Chromosomal alterations in human pancreatic endocrine tumors

Whole Exome Sequencing of Biliary Tubulopapillary Neoplasms Reveals Common Mutations in Chromatin Remodeling Genes

Simple Summary

Intraductal tubulopapillary neoplasms (ITPN) have recently been described as rare precursor lesions of pancreatic ductal adenocarcinoma and cholangiocarcinoma. Despite a high number of associated invasive adenocarcinomas at the time of diagnosis, patients with ITPN tend to have a much better clinical outcome than those with classical pancreato-biliary adenocarcinoma. Furthermore, rare molecular studies of ITPN show an unexpected lack of hotspot mutations in common driver genes of pancreato-biliary adenocarcinoma, including KRAS. This article reports the first large comprehensive and comparative molecular study of pancreato-biliary ITPN. In the absence of KRAS mutations, we found a high genetic heterogeneity with enrichment in core signaling pathways, including putative actionable genomic targets in one-third of the cases. Whereas, pancreatic ITPN demonstrates a highly distinct genetic profile, differing from classical pancreatic carcinogenesis, biliary ITPN and classical cholangiocarcinoma share common alterations in key genes of the chromatin remodeling pathway, and therefore, appear more closely related than pancreatic ITPN and classical pancreatic ductal adenocarcinoma PDAC.

Abstract

The molecular carcinogenesis of intraductal tubulopapillary neoplasms (ITPN), recently described as rare neoplasms in the pancreato-biliary tract with a favorable prognosis despite a high incidence of associated pancreato-biliary adenocarcinoma, is still poorly understood. To identify driver genes, chromosomal gains and losses, mutational signatures, key signaling pathways, and potential therapeutic targets, the molecular profile of 11 biliary and 6 pancreatic ITPNs, associated with invasive adenocarcinoma in 14/17 cases, are studied by whole exome sequencing (WES). The WES of 17 ITPNs reveals common copy number variants (CNVs) broadly distributed across the genome, with recurrent chromosomal deletions primarily in 1p36 and 9p21 affecting the tumor suppressors CHD5 and CDKN2A, respectively, and gains in 1q affecting the prominent oncogene AKT3. The identified somatic nucleotide variants (SNVs) involve few core signaling pathways despite high genetic heterogeneity with diverse mutational spectra: Chromatin remodeling, the cell cycle, and DNA damage/repair. An OncoKB search identifies putative actionable genomic targets in 35% of the cases (6/17), including recurrent missense mutations of the FGFR2 gene in biliary ITPNs (2/11, 18%). Our results show that somatic SNV in classical cancer genes, typically associated with pancreato-biliary carcinogenesis, were absent (KRAS, IDH1/2, GNAS, and others) to rare (TP53 and SMAD4, 6%, respectively) in ITPNs. Mutational signature pattern analysis reveals a predominance of an age-related pattern. Our findings highlight that biliary ITPN and classical cholangiocarcinoma display commonalities, in particular mutations in genes of the chromatin remodeling pathway, and appear, therefore, more closely related than pancreatic ITPN and classical pancreatic ductal adenocarcinoma.

Application of multiomics sequencing and advances in the molecular mechanisms of pancreatic neuroendocrine neoplasms

The incidence of pancreatic neuroendocrine neoplasms (PanNENs) has gradually increased. PanNENs comprise two subtypes with different clinical manifestations and molecular mechanisms: functional PanNENs and nonfunctional PanNENs. Excessive hormones and tumor progression severely affect the quality of life of patients or are even life threatening. However, the molecular mechanisms of hormone secretion and tumor progression in PanNENs have not yet been fully elucidated. At present, advancements in sequencing technologies have led to the exploration of new biological markers and an advanced understanding of molecular mechanisms in PanNENs. Multiomics sequencing could reveal differences and similarities in molecular features in different fields. However, sequencing studies of PanNENs are booming and should be summarized to integrate the current findings. In this review, we summarize the current status of multiomics sequencing in PanNENs to further guide its application. We explore mainly advancements in the genome, transcriptome, and DNA methylation fields. In addition, the cell origin of PanNENs, which has been a hot issue in sequencing research, is described in multiple fields.

