Expression Of Somatostatin Receptor Subtypes Research Articles

Preoperative Normalization of Cortisol Levels in Cushing's Disease After Medical Treatment: Consequences for Somatostatin and Dopamine Receptor Subtype Expression and In Vitro Response to Somatostatin Analogs and Dopamine Agonists

Corticotroph pituitary adenomas often highly express the dopamine 2 receptor (D₂R) and somatostatin receptor subtype 5 (sst₅). The sst₂ expression is relatively low, likely resulting from downregulating effects of high cortisol levels. This may explain why the sst₂-preferring somatostatin analog octreotide, compared with the multi-receptor-targeting somatostatin analog pasireotide, is generally ineffective in Cushing's disease. Our objective was to compare sst and D₂R expression levels between adenomas from patients with elevated and normalized preoperative urinary free cortisol excretion. Corticotroph adenoma tissue was examined from patients from group 1 (n = 22; elevated preoperative urinary free cortisol) and group 2 (n = 11; mean duration of preoperative normocortisolism 10 weeks). Somatotroph adenoma tissue from 10 acromegalic patients was examined to compare receptor expression profiles. We evaluated receptor mRNA and protein expression levels and effects of octreotide, pasireotide, and cabergoline on ACTH secretion by cultured human corticotroph adenoma cells. The sst₂ mRNA expression in group 2 was 10-fold higher than in group 1 (P < .01), even comparable to that in somatotroph adenomas. There were no statistically significant differences in sst₅ and D₂R mRNA expression or in sst₂, sst₅, and D₂R protein expression between both groups of corticotroph adenomas. In responders, octreotide (n = 2 out of 4; -30.5% ± 10.4%) was less potent than pasireotide (n = 5 out of 6; -47.0% ± 4.2%) and cabergoline (n = 3 out of 4; -41.9% ± 3.1%) with respect to inhibition of ACTH secretion by adenomas from group 2. After achieving normocortisolism induced by medical therapy, cortisol-mediated sst₂ downregulation on corticotroph adenomas appears to be a reversible process at the mRNA but not at the protein level. Octreotide remains less potent than pasireotide and cabergoline with respect to in vitro inhibition of ACTH secretion. Whether sustained normocortisolism induced by medical therapy induces re-expression of functional sst₂ protein in corticotroph adenomas and whether this increases the ACTH-lowering potency of octreotide remains to be established.

Molecular and functional properties of densely and sparsely granulated GH-producing pituitary adenomas

GH-producing pituitary adenomas display two distinct morphological patterns of cytoplasmic GH-containing secretory granules, namely the densely and sparsely granulated somatotroph adenoma subtype. It is unknown whether these morphological variants reflect distinct pathophysiological entities at the molecular level. In 28 GH-producing adenoma tissues from a consecutive set of patients undergoing pituitary surgery for acromegaly, we studied the GH granulation pattern, the expression of somatostatin receptor subtypes (SSTR) as well as the calcium, cAMP and ZAC1 pathways in primary adenoma cell cultures. The expression of GSP oncogene was similar between densely and sparsely granulated somatotroph adenoma cells. There were no differences in the calcium, cAMP and ZAC1 pathways as well as in their regulation by SSTR agonists. SSTR2 was exclusively expressed in densely but not in sparsely granulated tumours (membrane expression 86 vs 0%; cytoplasmic expression 67 vs 0%). By contrast, expression of SSTR5 was only found in sparsely but not in densely granulated somatotroph adenomas (membrane expression 29 vs 0%; cytoplasmic expression 57 vs 0%). Our results indicate that different granulation patterns in GH-producing adenomas do not reflect differences in pathways and factors pivotal for somatotroph differentiation and function. In vitro, the vast majority of both densely and sparsely granulated tumour cells were responsive to SSTR activation at the molecular level. Sparsely granulated adenomas lacking SSTR2, but expressing SSTR5, might be responsive to novel SSTR agonists with increased affinity to SSTR5.

