GEP-NETs UPDATE: Secreting gastro-enteropancreatic neuroendocrine tumours and biomarkers

Relation between WHO Classification and Location- and Functionality-Based Classifications of Neuroendocrine Neoplasms of the Digestive Tract

Practice of neuroendocrine neoplasms (NENs) of the digestive tract, which comprise of a highly diverse group of tumors with a rising incidence, faces multiple biological, diagnostic, and therapeutic issues. Part of these issues is due to misuse and misinterpretation of the classification and terminology of NENs of the digestive tract, which make it increasingly challenging to evaluate and compare the literature. For instance, grade 3 neuroendocrine tumors (NETs) are frequently referred to as neuroendocrine carcinomas (NECs) and vice versa, while NECs are, by definition, high grade and therefore constitute a separate entity from NETs. Moreover, the term NET is regularly misused to describe NENs in general, and NETs are frequently referred to as benign, while they should always be considered malignancies as they do have metastatic potential. To prevent misconceptions in future NEN-related research, we reviewed the most recent terminology used to classify NENs of the digestive tract and created an overview that combines the classification of these NENs according to the World Health Organization (WHO) with location- and functionality-based classifications. This overview may help clinicians and researchers in understanding the current literature and could serve as a guide in the clinic as well as for writing future studies on NENs of the digestive tract. In this way, we aim for the universal use of terminology, thereby providing an efficient foundation for future NEN-related research.

Hepatoid adenocarcinoma of the stomach with neuroendocrine differentiation: A case report and review of literature

BACKGROUND

Both hepatoid adenocarcinoma of the stomach (HAS) and neuroendocrine differentiation (NED) are rare histological subtypes of gastric cancer with unique clinicopathological features and unfavorable outcomes. HAS with NED is even rarer.

CASE SUMMARY

Here, we report a 61-year-old man with HAS with NED, as detected by gastric wall thickening by positron emission tomography/computed tomography for a pulmonary nodule. Distal gastrectomy was performed, and pathological examination led to the diagnosis of HAS with NED. However, liver metastases occurred 6 mo later despite adjuvant chemotherapy, and the patient died 27 mo postoperatively.

CONCLUSION

We treated a patient with HAS with NED who underwent adjuvant chemotherapy after radical surgery and still developed liver metastases. We first report the detailed processes of the treatment and development of HAS with NED, providing an important reference for the clinical diagnosis and treatment of this condition.

Hepatoid adenocarcinoma of the stomach with neuroendocrine differentiation: A case report and review of literature

BACKGROUND

Both hepatoid adenocarcinoma of the stomach (HAS) and neuroendocrine differentiation (NED) are rare histological subtypes of gastric cancer with unique clinicopathological features and unfavorable outcomes. HAS with NED is even rarer.

CASE SUMMARY

Here, we report a 61-year-old man with HAS with NED, as detected by gastric wall thickening by positron emission tomography/computed tomography for a pulmonary nodule. Distal gastrectomy was performed, and pathological examination led to the diagnosis of HAS with NED. However, liver metastases occurred 6 mo later despite adjuvant chemotherapy, and the patient died 27 mo postoperatively.

CONCLUSION

We treated a patient with HAS with NED who underwent adjuvant chemotherapy after radical surgery and still developed liver metastases. We first report the detailed processes of the treatment and development of HAS with NED, providing an important reference for the clinical diagnosis and treatment of this condition.

Management of Other Gastric and Duodenal Neuroendocrine Tumors

Gastric and duodenal neuroendocrine tumors (NETs) are increasing in incidence as a result of increased detection and awareness of neuroendocrine tumors as distinct tumor types. The three types of gastric NETs and duodenal NETs have different etiologies and tumor-specific factors, such as grade, location, and hormone-production, and the clinical settings influence management. Options for treatment include removal by local endoscopic resection and surgical resection. Medical therapy is used to treat the inciting condition or as systemic therapy in advanced disease. Although the overall prognosis for most is good, higher grade tumors behave aggressively and have reduced survival.

