Sporadic Pancreatic Endocrine Tumors Research Articles

Efficacy and Cost-Effectiveness of Immediate Surgery versus a Wait-and-See Strategy for Sporadic Nonfunctioning T1 Pancreatic Endocrine Neoplasms

Background: Whether patients with small (<2 cm), sporadic nonfunctioning pancreatic endocrine tumors (NF-PETs) should directly undergo pancreatic surgery or should be followed longitudinally to detect growth and malignancy still has to be defined. Study Design: Based on the pertinent literature of the past decade, a Markov model was developed to investigate this issue. In the wait-and-see strategy arm, surgery was performed if the tumor attained a size ≥2 cm or surpassed 20% of the initial size. In a Monte Carlo probabilistic analysis, 100 hypothetical patients undergoing a wait-and-see strategy were compared to 100 patients directly undergoing surgery, with the aim of investigating the efficacy and cost-effectiveness of the two strategies. Results: During the postdiagnostic lifetime, 63 NF-PETs in the wait-and-see group showed significant growth and underwent surgery: 38 were stage I, 10 were stage II, 15 were stage III and none were stage IV. In the base-case scenario, the mean life expectancy and quality-adjusted life expectancy were found to be superior after immediate surgery [26.1 years and 11.8 quality-adjusted life years (QALYs)] than with the wait-and-see strategy (22.1 years and 8.3 QALYs) as the consequence of ageing during the wait-and-see follow-up which increased mortality due to surgery, when surgery was needed. The model was sensitive to starting age and length of follow-up; in particular, for patients >65 years of age, the two strategies provided similar results but the wait-and-see strategy was more cost-effective. Conclusions: The wait-and-see strategy for NF-PETs <2 cm represents a reasonable approach in patients over 65 years of age; otherwise, immediate surgery is preferable.

Abstract LB-249: Reduced expression of the long non-coding RNA MEG3 in sporadic and MEN1-associated tumors.

Abstract Rapidly growing evidence shows the emerging tumor suppressor role of large non-coding RNAs (lncRNAs) in cancer pathogenesis. Maternally expressed gene 3 (MEG3) is a lncRNA that belongs to the imprinted DLK1-MEG3 locus located on human chromosome 14q32.3. Recent studies have shown reduced MEG3 expression and promoter hyper-methylation in common pituitary adenomas, classifying MEG3 as an epigenetically-regulated tumor suppressor gene. Pituitary tumor is one of the tumor types observed in the multiple endocrine neoplasia type 1 (MEN1) syndrome. MEN1 is caused by heterozygous germline mutations (1st hit) in the MEN1 tumor suppressor gene encoding menin. Subsequent tissue-specific inactivation of the normal copy of the MEN1 gene (2nd hit) leads to tumors in the parathyroids, anterior pituitary, and endocrine pancreas. Somatic MEN1 mutations are also observed in sporadic parathyroid and pancreatic endocrine tumors. We have recently demonstrated by ChIP-seq and gene expression analysis of mouse embryonic stem cells that, loss of menin results in significant loss of H3K4me3 at the Meg3 locus, and reduced expression of Meg3. These observations suggest menin-regulated epigenetic modification and expression of MEG3 as a probable mechanism for tumorigenesis. Characterization of the expression levels of MEG3 in the different tumor types associated with the MEN1 syndrome can provide valuable insights into the role of MEG3 in the pathogenesis of these tumors as well as sporadic tumors. In the current study, we used quantitative real-time PCR to evaluate the expression of MEG3 in sporadic parathyroid tumors (4 carcinoma, 8 hyperplasia, and 8 adenoma), pituitary tumors (3 sporadic ACTH-secreting, and 4 MEN1-associated: 1 ACTH secreting, 2 PRL-secreting, 1 non-functional), and sporadic pancreatic islet tumors (30 insulinomas). For pituitary tumor samples, the total RNAs were reverse transcribed to cDNA and used as templates for the RT-PCR. However, for parathyroid tumor RT-PCR templates, the total RNAs were subjected to one round of amplification prior to the cDNA synthesis. For insulinoma RT-PCR templates, we performed laser capture microdissection using PixCell IIe system on insulinoma tissue sections to obtain tumor and normal islets, isolated total RNA and performed cDNA synthesis. Our RT-PCR results showed decreased MEG3 expression in 13 out of 20 parathyroid samples (3 cancer, 6 hyperplasia, 4 adenoma) (p = 0.001-0.05). In pituitary tumors, PRL-secreting tumors from MEN1 patients showed less MEG3 compared to all 4 ACTH-secreting tumors. Analysis of sporadic insulinomas is in progress. Our results strongly indicate that MEG3 is silenced in sporadic or MEN1-associated endocrine tumor types supporting the tumor suppressor role of MEG3 in endocrine cells, and warrant further study to explore the possibility of restoring MEG3 expression as a potential therapeutic option or marker for the management of endocrine tumors. Citation Format: Sita D. Modali, Shruti S. Desai, Vaishali I. Parekh, Russel R. Lonser, Electron Kebebew, Michael Emmert-Buck, Sunita K. Agarwal. Reduced expression of the long non-coding RNA MEG3 in sporadic and MEN1-associated tumors. [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 LB-249. doi:10.1158/1538-7445.AM2013-LB-249