Profiling of somatostatin receptor subtype expression by quantitative PCR in pancreatic endocrine tumors

Profiling of somatostatin receptor subtype expression by quantitative PCR in pancreatic endocrine tumors

Poorly differentiated neuroendocrine carcinoma (NEC G3): Prognostic factors and potential novel targets.

e15071 Background: Poorly differentiated neuroendocrine carcinomas (NEC G3) represent a subgroup of neuroendocrine neoplasms with aggressive clinical behavior and poor prognosis, but showing quite variable clinical courses. In metastatic disease objective response to first-line therapy with cisplatin/ etoposide ranges between 40-67%, however median duration of response is short (4 to 9 months). There is no established second-line therapy. Methods: Clinical data of 42 patients with gastro-entero-pancreatic NEC G3 were analyzed in retrospect. In 26 cases tissue was analyzed for cell size, expression of p-mTOR and downstream effectors (p-eIF4E and p-4EBP1), somatostatin receptor (SSTR)-subtypes and growth factor receptors (EGFR and IGF-1R). Histopathological findings were analyzed using Kaplan-Meier curve, log rank test and Cox regression. Results: Patients with large cell NEC showed a more favorable survival than patients with small cell NEC. Median overall survival (mOS) was 31 versus 11 months (P=0.034). Expression of p-mTOR and p-eIF4E was seen in 64% and 24% of cases. High expression levels of p-mTOR (mOS 9 vs 25 months, P=0.026) and expression of p-eIF4E (mOS 9 vs 25 months, P=0.015) was significantly associated with shorter survival. In multivariate Cox regression p-mTOR and p-eIF4E proved to be independent prognostic factors for survival taking cell size and TNM staging into account. EGFR (cytoplasmatic and nuclear) and IGF-1R expression was found in 73.1%, 65.4% and 69.2% of the cases respectively, without significant association to survival. Expression of SSTR subtypes, Ki67 value and response to first line chemotherapy was not of prognostic value analyzed by log rank test. Conclusions: The clinical impact of cell size discrimination requires further evaluation in NEC G3. The mTOR pathway seems to play a role in tumor growth in some NEC and may represent a novel therapeutic target.

Abstract 92: Comparative expression analysis of somatostatin receptor subtypes in human neuroendocrine tumors using two sets of new monoclonal antibodies.

Abstract The expression and reliable detection of somatostatin receptor subtypes (SSTR1-5) is a prerequisite for the successful use of somatostatin analogues in neuroendocrine tumors (NET). Two sets of monoclonal antibodies (mAbs) against human SSTR1, 2A, 3 and 5 have recently been developed by two independent laboratories using rabbit and mouse hybridomas. Our aim was to evaluate the usefulness of both sets of mAbs for detection of SSTRs in NET samples as they are routinely collected in clinical practice. Mouse and rabbit mAbs were characterized in SSTR1, 2, 3 and 5-transfected HEK293 cells and human archival pancreatic tissue and NET samples. Comparative analysis of mAbs was also conducted by immunostaining of a tissue microarray composed of 75 cores of NET. Immunohistochemical analysis of HEK293 cells showed that both rabbit and mouse mAbs specifically detect their cognate receptor subtype, with mild cytoplasmic cross-reactivity observed for rabbit mAbs. Both sets of mAbs labeled normal pancreatic islets and showed similar patterns of immunoreactivity in NET controls. Direct comparison of mAb sets using a NET tissue microarray revealed a strong correlation between rabbit and mouse mAbs against SSTR1 and 5, and moderate correlation for SSTR3. The rabbit mAb against SSTR2A showed higher affinity for its cognate receptor than the corresponding mouse mAb, resulting in more reliable detection of this SSTR. In conclusion, mAbs from both sets are reliable tools for the detection of SSTR1, 3 and 5, whereas the rabbit mAb against SSTR2A is recommended for use in routine clinical testing due to its superior binding affinity. Citation Format: Chiara Lambertini, Patrizia Barzaghi-Rinaudo, Lisa D'Amato, Stefan Schulz, Paolo Nuciforo, Herbert A. Schmid. Comparative expression analysis of somatostatin receptor subtypes in human neuroendocrine tumors using two sets of new monoclonal antibodies. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 92. doi:10.1158/1538-7445.AM2013-92

