Small cell and large cell neuroendocrine carcinomas of the pancreas are genetically similar and distinct from well-differentiated pancreatic neuroendocrine tumors. Am J Surg Pathol. 2012;36:173-184. [PMID: 22251937 DOI: 10.1097/pas.0b013e3182417d36]

Current understanding of the molecular biology of pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors (PanNETs) are complicated and often deadly neoplasms. A recent increased understanding of their molecular biology has contributed to expanded treatment options. DNA sequencing of samples derived from patients with PanNETs and rare genetic syndromes such as multiple endocrine neoplasia type 1 (MEN1) and Von Hippel-Lindau (VHL) syndrome reveals the involvement of MEN1, DAXX/ATRX, and the mammalian target of rapamycin (mTOR) pathways in PanNET tumorigenesis. Gene knock-out/knock-in studies indicate that inactivation of factors including MEN1 and abnormal PI3K/mTOR signaling uncouples endocrine cell cycle progression from the control of environmental cues such as glucose, leading to islet cell overgrowth. In addition, accumulating evidence suggests that further impairment of endothelial-endocrine cell interactions contributes to tumor invasion and metastasis. Recent phase III clinical trials have shown that therapeutic interventions, such as sunitinib and everolimus, targeting those signal transduction pathways improve disease-free survival rates. Yet, cure in the setting of advanced disease remains elusive. Further advances in our understanding of the molecular mechanisms of PanNETs and improved preclinical models will assist in developing personalized therapy utilizing novel drugs to provide prolonged control or even cure the disease.

Immunohistochemical analysis of chromatin remodeler DAXX in high grade urothelial carcinoma

Background/Aims

The chromatin remodeler DAXX, a predominantly nuclear protein, regulates the status of chromatin organization. The aim of this exploratory immunohistochemical study was to evaluate DAXX protein expression in high grade invasive urothelial carcinoma (UC) of the bladder as a biological regulator of aggressiveness.

Methods

Quantitative analysis was made on DAXX immunostained nuclei in tissue sections from 5 cases of bladder normal urothelium (NU) and 5 cases of bladder pT1 UC. Carcinoma in situ (CIS) and high grade papillary carcinoma (HGPCa) were identified in 2 out of 5 UC cases.

Results

The nuclei in UC show an open configuration of the chromatin composed of granules varying in size and distribution and a mean nuclear area 1.7 times greater than that in NU (UC: mean and SD 24.4 ± 11.4 square microns; NU: 14.8 6.5 square microns. The differences are statistically significant). 70% of the NU nuclei are immunostained, whereas 90% of UC nuclei are positive. The mean gray level value in UC, related to the intensity of nuclear immunostaining, is lower than in NU by a factor of 0.94 (UC: mean and SD 100 ± 15; NU: 106 ± 15. The differences are statistically significant). In particular, the value in the nuclei adjacent to the stroma in UC is slightly lower than in the intermediate cell layers by factor of 0.98, whereas in NU it is slightly greater by a factor 1.02 and 1.04 compared to the intermediate and superficial cell layers. The values in CIS and HGPCa are similar to those in UC.

Conclusions

The quantitative immunohistochemical analysis shows an altered protein expression of chromatin remodeler DAXX in UC and in its preinvasive phases, when compared to NU. DAXX evaluation, if associated with markers related to global DNA methylation and histone acetylation, could be used in clinical practice as a marker of aggressiveness.

Virtual slides

The virtual slides for this article can be found here:

http://www.diagnosticpathology.diagnomx.eu/vs/1398457297102379

ISL1 expression is not restricted to pancreatic well-differentiated neuroendocrine neoplasms, but is also commonly found in well and poorly differentiated neuroendocrine neoplasms of extrapancreatic origin