The embryonic transcription factor Hlxb9 is a menin interacting partner that controls pancreatic β-cell proliferation and the expression of insulin regulators

The multiple endocrine neoplasia type 1 (MEN1) syndrome is caused by germline mutations in the MEN1 gene encoding menin, with tissue-specific tumors of the parathyroids, anterior pituitary, and enteropancreatic endocrine tissues. Also, 30-40% of sporadic pancreatic endocrine tumors show somatic MEN1 gene inactivation. Although menin is expressed in all cell types of the pancreas, mouse models with loss of menin in either pancreatic α-cells, or β-cells, or total pancreas develop β-cell-specific endocrine tumors (insulinomas). Loss of widely expressed tumor suppressor genes may produce tissue-specific tumors by reactivating one or more embryonic-specific differentiation factors. Therefore, we determined the effect of menin overexpression or knockdown on the expression of β-cell differentiation factors in a mouse β-cell line (MIN6). We show that the β-cell differentiation factor Hlxb9 is posttranscriptionally upregulated upon menin knockdown, and it interacts with menin. Hlxb9 reduces cell proliferation and causes apoptosis in the presence of menin, and it regulates genes that modulate insulin level. Thus, upon menin loss or from other causes, dysregulation of Hlxb9 predicts a possible combined mechanism for β-cell proliferation and insulin production in insulinomas. These observations help to understand how a ubiquitously expressed protein such as menin might control tissue-specific tumorigenesis. Also, our findings identify Hlxb9 as an important factor for β-cell proliferation and insulin regulation.

Molecular pathology of pancreatic neuroendocrine tumors.

Pancreatic endocrine tumors (PETs) are rare neoplasms which account for 1% to 2% of all pancreatic malignancies. The diagnostic, grading and prognostic criteria for PETs have been controversial in surgical pathology and clinical medicine. The newly updated 2010 WHO classification introduced in clinical practice will give more insight into genetic and molecular changes related to PET subtypes. These neoplasms can be graded into 1 of 3 tiers, based on histologic characteristics in likeness to epithelial neuroendocrine tumors in other anatomic sites. Most PETs are sporadic, however, some of them, may occur as part of familial tumors (inherited syndromes) such as multiple endocrine neoplasia type 1 (MEN1 syndrome), von Hippel-Lindau disease (VHL), neurofibromatosis type 1 (NF-1), and tuberous sclerosis (TSC). In sporadic endocrine pancreatic tumors, losses of chromosome 1 and 11q as well as gain on 9q appear to be early events in the development of pancreatic tumors. Multiple genetic defects may accumulate with time and result in pancreatic neuroendocrine tumor progression and malignancy. Although PETs may be similar or identical in histologic appearance to neuroendocrine tumors of the gastrointestinal tract, differences in their underlying biology and likely differences in response to therapeutic agents suggest that they should be treated and investigated as a distinct entity. The correlation of PI3K/Akt/mTOR pathway in the pathogenesis of PETs has been reported, and clinical trials data of mTOR inhibitors is promising.