Differential Expression of Somatostatin Receptor Subtype 1–5 Proteins in Numerous Human Normal Tissues

5 Human somatostatin receptor subtypes (sst1-5) mediate the antisecretory and antiproliferative effects of somatostatin. We examined somatostatin receptor protein expression in 28 human normal tissues. Immunostaining was performed with specific polyclonal antibodies for sst1-5. Staining pattern and distribution of ssts were evaluated. Anterior pituitary was positively stained for all 5 ssts. Pancreatic islets exhibited a positive staining for sst1-3 and sst5. Adrenal cortex expressed all 5 receptor subtypes, while the medulla was positive for sst3 and sst5 only. The thyroid expressed sst5 only, limited to single interfollicular cells. All 5 ssts were detected in the ovary, limited to luteinized granulosa cells of the corpus luteum. In the testis, sst2A was detected in the basal parts of the tubules, while sst5 was positively stained in the luminal parts. Sst1 was found in Leydig cells only. Stomach was positively stained for all 5 ssts. Investigation of the kidney revealed differential expression, with sst2A being found in the glomerules. The tubules expressed all 5 ssts. In the bone marrow cells of the granulocytopoiesis expressed sst2A only. The cerebellum expressed sst5 in a certain cell type, representing presumably Purkinje cells, while sst2A was stained in intercellular fibers. The expression of somatostatin receptor subtypes in a variety of human normal tissues may indicate a physiological role in these organs. Somatostatin analogues may offer new diagnostic and therapeutic implications for tumours related to these tissues. However, treatment of defined tumours with somatostatin analogues may also alter other normal tissues.

Somatostatin receptor expression in non-medullary thyroid carcinomas

Peptide receptor radionuclide therapy (PRRT) is dependent upon binding of radiolabelled peptides to their respective receptor expressing cells. The main objective of this study was to characterize the expression of somatostatin receptor (SSTR) subtypes in non-medullary thyroid cancers in order to be able to recommend the use of PRRT as a treatment option in patients with progressive local or metastatic disease. We constructed tissue microarrays from paraffin blocks prepared from 47 cases of non-medullary thyroid carcinomas and related normal thyroid tissue. Immunohistochemical staining was performed with five different polyclonal SSTR antibodies. SSTR subtypes sst2 and sst3 were expressed in all non-medullary thyroid carcinomas, sst1 and sst5 in 75%, and sst4 in 38%. Coexpression of more than three subtypes was detected in 36 of the 47 cases. The expression of SSTR subtypes in normal thyroid tissue was low or absent. Non-medullary thyroid carcinomas frequently express all SSTR subtypes. This expression provides a basis for further studies with the aim of exploring PRRT as a possible new treatment for iodine-131 refractory metastatic non-medullary thyroid carcinomas.

Expression of the proliferation marker Ki‐67 associates with tumour staging and clinical outcome in differentiated thyroid carcinomas