The human insulin gene enhancer-binding protein islet-1 (ISL1) is a transcription factor involved in the differentiation of the neuroendocrine pancreatic cells. Recent studies identified ISL1 as a marker for pancreatic well-differentiated neuroendocrine neoplasms. However, little is known about ISL1 expression in pancreatic poorly differentiated and in extrapancreatic well and poorly differentiated neuroendocrine neoplasms. We studied the immunohistochemical expression of ISL1 in 124 neuroendocrine neoplasms. Among pancreatic neuroendocrine neoplasms, 12/13 with poor differentiation were negative, whereas 5/7 with good differentiation but a Ki67 >20% were positive. In extrapancreatic neuroendocrine neoplasms, strong positivity was found in Merkel cell carcinomas (25/25), pulmonary small cell neuroendocrine carcinomas (21/23), medullary thyroid carcinomas (9/9), paragangliomas/pheochromocytomas (6/6), adrenal neuroblastomas (8/8) and head and neck neuroendocrine carcinomas (4/5), whereas no or only weak staining was recorded in pulmonary carcinoids (3/15), olfactory neuroblastomas (1/4) and basaloid head and neck squamous cell carcinomas (0/15). ISL1 stained the neuroendocrine carcinoma component of 5/8 composite carcinomas and also normal neuroendocrine cells in the thyroid, adrenal medulla, stomach and colorectum. Poorly differentiated neuroendocrine neoplasms, regardless of their ISL1 expression, were usually TP53 positive. Our results show the almost ubiquitous expression of ISL1 in extrapancreatic poorly differentiated neuroendocrine neoplasms and neuroblastic malignancies and its common loss in pancreatic poorly differentiated neuroendocrine neoplasms. These findings modify the role of ISL1 as a marker for pancreatic neuroendocrine neoplasms and suggest that ISL1 has a broader involvement in differentiation and growth of neuroendocrine neoplasms than has so far been assumed.

Guidelines for biomarker testing in gastroenteropancreatic neuroendocrine neoplasms: a national consensus of the Spanish Society of Pathology and the Spanish Society of Medical Oncology

The annual incidence of neuroendocrine tumours in the Caucasian population ranges from 2.5 to 5 new cases per 100,000 inhabitants. Gastroenteropancreatic neuroendocrine tumours is a family of neoplasms widely variable in terms of anatomical location, hormone composition, clinical syndromes they cause and in their biological behaviour. This high complexity and clinical heterogeneity, together with the known difficulty of predicting their behaviour from their pathological features, are reflected in the many classifications that have been developed over the years in this field. This article reviews the main tissue and clinical biomarkers and makes recommendations for their use in medical practice. This document represents a consensus reached jointly by the Spanish Society of Medical Oncology (SEOM) and the Spanish Society of Pathology (SEAP).

Molecular pathogenesis of neuroendocrine tumors: implications for current and future therapeutic approaches

The treatment landscape and biologic understanding of neuroendocrine tumors (NET) has shifted dramatically in recent years. Recent studies have shown that somatostatin analogues have the potential not only to control symptoms of hormone hypersecretion but also have the ability to slow tumor growth in patients with advanced carcinoid. The results of clinical trials have further shown that the VEGF pathway inhibitor sunitinib and the mTOR inhibitor everolimus have efficacy in patients with advanced pancreatic NETs. The efficacy of these targeted therapies in NET suggests that the molecular characterization of NETs may provide an avenue to predict both which patients may benefit most from the treatment and to overcome potential drug resistance. Recent genomic studies of NETs have further suggested that pathways regulating chromatin remodeling and epigenetic modification may play a key role in regulating NET growth. These observations offer the potential for new therapeutic and diagnostic advances for patients with NET.

Pathology reporting of neuroendocrine tumors: essential elements for accurate diagnosis, classification, and staging

Much recent debate has focused on the optimal classification of epithelial neuroendocrine tumors (NETs). Multiple different systems of terminology, grading, and staging have been proposed, and some systems combine elements of grade and stage into a single prognostic classification. Recently, national and international consensus groups have attempted to standardize the classification of NETs, especially for those arising in the gastrointestinal tract and pancreas. Furthermore, the recognition that common classification criteria (such as proliferative rate) span multiple different systems allows the basic data necessary to predict outcome and tailor therapy to be included in pathology reports, even though a single uniform system of terminology may remain elusive. Formal tumor-node-metastasis (TNM)-based staging systems also have been developed recently, and advances in the treatment of some NETs (pancreatic in particular) are pointing towards the need to assess therapeutic biomarkers in routine practice. This review will present the most widely used systems for classifying, grading, and staging NETs and will summarize the recommendations for the data to be included in standard pathology reports of these uncommon tumors.