Genome-Wide Characterization of Menin-Dependent H3K4me3 Reveals a Specific Role for Menin in the Regulation of Genes Implicated in MEN1-Like Tumors

Inactivating mutations in the MEN1 gene predisposing to the multiple endocrine neoplasia type 1 (MEN1) syndrome can also cause sporadic pancreatic endocrine tumors. MEN1 encodes menin, a subunit of MLL1/MLL2-containing histone methyltransferase complexes that trimethylate histone H3 at lysine 4 (H3K4me3). The importance of menin-dependent H3K4me3 in normal and transformed pancreatic endocrine cells is unclear. To study the role of menin-dependent H3K4me3, we performed in vitro differentiation of wild-type as well as menin-null mouse embryonic stem cells (mESCs) into pancreatic islet-like endocrine cells (PILECs). Gene expression analysis and genome-wide H3K4me3 ChIP-Seq profiling in wild-type and menin-null mESCs and PILECs revealed menin-dependent H3K4me3 at the imprinted Dlk1-Meg3 locus in mESCs, and all four Hox loci in differentiated PILECs. Specific and significant loss of H3K4me3 and gene expression was observed for genes within the imprinted Dlk1-Meg3 locus in menin-null mESCs and the Hox loci in menin-null PILECs. Given that the reduced expression of genes within the DLK1-MEG3 locus and the HOX loci is associated with MEN1-like sporadic tumors, our data suggests a possible role for menin-dependent H3K4me3 at these genes in the initiation and progression of sporadic pancreatic endocrine tumors. Furthermore, our investigation also demonstrates that menin-null mESCs can be differentiated in vitro into islet-like endocrine cells, underscoring the utility of menin-null mESC-derived specialized cell types for genome-wide high-throughput studies.

Abstract LB-140: Menin-mediated regulation of pancreatic β-cell differentiation factors

Abstract Pancreatic endocrine tumors occur sporadically or in familial multiple tumor syndromes such as MEN1 (Multiple Endocrine Neoplasia type 1). Biallelic loss/inactivation of the MEN1 tumor suppressor gene is only found in 20–30% of sporadic pancreatic endocrine tumors. Therefore, identification of other molecular and genetic causes of pancreatic endocrine tumorigenesis is an area of intense investigation. Because MEN1 is the main gene reported so far that affects pancreatic endocrine tumors, analyzing downstream effects of menin (MEN1 gene encoded protein) could uncover other candidate genes and pathways responsible for pancreatic endocrine tumorigenesis. During the process of endocrine pancreas development, a cascade of transcription factors under tight sequential- and temporal-regulated expression ensures normal organogenesis. Alteration of such developmental and differentiation factors could potentially lead to tumorigenesis. To study cellular transformation related to menin loss in the pancreatic β-cell, we used the mouse pancreatic β-cell line MIN6 as a model system. RNA and protein were isolated from MIN6 cells after menin knockdown or after menin over-expression as well as from their respective controls. Twelve transcription factors associated with β-cell differentiation were analyzed using QRT-PCR and western blot: Hlxb9, Hnf3β, Isl-1, MafA, MafB, NeuroD1, Ngn3, Nkx2.2, Nkx6.1, Pax4, Pax6, and Pdx1. Three different sources of menin siRNAs and four different transfection reagents were tested in time course knockdown experiments. Significant menin knockdown in MIN6 cells was observed with 74.3% ± 15.03% (n=6) knockdown efficiency at 72 hours post-transfection. For transient menin over-expression in MIN6 cells, the transfection efficiency was close to 60% (based on GFP plasmid transfection). Endogenous expression of all factors, except Ngn3, was detectable in MIN6 cells. None of the eleven transcription factors showed significantly altered RNA expression upon menin knockdown or upon menin over-expression. Western blot analyses showed 4–5 factors that were up-regulated upon menin knockdown, and down-regulated upon menin over-expression. Evolutionarily conserved promoter regions of Hlxb9, Isl-1, Nkx6.1, or Pax4 were not regulated upon menin knockdown or upon menin over-expression. These data indicate that menin could regulate some β-cell differentiation factors in a post-transcriptional manner. Mechanism of menin-mediated post-transcriptional regulation and downstream consequences on β-cell transformation and tumorigenesis is under investigation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-140. doi:10.1158/1538-7445.AM2011-LB-140