Cardiovascular Mortality Risk among Patients with Gastroenteropancreatic Neuroendocrine Neoplasms: A Registry-Based Analysis

Background

This research is aimed to explore mortality patterns and quantitatively assess the risks of cardiovascular mortality (CVM) in patients with primary gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs).

Methods

We extracted data from the Surveillance, Epidemiology, and End Results (SEER) database for patients diagnosed with GEP-NENs between 2000 and 2015. The standardized mortality ratio (SMR) and the absolute excess risk were obtained based on the reference of the general US population. The cumulative incidence function curves were constructed for all causes of death. Predictors for CVM were identified using a multivariate competing risk model.

Results

Overall, 42027 patients were enrolled from the SEER database, of whom 1598 (3.8%) died from cardiovascular disease (CVD). The SMR for CVM was 1.20 (95% CI: 1.14-1.26) among GEP-NEN patients. The cumulative mortality of CVD was the lowest among all causes of death, including primary cancer, other cancer, and other noncancer diseases. Furthermore, age at diagnosis, race, Hispanic origin, sex, marital status, year of diagnosis, grade, education level, region, SEER stage, primary site, surgery, and chemotherapy were identified as independent predictors of CVM in GEP-NEN patients.

Conclusions

GEP-NEN patients have a significantly increased risk of CVM relative to the general population. Cardioprotective interventions might be considered a preferred method for these patients.

Coping with social consequences of disease-related symptoms in patients with a metastatic small intestinal neuroendocrine tumour: A qualitative study

Patients with small intestine neuroendocrine tumours (SINETs) face various disease-related symptoms that can affect their social functioning and quality of life. The present study aimed to explore the social consequences of disease-related symptoms in patients with a metastatic SINET and to develop a theory on how these patients experience their disease. Patients were eligible when they were diagnosed with a metastatic SINET between 2009 and 2016 and were younger than 60 years of age during diagnosis, and had a good functional performance status. Semi-structured interviews were conducted between January and June 2018. Data were transcribed and analysed independently by two researchers using grounded theory. Data saturation was reached at 10 interviews and, in total, 12 patients participated. A core component that arose from the interviews was resilience in the face of social consequences of having a metastatic SINET. Prominent physical symptoms were fatigue, diarrhoea and flushes. All of these symptoms were associated with limitations to function in work-related and social activities, as well as feelings of embarrassment and shame. Adaptive strategies, such as careful planning, or focusing on the perspective to live well with a neuroendocrine tumour, helped patients to experience the consequences as less burdensome. Other helpful factors that were identified constituted social support, engaging in meaningful activities and financial stability. Patients with a metastatic SINET experienced social consequences of disease-related symptoms in daily life, although they were able to attenuate the burden of these consequences by using adaptive problem-based, emotion-based and meaning-based coping strategies. Clinicians could explore the perceived consequences and educate patients about adaptive strategies.

Neuroendocrine neoplasia of the gastrointestinal tract revisited: towards precision medicine

Over the past 5 years, a number of notable research advances have been made in the field of neuroendocrine cancer, specifically with regard to neuroendocrine cancer of the gastrointestinal tract. The aim of this Review is to provide an update on current knowledge that has proven effective for the clinical management of patients with these tumours. For example, for the first time in the tubular gastrointestinal tract, well-differentiated high-grade (grade 3) tumours and mixed neuroendocrine-non-neuroendocrine neoplasms (MiNENs) are defined in the WHO classification. This novel classification enables efficient identification of the most aggressive well-differentiated neuroendocrine tumours and helps in defining the degree of aggressiveness of MiNENs. The Review also discusses updates to epidemiology, cell biology (including vesicle-specific components) and the as-yet-unresolved complex genetic background that varies according to site and differentiation status. The Review summarizes novel diagnostic instruments, including molecules associated with the secretory machinery, novel radiological approaches (including pattern recognition techniques), novel PET tracers and liquid biopsy combined with DNA or RNA assays. Surgery remains the treatment mainstay; however, peptide receptor radionuclide therapy with novel radioligands and new emerging medical therapies (including vaccination and immunotherapy) are evolving and being tested in clinical trials, which are summarized and critically reviewed here.