Centromeric cohesion failure invokes a conserved choreography of chromosomal mis-segregations in pancreatic neuroendocrine tumor

BACKGROUND

Pancreatic neuroendocrine tumors (PANETs) are rare, slow growing cancers that often present with local and distant metastasis upon detection. PANETS contain distinct karyotypes, epigenetic dysregulation, and recurrent mutations in MEN1, ATRX, and DAXX (MAD+); however, the molecular basis of disease progression remains uncharacterized.

METHODS

We evaluated associations between aneuploidy and the MAD+ mutational state of 532 PANETs from 11 published genomic studies and 19 new cases using a combination of exome, targeted panel, shallow WGS, or RNA-seq. We mapped the molecular timing of MAD+ PANET progression using cellular fractions corrected for inferred tumor content.

RESULTS

In 287 PANETs with mutational data, MAD+ tumors always exhibited a highly recurrent signature of loss of heterozygosity (LOH) and copy-number alterations affecting 11 chromosomes, typically followed by genome doubling upon metastasis. These LOH chromosomes substantially overlap with those that undergo non-random mis-segregation due to ectopic CENP-A localization to flanking centromeric regions in DAXX-depleted cell lines. Using expression data from 122 PANETs, we found decreased gene expression in the regions immediately adjacent to the centromere in MAD+ PANETs. Using 43 PANETs from AACR GENIE, we inferred this signature to be preceded by mutations in MEN1, ATRX, and DAXX. We conducted a meta-analysis on 226 PANETs from 8 CGH studies to show an association of this signature with metastatic incidence. Our study shows that MAD+ tumors are a genetically diverse and aggressive subtype of PANETs that display extensive chromosomal loss after MAD+ mutation, which is followed by genome doubling.

CONCLUSIONS

We propose an evolutionary model for a subset of aggressive PANETs that is initiated by mutation of MEN1, ATRX, and DAXX, resulting in defects in centromere cohesion from ectopic CENP-A deposition that leads to selective loss of chromosomes and the LOH phenotype seen in late-stage metastatic PANETs. These insights aid in disease risk stratification and nominate potential therapeutic vulnerabilities to treat this disease.

Phosphatidylinositol-3,4,5-Trisphosphate Dependent Rac Exchange Factor 1 (PREX1) is a Novel Predictor of Prognosis for Breast Cancer Patients: A Retrospective Case Series

Background

In previous studies, higher expression of PREX1 (PtdIns (3,4,5)P3-dependent Rac exchanger 1) has been detected in some subsets of breast cancer, and activation of PREX1 has been associated with tumor progression in vivo. However, an association between PREX1 and breast cancer prognosis has not been examined.

Material/Methods

In this study, we investigated the expression and correlation of PREX1 with important clinical factors and prognosis of patients with breast cancer. Immunohistochemical staining was performed for 121 tumor tissue specimens obtained from primary breast cancer lesions.

Results

We found that 55 tissues exhibited positive staining for PREX1. Moreover, tumors positive for PREX1 were found to have significant association with recurrence rate (P=0.000) and metastasis rate (P=0.001). Univariate and multivariate regression analyses also identified PREX1 expression as an independent variable of disease-free survival. Our analyses indicate that high levels of PREX1 expression were related to longer disease-free survival in patients with breast cancer (P=0.013).

Conclusions

PREX1 is a favorable variable of prognosis for breast cancer patients, these study results need to be confirmed in larger research studies.

Upregulation of INS-IGF2 read-through expression and identification of a novel INS-IGF2 splice variant in insulinomas

Fusion transcripts arising from the combination of exons residing on neighboring genes on the same chromosome may give rise to chimeric or novel proteins. Such read-through transcripts have been detected in different cancers where they may be of pathogenetic interest. In this study, we describe for the first time the expression of a read-through transcript in insulinomas, a functioning neuroendocrine pancreatic neoplasm. The read-through transcript INS-IGF2, composed of exons from the two genes proinsulin precursor (INS) and insulin‑like growth factor 2 (IGF2), both mapping to chromosomal subband 11p15.5, was highly expressed in the two insulinomas analyzed. More precisely, version 2 of the INS-IGF2 transcript was expressed, indicating possible expression of the chimeric INS-IGF2 protein. We further identified a novel splice variant of the INS-IGF2 read-through transcript in one of the insulinomas, composed of exon 1 of INS3 and exons of IGF2. In the same tumor, we found high expression of INS3 and the presence of the A allele at SNP rs689. SNP rs689 has been previously described to regulate splicing of the INS transcript, indicating that this regulatory mechanism also affects splicing of INS-IGF2. The identification of the INS-IGF2 read-through transcript specifically in tumor tissue but not in normal pancreatic tissue suggests that high expression of INS-IGF2 could be neoplasia‑specific. These results may have potential clinical applications given that the read-through transcript could be used as a biomarker in insulinoma patients.

