4-6) of the human sst genes. Homology to rat sequences were lower. PCR products were obtained from first-strand cDNA derived from DNase I-treated RNA from dispersed guinea pig gastric and colonic smooth muscle cells. In gastric and colonic smooth muscle cells, we detected sst(1)-sst(3) and sst(5), and all were confirmed by sequencing. The presence of sst(4) was shown by Southern blot analysis and hybridization with a guinea pig sst(4)-specific primer. RT-PCR from cultured colonic and gastric smooth muscle cells devoid of any neural elements gave identical results. These results demonstrate that in the guinea pig all five sst subtypes are present directly on gastric and colonic smooth muscle cells. Previous studies have suggested that a predominant sst(3) subtype on gastric and a sst(5) subtype on colonic muscle cells mediated somatostatin's contractile effects, but the finding here that all five sst subtypes exist on both of these cells suggests that other sst subtypes have only a small or no contractile effect, sst subtypes in guinea pig have a different pharmacological profile from rat or human sst, or these other sst subtypes have some yet undescribed physiological function in muscle cells.

Indium-111 pentetreotide lung uptake in infectious lung disease

Bilateral diffuse lung uptake of In-111 pentetreotide (OCT) was observed during a whole-body scan performed in a 68-year-old woman with Cushing's syndrome and suspected ectopic adrenocorticotropic hormone secretion. A few days later, she was found to have bilateral bacterial pneumonia (of mixed anaerobic origin). Cushing's syndrome was finally proved to be of pituitary origin. The OCT lung uptake in pneumonia probably resulted from tracer binding by somatostatin receptors on the inflammatory leukocytes. Although the rapid wash-out from experimentally induced abscesses does not make OCT a suitable tracer for detecting acute infections, the images and data here reported suggest that infectious lung disease should be excluded before diagnosing lung involvement by neuroendocrine tumors.

The Somatostatin Analog Octreotide Inhibits Growth of Interleukin-6 (IL-6)–Dependent and IL-6–Independent Human Multiple Myeloma Cell Lines

Somatostatin and its analogs can inhibit growth in several cell types, in part by interfering with insulin-like growth factor-I (IGF-I) signaling. Our previous studies point to the importance of paracrine and autocrine IGF-I in the support of growth and survival of human multiple myeloma (MM) cell lines. In this report, we have investigated the potential role of a somatostatin analog, octreotide, in regulating growth and/or survival in MM. The results show that all MM cell lines express functional somatostatin receptors (sst). The MM cell lines express the subtypes sst2, sst3, and predominantly sst5 as determined by reverse-transcriptase polymerase chain reaction and fluorescence-activated cell sorter analysis. Octreotide inhibited the growth of both the interleukin-6 (IL-6)–dependent and the IL-6–independent MM cell lines. The effect is mainly cytostatic, resulting in 25% to 45% growth inhibition, and in three of eight of the MM cell lines a weak induction of apoptosis was recorded. Our results also show that octreotide may act as an inducer of apoptosis in primary B-B4+ plasma cells isolated from bone marrow of MM patients. In conclusion, the results show a novel pathway for growth inhibition of MM cells: the activation of somatostatin receptor signaling.

The Somatostatin Analog Octreotide Inhibits Growth of Interleukin-6 (IL-6)–Dependent and IL-6–Independent Human Multiple Myeloma Cell Lines

Somatostatin and its analogs can inhibit growth in several cell types, in part by interfering with insulin-like growth factor-I (IGF-I) signaling. Our previous studies point to the importance of paracrine and autocrine IGF-I in the support of growth and survival of human multiple myeloma (MM) cell lines. In this report, we have investigated the potential role of a somatostatin analog, octreotide, in regulating growth and/or survival in MM. The results show that all MM cell lines express functional somatostatin receptors (sst). The MM cell lines express the subtypes sst2, sst3, and predominantly sst5 as determined by reverse-transcriptase polymerase chain reaction and fluorescence-activated cell sorter analysis. Octreotide inhibited the growth of both the interleukin-6 (IL-6)–dependent and the IL-6–independent MM cell lines. The effect is mainly cytostatic, resulting in 25% to 45% growth inhibition, and in three of eight of the MM cell lines a weak induction of apoptosis was recorded. Our results also show that octreotide may act as an inducer of apoptosis in primary B-B4+ plasma cells isolated from bone marrow of MM patients. In conclusion, the results show a novel pathway for growth inhibition of MM cells: the activation of somatostatin receptor signaling.