Impact of CT-based diagnostic imaging on management and outcome of nonfunctioning pancreatic tumors

Sporadic malignant non-functioning pancreatic endocrine tumors (NF-PETs) are an important subset of pancreatic neoplasms. The aim of this study was to assess the impact of improved imaging on these features in a tertiary referral centre within a 20-year follow-up. From 1988 to 2009, 51 patients were treated for sporadic malignant NF-PETs. Forty-one patients who underwent tumor resection were retrospectively attributed according to the date of the initial diagnosis, group 1: 1988-1999 vs. group 2: 2000-2009. Cross-sectional imaging led to positive prediction of NF-PETs in all patients. Curative resection was achieved in 76%. Synchronous metastases were present in 56% with a positive prediction of 43%. In group 1, the mean reported CT-determined tumor size was 56 vs. 54mm in group 2 (p = 0.89). Synchronous metastases were present in 61% in group 1 vs. 57% (p = 0.99) in group 2. Metachronous metastases were recorded in 39% in group 1 vs. 43% (p = 0.84) in group 2. The mean interval from initial resection to diagnosis of metastatic disease was significantly shorter (p = 0.01) in patients from group 1 (14 vs. 61months). Cumulative 5- and 10-year survival rates were 77% and 72% in group 1 vs. a 5-year survival rate of 66% in group 2. So far, improved CT-based imaging has no impact on earlier detection of initial synchronous metastases in sporadic malignant NF-PETs, while metachronous metastases are detected earlier.

Pancreatic Cystic Endocrine Tumors: A Different Morphological Entity Associated with a Less Aggressive Behavior

Background: Cystic pancreatic endocrine tumors (CPETs) are rare lesions and their biological features have been scarcely investigated. Aim: To compare clinical and pathological features of resected non-functioning sporadic CPETs (NF-CPETs) with solid pancreatic endocrine tumors (SPETs) in a single-institution experience. Methods: All patients with a pathologically confirmed diagnosis of sporadic non-functioning pancreatic endocrine tumors who underwent curative resection between 1990 and 2008 were included. A comparison of demographic, clinical and pathological characteristics between CPETs and SPETs was made. Univariate and multivariable analyses were performed to identify preoperative predictors of carcinoma (non-functioning pancreatic endocrine carcinoma). Results: Twenty-one (11.5%) patients with a histological diagnosis of NF-CPET were identified. The median age was 60 years (IQR 46.5–73.5 years) and a diagnosis of carcinoma (non-functioning pancreatic endocrine carcinoma) was made in 3 (14.3%) cases. In the comparison with NF-SPETs, no differences were found in terms of gender (p = 0.75), age (p = 0.81), presenting symptoms (p = 0.43), localization of the tumors (p = 0.46) and type of resection (p = 0.31). The incidence of non-functioning pancreatic endocrine carcinoma was significantly lower in the NF-CPET versus the NF-SPET group (14.3 vs. 40.4%, p = 0.04). By univariate analysis, preoperative predictors of non-functioning pancreatic endocrine carcinoma included the presence of symptoms (OR 3.96, 95% CI 2.06–7.63) and an increase in the absolute value of radiological diameter (OR 1.05, 95% CI 1.03–1.07). A cystic morphology of the lesion turned out to be a negative predictor of carcinoma (OR 0.25, 95% CI 0.70–0.87). These results were confirmed by multivariable analysis. Conclusions: NF-CPETs have a measurable propensity to be benign. In those patients affected by small and asymptomatic NF-CPET a more conservative surgical approach or a follow-up policy could be considered.

MEN1 in pancreatic endocrine tumors: analysis of gene and protein status in 169 sporadic neoplasms reveals alterations in the vast majority of cases