Although the prognosis of differentiated thyroid carcinoma (DTC) is excellent, with 10-year survival rates of about 90%, about one-third of patients experiences recurrent disease. We aimed to identify novel histological prognostic factors to optimize treatment and follow-up of patients at risks. Retrospective analysis of patients diagnosed from January 1990 to March 2004. A total of 93 patients diagnosed with DTC of which 67 with papillary and 26 with follicular histology. Analysis of immunohistochemical expression of somatostatin receptor (sst) subtypes 1-5, glucose transporter-1 (GLUT-1), receptor tyrosine kinase c-KIT, oestrogen and progesterone receptors, and proliferation marker Ki-67 and correlation with the patients' clinical outcome. DTC showed immunohistochemical expression of GLUT-1, C-KIT and progesterone receptor in a high percentage of cases (range: 57-80%). In contrast, the oestrogen receptor as well as the sst subtypes 1-5 was less frequently detected (range: 15-29%). Mean staining of the proliferation marker Ki-67 was 6% positive cells (range 0-20%). Ki-67 expression was significantly associated with tumour staging (ρ=0·2076, P=0·0459), whereas the other histopathological markers were not associated with gender, age, tumour entity, or tumour classification. Tumour staging and expression of Ki-67, oestrogen receptor and sst2, but of none of the other histopathological factors, independently predicted the clinical outcome 5years after definitive treatment (P<0·0001, P<0·0001, P=0·0004 and P=0·0206, respectively). In patients with DTC, Ki-67 expression associates with tumour staging and clinical outcome.

Immunohistochemical Distribution of Somatostatin and Somatostatin Receptor Subtypes (SSTR1–5) in Hypothalamus of ApoD Knockout Mice Brain

In the present study, the expression of somatostatin (SST) and somatostatin receptor subtypes (SSTR1-5) was determined in the hypothalamus of wild-type (wt) and apolipoprotein D knockout (ApoD(-/-)) mice brain. SST-like immunoreactivity, while comparable in most regions of hypothalamus, diminished significantly in arcuate nucleus of ApoD(-/-) mice. SSTR1 strongly localized in all major hypothalamic nuclei as well as in the median eminence and ependyma of the third ventricle of wt mice brain. SSTR1-like immunoreactivity increases in hypothalamus except in paraventricular nucleus of ApoD(-/-) mice. SSTR2 was well expressed in most of the hypothalamic regions whereas it decreases significantly in ventromedial and arcuate nucleus of ApoD(-/-) mice. SSTR3 and SSTR4-like immunoreactivity increases in ApoD(-/-) mice in all major nuclei of hypothalamus, median eminence, and ependymal cells of third ventricle. SSTR5 is well expressed in ventromedial and arcuate nucleus whereas weakly expressed in paraventricular nucleus. In comparison to wt, ApoD(-/-) mice exhibit increased SSTR5-like immunoreactivity in paraventricular nuclei and decreased receptor expression in ventromedial hypothalamus and arcuate nucleus. In conclusion, the changes in hypothalamus of ApoD(-/-) mice may indicate potential role of ApoD in regulation of endocrine functions of somatostatin in a receptor-dependent manner.

Immunohistochemical expression of somatostatin receptor subtypes 2 and 5 in colorectal cancer

To determine the immunohistochemical expression levels of the somatostatin receptor subtypes 2 and 5 (Sst2 and Sst5) in patients with colorectal cancer (CRC) and to investigate the association of Sst2 and Sst5 expression with clinicopathological parameters. A retrospective analysis of formalin-fixed and paraffin-embedded CRC surgical specimens from 81 patients assessed by immunohistochemistry for Sst2 and Sst5 expression. Sst2 and Sst5 expression levels showed significant, negative association with CRC invasion and liver metastasis (P values < 0·05) while Sst2 also showed significantly increased expression in lower-grade tumours as well as in tumours located in the rectum (P values < 0·05). Patients with CRC expressing either Sst2 or Sst5 had significantly longer survival rates (P values < 0·05), although Sst expression was not found to be an independent predictor of survival after controlling for other known prognostic clinicopathological variables (P values > 0·05). The present data confirm the relationship of Sst2 and Sst5 expression levels with reduced tumour aggressiveness.

