Expression of somatostatin receptors in hemangioblastomas associated with von Hippel-Lindau disease as a novel diagnostic, therapeutic, and follow-up opportunity: A case report and literature review.

Hemangioblastomas associated with von Hippel-Lindau (VHL) disease are frequently multiple and recur during prolonged follow-up. Currently, no systemic treatment is available for these tumors. Recent studies have shown the expression of somatostatin receptors in these types of hemangioblastomas. Notably, increased somatostatin receptor expression in a tumor, as determined by peptide-receptor radionuclide imaging, is a predictive factor of response to treatment with somatostatin analogs and peptide-receptor radionuclide therapy. The aim of this study was to describe the case of a patient with increased expression of somatostatin receptors in a suprasellar hemangioblastoma associated with VHL disease and conduct a literature review on somatostatin receptor expression in patients with VHL-associated hemangioblastomas. We describe herein the case of a 51-year-old man with VHL disease who had a suprasellar hemangioblastoma detected on magnetic resonance imaging. Peptide-receptor radionuclide imaging using gallium-68-DOTATOC (68Ga-DOTATOC) identified increased expression of somatostatin receptors in the suprasellar hemangioblastoma, along with multiple pancreatic neuroendocrine tumors and bilateral pheochromocytomas. The patient was treated for 1 year with lanreotide, a somatostatin analog. A repeat 68Ga-DOTATOC 1 year after starting lanreotide revealed decreased radiotracer uptake by the hemangioblastoma, consistent with a metabolic response. The presence of somatostatin receptors in hemangioblastomas associated with VHL disease is a novel finding. The decreased expression of these receptors after treatment with a somatostatin analog, as described in the present case, positions the somatostatin receptor as a new target for novel diagnostic, therapeutic, and follow-up opportunities in patients with VHL disease.

Somatostatin receptor subtype expression and radiomics from DWI-MRI represent SUV of [68Ga]Ga-DOTATOC PET in patients with meningioma.

OBJECTIVE: This retrospective study aimed to analyse the correlation between somatostatin receptor subtypes (SSTR 1-5) and maximum standardized uptake value (SUVmax) in meningioma patients using Gallium-68 DOTA-D-Phe1-Tyr3-octreotide Positron Emission Tomography ([68Ga]Ga-DOTATOC PET). Secondly, we developed a radiomic model based on apparent diffusion coefficient (ADC) maps derived from diffusion weighted magnetic resonance images (DWI MRI) to reproduce SUVmax. METHOD: The study included 51 patients who underwent MRI and [68Ga]Ga-DOTATOC PET before meningioma surgery. SUVmax values were quantified from PET images and tumour areas were segmented on post-contrast T1-weighted MRI and mapped to ADC maps. A total of 1940 radiomic features were extracted from the tumour area on each ADC map. A random forest regression model was trained to predict SUVmax and the model's performance was evaluated using repeated nested cross-validation. The expression of SSTR subtypes was quantified in 18 surgical specimens and compared to SUVmax values. RESULTS: The random forest regression model successfully predicted SUVmax values with a significant correlation observed in all 100 repeats (p < 0.05). The mean Pearson's r was 0.42 ± 0.07 SD, and the root mean square error (RMSE) was 28.46 ± 0.16. SSTR subtypes 2A, 2B, and 5 showed significant correlations with SUVmax values (p < 0.001, R2 = 0.669; p = 0.001, R2 = 0.393; and p = 0.012, R2 = 0.235, respectively). CONCLUSION: SSTR subtypes 2A, 2B, and 5 correlated significantly with SUVmax in meningioma patients. The developed radiomic model based on ADC maps effectively reproduces SUVmax using [68Ga]Ga-DOTATOC PET.

Correlation of somatostatin receptor PET/CT imaging features and immunohistochemistry in neuroendocrine tumors of the lung: a retrospective observational study.