Treatment Patterns and Survival among Patients with Metastatic Gastroenteropancreatic Neuroendocrine Tumours in Sweden - a Population-based Register-linkage and Medical Chart Review Study

Background: Gastroenteropancreatic neuroendocrine tumours (GEP-NETs) are neoplasms derived from the endocrine system in the gastrointestinal tract and pancreas. Treatment options include surgery; pharmacological treatments like somatostatin analogues (SSA), interferon alpha, molecular targeted therapy and chemotherapy; and peptide receptor radionuclide therapy.

The objective of this study was to describe treatment patterns and survival among patients with metastatic GEP-NET grade 1 or 2 in Sweden.

Methods: Data was obtained via linkage of nationwide registers. Patients diagnosed with metastatic GEP-NET grade 1 or 2 in Sweden between 2005 and 2013 were included (n=811; National population). In addition, medical chart review was performed for the subpopulation diagnosed at Sahlgrenska University Hospital, Gothenburg (n=127; Regional population). Treatment patterns, including treatment sequences, and overall survival were assessed.

Results: Most patients had small intestinal NET (76%). In the regional population, 72% had grade 1 tumours; 50% had functioning tumours. The two most common first-line treatments were surgery (57%) and SSA (25%). After first-line surgery, 46% received SSA, while 40% had no further treatment. After first-line SSA, 52% received surgery, while 27% had no further treatment. Overall median survival time from date of diagnosis was 7.0 years (95% CI 6.2-not reached). Among patients with distant metastases, pancreatic NET (vs. small intestinal NET) was associated with poorer survival (HR 1.9; 95% CI 1.1-3.3), as were liver metastases (HR 3.2; 95% CI 1.5-7.0).

Conclusions: First-line surgery was typically followed by SSA or no further treatment. Among patients with distant metastases, pancreatic NET or liver metastases were associated with a poorer survival.

Resection of the primary tumor improves survival in patients with gastro-entero-pancreatic neuroendocrine neoplasms with liver metastases: A SEER-based analysis

Patients who suffer from gastro‐entero‐pancreatic neuroendocrine neoplasms (GEP‐NENs) often present with liver metastatic disease. The efficacy of primary tumor resection (PTR) for these patients remains controversial due to the relatively heterogeneous behavior of the primary tumor and the lack of clinical evidence. In this series, GEP‐NEN patients with liver metastases (LM) were selected from the Surveillance, Epidemiology, and End Results database between 2010 and 2015. A logistic regression model was used to analyze variables that were associated with PTR. A Cox proportional hazards model was used to identify independent prognostic risk factors. In total, 1547 patients were enrolled in our study, including 897 patients who underwent PTR. Resection of the primary tumor was associated with prolonged survival in all patients (5‐year overall survival (OS) rates: 57.0% vs 15.4%, P < .001), and improved 5‐year OS rates were observed in patients with gastric, small intestinal, colorectal, and pancreatic subtypes (39.7%, 73.3%, 24.6%, and 59.7%, respectively). On the multivariate analysis, PTR was an independent prognostic factor of prolonged OS (HR = 0.48, 95% CI: 0.39‐0.59, P < .001). Patients with a young age (≤60 years), small intestinal or colorectal NENs, a large primary tumor, lymph node (LN) metastases, and high tumor differentiation were more likely to undergo PTR. However, patients with colorectal NENs or a large primary tumor (≥4 cm) were at an increased risk of death independently in the PTR subgroup. The risk factors for OS also included old age, gastric tumor location, and poor differentiation. In conclusion, although PTR prolonged OS in all GEP‐NEN patients presenting with LM, surgical recipients should be considered carefully. Age, primary tumor site, size, and differentiation might help surgeons identify patients who could benefit from PTR.