Expression of Somatostatin Receptor (SSTR) Subtypes (SSTR-1, 2A, 3, 4 and 5) in Neuroendocrine Tumors Using Real-time RT-PCR Method and Immunohistochemistry

Molecule targeting therapy using somatostatin (SS) analogues has become a widely accepted modality to treat neuroendocrine tumors (NETs), particularly gastrointestinal (GI) and pancreatic endocrine tumors. On the other hand, little is known about the expression of somatostatin receptor (SSTR) subtypes in neuroendocrine carcinomas (NECs). We investigated the expression of SSTR subtypes (SSTR-1, 2A, 3, 4 and 5) using real-time reverse transcription polymerase chain reaction (RT-PCR) method and immunohistochemistry in 32 neuroendocrine neoplasms (9 NET G1, 2 NET G2, 18 NECs G3 and 3 mixed NEC G3) of various primary sites. Expression of more than two SSTR subtypes was detected in all neuroendocrine neoplasms examined. Expression of SSTR-2A mRNA was significantly higher than other subtypes. In addition, mRNA expression of SSTR-3 and SSTR-5 was significantly low or below the detection level except for gastroduodenal NET G1. No significant difference of the expression of SSTR subtypes was observed between the NET and NEC groups. The expression of protein and mRNA was generally well correlated. In conclusion, NECs would be a good candidate for molecule targeting therapy using SS analogues, and the expression of SSTR-2A can be useful as a biomarker of neuroendocrine differentiation. We have demonstrated that NEC G3 small cell type shows a different expression profile of SSTR subtypes compared with NET and NEC non-small cell type.

Treatment with octreotide LAR in clinically non-functioning pituitary adenoma: results from a case–control study

Surgical cure cannot be achieved in most patients with invasive non-functioning pituitary macroadenoma (NFPA). Short-term residual tumor treatment with somatostatin analogs has produced disappointing results. This prospective case-control study assessed the efficacy of chronic treatment with long acting octreotide (octreotide LAR) on tumor volume in patients harboring post-surgical NFPA residue. The study population comprised 39 patients with NFPAs not cured by surgery. All patients underwent somatostatin receptor scintigraphy at least 6 months after the last surgery. Patients with a positive pituitary level octreoscan at (n = 26) received octreotide LAR (20 mg every 28 days) for ≥ 12 months (mean follow-up 37 ± 18 months) (Treated group). Moreover, a fragment of tumor tissue from patients in the treated group was retrospectively collected to assess the immunohistochemical expression of somatostatin receptor subtypes (SSTRs). The patients with a negative octreoscan (n = 13) formed the control group (mean follow-up 37 ± 16 months). Hormonal, radiological and visual field parameters were periodically assessed. In the treated group, all tumors expressed at least one SSTR subtype. The SSTR5 subtype was the most abundant, followed by SSTR3. The tumor residue increased in five of 26 patients (19%) in the treated group and in seven of 13 controls (53%). Visual field and pituitary function did not change in any patient. This study indicates that SSTR5 and SSTR3 are the most frequently expressed SSTR subtypes in NFPAs and supports a potential role of SSTR subtypes in stabilization of tumor remnant from NFPAs.

Somatostatin Inhibition of GnRH Neuronal Activity and the Morphological Relationship between GnRH and Somatostatin Neurons in Rats

In rodents, GnRH neurons are diffusely distributed from the medial septum through to the medial preoptic area and control gonadal functions through the pituitary. The activity of GnRH neurons is regulated by a variety of bioactive substances, including the inhibitory peptide somatostatin. In the present study, we focused on somatostatin because intracerebroventricular injection of somatostatin inhibits the LH surge in rats and reduces LH secretion in ewes. Somatostatin also decreases GnRH release from rat hypothalamic slices. In mice, somatostatin is also thought to suppress GnRH neuronal activity through contact on the soma of GnRH neurons. However, similar data are missing in rats. Moreover, rat GnRH neurons receive only a few synaptic inputs. In this study, we assessed the morphological relationship between GnRH and somatostatin neurons. Confocal microscopy on the sections from the medial septum through medial preoptic area revealed about 35 close contacts per rat between the GnRH and somatostatin neuronal fibers in the organum vasculosum of the lamina terminalis region. No contact of somatostatin fibers on the GnRH neuronal somata was observed. Multicell RT-PCR for somatostatin receptor mRNA in rat GnRH neurons was also performed, which revealed moderate expression of somatostatin receptor subtypes 1-5. In addition, patch clamp experiments were carried out in acute slice preparations. Somatostatin suppressed neuronal firing in cells recorded in a cell-attached configuration and also induced whole-cell outward currents in GnRH neurons. These findings suggest that somatostatin directly inhibits the activity of rat GnRH neurons through volume transmission in the organum vasculosum of the lamina terminalis region.