PURPOSE: To correlate somatostatin receptor (SSTR) and proliferative activity profile (SSTR2, SSTR5, Ki-67) at immunohistochemistry (IHC) with SSTR-PET/CT imaging features in a retrospective series of lung neuroendocrine tumors (NET). Proliferative activity by Ki-67 and 18F-FDG-PET/CT parameters (when available) were also correlated. METHODS: Among 551 patients who underwent SSTR-PET/CT with 68Ga-DOTA-somatostatin analogs (SSA) between July 2011 and March 2020 for lung neuroendocrine neoplasms, 32 patients with a confirmed diagnosis of NET were included. For 14 of them, 18F-FDG-PET/CT was available. PET/CT images were reviewed by qualitative and semi-quantitative analyses. Immunohistochemistry for SSTR2, SSTR5, and Ki-67 was assessed. Inferential analysis was performed including kappa statistics and Spearman's rank correlation test. RESULTS: Definitive diagnosis consisted of 26 typical carcinoids-G1 and six atypical carcinoids-G2. Positive SSTR2-IHC was found in 62.5% of samples while SSTR5-IHC positivity was 19.4%. A correlation between SSTR2-IHC and SSTR-PET/CT was found in 24/32 cases (75.0%, p = 0.003): 20 were concordantly positive, 4 concordantly negative. For positive IHC, 100% concordance with SSTR-PET/CT (both positive) was observed, while for negative IHC concordance (both negative) was 33.3%. In 8 cases, IHC was negative while SSTR-PET/CT was positive, even though with low-grade uptake in all but one. A significant correlation between SUVmax values at SSTR-PET/CT and the SSTR2-IHC scores was found, with low SUVmax values corresponding to negative IHC and higher SUVmax values to positive IHC (p = 0.002). CONCLUSION: This retrospective study showed an overall good agreement between SSTR2-IHC and tumor uptake at SSTR-PET/CT in lung NETs. SSTR-PET/CT SUVmax values can be used as a parameter of SSTR2 density. Within the limits imposed by the relatively small cohort, our data suggest that SSTR2-IHC may surrogate SSTR-PET/CT in selected lung NET patients for clinical decision making when SSTR-PET/CT is not available.

Clinicopathologic features and BRAF mutation status of tracheal glomus tumors - Characterization of 4 cases and the distinction from low-grade neuroendocrine tumors.

BACKGROUND: Glomus tumors are uncommon and mostly benign mesenchymal neoplasms of the perivascular family. To date, only a few cases of glomus tumors occurring in the trachea have been reported. Tracheal glomus tumors simulated low-grade neuroendocrine tumors on clinical and histomorphological examination, so the differential diagnosis between these two entities is very necessary. The latest studies showed that BRAF mutation may be associated with a malignant phenotype of glomus tumors. METHODS: We investigated the clinical, histopathologic, immunohistochemical, and BRAF V600E mutation status of four cases of tracheal glomus tumors. RESULTS: The cases showed a female predilection (male:female, 1:3) with a median age of 35.5. All of the cases had the typical morphological characteristics of glomus tumors, such as uniform round tumor cells with nest-like distribution surrounding thin-walled vessels; two of them met the malignant diagnostic criteria based on the 5th edition of WHO classification, including marked nuclear atypia and any level of mitotic activity. Immunohistochemistry showed diffusely positive for vimentin (4/4), α-SMA (4/4) and collagen IV (4/4), variably reactive for synaptophysin (3/4) and SSTR2 (2/2), and negative for AE1/AE3 (0/4) and chromogranin A (0/4). Three tested cases harbored no BRAF V600E mutation. Three follow-up cases were alive and free of disease with an average follow-up of 89.3 months. CONCLUSIONS: Tracheal glomus tumors are rare mesenchymal tumors that have overlapping morphologic and immunohistochemical features with neuroendocrine neoplasms. Our cases highlight the importance of careful histomorphological examination and comprehensive immunohistochemical study in reaching a correct diagnosis of glomus tumors of the trachea. Other than BRAF mutation, malignant glomus tumors may have a complex mutational profile.

Somatostatin receptor 2 is highly sensitive and specific for Epstein-Barr virus-associated nasopharyngeal carcinoma.