PtdIns(3,4,5)P3-dependent Rac Exchanger 1 (PREX1) Rac-Guanine Nucleotide Exchange Factor (GEF) Activity Promotes Breast Cancer Cell Proliferation and Tumor Growth via Activation of Extracellular Signal-regulated Kinase 1/2 (ERK1/2) Signaling

PtdIns(3,4,5)P3-dependent Rac exchanger 1 (PREX1) is a Rac-guanine nucleotide exchange factor (GEF) overexpressed in a significant proportion of human breast cancers that integrates signals from upstream ErbB2/3 and CXCR4 membrane surface receptors. However, the PREX1 domains that facilitate its oncogenic activity and downstream signaling are not completely understood. We identify that ERK1/2 MAPK acts downstream of PREX1 and contributes to PREX1-mediated anchorage-independent cell growth. PREX1 overexpression increased but its shRNA knockdown decreased ERK1/2 phosphorylation in response to EGF/IGF-1 stimulation, resulting in induction of the cell cycle regulators cyclin D1 and p21(WAF1/CIP1) PREX1-mediated ERK1/2 phosphorylation, anchorage-independent cell growth, and cell migration were suppressed by inhibition of MEK1/2/ERK1/2 signaling. PREX1 overexpression reduced staurosporine-induced apoptosis whereas its shRNA knockdown promoted apoptosis in response to staurosporine or the anti-estrogen drug tamoxifen. Expression of wild-type but not GEF-inactive PREX1 increased anchorage-independent cell growth. In addition, mouse xenograft studies revealed that expression of wild-type but not GEF-dead PREX1 resulted in the formation of larger tumors that displayed increased phosphorylation of ERK1/2 but not AKT. The impaired anchorage-independent cell growth, apoptosis, and ERK1/2 signaling observed in stable PREX1 knockdown cells was restored by expression of wild-type but not GEF-dead-PREX1. Therefore, PREX1-Rac-GEF activity is critical for PREX1-dependent anchorage-independent cell growth and xenograft tumor growth and may represent a possible therapeutic target for breast cancers that exhibit PREX1 overexpression.

[Von Hippel-Lindau disease type 2-related pancreatic neuroendocrine tumor and adrenal myelolipoma]

The paper describes a case of von Hippel--Lindau-related pancreatic neuroendocrine tumor and adrenal myelolipoma in a 44-year-old woman. The pancreatic tumor and a left retroperitoneal mass were removed in the women in July 2014 and May 2015. Histological examination of the pancreatic tumor revealed that the latter consisted of clear cells forming tubular and tubercular structures showing the expression of chromogranin A, synaptophysin, and cytokeratins 18 and 19 and a negative response to CD10 and RCC. The adrenal medullary mass presented as clear-cell alveolar structures with inclusions of adipose tissue mixed with erythroid, myeloid, and lymphoid cells. The clear-cell component of the adrenal gland expressed neuroendocrine markers with a negative response to cytokeratins, CD10, and RCC. Molecular genetic examination yielded a signal corresponding to two copies of the VHL gene. No deletions or amplifications of the gene were detected. Cases of von Hippel--Lindau disease concurrent with adrenal pheochromocytoma and myelolipoma and simultaneous pancreatic involvement were not found in the literature.

Histologic and Molecular Profile of Pediatric Insulinomas: Evidence of a Paternal Parent-of-Origin Effect

CONTEXT

Acquired insulinomas are rare causes of hyperinsulinemic hypoglycemia in children and are much less common than focal lesions of congenital hyperinsulinism. The latter are known to be associated with isodisomy for paternally transmitted ATP-sensitive potassium channel mutations on 11p15; however, the molecular basis for pediatric insulinomas is not well characterized.