Somatostatin Receptor 1 and 5 Double Knockout Mice Mimic Neurochemical Changes of Huntington's Disease Transgenic Mice

BackgroundSelective degeneration of medium spiny neurons and preservation of medium sized aspiny interneurons in striatum has been implicated in excitotoxicity and pathophysiology of Huntington's disease (HD). However, the molecular mechanism for the selective sparing of medium sized aspiny neurons and vulnerability of projection neurons is still elusive. The pathological characteristic of HD is an extensive reduction of the striatal mass, affecting caudate putamen. Somatostatin (SST) positive neurons are selectively spared in HD and Quinolinic acid/N-methyl-D-aspartic acid induced excitotoxicity, mimic the model of HD. SST plays neuroprotective role in excitotoxicity and the biological effects of SST are mediated by five somatostatin receptor subtypes (SSTR1-5).Methods and FindingsTo delineate subtype selective biological responses we have here investigated changes in SSTR1 and 5 double knockout mice brain and compared with HD transgenic mouse model (R6/2). Our study revealed significant loss of dopamine and cAMP regulated phosphoprotein of 32 kDa (DARPP-32) and comparable changes in SST, N-methyl-D-aspartic acid receptors subtypes, calbindin and brain nitric oxide synthase expression as well as in key signaling proteins including calpain, phospho-extracellular-signal-regulated kinases1/2, synapsin-IIa, protein kinase C-α and calcineurin in SSTR1/5−/− and R6/2 mice. Conversely, the expression of somatostatin receptor subtypes, enkephalin and phosphatidylinositol 3-kinases were strain specific. SSTR1/5 appears to be important in regulating NMDARs, DARPP-32 and signaling molecules in similar fashion as seen in HD transgenic mice.ConclusionsThis is the first comprehensive description of disease related changes upon ablation of G- protein coupled receptor gene. Our results indicate that SST and SSTRs might play an important role in regulation of neurodegeneration and targeting this pathway can provide a novel insight in understanding the pathophysiology of Huntington's disease.

Clinical Significance of Protein Expression of Cyclooxygenase-2 and Somatostatin Receptors in Gastroenteropancreatic Neuroendocrine Tumors

PurposeThis study was undertaken to evaluate the significance of cyclooxygenase-2 (COX2) overexpression and the expression of somatostatin receptor (SSTR) subtypes in gastroenteropancreatic neuroendocrine tumors (GEP-NETs).Materials and MethodsTwo hundred and forty-seven cases of GEP-NET, comprising 86 foregut and 156 hindgut primary NETs, and 5 metastatic NETs in the liver, were studied retrospectively with immunohistochemistry for COX2, chromogranin A, Ki-67, SSTR1, SSTR2, and SSTR5.ResultsCOX2 overexpression was observed in 54%(126 of 234), and SSTR1, SSTR2, and SSTR5 positivity in 84%(196 of 233), 72%(168 of 233), and 55%(128 of 232), respectively. COX2 overexpression was found to be positively correlated with Ki-67 labeling index and inversely correlated with the expression of SSTR subtypes. In addition, the expression of SSTR subtypes was tightly correlated in any comparative pairs. A significant inverse correlation was found between COX2 and SSTR2 expression in the foregut, but not hindgut NETs. Kaplan-Meier analyses showed that COX2 overexpression (p=0.003) and high Ki-67 labeling index (p<0.001) were associated with poor overall survival (OS), whereas expression of SSTR2 (p<0.001) was associated with better OS of GEP-NET patients. Multivariate analysis revealed negative SSTR2 expression as an independent prognostic marker in GEP-NET patients (p<0.001).ConclusionOur results suggest that expression of SSTR subtypes is associated with favorable prognosis, whereas COX2 overexpression is associated with poor prognosis in GEP-NETs. Taken together, COX2 could be a possible therapeutic target in some subsets of GEP-NETs.