Pancreatic endocrine tumors (PETs) may be part of hereditary multiple endocrine neoplasia type 1 (MEN1) syndrome. While MEN1 gene mutation is the only ascertained genetic anomaly described in PETs, no data exist on the cellular localization of MEN1-encoded protein, menin, in normal pancreas and PETs. A total of 169 PETs were used to assess the i) MEN1 gene mutational status in 100 clinically sporadic PETs by direct DNA sequencing, ii) immunohistochemical expression of menin in normal pancreas and 140 PETs, including 71 cases screened for gene mutations, and iii) correlation of these findings with clinical-pathological parameters. Twenty-seven PETs showed mutations that were somatic in 25 patients and revealed to be germline in 2 patients. Menin immunostaining showed strong nuclear and very faint cytoplasmic signal in normal islet cells, whereas it displayed abnormal location and expression levels in 80% of tumors. PETs harboring MEN1 truncating mutations lacked nuclear protein, and most PETs with MEN1 missense mutations showed a strong cytoplasmic positivity for menin. Menin was also misplaced in a significant number of cases lacking MEN1 mutations. In conclusion, the vast majority of PETs showed qualitative and/or quantitative alterations in menin localization. In 30% of cases, this was associated with MEN1 mutations affecting sequences involved in nuclear localization or protein-protein interaction. In cases lacking MEN1 mutations, the alteration of one of the menin interactors may have prevented its proper localization, as suggested by recent data showing that menin protein shuttles between the nucleus and cytoplasm and also affects the subcellular localization of its interactors.

Clinicopathological Features of Pancreatic Endocrine Tumors: A Prospective Multicenter Study in Italy of 297 Sporadic Cases

Information on pancreatic endocrine tumors (PETs) comes mostly from small, retrospective, uncontrolled studies conducted on highly selected patients. The aim of the study was to describe the clinical and pathological features of PETs in a prospective, multicenter study. Newly diagnosed, histologically proven, sporadic PETs observed from June 2004 to March 2007 in 24 Italian centers were included in a specific data set. Two hundred ninety-seven patients (mean age 58.6+/-14.7 years, females 51.2%, males 48.8%) were analyzed. In 73 cases (24.6%), the tumor was functioning (F) (53 insulinomas, 15 gastrinomas, 5 other syndromes) and in 232 (75.4%) it was non-functioning (NF); in 115 cases (38.7%), the diagnosis was incidental. The median tumor size was 20 mm (range 2-150). NF-PETs were significantly more represented among carcinomas (P<0.001). Nodal and liver metastases were detected in 84 (28.3%) and 85 (28.6%) cases, respectively. The presence of liver metastases was significantly higher in the NF-PETs than in the F-PETs (32.1% vs. 17.8%; P<0.05), and in the symptomatic than in the asymptomatic patients (34.6% vs. 19.1%; P<0.005). At the time of recruitment, the majority of patients (251, 84.5%) had undergone surgery, with complete resection in 209 cases (83.3%). This study points out the high number of new cases of PETs observed in Italy, with a high prevalence of NF and incidentally discovered forms. The size of the tumor was smaller and the rate of metastasis was lower than usually reported, suggesting a trend toward an earlier diagnosis.

VHL inactivation is an important pathway for the development of malignant sporadic pancreatic endocrine tumors

A small subset of familial pancreatic endocrine tumors (PET) arises in patients with von Hippel-Lindau syndrome and these tumors may have an adverse outcome compared to other familial PET. Sporadic PET rarely harbors somatic VHL mutations, but the chromosomal location of the VHL gene is frequently deleted in sporadic PET. A subset of sporadic PET shows active hypoxia signals on mRNA and protein level. To identify the frequency of functionally relevant VHL inactivation in sporadic PET and to examine a possible prognostic significance we correlated epigenetic and genetic VHL alterations with hypoxia signals. VHL mutations were absent in all 37 PETs examined. In 2 out of 35 informative PET (6%) methylation of the VHL promoter region was detected and VHL deletion by fluorescence in situ hybridization was found in 14 out of 79 PET (18%). Hypoxia inducible factor 1alpha (HIF1-alpha), carbonic anhydrase 9 (CA-9), and glucose transporter 1 (GLUT-1) protein was expressed in 19, 27, and 30% of the 152 PETs examined. Protein expression of the HIF1-alpha downstream target CA-9 correlated significantly with the expression of CA-9 RNA (P<0.001), VHL RNA (P<0.05), and VHL deletion (P<0.001) as well as with HIF1-alpha (P<0.005) and GLUT-1 immunohistochemistry (P<0.001). These PET with VHL alterations and signs of hypoxia signalling were characterized by a significantly shortened disease-free survival. We conclude that VHL gene impairment by promoter methylation and VHL deletion in nearly 25% of PET leads to the activation of the HIF-pathway. Our data suggest that VHL inactivation and consecutive hypoxia signals may be a mechanism for the development of sporadic PET with an adverse outcome.