OBJECTIVE

The purpose of this study was to characterize the histopathological and molecular defects in a large group of 12 pediatric insulinomas seen at The Children's Hospital of Philadelphia.

RESULTS

Twelve children with insulinomas were seen between 1971 and 2013, compared to 201 cases with focal congenital hyperinsulinism seen between 1997 and 2014. The age of insulinoma patients ranged from 4-16 years at the time of surgery. Features of MEN1 syndrome were present in five of the 12, including four cases with heterozygous mutations of MEN1 on 11q. Immunohistochemical analysis revealed nuclear loss of p57 staining consistent with loss of the maternal 11p15 allele in 11 of the 12 insulinomas, including all five MEN1-associated tumors. Imbalance of the paternal 11p allele was confirmed by single nucleotide polymorphism genotyping and methylation assays of the 11p imprinting control loci in four of five MEN1-associated tumors and six of seven sporadic insulinomas. In addition, single nucleotide polymorphism genotyping revealed extensive tumor aneuploidy beyond chromosome 11.

CONCLUSIONS

These data indicate that MEN1 mutations are more common in insulinomas in children than in adults. Aneuploidy of chromosome 11 and other chromosomes is common in both MEN1 and non-MEN1 insulinomas. The novel observation of a paternal parent-of-origin effect in all MEN1 and most non-MEN1 tumors suggests a critical role for imprinted growth-regulatory genes in the 11p region in the genesis of β-cell endocrine tumors in children.

The Phosphatidylinositol (3,4,5)-Trisphosphate-dependent Rac Exchanger 1·Ras-related C3 Botulinum Toxin Substrate 1 (P-Rex1·Rac1) Complex Reveals the Basis of Rac1 Activation in Breast Cancer Cells

The P-Rex (phosphatidylinositol (3,4,5)-trisphosphate (PIP3)-dependent Rac exchanger) family (P-Rex1 and P-Rex2) of the Rho guanine nucleotide exchange factors (Rho GEFs) activate Rac GTPases to regulate cell migration, invasion, and metastasis in several human cancers. The family is unique among Rho GEFs, as their activity is regulated by the synergistic binding of PIP3 and Gβγ at the plasma membrane. However, the molecular mechanism of this family of multi-domain proteins remains unclear. We report the 1.95 Å crystal structure of the catalytic P-Rex1 DH-PH tandem domain in complex with its cognate GTPase, Rac1 (Ras-related C3 botulinum toxin substrate-1). Mutations in the P-Rex1·Rac1 interface revealed a critical role for this complex in signaling downstream of receptor tyrosine kinases and G protein-coupled receptors. The structural data indicated that the PIP3/Gβγ binding sites are on the opposite surface and markedly removed from the Rac1 interface, supporting a model whereby P-Rex1 binding to PIP3 and/or Gβγ releases inhibitory C-terminal domains to expose the Rac1 binding site.

Acinar cell carcinomas of the pancreas: a molecular analysis in a series of 57 cases

Pancreatic acinar cell carcinomas (PACs) are rare but are distinct aggressive neoplasms that phenotypically differ from pancreatic ductal adenocarcinomas (PDACs) and pancreatic neuroendocrine neoplasms (PNENs). Despite recent work on the genetic changes of PACs, their molecular pathogenesis is still poorly understood. In this study, we focus on a comparative genomic hybridization analysis. Based on frequent chromosomal imbalances, the involvement of DCC and c-MYC in the pathogenesis of PACs is further investigated. Moreover, we examine markers harboring potential therapeutic relevance (K-RAS, BRAF, EGFR, MGMT, HSP90, L1CAM, Her2). PACs revealed a microsatellite stable, chromosomal unstable genotype, defined by recurrent chromosomal losses of 1p, 3p, 4q, 5q, 6q, 8p, 9p, 11q, 13q, 16q, and 18, as well as gains of 1q, 7, 8q, 12, 17q, and 20q. Subsets of PAC displayed reduction/loss of DCC (79 %) and c-MYC-amplification (17 %). Significant EGFR expression occurred in 42 %, HSP90 expression in 98 %, L1CAM expression in 72 %, and loss of MGMT in 26 %. Two cases carried a K-RAS mutation. Mutations of EGFR or BRAF were not detected. All cases were Her2/neu-negative. PACs display characteristic chromosomal imbalances which are distinctly different from those in pancreatic ductal adenocarcinomas and pancreatic neuroendocrine neoplasms. Our findings suggest that DCC and c-MYC alterations may play an important role in the pathogenesis of PACs. Furthermore, EGFR, MGMT, HSP90, and L1CAM may be useful as therapeutic markers and predictors of response to therapy in a subset of PACs.