‘Reverse discordance’ between 68Ga-DOTA-NOC PET/CT and 177Lu-DOTA-TATE posttherapy scan

In this technical note, an unusual discordance between diagnostic and posttherapeutic scan resulting from the use of different somatostatin receptor ligands in two settings is described. Such observation, we believe, is multifactorial, but most importantly arises due to different receptor affinity profile of the ligands and different somatostatin receptor subtype expression in different tumors. It is important for the treating physician to be aware of this phenomenon that would aid in improving our understanding of complex ligand-receptor interactions in various somatostatin receptor-positive tumors with its possible implications for therapeutic decision making with radiolabeled somatostatin receptor analogues.

Immunohistochemical expression and localization of somatostatin receptor subtypes in androgen ablated prostate cancer

The aim was to examine the expression and localization of the five somatostatin receptors (termed SSTR1 to 5) in radical prostatectomies (RPs) from patients with prostatic adenocarcinoma (PCa) under complete androgen ablation (CAA) before operation. The five SSTRs were evaluated in the epithelial, smooth muscle and endothelial cells of normal-looking epithelium (Nep), high-grade prostatic intraepithelial neoplasia (HGPIN) and PCa in 20 RPs with clinically detected PCa from patients under CAA. Twenty RPs with clinically detected PCa from hormonally untreated patients were used as control group. Concerning the secretory cells (i) Membrane staining was seen for SSTR3 and SSTR4; the mean percentages of positive cells, higher in SSTR3 than in SSTR4, decreased sharply in HGPIN and PCa compared with Nep; the mean percentages in the androgen ablated group were 30% to 90% lower than in the untreated; (ii) Cytoplasmic staining was seen for all five SSTRs; the mean percentages of positive cells in Nep, HGPIN and PCa of the untreated group were similar, and in general as high as 80% or more; in the treated group, the Nep values were similar to those in the untreated, whereas the values in HGPIN and PCa were lower for SSTR1, three and five, with a decrease of 30% for SSTR1; (iii) Nuclear staining was seen with SSTR4 and SSTR5, the mean percentages for the former being much lower than for the latter; treatment affected both HGPIN and PCa, whose proportions of stained cells were 30% to 55% lower than in the untreated group. Cytoplasmic staining in the basal cells was seen for all five SSTRs, both in Nep and HGPIN. The values in the treated group were lower than in the other, the difference between the two group being in general comprised between 10% and 40%. Treatment did not affect SSTR staining in the smooth muscle and endothelial cells. The present study expands our knowledge on the expression and localization of the five SSTRs in the prostate following CAA.

SSTR2-Based Reporters for Assessing Gene Transfer into Non–Small Cell Lung Cancer: Evaluation Using an Intrathoracic Mouse Model