Viruses are known drivers of head and neck squamous cell carcinomas (HNSCC), particularly Epstein-Barr virus (EBV) and human papillomavirus (HPV). Both EBV-positive nasopharyngeal carcinoma (EBVNPC) and HPV-positive oropharyngeal SCC (OPSCC) can have overlapping histomorphology and molecular signatures, including nuclear factor kappa-light-chain-enhancer of activated B cells (NFKB) pathway mutations. A recent study showed that NFKB activation in EBVNPC drives somatostatin receptor 2 (SSTR2) expression that is detectable by immunohistochemistry and by imaging with 68-Gadolinium-DOTA-peptide radioconjugate. However, whether a similar NFKB-SSTR2 signaling mechanism exists for other virus-positive HNSCC, namely HPV-positive sinonasal carcinomas and OPSCC, remains unclear. Here we examined SSTR2 expression in a cohort of EBV-positive, HPV-positive, and virus-negative HNSCC with immunohistochemistry. SSTR2 immunohistochemistry was performed on our cohort of primary and/or metastatic EBVNPC, HPV-positive sinonasal SCC, OPSCC, HPV-negative sinonasal and oral cavity SCC, and benign tonsil and adenoid tissue. For SSTR2 staining, the extent was categorized as focal, multifocal, or diffuse, and the intensity was categorized as weak, moderate, or strong. Multifocal/diffuse SSTR2 staining of any intensity was considered positive. Among primary, recurrent, and/or undifferentiated NPC, 90% showed multifocal to diffuse strong SSTR2 expression. One HPV-positive sinonasal carcinoma showed patchy SSTR2 staining. None of the remaining HPV-positive sinonasal carcinomas, OPSCC, or oral cavity HNSCC showed significant SSTR2 staining. Overall, SSTR2 is highly sensitive and specific for EBVNPC and could represent a surrogate biomarker. Among HNSCC assessed here, we recommend testing primary NPC for SSTR2 because of its relevance for diagnosis, associated imaging modalities, and its therapeutic implications for patient care.

An algorithmic approach utilizing CK7, TTF1, beta-catenin, CDX2, and SSTR2A can help differentiate between gastrointestinal and pulmonary neuroendocrine carcinomas.

Primary gastrointestinal neuroendocrine carcinoma (GI-NEC) cannot be distinguished morphologically from pulmonary neuroendocrine carcinoma (P-NEC). This can present a significant diagnostic challenge in cases where site of origin cannot be readily determined. To identify immunohistochemical (IHC) markers that can be used to reliably distinguish between GI-NECs and P-NECs, we constructed 3-mm tissue microarrays, one containing 13 GI-NECs and one containing 20 P-NECs. IHC was performed on both microarrays using 21 stains: AE1/AE3, CK7, CK20, synaptophysin, chromogranin, CD56, INSM1, SSTR2A, CDX2, SATB2, TTF1, Napsin A, PR, GATA3, PAX8, ISL1, beta-catenin, AFP, SMAD4, Rb, and p53. For GI-NEC, the most strongly expressed marker was synaptophysin (mean H-score 248), while AE1/AE3 was the most strongly expressed in P-NEC (mean H-score 230), which was stronger than in GI-NEC (p = 0.011). Other markers that were stronger overall in P-NEC than in GI-NEC included CK7 (p < 0.0001) and TTF1 (p < 0.0001). Markers that were stronger overall in GI-NEC than in P-NEC included SSTR2A (p = 0.0021), SATB2 (p = 0.018), CDX2 (p = 0.019), and beta-catenin (nuclear; p = 0.029). SMAD4, Rb, and p53 showed similar rates of abnormal protein expression. Based on these results, a stepwise algorithmic approach utilizing CK7, TTF1, beta-catenin, CDX2, and SSTR2A had a 91% overall accuracy in distinguishing these GI-NEC from P-NEC. This was tested on a second cohort of 10 metastatic GI-NEC and 10 metastatic P-NEC, with an accuracy in this cohort of 85% and an overall accuracy of 89% for the 53 cases tested. Our algorithm reasonably discriminates GI-NEC from P-NEC using currently available IHC stains.

Somatostatin receptor-positive breast lesions on 68Ga-DOTATATE PET/CT.