Utilization of ancillary studies in the cytologic diagnosis of biliary and pancreatic lesions: The Papanicolaou Society of Cytopathology Guidelines

The Papanicolaou Society of Cytopathology has developed a set of guidelines for pancreatobiliary cytology including indications for endoscopic ultrasound guided fine needle aspiration, terminology and nomenclature of pancreatobiliary disease, ancillary testing and post-biopsy management. All documents are based on the expertise of the authors, a review of the literature, discussion of the draft document at several national and international meetings and synthesis of selected online comments of the draft document. This document presents the results of these discussions regarding the use of ancillary testing in the cytologic diagnosis of biliary and pancreatic lesions. Currently, fluorescence in-situ hybridization (FISH) appears to be the most clinically relevant ancillary technique for cytology of bile duct strictures. The addition of FISH analysis to routine cytologic evaluation appears to yield the highest sensitivity without loss in specificity. Loss of immunohistochemical staining for the protein product of the SMAD4 gene and positive staining for mesothelin support a diagnosis of ductal adenocarcinoma. Immunohistochemical markers for endocrine and exocrine differentiation are sufficient for a diagnosis of endocrine and acinar tumors. Nuclear staining for beta-catenin supports a diagnosis of solid-pseudopapillary neoplasm. Cyst fluid analysis for amylase and carcinoembryonic antigen aids in the pre-operative classification of pancreatic cysts. A number of gene mutations (KRAS, GNAS, von Hippel-Lindau, RNF43 and CTNNB1) may be of aid in the diagnosis of cystic neoplasms. Other ancillary techniques do not appear to improve diagnostic sensitivity sufficiently to justify their increased costs.

Utilization of ancillary studies in the cytologic diagnosis of biliary and pancreatic lesions: the Papanicolaou Society of Cytopathology guidelines for pancreatobiliary cytology

The Papanicolaou Society of Cytopathology has developed a set of guidelines for pancreatobiliary cytology including indications for endoscopic ultrasound-guided fine-needle aspiration, terminology and nomenclature of pancreatobiliary disease, ancillary testing, and post-biopsy management. All documents are based on the expertise of the authors, a review of the literature, discussions of the draft document at several national and international meetings, and synthesis of selected online comments of the draft document. This document presents the results of these discussions regarding the use of ancillary testing in the cytologic diagnosis of biliary and pancreatic lesions. Currently, fluorescence in situ hybridization (FISH) appears to be the most clinically relevant ancillary technique for cytology of bile duct strictures. The addition of FISH analysis to routine cytologic evaluation appears to yield the highest sensitivity without loss in specificity. Loss of immunohistochemical staining for the protein product of the SMAD4 gene and positive staining for mesothelin support a diagnosis of ductal adenocarcinoma. Immunohistochemical markers for endocrine and exocrine differentiation are sufficient for a diagnosis of endocrine and acinar tumors. Nuclear staining for beta-catenin supports a diagnosis of solid-pseudopapilary neoplasm. Cyst fluid analysis for amylase and carcinoembryonic antigen aids in the preoperative classification of pancreatic cysts. Many gene mutations (KRAS, GNAS, VHL, RNF43, and CTNNB1) may be of aid in the diagnosis of cystic neoplasms. Other ancillary techniques do not appear to improve diagnostic sensitivity sufficiently to justify their increased costs.