The most common cause of cancer-related deaths in North America is lung cancer, 85% of which is non-small cell lung cancer (NSCLC). Gene therapy is a promising approach, but has been hindered by lack of methods for localizing and quantifying gene expression in vivo. Human somatostatin receptor subtype-2 (SSTR2)-based reporters can be used to follow gene expression in vivo using ligands with greater affinity for this subtype. NSCLCs can express SSTR subtypes, which may interfere with SSTR2-based reporters. We assessed whether a SSTR2-based reporter can serve as a reporter of gene transfer into NSCLCs. SSTR subtype expression was assessed in NSCLC cell lines A549, H460, and H1299 using RT-PCR. After infection with an adenovirus containing hemagglutinin-A-tagged-SSTR2 (Ad-HA-SSTR2) or control insert, expression was assessed by immunologic techniques and binding to clinically-approved (111)In-octreotide. In vivo, after magnetic resonance (MR) imaging, intrathoracic H460 tumors were injected with Ad-HA-SSTR2 or control virus (n = 6 mice/group) under ultrasound guidance. Intravenous injection of (111)In-octreotide 2 days later was followed by planar and single-photon emission computed tomography (SPECT) imaging. Biodistribution into tumors was assessed in vivo using anatomic MR and functional gamma-camera images and ex vivo using excised organs/tumors. In human lung tumor samples (n = 70), SSTR2 expression was assessed using immunohistochemistry. All three NSCLC cell lines expressed different SSTR subtypes, but none expressed SSTR2. Upon Ad-HA-SSTR2 infection, HA-SSTR2 expression was seen in all three cell lines using antibodies targeting the HA domain or (111)In-octreotide targeting the receptor domain (p < 0.05). Intrathoracic tumors infected with Ad-HA-SSTR2 were clearly visible by gamma-camera imaging; expression was quantified by both in vivo and ex vivo biodistribution analysis and demonstrated greater uptake in tumors infected with Ad-HA-SSTR2 compared with control virus (p < 0.05). Immunohistochemistry found that 78% of NSCLCs are negative for and 13% have low levels of SSTR2 expression. It is concluded that SSTR2-based reporters can serve as reporters of gene transfer into NSCLCs.

Differentiated expression of somatostatin receptor subtypes in experimental models and clinical neuroblastoma

Neuroblastoma (NB) is a solid tumor of childhood originating from the adrenal medulla or sympathetic nervous system. Somatostatin (SS) is an important regulator of neural and neuroendocrine function, its actions being mediated through five specific membrane receptors. The aim of this study was to investigate the expression of the different somatostatin receptors (SSTRs) in NB tumor cells that may form targets for future therapeutic development. Tumor specimens from 11 children with stage II-IV disease were collected before and/or after chemotherapy. Experimental tumors derived from five human NB cell lines were grown subcutaneously in nude mice. Expression of SSRTs, the neuroendocrine marker chromogranin A (CgA) and SS was detected by immunohistochemistry using specific antibodies. SSTR2 was detected in 90%, SSTR5 in 79%, SSTR1 in 74%, SSTR3 in 68% whereas SSTR4 was expressed in 21% of the clinical tumors. The experimental tumors expressed SSTRs in a high but variable frequency. All clinical tumors showed immunoreactivity for CgA but not for SS. The frequent expression of SSTRs indicates that treatment with unlabeled or radiolabeled SS analogs should be further explored in NB.

Profiling of Somatostatin Receptor Subtype Expression by Quantitative PCR and Correlation With Clinicopathological Features in Pancreatic Endocrine Tumors

Pancreatic endocrine tumor (PET) presents variable clinical features. Five subtypes of somatostatin receptor (SSTR) are involved in hormone secretion and cell proliferation. In this paper, we explore the correlation between the SSTR subtype messenger RNA (mRNA) expression and clinicopathological features of PET. Twenty-one cases of PET and 5 cases of pancreatic adenocarcinomas (AC) were studied. Using total RNA extracted from paraffin sections and fresh tissues, SSTR subtype mRNA was quantified by real-time polymerase chain reaction. The hormones and MIB1 index were examined using immunohistochemical techniques. The mRNA levels of SSTR1, SSTR2, SSTR3, and SSTR5 were high in PET compared with AC, whereas the expression of SSTR4 was low in PET and AC. Levels of each subtype did not vary with histological grades. Somatostatin receptor 2 levels in functioning tumors were slightly low compared with nonfunctioning tumors. Four distinct groups of PET were identified by hierarchical cluster analysis, and two of these groups showed reduced SSTR5 with elevation of MIB1 index. The study showed a heterogeneous expression profile of SSTR subtype mRNA and the association of reduction in SSTR5 with high proliferative activity. Such profiling of SSTR subtypes may provide useful information on tumor biology and treatment of PET.