OBJECTIVE: This study sets out to evaluate patients with increased uptake in breast lesions on 68Ga-DOTATATE PET/CT (DOTA PET) and determine the clinical significance of somatostatin receptor (SSTR) positive breast lesions. METHODS: We retrospectively evaluated all patients with increased SSTR uptake in breast lesions on DOTA PET. Patients with physiological (e.g., lactation) or normal variant breast uptake (e.g., mild diffuse glandular uptake) were excluded. The maximum standard uptake value (SUVmax) was calculated using a manually drawn region of interest in the most intense uptake of breast lesions. All lesions were correlated with breast imaging, including mammography and ultrasonography. Histopathological correlation was performed if the lesion was suspicious for malignancy. Lesions were followed up radiologically (1-8 years). RESULTS: Out of 1573 retrospectively analyzed DOTA PET scans, the incidence of SSTR + breast lesions was measured as 1.1% (n = 18); however, 4 of 18 patients were excluded due to the lack of final diagnosis of lesions. The median age was 35 (range 14-58 years), and all patients were female. The median SUVmax of SSTR + breast lesions was 5.2 (range 1.5-12.6) for a total of 14 patients. Twelve patients had a single SSTR + breast lesion, while 2 patients had multiple SSTR + lesions on bilateral breasts. In 6 patients, single SSTR + lesions were considered as fibroadenoma; in 2 patients, multiple SSTR + lesions were considered as metastases of NET, based on correlative breast imaging. In 6 patients, histopathological confirmation was needed for the final diagnosis. Histopathologic findings confirmed fibroadenoma in 4 patients by biopsy, in 1 patient with surgical removal of the lesion. The last patient who had a history of IDC was diagnosed with a recurrence of IDC with biopsy. The median SUVmax was 5.1 (range 1.5-9.4) for malignant breast lesions and 5.4 (range 2.2-12.6) for benign breast lesions. CONCLUSION: SSTR + breast lesions on DOTA PET are rarely seen in clinical practice. Uptakes of breast lesions in our cases were variable and not useful for differential diagnosis of lesions. It seems that SSTR + breast lesions should be evaluated with clinical and radiological characteristics, and correlative breast imaging and/or histopathological verification should be performed for suspicious lesions to avoid misdiagnosis.

A simple novel approach for detecting blood-brain barrier permeability using GPCR internalization.

AIMS: Impairment of blood-brain barrier (BBB) is involved in numerous neurological diseases from developmental to aging stages. Reliable imaging of increased BBB permeability is therefore crucial for basic research and preclinical studies. Today, the analysis of extravasation of exogenous dyes is the principal method to study BBB leakage. However, these procedures are challenging to apply in pups and embryos and may appear difficult to interpret. Here we introduce a novel approach based on agonist-induced internalization of a neuronal G protein-coupled receptor widely distributed in the mammalian brain, the somatostatin receptor type 2 (SST2). METHODS: The clinically approved SST2 agonist octreotide (1 kDa), when injected intraperitoneally does not cross an intact BBB. At sites of BBB permeability, however, OCT extravasates and induces SST2 internalization from the neuronal membrane into perinuclear compartments. This allows an unambiguous localization of increased BBB permeability by classical immunohistochemical procedures using specific antibodies against the receptor. RESULTS: We first validated our approach in sensory circumventricular organs which display permissive vascular permeability. Through SST2 internalization, we next monitored BBB opening induced by magnetic resonance imaging-guided focused ultrasound in murine cerebral cortex. Finally, we proved that after intraperitoneal agonist injection in pregnant mice, SST2 receptor internalization permits analysis of BBB integrity in embryos during brain development. CONCLUSIONS: This approach provides an alternative and simple manner to assess BBB dysfunction and development in different physiological and pathological conditions.

Properties of primary cilia in melanin-concentrating hormone receptor 1-bearing hippocampal neurons in vivo and in vitro.

The primary cilium is a solitary organelle that organizes a sensitive signaling hub in a highly ordered microenvironment. Cilia are plastic structures, changing their length in response to bioactive substances, and ciliary length may be regulated to ensure efficient signaling capacity. Mammalian brain neurons possess primary cilia that are enriched in a set of G protein-coupled receptors (GPCRs), including the feeding-related melanin-concentrating hormone (MCH) receptor 1 (MCHR1). We previously demonstrated a novel biological phenomenon, ciliary MCHR1-mediated cilia length shortening through Gi/o and Akt signaling, using a simple cell culture model of human retinal pigmented epithelial RPE1 cells exogenously expressing MCHR1. In the present study, we characterized the properties of endogenous MCHR1-expressing primary cilia in hippocampal neurons in rodents. Using cultured dissociated rat hippocampal neurons in vitro, we showed that MCH triggered cilia length reduction involved in MCHR1-Gi/o and -Akt signaling. In rat hippocampal slice cultures with preservation of the cytoarchitecture and cell populations, ciliary MCHR1 was abundantly located in the CA1 and CA3 regions, but not in the dentate gyrus. Notably, treatment of slice cultures with MCH induced Gi/o- and Akt-dependent cilia shortening in the CA1 region without influencing cilia length in the CA3 region. Regarding the in vivo mouse brain, we observed higher levels of ciliary MCHR1 in the CA1 and CA3 regions as well as in slice cultures. In the starved state mice, a marked increase in MCH mRNA expression was detected in the lateral hypothalamus. Furthermore, MCHR1-positive cilia length in the hippocampal CA1 region was significantly shortened in fasted mice compared with fed mice. The present findings focused on the hippocampus provide a potential approach to investigate how MCHR1-driven cilia shortening regulates neuronal activity and physiological function toward feeding and memory tasks.