Molecular pathology and genetics of pancreatic endocrine tumours

Pancreatic neuroendocrine tumours (PETs) are the second most frequent pancreatic neoplasms. Their poor chemosensitivity, high rate of metastatic disease and relatively long survival make PETs an ideal field to be explored for novel therapies based on specific molecular changes. PETs are generally sporadic but can also arise within hereditary syndromes, such as multiple endocrine neoplasia type 1, von Hippel-Lindau, neurofibromatosis type 1 and tuberous sclerosis complex, which represent a model for sporadic cases too. Among allelic imbalances, main genomic changes involve gain of 17q, 7q and 20q and loss of 11q, 6q and 11p, which identify regions of putative candidate oncogenes or tumour suppressor genes (TSGs), respectively, sometime with potential prognostic significance. Overexpression of Src-like kinases and cyclin D1 (CCND1) oncogene has been described. As for TSGs, P53 (TP53), DPC4/SMAD4 and RB (RB1) are not implicated in PET tumorigenesis, while for p16INK4a (CDKN2A), TIMP3, RASSF1A and hMLH1, more data are available, suggesting a role for methylation as a silencing mechanism. In the last decade, gene expression profile studies, analysis of microRNAs and, more recently, large-scale mutational analysis have highlighted commonly altered molecular pathways in the pathology of PETs. The roles of the mammalian target of rapamycin pathway, and its connection with Src kinases, and the activity of a number of tyrosine kinase receptors seem to be pivotal, as confirmed by the results of recent clinical trials with targeted agents. Mutations of DAXX and ATRX are common and related to altered telomeres but not to prognosis.

Identification of P-Rex1 as a novel Rac1-guanine nucleotide exchange factor (GEF) that promotes actin remodeling and GLUT4 protein trafficking in adipocytes

Phosphoinositide 3-kinase (PI3K) signaling promotes the translocation of the glucose transporter, GLUT4, to the plasma membrane in insulin-sensitive tissues to facilitate glucose uptake. In adipocytes, insulin-stimulated reorganization of the actin cytoskeleton has been proposed to play a role in promoting GLUT4 translocation and glucose uptake, in a PI3K-dependent manner. However, the PI3K effectors that promote GLUT4 translocation via regulation of the actin cytoskeleton in adipocytes remain to be fully elucidated. Here we demonstrate that the PI3K-dependent Rac exchange factor, P-Rex1, enhances membrane ruffling in 3T3-L1 adipocytes and promotes GLUT4 trafficking to the plasma membrane at submaximal insulin concentrations. P-Rex1-facilitated GLUT4 trafficking requires a functional actin network and membrane ruffle formation and occurs in a PI3K- and Rac1-dependent manner. In contrast, expression of other Rho GTPases, such as Cdc42 or Rho, did not affect insulin-stimulated P-Rex1-mediated GLUT4 trafficking. P-Rex1 siRNA knockdown or expression of a P-Rex1 dominant negative mutant reduced but did not completely inhibit glucose uptake in response to insulin. Collectively, these studies identify a novel RacGEF in adipocytes as P-Rex1 that, at physiological insulin concentrations, functions as an insulin-dependent regulator of the actin cytoskeleton that contributes to GLUT4 trafficking to the plasma membrane.

Dysregulation of the cell cycle and chromosomal imbalances in juxtaglomerular cell tumors - a comparative study with endocrine tumors of the pancreas

Two juxtaglomerular cell tumors (JGCTs) were investigated in comparison with 14 endocrine tumors of the pancreas (ETPs), focusing on the cell cycle, apoptosis, and cytogenetic changes. JGCTs revealed nuclear accumulation of Cyclin D(1), together with the cyclin-dependent kinase inhibitors p21(Cip1/Waf1) and p27(Kip1). In contrast, no accumulation of Cyclin D(3), p53, p16(INK4a), or Mdm-2 was seen. Bcl-2 protein was intensively, but Rb only moderately, expressed. This immunoreactive profile was not found in the ETPs, which were negative for Bcl-2, p27(Kip1), p21(Cip1/Waf1), and - with one exception - for Cyclin D(1) (1/14) but expressed Cyclin D(3) in 7/14 cases. JGCTs displayed characteristic genetic alterations with combined losses of chromosomes 9, 11, 15, and 21 and gains of chromosome 18. In contrast, no characteristic pattern of genetic alterations was found in ETPs. In both, the amount of chromosomal aberrations correlated with tumor size. In small ETPs and JGCTs, genetic losses dominated over gains of chromosomes, whereas in large/malignant ETPs, gains and losses were equally affected. Thus, JGCTs represent a special type of renal endocrine neoplasm characterized by deregulation of cell cycle components and a typical profile of chromosomal aberrations. Since only two JCTs were investigated, further studies for validation of these results are, however, necessary.