Selective internal radiation therapy: an effective treatment for hormonal syndromes in pancreatic neuroendocrine tumors

The hormone secretion in pancreatic neuroendocrine tumors (pNET) causes an important interference in patients' quality of life. We present two cases of pNET metastatic to the liver (a pancreatic endocrine carcinoma with a severe hormonal syndrome and an insulinoma with severe crisis of hypoglycemia and coma) refractory to conventional treatments, which were finally solved with selective internal radiation therapy (SIRT), a nonstandard level 1 therapy. We show two examples of an excellent control of symptoms together with a long survival after treatment with SIRT. The evidence supporting the use of this therapy is level 2. Our case reports strongly support the use of SIRT for the severe clinical syndrome in pNET metastatic to the liver and refractory to somatostatin analogs.

CLEC3A, MMP7, and LCN2 as novel markers for predicting recurrence in resected G1 and G2 pancreatic neuroendocrine tumors

Although the postoperative recurrence rate for pancreatic neuroendocrine tumors (PNETs) is reported to be 13.5%-30%, the paucity of valuable biomarkers to predict recurrence poses a problem for the early detection of relapse. Hence, this study aimed to identify new biomarkers to predict the recurrence of PNETs. We performed RNA sequencing (RNA-Seq) on RNA isolated from frozen primary tumors sampled from all localized G1/G2 PNETs resected curatively from 1998 to 2015 in our institution. We calculated differentially expressed genes (DEGs) in tumor with and without recurrence (≥3 years) for the propensity-matched cohort. Gene ontology analysis for the identified DEGs was also performed. Furthermore, we evaluated the expression levels of candidate genes as recurrence predictors via immunostaining. Comparison of transcriptional levels in tumors with and without recurrence identified 166 DEGs. Up- and downregulated genes with high significance in these tumors were mainly related to extracellular organization and cell adhesion, respectively. We observed the top three upregulated genes, C-type lectin domain family 3 member A (CLEC3A), matrix metalloproteinase-7 (MMP7), and lipocalin2 (LCN2) immunohistochemically and compared their levels in recurrent and nonrecurrent tumors. Significantly higher recurrence rate was shown in patients with positive expression of CLEC3A (P = 0.028), MMP7 (P = 0.003), and LCN2 (P = 0.040) than that with negative expression. We identified CLEC3A, MMP7, and LCN2 known to be associated with the phosphatidylinositol-3-kinase/Akt pathway, as potential novel markers to predict the postoperative recurrence of PNETs.

Multilayered heterogeneity as an intrinsic hallmark of neuroendocrine tumors

Neuroendocrine tumors (NETs) comprise a complex and highly heterogeneous group of neoplasms that can arise all over the body, originating from neuroendocrine cells. NETs are characterized by a general lack of symptoms until they are in advanced phase, and early biomarkers are not as available and useful as required. Heterogeneity is an intrinsic, pivotal feature of NETs that derives from diverse causes and ultimately shapes tumor fate. The different layers that conform NET heterogeneity include a wide range of distinct characteristics, from the mere location of the tumor to its clinical and functional features, and from its cellular properties, to the core signaling and (epi)genetic components defining the molecular signature of the tumor. The importance of this heterogeneity resides in that it translates into a high variability among tumors and, hence, patients, which hinders a more precise diagnosis and prognosis and more efficacious treatment of these diseases. In this review, we highlight the significance of this heterogeneity as an intrinsic hallmark of NETs, its repercussion on clinical approaches and tumor management, and some of the possible factors associated to such heterogeneity, including epigenetic and genetic elements, post-transcriptional regulation, or splicing alterations. Notwithstanding, heterogeneity can also represent a valuable and actionable feature, towards improving medical approaches based on personalized medicine. We conclude that NETs can no longer be viewed as a single disease entity and that their diagnosis, prognosis and treatment must reflect and incorporate this heterogeneity.