Neuroendocrine Tumors of the Pancreatobiliary and Gastrointestinal Tracts.

Incidence of neuroendocrine tumors (NETs) is increasing, including those of the gastroenteropancreatic tract. A proper understanding of the management of this disease has become necessary for the general surgeon. This article addresses current guidelines for diagnosis and localization of NETs, including somatostatin receptor PET. Updated treatment and outcomes of NETs by primary tumor site are discussed as well as those metastatic to the liver.

Expression of potential therapeutic target SSTR2a in primary and metastatic non-keratinizing nasopharyngeal carcinoma.

Somatostatin receptor 2a (SSTR2a) is an important diagnostic and scintigraphic marker in several tumors, as well as a potential therapeutic target. However, the expression and clinicopathologic significance of SSTR2a in nasopharyngeal carcinoma (NPC) remain unknown. The expression of SSTR2a was retrospectively analyzed in a large series of NPC tissue samples (106 primary NPC samples, comprising 99 primary non-keratinizing NPC (NK-NPC) and 7 keratinizing NPC (K-NPC) samples, and 41 metastatic NPC samples) by immunohistochemistry, with 24 cases of normal nasopharyngeal mucosa tissues used as a control group. Normal epithelia in nasopharyngeal mucosa were negative for SSTR2a in all 24 cases. The expression of SSTR2a in primary NPC was correlated to the histological subtype. Most cases of primary NK-NPC showed expression of SSTR2a (93.9%, 93/99 cases). The percentage of SSTR2a-positive tumor cells ranged from 10 to 100%, while the intensity ranged from 2+ to 4+. None of the primary K-NPC samples showed SSTR2a expression (0/7, 100%). All cases of NPC showed negative expression of other neuroendocrine markers, including synaptophysin, chromogranin A, and CD56. Of all 41 cases of metastatic NK-NPC lesions, SSTR2a expression is concordant with that of the primary lesions, which shows statistical significance (p < 0.001). Our observations expand the spectrum of recognized SSTR2a-positive tumors and demonstrate for the first time that SSTR2a is frequently expressed in primary and metastatic NK-NPC, highlighting its potential as a scintigraphic and therapeutic target in this disease.

Effect of Immune Activation during Early Gestation or Late Gestation on Inhibitory Markers in Adult Male Rats.

People with schizophrenia exhibit deficits in inhibitory neurons and cognition. The timing of maternal immune activation (MIA) may present distinct schizophrenia-like phenotypes in progeny. We investigated whether early gestation [gestational day (GD) 10] or late gestation (GD19) MIA, via viral mimetic polyI:C, produces deficits in inhibitory neuron indices (GAD1, PVALB, SST, SSTR2 mRNAs) within cortical, striatal, and hippocampal subregions of male adult rat offspring. In situ hybridisation revealed that polyI:C offspring had: (1) SST mRNA reductions in the cingulate cortex and nucleus accumbens shell, regardless of MIA timing; (2) SSTR2 mRNA reductions in the cortex and striatum of GD19, but not GD10, MIA; (3) no alterations in cortical or striatal GAD1 mRNA of polyI:C offspring, but an expected reduction of PVALB mRNA in the infralimbic cortex, and; (4) no alterations in inhibitory markers in hippocampus. Maternal IL-6 response negatively correlated with adult offspring SST mRNA in cortex and striatum, but not hippocampus. These results show lasting inhibitory-related deficits in cortex and striatum in adult offspring from MIA. SST downregulation in specific cortical and striatal subregions, with additional deficits in somatostatin-related signalling through SSTR2, may contribute to some of the adult behavioural changes resulting from MIA and its timing.