Expression of somatostatin receptors in peritumoral veins of human tumors

BACKGROUND

The vascular system of the tumor bed plays an important function in tumor growth regulation. Recent studies have suggested that the vasoactive peptides somatostatin and substance P may have a potential role in the tumor bed of selected tumors.

METHODS

In the current study, somatostatin receptors were evaluated with in vitro receptor autoradiography using 125I-[Tyr3]-octreotide in the peritumoral vessels of a large group of 215 primary human tumors and 25 metastases of various tumor origin, with particular emphasis on receptor incidence, distribution, homogeneity, and density.

RESULTS

High affinity somatostatin receptors were found in the peritumoral veins of 22 of 22 gastric carcinomas, 25 of 39 breast carcinomas, 15 of 20 renal cell carcinomas, 14 of 27 prostate carcinomas, 4 of 10 endometrial carcinomas, 4 of 11 pancreatic adenocarcinomas, 4 of 13 nonsmall cell lung carcinomas, as well as in 3 of 4 parathyroid adenomas, 3 of 3 medullary thyroid carcinomas, 3 of 23 gastroenteropancreatic tumors, 14 of 25 soft tissue tumors, 3 of 5 melanomas but in none (0 of 13) of the ovarian carcinomas studied. In addition, somatostatin receptors were identified in veins surrounding lymph node, bone, and lung metastases of various tumor types. In all investigated tissues, receptors could not be identified in arteries. There was a considerable variability in the relative number of veins expressing somatostatin receptors and in the receptor density levels. Evidence of an overexpression of somatostatin receptors could be established in the peritumoral veins of gastric carcinoma when compared with the receptor expression in normal gastric vessels.

CONCLUSIONS

The expression of somatostatin receptors in peritumoral veins appears to be a general, tumor-related, but highly variable phenomenon. Although their pathophysiologic role is unclear, these receptors may be considered as novel targets for cancer diagnosis and therapy with somatostatin analogs.

Expression of somatostatin receptors in peritumoral veins of human tumors

BACKGROUND

The vascular system of the tumor bed plays an important function in tumor growth regulation. Recent studies have suggested that the vasoactive peptides somatostatin and substance P may have a potential role in the tumor bed of selected tumors.

METHODS

In the current study, somatostatin receptors were evaluated with in vitro receptor autoradiography using 125I-[Tyr3]-octreotide in the peritumoral vessels of a large group of 215 primary human tumors and 25 metastases of various tumor origin, with particular emphasis on receptor incidence, distribution, homogeneity, and density.

RESULTS

High affinity somatostatin receptors were found in the peritumoral veins of 22 of 22 gastric carcinomas, 25 of 39 breast carcinomas, 15 of 20 renal cell carcinomas, 14 of 27 prostate carcinomas, 4 of 10 endometrial carcinomas, 4 of 11 pancreatic adenocarcinomas, 4 of 13 nonsmall cell lung carcinomas, as well as in 3 of 4 parathyroid adenomas, 3 of 3 medullary thyroid carcinomas, 3 of 23 gastroenteropancreatic tumors, 14 of 25 soft tissue tumors, 3 of 5 melanomas but in none (0 of 13) of the ovarian carcinomas studied. In addition, somatostatin receptors were identified in veins surrounding lymph node, bone, and lung metastases of various tumor types. In all investigated tissues, receptors could not be identified in arteries. There was a considerable variability in the relative number of veins expressing somatostatin receptors and in the receptor density levels. Evidence of an overexpression of somatostatin receptors could be established in the peritumoral veins of gastric carcinoma when compared with the receptor expression in normal gastric vessels.