Atrx deficiency induces telomere dysfunction, endocrine defects, and reduced life span

Human ATRX mutations are associated with cognitive deficits, developmental abnormalities, and cancer. We show that the Atrx-null embryonic mouse brain accumulates replicative damage at telomeres and pericentromeric heterochromatin, which is exacerbated by loss of p53 and linked to ATM activation. ATRX-deficient neuroprogenitors exhibited higher incidence of telomere fusions and increased sensitivity to replication stress-inducing drugs. Treatment of Atrx-null neuroprogenitors with the G-quadruplex (G4) ligand telomestatin increased DNA damage, indicating that ATRX likely aids in the replication of telomeric G4-DNA structures. Unexpectedly, mutant mice displayed reduced growth, shortened life span, lordokyphosis, cataracts, heart enlargement, and hypoglycemia, as well as reduction of mineral bone density, trabecular bone content, and subcutaneous fat. We show that a subset of these defects can be attributed to loss of ATRX in the embryonic anterior pituitary that resulted in low circulating levels of thyroxine and IGF-1. Our findings suggest that loss of ATRX increases DNA damage locally in the forebrain and anterior pituitary and causes tissue attrition and other systemic defects similar to those seen in aging.

Altered PTEN, ATRX, CHGA, CHGB, and TP53 expression are associated with aggressive VHL-associated pancreatic neuroendocrine tumors

Von Hippel-Lindau (VHL) syndrome is an inherited cancer syndrome in which 8-17 % of germline mutation carriers develop pancreatic neuroendocrine tumors (PNETs). There is limited data on prognostic markers for PNETs other than Ki-67, which is included in the World Health Organization classification system. Recently, specific genes and pathways have been identified by whole exome sequencing which may be involved in the tumorigenesis of PNETs and may be markers of disease aggressiveness. The objective of this study was to identify molecular markers of aggressive disease in VHL-associated PNETs. The protein expression of eight genes (PTEN, CHGA, CHGB, ATRX, DAXX, CC-3, VEGF, and TP53) was analyzed in PNETs by immunohistochemistry and compared to clinical data, VHL genotype, functional imaging results, and pathologic findings. Subcellular distribution of phosphatase and tensin (PTEN), chromogranin A (CHGA), and alpha thalassemia/mental retardation syndrome X-linked (ATRX) were significantly different by WHO classifications (p ≤ 0.05). There was decreased PTEN nuclear to cytoplasmic ratio (p < 0.01) and decreased CHGA nuclear expression (p = 0.03) in malignant samples as compared to benign. Lower cytoplasmic chromogranin B (CHGB) expression (p = 0.03) was associated with malignant tumors and metastasis. Higher nuclear expression of PTEN was associated with VHL mutations in exon 3 (p = 0.04). Higher PTEN and CHGB expression was associated with higher FDG-PET avidity (p < 0.05). Cytoplasmic expression of CC-3 was associated with higher serum chromogranin A levels (ρ = 0.72, p = 0.02). Lastly, greater cytoplasmic expression of p53 was associated with metastasis. Our findings suggest that altered PTEN, ATRX, CHGA, and CHGB expression are associated with aggressive PNET phenotype in VHL and may serve as useful adjunct prognostic markers to Ki-67 in PNETs.

Clinical significance of the genetic landscape of pancreatic cancer and implications for identification of potential long-term survivors

PURPOSE

Genetic alterations of KRAS, CDKN2A, TP53, and SMAD4 are the most frequent events in pancreatic cancer. We determined the extent to which these 4 alterations are coexistent in the same carcinoma, and their impact on patient outcome.

EXPERIMENTAL DESIGN

Pancreatic cancer patients who underwent an autopsy were studied (n = 79). Matched primary and metastasis tissues were evaluated for intragenic mutations in KRAS, CDKN2A, and TP53 and immunolabeled for CDKN2A, TP53, and SMAD4 protein products. The number of altered driver genes in each carcinoma was correlated to clinicopathologic features. Kaplan-Meier estimates were used to determine median disease free and overall survival, and a Cox proportional hazards model used to compare risk factors.

RESULTS

The number of genetically altered driver genes in a carcinoma was variable, with only 29 patients (37%) having an alteration in all 4 genes analyzed. The number of altered driver genes was significantly correlated with disease free survival (P = 0.008), overall survival (P = 0.041), and metastatic burden at autopsy (P = 0.002). On multivariate analysis, the number of driver gene alterations in a pancreatic carcinoma remained independently associated with overall survival (P = 0.046). Carcinomas with only 1 to 2 driver alterations were enriched for those patients with the longest survival (median 23 months, range 1 to 53).

CONCLUSIONS

Determinations of the status of the 4 major driver genes in pancreatic cancer, and specifically the extent to which they are coexistent in an individual patients cancer, provides distinct information regarding disease progression and survival that is independent of clinical stage and treatment status.