64Cu-DOTATATE PET/CT for Imaging Patients with Known or Suspected Somatostatin Receptor-Positive Neuroendocrine Tumors: Results of the First U.S. Prospective, Reader-Masked Clinical Trial.

Studies demonstrate that the investigational 64Cu-DOTATATE radiopharmaceutical may provide diagnostic and logistical benefits over available imaging agents for patients with somatostatin receptor (SSTR)-positive neuroendocrine tumors (NETs). Accordingly, we aimed to prospectively determine the lowest dose of 64Cu-DOTATATE that facilitates diagnostic-quality scans and evaluated the diagnostic performance and safety in a phase III study of patients with SSTR-expressing NETs. Methods: A dose-ranging study was conducted on 12 patients divided into 3 dose groups (111 MBq [3.0 mCi], 148 MBq [4.0 mCi], and 185 MBq [5.0 mCi] ± 10%) to determine the lowest dose of 64Cu-DOTATATE that produced diagnostic-quality PET/CT images. Using the 64Cu-DOTATATE dose identified in the dose-ranging study, 3 independent nuclear medicine physicians who were masked to all clinical information read PET/CT scans from 21 healthy volunteers and 42 NET-positive patients to determine those with disease or no disease, as well as those with localized versus metastatic status. Masked-reader evaluations were compared with a patient-specific standard of truth, which was established by an independent oncologist who used all previously available pathology, clinical, and conventional imaging data. Diagnostic performance calculated for 64Cu-DOTATATE included sensitivity, specificity, negative predictive value, positive predictive value, and accuracy. Inter- and intrareader reliability, as well as ability to differentiate between localized and metastatic disease, was also determined. Adverse events were recorded from 64Cu-DOTATATE injection through 48 h after injection. Results: The dose-ranging study identified 148 MBq (4.0 mCi) as the optimal dose to obtain diagnostic-quality PET/CT images. After database lock, diagnostic performance from an initial majority read of the 3 independent readers showed a significant 90.9% sensitivity (P = 0.0042) and 96.6% specificity (P < 0.0001) for detecting NETs, which translated to a 100.0% sensitivity and 96.8% specificity after correcting for an initial standard-of-truth misread. Excellent inter- and intrareader reliability, as well as ability to distinguish between localized and metastatic disease, was also noted. No adverse events were related to 64Cu-DOTATATE, and no serious adverse events were observed. Conclusion:64Cu-DOTATATE PET/CT is a safe imaging technique that provides high-quality and accurate images at a dose of 148 MBq (4.0 mCi) for the detection of somatostatin-expressing NETs.

On the G Protein-Coupled Receptor Neuromodulation of the Claustrum.

G protein-coupled receptors modulate the synaptic glutamate and GABA transmission of the claustrum. The work focused on the transmitter-receptor relationships in the claustral catecholamine system and receptor-receptor interactions between kappa opioid receptors (KOR) and SomatostatinR2 (SSTR2) in claustrum. Methods used involved immunohistochemistry and in situ proximity ligation assay (PLA) using confocal microscopy. Double immunolabeling studies on dopamine (DA) D1 receptor (D1R) and tyrosine hydroxylase (TH) immunoreactivities (IR) demonstrated that D1R IR existed in almost all claustral and dorsal endopiriform nucleus (DEn) nerve cell bodies, known as glutamate projection neurons, and D4R IR in large numbers of nerve cell bodies of the claustrum and DEn. However, only a low to moderate density of TH IR nerve terminals was observed in the DEn versus de few scattered TH IR terminals found in the claustrum. These results indicated that DA D1R and D4R transmission in the rat operated via long distance DA volume transmission in the rat claustrum and DEn to modulate claustral-sensory cortical glutamate transmission. Large numbers of these glutamate projection neurons also expressed KOR and SSTR2 which formed KOR-SSTR2 heteroreceptor complexes using PLA. Such receptor-receptor interactions can finetune the activity of the glutamate claustral-sensory cortex projections from inhibition to enhancement of their sensory cortex signaling. This can give the sensory cortical regions significant help in deciding on the salience to be given to various incoming sensory stimuli.

Somatostatin receptors (SSTR1-5) on inhibitory interneurons in the barrel cortex.