CONCLUSIONS

The expression of somatostatin receptors in peritumoral veins appears to be a general, tumor-related, but highly variable phenomenon. Although their pathophysiologic role is unclear, these receptors may be considered as novel targets for cancer diagnosis and therapy with somatostatin analogs.

Visualization of intestinal splenosis by somatostatin receptor scintigraphy

A case of intestinal splenosis in a splenectomized patient is presented. (111)In-DTPA-D-Phe-1-octreotide ((111)In-OCT) scintigraphy, computed tomography, as well as magnetic resonance imaging suggested a tumor in the small intestine. The histopathological finding after operation revealed an intestinal splenosis. This case illustrates that intestinal splenosis may mimic a tumor by (111)In-OCT scan. In a splenectomized patient, a splenosis should therefore be considered.

Localization of Receptors for Vasoactive Intestinal Peptide, Somatostatin, and Substance P in Distinct Compartments of Human Lymphoid Organs

Regulatory peptides, such as vasoactive intestinal peptide (VIP), somatostatin (SS), or substance P (SP), are considered to play a role in immune regulation. To localize the targets of these peptides in the human immune system, their receptors have been evaluated with in vitro receptor autoradiography in lymph nodes, tonsils, appendix, Peyer's patches, spleen, and thymus. The three peptide receptors were detected in all lymphoid tissues tested, but, unexpectedly, usually in distinct compartments. In lymph nodes, palatine tonsils, vermiform appendix, and Peyer's patches, VIP receptors were found in the CD3 positive zone around lymphoid follicles; SS receptors in the germinal centers of secondary follicles; and SP receptors mainly in interfollicular blood vessels. In the spleen, VIP receptors were detected in periarterial lymphatic sheaths, SS receptors in the red pulp, and SP receptors in the central arteries. In the thymus, VIP receptors were present in cortex and medulla, SS receptors in the medulla, and SP receptors in blood vessels. For comparison, cholecystokinin (CCK)-A and -B receptors were not demonstrated in any of these tissues. These results suggest a strong compartmentalization of the three peptide receptors in human lymphoid tissues and represent the molecular basis for the understanding of a very complex and interactive mode of action of these peptides.

Preprosomatostatin Messenger RNA Is Expressed by Inflammatory Cells and Induced by Inflammatory Mediators and Cytokines

Somatostatin (SOM) is a 14-amino acid cyclic peptide that regulates granulomatous inflammation. SOM inhibits the release of IFN-γ from murine granuloma T cells that express SOM receptors. SOM is synthesized as preprosomatostatin (ppSOM), a precursor peptide that is cleaved to release active SOM. In this paper, we demonstrate that granuloma cells express mRNA for this important immunoregulator, and that inflammatory mediators rapidly induce ppSOM mRNA in the splenocytes of uninfected, normal (NL) mice. We developed a sensitive, quantitative PCR assay that measures ppSOM mRNA down to 100 transcripts per μg of total RNA. Dispersed granuloma cells expressed authentic ppSOM mRNA as determined by RT-PCR and cDNA sequencing. The PCR assay readily detected ppSOM mRNA in splenocytes isolated from schistosome-infected mice, but not in splenocytes from NL mice. Splenic ppSOM mRNA expression correlated with the onset of parasite egg deposition and granuloma formation. A 4-h in vitro stimulation with LPS, rIL-10, rIFN-γ, rTNF-α, prostaglandin E2, or dibutyryl cAMP induced ppSOM mRNA in NL splenocytes that otherwise lacked this transcript. Splenocytes from severe combined immunodeficient or recombination activating gene 1-deficient mice expressed ppSOM after exposure to rIL-10, suggesting that neither T nor B cells are necessary for ppSOM mRNA induction. A survey of cell lines demonstrated expression of ppSOM mRNA by P388D1 and J774A.1 macrophage-like cells. These data suggest that SOM, which is probably derived from macrophages, is an inducible component of the innate immune system that regulates T cell IFN-γ production.