Treatment Patterns and Clinical Outcomes in Patients With Metastatic Gastroenteropancreatic Neuroendocrine Tumors Treated in the Community Practice Setting in the United States

OBJECTIVE

This study was conducted to understand treatment patterns and clinical outcomes in metastatic gastroenteropancreatic neuroendocrine tumor patients treated in a large community oncology network.

METHODS

This retrospective study used the McKesson Specialty Health/US Oncology Network iKnowMed electronic health record database with supplemental chart review. Eligibility criteria included a metastatic neuroendocrine tumor diagnosis between January 1, 2008, and to December 31, 2012; at least 2 US Oncology Network visits; and age at least 18 years. Follow-up was through October 31, 2014.

RESULTS

Among the 229 patients identified, median age was 64.0 years, 52.4% were male, 69.4% were white, and 62.9% were overweight/obese. Primary tumor sites included small bowel (47.6%), pancreas (31.4%), and stomach/colorectum (21.0%). There were 16.2% under observation without treatment, 52.4% received only somatostatin analogs (SSAs), and 31.4% received chemotherapy/targeted therapy during treatment. In the first-line setting (n = 192), 77% received SSAs, 12% received chemotherapy, and 10.9% received targeted therapy. Fifty percent of patients receiving octreotide had a relative dose intensity of less than 85%, and 16.7% received above-label dose. Toxicities of SSAs included diarrhea (18.2%), abdominal pain (16.9%), and fatigue (13.5%). Median overall survival from diagnosis was 68.0 months (95% confidence interval, 57.1 to not reached).

CONCLUSIONS

Most metastatic gastroenteropancreatic neuroendocrine tumor patients received systemic treatment with SSAs. Patient treatment used an individualized dosing approach. Overall survival and toxicity were consistent with the published literature.

Blood Transcript Profiling for the Detection of Neuroendocrine Tumors: Results of a Large Independent Validation Study

Background: Available neuroendocrine biomarkers are considered to have insufficient accuracy to discriminate patients with gastro-entero-pancreatic neuroendocrine tumors (GEP-NETs) from healthy controls. Recent studies have demonstrated a potential role for circulating neuroendocrine specific transcripts analysis-the NETest-as a more accurate biomarker for NETs compared to available biomarkers. This study was initiated to independently validate the discriminative value of the NETest as well as the association between tumor characteristics and NETest score. Methods: Whole blood samples from 140 consecutive GEP-NET patients and 113 healthy volunteers were collected. Laboratory investigators were blinded to the origin of the samples. NETest results and chromogranin A (CgA) levels were compared with clinical information including radiological imaging to evaluate the association with tumor characteristics. Results: The median NETest score in NET patients was 33 vs. 13% in controls (p < 0.0001). The NETest did not correlate with age, gender, tumor location, grade, load, or stage. Using the cut-off of 14% NETest sensitivity and specificity were 93 and 56%, respectively, with an AUC of 0.87. The optimal cut-off for the NETest in our population was 20%, with sensitivity 89% and specificity 72%. The upper limit of normal for CgA was established as 100 μg/l. Sensitivity and specificity of CgA were 56 and 83% with an AUC of 0.76. CgA correlated with age (rs = 0.388, p < 0.001) and tumor load (rs = 0.458, p < 0.001). Conclusions: The low specificity of the NETest precludes its use as a screening test for GEP-NETs. The superior sensitivity of the NETest over CgA (93 vs. 56%; p < 0.001), irrespective of the stage of the disease, emphasize its potential as a marker of disease presence in follow up as well as an indicator for residual disease after surgery.