Inhibitory interneurons in the cerebral cortex contain specific proteins or peptides characteristic for a certain interneuron subtype. In mice, three biochemical markers constitute non-overlapping interneuron populations, which account for 80-90% of all inhibitory cells. These interneurons express parvalbumin (PV), somatostatin (SST), or vasoactive intestinal peptide (VIP). SST is not only a marker of a specific interneuron subtype, but also an important neuropeptide that participates in numerous biochemical and signalling pathways in the brain via somatostatin receptors (SSTR1-5). In the nervous system, SST acts as a neuromodulator and neurotransmitter affecting, among others, memory, learning, and mood. In the sensory cortex, the co-localisation of GABA and SST is found in approximately 30% of interneurons. Considering the importance of interactions between inhibitory interneurons in cortical plasticity and the possible GABA and SST co-release, it seems important to investigate the localisation of different SSTRs on cortical interneurons. Here, we examined the distribution of SSTR1-5 on barrel cortex interneurons containing PV, SST, or VIP. Immunofluorescent staining using specific antibodies was performed on brain sections from transgenic mice that expressed red fluorescence in one specific interneuron subtype (PV-Ai14, SST-Ai14, and VIP-Ai14 mice). SSTRs expression on PV, SST, and VIP interneurons varied among the cortical layers and we found two patterns of SSTRs distribution in L4 of barrel cortex. We also demonstrated that, in contrast to other interneurons, PV cells did not express SSTR2, but expressed other SSTRs. SST interneurons, which were not found to make chemical synapses among themselves, expressed all five SSTR subtypes.

PET/TC con análogos de la somatostatina en el estudio de tumores neuroendocrinos, experiencia inicial / PET/TC imaging with somatostatin analogues for assessment of neuroendocrine tumors, initial experience

La PET con análogos de la somatostatina permite detectar aquellas células con sobreexpresión de receptores de somatostatina, especialmente del subtipo 2 y 5, siendo variable esta detección según el tipo de molécula que se utilice. Esta es la base para su uso en el estudio de los tumores neuroendocrinos (NET), los cuales se caracterizan por presentar una sobreexpresión de estos receptores en más del 80% de los subtipos. Esta PET llega a nuestro país avalada por los buenos resultados publicados por otros grupos, superiores a los de otras técnicas de imagen. Presentamos dos de los primeros casos de PET con análogos de la somatostatina: 68Ga-edetreótida (SomaKit TOC(R)) realizados en nuestro centro. La PET fue la prueba que determinó finalmente el manejo clínico de ambos pacientes

PET with somatostatin analogues (SSA PET/CT) enables the detection of cells with overexpression of somatostatin receptors, especially subtypes 2 and 5; this detection is variable depending on the type of molecule used. This is the basis for its use in the study of neuroendocrine tumours (NETs), which are characterized by an overexpression of these receptors in more than 80% of the subtypes. This PET is now being used in our country supported by the good results published by other groups, that were superior to those of other imaging techniques. We present two of the first cases of SSA-PET/CT with 68Ga-edotreotide (SomaKit TOC(R)) performed in our centre. SSA-PET/CT was the test that finally determined the clinical management of both patients

Immunohistochemical Expression of Somatostatin Receptor Subtypes in a Panel of Neuroendocrine Neoplasias.

Neuroendocrine neoplasias (NENs) are known to express somatostatin receptors (SSTRs) 1-5, which are G-protein-coupled cell membrane receptors. Somatostatin receptor imaging and therapy utilizes the SSTR expression. Synthetic somatostatin analogs with radioligands are used to detect primary tumors, metastases, and recurrent disease. Receptor analogs are also used for treating NENs. Furthermore, commercially available SSTR antibodies can be used for the immunohistochemical (IHC) detection of SSTRs. We investigated different SSTR antibody clones applying diverse IHC protocol settings to identify reliable clones and feasible protocols for NENs. A tissue microarray including NENs from 12 different primary sites were stained. Only UMB clones were able to localize SSTR on the cell membranes of NENs. SSTR2 (UMB1) emerged as the most common subtype followed by SSTR5 (UMB4) and SSTR1 (UMB7). SSTR3 (UMB5) expression was mainly cytoplasmic. Yet, SSTR4 expression was weak and located primarily in the cytoplasm. Thus, appropriate IHC protocols, including proper positive and negative controls, represent requirements for high-quality NEN diagnostics and for planning personalized therapy.

Prognostic value of somatostatin receptor expressing tumor volume calculated from 68Ga-DOTATATE PET/CT in patients with well-differentiated neuroendocrine tumors.