Emerging frontiers in pancreatic cancer research: elaboration of key genes, cells and the extracellular milieu

PURPOSE OF REVIEW

We review recent literature with a view to forge an integrative understanding of the molecular, cellular and extracellular milieu of pancreatic cancer, and discuss them in the context of development of novel, personalized therapeutic options.

RECENT FINDINGS

Pancreatic tumorigenesis, examined using genetically engineered mouse models, appears to be driven by local inflammation, in concert with the 'big four' mutations involving oncogenic KRAS, SMAD4, CDKN2A, and TP53, through induction of epithelial-to-mesenchymal transition (EMT) and cancer stem cells, and accompanied by metastasis. High-throughput sequencing of pancreatic ductal adenocarcinoma as well as neuroendocrine tumors and rarer subtypes of cancers of the pancreas has revealed several novel mutations in genes like PALB2, guanine nucleotide-binding protein, alpha stimulating, death-domain-associated protein, α thalassemia/mental retardation syndrome X linked, switch/sucrose nonfermentable pathway related, and in genes in the ubiquitin-dependent pathways such as USP9X. Therapeutic targeting of the tumor-stroma axis by cytokines and immune response modulators and the role of autophagy in pancreatic cancer are some other salient themes explored in the recent publications.

SUMMARY

Recent publications shed new light on the mutational landscape of pancreatic cancer and further delineate the distinctive pancreatic cancer-stroma ecosystem as determined by the dynamic interplay of inflammation, hallmark mutations, EMT, and cancer stem cells.

Chemotherapy in gastroenteropancreatic (GEP) neuroendocrine carcinomas (NEC): a critical view

Neuroendocrine tumors (NET) are classified according to the Ki67 in low-intermediate grade (Ki67<20%) and high grade (Ki67>20%). The NET of the latter group are also known as neuroendocrine carcinoma (NEC), and their prognosis is dismail. While in the former group biotherapy and radionuclide therapy can be proposed, chemotherapy represents the only treatment usually proposed for NEC. Cisplatin/etoposide combination is usually chosen based on the rationale that NEC are clinically similar to small cell lung cancer. However, evidence for cisplatin/etoposide in NEC is poor and controversial, and different schedules and response rate have been published so far. These aspects, combined with the heterogeneous characteristics of NEC, prompt us to have some doubt in considering cisplatin/etoposide as the gold standard. Some evidence exists that carboplatin can be used instead of cisplatin and irinotecan instead of etoposide without reducing efficacy. Furthermore other drugs, as gemcitabine, oxaliplatin or temozolomide can be evaluated in NEC with non-neuroendocrine component or in mixed adenoneuroendocrine carcinomas. NEC are a category of NET that should be deeply studied to verify if the response to cisplatin/etoposide is homogeneous related to the different Ki67, different morphology and/or different primary site.

Inactivation of X-linked tumor suppressor genes in human cancer

Cancer cells silence autosomal tumor suppressor genes by Knudson's two-hit mechanism in which loss-of-function mutations and then loss of heterozygosity occur at the tumor suppressor gene loci. However, the identification of X-linked tumor suppressor genes has challenged the traditional theory of 'two-hit inactivation' in tumor suppressor genes, introducing the novel concept that a single genetic hit can cause loss of tumor suppressor function. The mechanism through which these genes are silenced in human cancer is unclear, but elucidating the details will greatly enhance our understanding of the pathogenesis of human cancer. Here, we review the identification of X-linked tumor suppressor genes and discuss the potential mechanisms of their inactivation. In addition, we also discuss how the identification of X-linked tumor suppressor genes can potentially lead to new approaches in cancer therapy.

Well-differentiated pancreatic neuroendocrine tumors: from genetics to therapy

Well-differentiated pancreatic neuroendocrine tumors (PanNETs) comprise ∼1-3% of pancreatic neoplasms. Although long considered as reasonably benign lesions, PanNETs have considerable malignant potential, with a 5-year survival of ∼65% and a 10-year survival of 45% for resected lesions. As PanNETs have a low incidence, they have been understudied, with few advances made until the completion of their exomic sequencing in the past year. In this Review, we summarize some of the latest insights into the genetics of PanNETs, and their probable implications in the context of prognosis and therapy. In particular, we discuss two genes (DAXX and ATRX) that have collectively been identified as mutated in >40% of PanNETs, and the biological and prognostic implications of these novel mutations. The identification of recurrent somatic mutations within the mTOR signaling pathway and the therapeutic implications for personalized therapy in patients with PanNETs are also discussed. Finally, this Review outlines state-of-the-art advances in the biology of PanNETs that are of emerging translational importance.