Neurotensin Receptor 3/Sortilin Contributes to Tumorigenesis of Neuroendocrine Tumors Through Augmentation of Cell Adhesion and Migration

Neurotensin (NTS), a 13–amino acid peptide which is distributed predominantly along gastrointestinal tract, has multiple physiologic and pathologic functions, and its effects are mediated by three distinct NTS receptors (NTSRs). Overexpression and activation of NTS signaling components, especially NTS and/or NTSR1, are closely linked with cancer progression and metastasis in various types of cancers including neuroendocrine tumors (NETs). Although deregulation of NTSR3/sortilin has been implicated in a variety of human diseases, the expression and role of NTSR3/sortilin in NETs have not been elucidated. In this study, we investigated the expression and oncogenic effect of NTSR3/sortilin in NETs. Increased protein levels of NTSR3/sortilin were noted in the majority of human clinical NETs (n = 21) by immunohistochemical analyses compared with normal tissues (n = 12). Expression of NTS and NTSR3/sortilin was also noted in all tested NET cell lines. In addition, small interfering RNA–mediated knockdown of NTSR3/sortilin decreased cell number without alteration of cell cycle progression and apoptosis induction in NET cell lines BON and QGP-1. Moreover, silencing of NTSR3/sortilin significantly suppressed cell adhesion and cell migration with inhibition of focal adhesion kinase and Src phosphorylation in the NET cells. Our results demonstrate increased expression of NTSR3/sortilin in NET patient tissues and a critical role of NTSR3/sortilin on NET cell adhesion and migration suggesting that NTSR3/sortilin contributes to NET tumorigenesis.

Comparison of Recurrence Between Pancreatic and Duodenal Neuroendocrine Neoplasms After Curative Resection: A Single-Institution Analysis

BACKGROUND

The primary site of a neuroendocrine neoplasms (NEN) around the head of the pancreas is sometimes difficult to assess before resection, and the characteristics of the primary site around this region have not been elucidated for recurrence after curative resection. In this study, the clinicopathologic characteristics of pancreatic NEN (PanNEN) and duodenal NEN (DuNEN) were evaluated, and the risk factors as well as the recurrence types after resection were investigated.

METHODS

Consecutively diagnosed NEN patients at the authors' hospital from January 2000 to July 2016 were evaluated in this study. For 117 PanNEN patients and 31 non-ampullary DuNEN patients, R0 resection was achieved. The median follow-up period was 8.1 years.

RESULTS

In this study, 27 PanNEN patients (23.1%) had recurrences, with a median disease-free survival (DFS) of 133 months, whereas 11 DuNEN patients (35.5%) had recurrences, with a median DFS of 156 months. The PanNEN patients tended to have primary recurrence in the liver (85.2%), followed by lymph nodes (11.1%). The independent risk factors for short DFS were lymph node metastasis at resection (p = 0.001) and microvascular invasion (p = 0.048). In contrast, the DuNEN patients were likely to have lymph node metastasis (81.8%). The independent risk factors for short DFS were lymph node metastasis at resection (p = 0.003) and large diameter (p = 0.013).

CONCLUSIONS

Most initial recurrences of PanNEN occurred in the liver, whereas those of DuNEN appeared in lymph nodes, suggesting that proper diagnosis of the primary site and appropriate imaging methods for surveillance after resection are necessary.

Clinical Validation of a Pixon-Based Reconstruction Method Allowing a Twofold Reduction in Planar Images Time of 111In-Pentetreotide Somatostatin Receptor Scintigraphy

Objective

Methods

Results

Conclusion

Circulating tumor cells and miRNAs as prognostic markers in neuroendocrine neoplasms

The prognosis of neuroendocrine neoplasms (NENs) is widely variable and has been shown to associate with several tissue- and blood-based biomarkers in different settings. The identification of prognostic factors predicting NEN outcome is of paramount importance to select the best clinical management for these patients. Prognostic markers have been intensively investigated, also taking advantage of the most modern techniques, in the perspective of personalized medicine and appropriate resource utilization. This review summarizes the available data on the possible role of circulating tumor cells and microRNAs as prognostic markers in NENs.