Risk Factors for Sporadic Pancreatic Endocrine Tumors

Pancreatic endocrine tumors (PETs) are heterogeneous tumors with increasing prevalence. Little is known about the molecular pathogenesis and risk factors for the occurrence of sporadic PETs. The aim of this study was to identify the risk factors associated with the occurrence of sporadic PETs. A case-control study comprising 162 sporadic PETs and 648 controls was undertaken. Subjects were interviewed using a specific questionnaire on demographics and potential risk factors, including smoking, alcohol, height, weight, medical history, and family history of cancer. A multiple hierarchical logistic regression analysis was performed with a stepwise variable- selection procedure. A first-degree family history of any cancer was a significant risk factor (odds ratio (OR) 2.2; 95% confidence interval (CI): 1.5-3.2). Among the different cancer sites, first-degree family history of pancreatic adenocarcinoma was more frequent in PETs than in controls (4.3 vs. 1.2%; P=0.01). A high alcohol intake (OR 4.8; 95% CI: 2.4-9.5), history of chronic pancreatitis (CP) (OR 8.6; 95% CI: 1.4-51), and recent-onset diabetes (OR 40.1; 95% CI: 4.8-328.9) were all independent risk factors. The history of diabetes was also associated with metastatic disease at the time of diagnosis. This case-control study identified family history of any cancer (and to a less extent of pancreatic adenocarcinoma), CP, high alcohol intake, and recent-onset diabetes as risk factors for PET, thus suggesting a possible partial overlap with risk factors for exocrine pancreatic carcinogenesis.

The outcomes after surgical resection in pancreatic endocrine tumors: An institutional experience

Aim Sporadic pancreatic endocrine tumors (PET) can be managed surgically with excellent outcomes. The aim of this study was to analyze surgical outcomes and factors influencing survival. Methods Between 1995 and 2007, 96 patients with sporadic PET who underwent surgery at our institution were retrospectively reviewed for clinicopathologic variables and outcomes according to the World Health Organization (WHO) classifications. Results Thirty-nine patients had well-differentiated tumors (WDT) with benign behavior, 23 had uncertain behavior, 27 had low-grade carcinoma, and 7 were diagnosed with high-grade carcinoma. R0 resection was performed in 84 patients. No recurrence was observed in WDT regardless of its behavior or curability but 16 of 34 patients with carcinoma had recurrence. Five-year overall survival (OS) for R0-resected patients with carcinoma was 57%, and OS at 3 years for R1/R2-resected patients was 23% ( P = 0.012). The WHO classification and R0 resection were independent prognostic factors in multivariate analysis. Conclusions This single institutional experience demonstrated that surgical resection is curative for WDT and recurrences are frequent in spite of curative resection for malignant PET. The WHO classification and R0 resection remained independent prognostic factor.

Genetics and molecular pathology of neuroendocrine gastrointestinal and pancreatic tumors (gastroenteropancreatic neuroendocrine tumors)

Gastrointestinal and pancreatic neuroendocrine tumors (GEP-NETs) originate from cells of the diffuse endocrine system. Most GEP-NETs are sporadic, however, some of them, especially pancreatic endocrine tumors, may occur as part of familial syndromes. The genetic and molecular pathology of neuroendocrine tumor development is incomplete and remains largely unknown. However, the WHO classification introduced in clinical practice will give more insight into genetic and molecular changes related to tumor subtypes. In sporadic endocrine pancreatic tumors, losses of chromosome 1 and 11q as well as gain on 9q appear to be early invents in development of pancreatic tumors because they are already present in small tumors. Multiple genetic defects may accumulate with time and result in pancreatic neuroendocrine tumor progression and malignancy. Gastrointestinal endocrine tumors (carcinoids) show predominantly genetic alterations concentrated on chromosome 18. There are losses of the entire chromosome as well as smaller deletions. The most frequently reported mutated gene in gastrointestinal neuroendocrine tumors is b-catenin. Overexpression of cyclin D1 and cMyc has also been reported. Recently, a set of genes NAP1L1, MAGE-2D and MTA1 has been correlated with malignant behavior of small intestinal carcinoids. Molecular profiling of GEP-NETs demonstrates that pancreatic endocrine tumors and gastrointestinal neuroendocrine tumors (carcinoids) display different genetic changes and should, therefore, be considered to be different tumor entities; thereby, also differently managed clinically. Although the number of genetic changes is higher in malignant tumors, we are still far away from defining a malignant profile in GEP-NETs.