Incidental appendix carcinoid. Value of somatostatin receptor imaging

PURPOSE

Somatostatin receptor scintigraphy is used to diagnose carcinoid of the gastrointestinal tract. Its sensitivity ranges from approximately 75%-100%. Therefore, it was hypothesized that it can be used in the postsurgical follow-up to detect residual carcinoid, recurrence, and metastatic disease.

RESULTS

This article is concerned with the findings of somatostatin receptor imaging performed on a 12-year-old girl 8 weeks after appendectomy. Histologic examination showed an incidental appendix carcinoid. Somatostatin receptor scintigraphy performed for detection of lymph node metastatic spread of the carcinoid showed focal tracer accumulation at the former operative site; subsequently, a right hemicolectomy was performed. However, histologic examination of the surgical tissue showed no evidence for carcinoid.

CONCLUSION

It is concluded that there are some potential pitfalls for somatostatin receptor imaging at least soon after surgery. Therefore, it should not be used to aid in reoperation.

Role of organized intestinal lymphoid aggregates in intestinal regeneration

Intestinal lymphoid tissue has a complex interrelationship with the epithelium. The epithelia of intestinal crypts associated with lymphoid aggregates have an increased proliferation rate. In the present study, the authors tested the hypothesis that organized intestinal lymphoid tissue (Peyer's patches) enhances intestinal regeneration by studying this process with and without an adjacent Peyer's patch. Forty adult male Sprague-Dawley rats had full-thickness ileal defects patched with cecal serosa to allow regeneration of ileal mucosa. Control animals (group I) had the patch constructed adjacent to a Peyer's patch, whereas this Peyer's patch was excised in group II. Intestinal regeneration in both groups was evaluated on the third, fifth, seventh, and ninth days after operation. During the early phase of regeneration, both epithelial cell proliferation and migration were decreased in the patched defect after excision of the Peyer's patch. Crypt cell production rate in the adjacent normal mucosa also was decreased after excision of the Peyer's patch. Excision of the Peyer's patch resulted in less well-developed crypts and villi. Wound contraction, however, was greater in the intestinal defect adjacent to the Peyer's patch until day 7. In conclusion, Peyer's patches have a facilitative effect on the healing of intestinal wounds by promoting both epithelial cell migration on the defect and epithelial cell proliferation in the crypts adjacent to the wound and by decreasing the rate of wound contraction. These findings support a role for intestinal lymphoid tissue in the regulation of epithelial cell maintenance.

The relevance of somatostatin receptor expression in malignant lymphomas

Somatostatin (SRIF) receptor (sst) expression on lymphoid cells may be related to activation or proliferation of these cells. We investigated the effectiveness of sst scintigraphy in the staging of malignant lymphomas compared with conventional methods. One hundred twenty-six patients with newly diagnosed, histologically proven malignant lymphoma (54 with Hodgkin's disease [HD] and 72 with non-Hodgkin's lymphoma [NHL]) received 111In-labeled DTPA-octreotide (> 200 MBq 111In) and were assessed by planar total-body scintigraphy and single-photon emission computed tomography (SPECT) images of the upper abdomen. The sst scintigraphy was positive in 98% of HD patients. Compared with conventional methods, additional lymphomas were detected in 37%, while lesions escaped detection in 7% (all located in the abdomen); 10 HD patients were downgraded and one was upgraded. The sst scintigraphy was positive in 85% of NHL patients, but positivity did not correlate with the degree of malignancy. Additional lesions were detected in 21% of NHL patients, with false-negatives in 7% and upgrading in 13 NHL patients. The results indicate that sst scintigraphy is sensitive in patients with HD and NHL and may reveal sites of active disease undetected by conventional methods, making it a useful diagnostic tool for malignant lymphomas. Further studies should define its value in clinical management.