PURPOSE: To evaluate the prognostic value of volumetric parameters calculated from 68Ga-1,4,7,10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid (DOTA)-Thr3-octreotate (68Ga-DOTATATE) positron emission tomography/computed tomography (PET/CT) in patients with well-differentiated neuroendocrine tumor (WD-NET). METHODS: Ninety-two patients (44 men and 48 women, mean age of 59.5-year-old) with pathologically confirmed WD-NET (grades 1 or 2) were enrolled in a prospective expanded access protocol. Selected data was analyzed retrospectively for this project. Maximum standardized uptake value (SUVmax) in the lesion with the highest 68Ga-DOTATATE uptake was measured and recorded for each patient. In addition, two volumetric parameters, namely, somatostatin receptor expressing tumor volume (SRETV) and total lesion somatostatin receptor expression (TLSRE), were calculated in each 68Ga-DOTATATE-avid lesion. SRETV was defined as tumor volume with higher 68Ga-DOTATATE uptake than the 50% of SUVmax within the volume of interest (VOI) for each lesion. TLSRE was calculated by multiplying SRETV and mean SUV within the same VOI. Thereafter, the sum of SRETV (ΣSRETV) and TLSRE (ΣTLSRE) for all detected lesions per patient were calculated. Progression-free survival (PFS) was set as primary endpoint. Kaplan-Meier survival analysis, log-rank test, and Cox's proportional hazard model were used for statistical analysis. RESULTS: Univariate analyses revealed significant difference of PFS for WHO tumor grade and ΣSRETV (P < 0.05), while there were no significant differences in age, sex, SUVmax, and ΣTLSRE (P > 0.05). Multivariate analysis identified WHO tumor grade and ΣSRETV as independent predictors of PFS. CONCLUSION: ΣSRETV calculated from 68Ga-DOTATATE PET/CT may have prognostic value of PFS in WD-NET patients.

Constant expression of somatostatin receptor 2a in minute pulmonary meningothelial-like nodules.

AIMS: Although ultrastructural studies showed that minute pulmonary meningothelial-like nodules (MPMNs) cells closely resembled meningothelial cells, their immunophenotype has not been well characterised, partly due to their rarity. METHODS: Somatostatin receptor 2a (SSTR2a) and other markers of meningioma, including epithelial membrane antigen (EMA), progesterone receptor (PR) and S100, were analysed retrospectively in 19 MPMN cases from two institutions in China. RESULTS: The median age of patients with MPMNs was 62.5 years (32-73 years), with a male-to-female ratio of 1:8.5. Most (15/19) patients with MPMNs had coexisting diseases, including adenocarcinomas (12 cases), bronchiectasis (1 case) and tuberculosis (2 cases). Just over half of the cases (10/19) were multifocal lesions (2-5 lesions). An additional 53 cases with 123 lesions from the literature were reviewed with reported immunophenotype information. In total, 162 lesions were included in the analysis. The size of nodules was 1-4 mm. All MPMN lesions (39/39) in the 19 cases showed strong and diffuse cytoplasmic expression of SSTR2a. The expression rate of SSTR2a was higher than that of conventional markers of meningioma, including EMA (86/138), PR (32/68) and S100 (1/125). CONCLUSIONS: Our observations expand the spectrum of recognised SSTR2a-positive lesions and once again demonstrated that MPMNs show immunohistochemical characteristics similar to meningothelial cells.

Receptor radionuclide targeting for neuroendocrine tumors (NET) diagnostic and therapy.

Neuroendocrine tumors (NET) represent a heterogeneous group of tumors originating from cells of neuroendocrine origin, which express somatostatin receptors (SSTR). This property allowed the successful development of radionuclides for diagnostic and peptide radionuclide radiation therapy (PRRT). This is the paradigm for the theragnostic concept in NET personalized medicine. The only phase III study to date (NETTER-1) clearly demonstrated the ability of 177Lutetium-based PRRT to improve progression-free survival in advanced intestinal NETs. In clinical practice, the indications are limited to G1-G2 well-differentiated NETs with high expression of SSTR. NETs with a low tumor burden and slow progression are probably the optimal indication. This treatment is now available in France. However, its precise position in the treatment algorithm remains to be explored. We provide an overview of receptor radionuclide utilization and mechanism in diagnostic and pretherapeutic imaging and we focus on PRRT for endocrine tumors.