Inherited pancreatic endocrine tumor syndromes: Advances in molecular pathogenesis, diagnosis, management, and controversies

Pancreatic endocrine tumors (PETs) can occur as part of 4 inherited disorders, including Multiple Endocrine Neoplasia type 1 (MEN1), von Hippel-Lindau disease (VHL), neurofibromatosis 1 (NF-1) (von Recklinghausen disease), and the tuberous sclerosis complex (TSC). The relative frequency with which patients who have these disorders develop PETs is MEN1>VHL>NF-1>TSC. Over the last few years, there have been major advances in the understanding of the genetics and molecular pathogenesis of these disorders as well in the localization and the medical and surgical treatment of PETs in such patients. The study of PETs in these disorders not only has provided insights into the possible pathogenesis of sporadic PETs but also has presented several unique management and treatment issues, some of which are applicable to patients with sporadic PETs. Therefore, the study of PETs in these uncommon disorders has provided valuable insights that, in many cases, are applicable to the general group of patients with sporadic PETs. In this article, these areas are reviewed briefly along with the current state of knowledge of the PETs in these disorders, and the controversies that exist in their management are summarized briefly and discussed.

Multiple primary malignancies in patients with sporadic pancreatic endocrine tumors

To investigate the appearance of multiple primary malignancies in patients with sporadic neuroendocrine pancreatic tumors (NEPTs). One hundred forty-five patients with NEPTs were treated at the Department of Surgery, Philipps-University Marburg. Multiple primary malignancies included tumors that were not considered to be a metastasis, invasion, or recurrence of NEPTs. Data on sex, age at diagnosis of cancer, follow-up time after diagnosis, and death rate were collected. Of 115 patients with sporadic NEPTs, 15 (13.0%) patients were identified with at least one malignant tumor, other than a NEPT. The median age at diagnosis of the associated tumor(s) was 57 years (range, 10-72 years). Two of the 15 patients had insulinomas, 5 had gastrinomas and 8 had non-functioning NEPTs, respectively. The risk of developing multiple cancers was the highest for patients with gastrinoma (21.7%), followed by patients with non-functioning NFPTs (20.5%). In patients with NEPTs multiple primary malignancies are found more frequently than in the general population. The etiology of the increased risk of other primaries is not clearly defined, but it may be the result of accumulated growth stimulation by the secreted hormones or a genetic alteration that leads to tumorogenesis in these patients.

Mutational Analysis of p27 (CDKN1 B) and p18 (CDKN2C) in Sporadic Pancreatic Endocrine Tumors Argues against Tumor-Suppressor Function

Pancreatic endocrine tumors (PETs) arise sporadically or are associated with multiple endocrine neoplasia type 1 (MENi) syndrome or von Hippel-Lindau syndrome. About 90% of patients with familial MENi display detectable MEN1 gene (menin) mutations. The cyclin-dependent kinase inhibitor p27 (CDKN1 B) is a downstream target of menin and has been recently shown to be responsible for the multiple endocrine neoplasia-like syndrome in rats, where affected animals develop multiple tumors and hyperplasia in endocrine tissues, including the pancreatic islets of Langerhans. A germline nonsense truncation mutation of p27 has been recently described in a suspected MENi family without MENi mutation, raising the possibility that p27 mutation could be responsible for MENi phenotype. Somatic MENi mutations occur at low frequency in sporadic PETs; here, we subjected p27 to mutational analysis in 27 sporadic PETs. As an additional menin target, analysis of the p18(CDKN2C) gene was included. In the p27 gene, one common polymorphism (V1 09G) and one novel polymorphism (g/a) in the noncoding part of exon 2 were identified. Three known polymorphisms were found in the p18 gene. These data suggest that p27 and p18 are unlikely to present classic tumor-suppressor genes in sporadic PETs.