Chromogranin A as a valid marker in oncology: Clinical application or false hopes?

Chromogranin A, due to its primary expression throughout the neuroendocrine system, is a widely accepted biomarker for the assessment of neuro-endocrine tumors. It has been traditionally used in the management of patients with tumors of gastro-enteropancreatic origin. Lately, it has also been implicated in various conditions and diseases, both benign and malignant. However, the paucity of data of adequate strength, as well as its relation with common physiologic conditions and its interaction with commonly prescribed medications, limit its clinical use in only a narrow spectrum. Herein, we present a thorough review to the most frequent conditions where its levels are affected, focusing specifically on its potential use as a prognostic and predictive biomarker in oncology.

Neuroendocrine Tumors of the Stomach

Gastric neuroendocrine tumors (NETs) are classified into three types. Type I gastric NETs are associated with chronic atrophic gastritis. They have a good prognosis and endoscopic resection is the mainstay of treatment. Type II gastric NETs are caused by hypergastrinemia. They have a poorer prognosis, and resection is required to control the disease. Endoscopic versus surgical resection is recommended for the gastric lesion. Type III gastric NETs are sporadic and not associated with any specific condition. They have the worst prognosis with the highest rate of metastatic disease, and oncologic resection is recommended. Medical therapies have some role.

Well-differentiated neuroendocrine tumor of the stomach: A rare case at an uncommon site

INTRODUCTION

A 13-year-old African-American female presented to her primary care physician's office with fatigue, syncope, and hematemesis. After initial evaluation, the patient was referred to pediatric gastroenterology clinic for further evaluation.

MAIN CONCERNS, IMPORTANT FINDINGS

An upper gastrointestinal endoscopy was performed to evaluate the source of her bleeding. Endoscopy revealed a 3-cm mass in the lesser curvature of the stomach, and a biopsy of the mass revealed a concern for carcinoid (neuroendocrine) features.

DIAGNOSIS

She underwent an open gastrectomy. Post-surgical pathology reports confirmed a well-differentiated neuroendocrine tumor of the stomach.

CONCLUSION

Neuroendocrine tumors of the stomach in children are rare and we presently do not have pediatric-specific diagnostic and treatment guidelines. Although adult-based The North American Neuroendocrine Tumor Society (NANETS) guidelines are helpful, they are clearly not geared toward pediatric patients. To establish pediatric guidelines and to assess effectiveness of treatments, multicenter data collection is essential. In the long run, accumulation of clinically useful treatment information and long-term follow-up guidelines should enable clinicians to improve standard of care given to children with neuroendocrine tumors.

Glutaminases in slowly proliferating gastroenteropancreatic neuroendocrine neoplasms/tumors (GEP-NETs): Selective overexpression of mRNA coding for the KGA isoform

Glutamine (Gln) is a crucial metabolite in cancer cells of different origin, and the expression and activity of different isoforms of the Gln-degrading enzyme, glutaminase (GA), have variable implications for tumor growth and metabolism. Human glutaminases are encoded by two genes: the GLS gene encodes the kidney-type glutaminases, KGA and GAC, while the GLS2 gene encodes the liver-type glutaminases, GAB and LGA. Recent studies suggest that the GAC isoform and thus high GAC/KGA ratio, are characteristic of highly proliferating tumors, while GLS2 proteins have an inhibitory effect on tumor growth. Here we analyzed the expression levels of distinct GA transcripts in 7 gastroenteropancreatic neuroendocrine tumors (GEP-NETs) with low proliferation index and 7 non-neoplastic tissues. GEP-NETs overexpressed KGA, while GAC, which was the most abundant isoform, was not different from control. The expression of the GLS2 gene showed tendency towards elevation in GEP-NETs compared to control. Collectively, the expression pattern of GA isoforms conforms to the low proliferative capacity of GEP-NETs encompassed in this study.