Clinicopathologic and immunohistochemical correlation in sporadic pancreatic endocrine tumors: possible roles of utrophin and cyclin D1 in malignant progression

Pancreatic endocrine tumors (PETs), both functioning and nonfunctioning, are usually well differentiated and progress slowly. The 2004 World Health Organization (WHO) criteria classify PETs according to clinicopathologic features and Ki-67 proliferative index. A tumor associated with poorer prognostic features may be considered "uncertain" in behavior, but the malignant classifications are reserved for tumors showing clear signs of aggressive behavior. It remains difficult to predict malignant progression in any individual PET. The cytoskeletal protein utrophin is encoded on chromosome 6q, a region frequently lost in malignant PETs. Cyclin D1 is a highly regulated mediator of the cell cycle and is frequently overexpressed in sporadic PETs. Sporadic PETs resected or biopsied from 40 patients were identified and classified using WHO criteria (19 benign/uncertain, 21 malignant). Distinctive patterns of biologic activity in unequivocally malignant PETs were demonstrated by immunohistochemistry for utrophin and cyclin D1. Utrophin localized to cell membranes (76% in malignant versus 21% in benign/uncertain PETs, P < .0006) and cyclin D1 staining showed nuclear positivity (67% in malignant versus 17% in benign/uncertain PETs, P < .003). Membranous utrophin localization was associated with significantly reduced patient survival (P = .045). Both membranous utrophin and nuclear cyclin D1 staining were also associated with higher Ki-67 proliferative indices. In our series, neither utrophin nor cyclin D1 was predictive of malignant progression in uncertain (WHO 1.2) PETs. Further studies are warranted to elucidate the role of utrophin and cyclin D1 in the malignant progression of PETs.

Mutational analyses of WNT7A and HDAC11 as candidate tumour suppressor genes in sporadic malignant pancreatic endocrine tumours

We and others have reported loss of heterozygosity (LOH) on chromosome 3p25 in sporadic malignant pancreatic endocrine tumours (PETs). A common region of deletion on chromosome 3p25 contains numerous genes, including VHL and PPARgamma, that have been excluded previously as candidate tumour suppressor genes by DNA sequencing analysis. We have analysed whether WNT7A or HDAC11 was biallelically inactivated in a group of well-characterized PETs. Ten PETs from eight patients were selected from a previous study, where LOH on chromosome 3p25 was found in 11 out of 22 sporadic PETs. These tumours were examined for inactivating mutations of WNT7A and HDAC11 by direct sequencing of all exons and intron-exon boundaries. Inactivation of WNT7A expression by aberrant CpG island methylation and WNT7A protein expression were evaluated by methylation-specific polymerase chain reaction (PCR) and immunohistochemistry, respectively. HDAC11 protein expression was also examined. No point mutations, deletion or insertions were detected in either WNT7A or HDAC11 in any of the PETs. Two polymorphisms were identified in the third exon of the WNT7A gene. CpG methylation of the WNT7A gene was not detected and the WNT7A and HDAC11 proteins were normally expressed. The absence of tumour-specific somatic events in WNT7A and HDAC11 suggests that these genes are unlikely to have a classical tumour suppressor gene role in sporadic malignant PETs. The putative 3p25 tumour suppressor remains to be identified.

Pancreatic endocrine tumors: an update.

The morphology of pancreatic endocrine tumors (PETs) is similar to that of endocrine tumors elsewhere in the body. PETs are usually encountered in adults. They may be clinically functional and associated with various syndromes related to hormone excess. However, it must be remembered that absence of obvious clinical symptoms may not necessarily reflect true lack of clinical function, and subtle clinical manifestations may be missed. Current thinking indicates that PETs arise from totipotential stem cells as well as preexisting endocrine cells. PETs may be hereditary or sporadic. The hereditary forms are associated with multiple endocrine neoplasia type 1 (MEN-1), von Hippel-Lindau syndrome, neurofibromatosis, and tuberous sclerosis. In sporadic PETs, the most consistent and recurring chromosomal abnormality is allelic loss of chromosome 11q, which includes the MEN-1 locus. Loss of a sex chromosome has been shown to be associated with metastasis, local invasion, and poor survival.