Pancreatic endocrine tumor EUS-guided FNA DNA microsatellite loss and mortality

BACKGROUND

The clinical course of pancreatic endocrine tumors (PET) depends on tumor size, the presence of invasion or metastasis, the Ki-67 index, mitoses per high power field, and mutational damage. Most of this information is not available before surgery for clinical decision making or prognostication.

OBJECTIVE

To evaluate PET EUS-guided FNA (EUS-FNA) microsatellite loss analysis in the context of PET-related mortality.

DESIGN

A single institution retrospective cohort.

PATIENTS

Patients with PET diagnosed by EUS-FNA who underwent DNA microsatellite loss analysis and at least 1 year of follow-up or subsequent death.

INTERVENTION

PET microsatellite loss analysis results and current clinical status were compared.

RESULTS

Twenty-nine patients were included in the final analysis; the mean age of the patients was 57 years, and 10 were women (35%). The mean follow-up was 33.7 months (median 30 months, range 2-66 months). Twelve patients had disease progression, and 8 died, all from disease-specific causes. Malignant PET contained multiple microsatellite losses, with a median fractional allelic loss (FAL) of 0.37 (range 0.12-0.69, interquartile range [IQR] 0.23-0.42), significantly different from benign PET, median FAL 0 (range 0-0.18, IQR 0-0.08, P < .0001). Survival analysis revealed a significant difference in disease recurrence or progression at 2 years (P < .0001) and in the 5-year survival between patients with FAL </=0.2 compared with >0.2 (P < .0001). Logistic regression could not be performed because of the perfect association between an FAL >0.2 and disease status or mortality.

LIMITATIONS

Retrospective design, referral bias, and DNA analysis availability.

CONCLUSIONS

PET EUS-FNA microsatellite loss analysis provides preoperative prognostic information. An FAL >0.2 is not only associated with disease progression but also with mortality.

Endocrine neoplasms of the pancreas: pathologic and genetic features

CONTEXT

Pancreatic endocrine neoplasms (PENs) are diagnostically challenging tumors whose natural history is largely unknown. Histopathology allows the distinction of 2 categories: poorly differentiated high-grade carcinomas and well-differentiated neoplasms. The latter include more than 90% of PENs whose clinical behavior varies from indolent to malignant and cannot be predicted by their morphology.

OBJECTIVES

To review the literature and report on additional primary material about the clinicopathologic features, classification, staging, grading, and genetic features of PENs.

DATA SOURCES

Literature review of relevant articles indexed in PubMed (US National Library of Medicine) and primary material from the authors' institution.

CONCLUSIONS

The diagnosis of PEN is generally easy, but unusual features may induce misdiagnosis. Immunohistochemistry solves the issue, provided that the possibility of a PEN has been considered. Morphology allows the distinction of poorly differentiated aggressive carcinomas from well-differentiated neoplasms. The World Health Organization classification criteria allow for the discernment of the latter into neoplasms and carcinomas with either benign or uncertain behavior. The recently proposed staging and grading systems hold great promise for permitting a stratification of carcinomas into clinically significant risk categories. To date, inactivation of the MEN1 gene remains the only ascertained genetic event involved in PEN genesis. It is inactivated in roughly one-third of PENs. The degree of genomic instability correlates with the aggressiveness of the neoplasm. Gene silencing by promoter methylation has been advocated, but a formal demonstration of the involvement of specific genes is still lacking. Expression profiling studies are furnishing valuable lists of mRNAs and noncoding RNAs that may advance further the research to discover novel markers and/or therapeutic targets.

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

PURPOSE OF REVIEW

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.

RECENT FINDINGS

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.

SUMMARY

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.

Array comparative genomic hybridization analysis of olfactory neuroblastoma

Olfactory neuroblastoma is an unusual neuroectodermal malignancy, which is thought to arise at the olfactory membrane of the sinonasal tract. Due to its rarity, little is understood regarding its molecular and cytogenetic abnormalities. The aim of the current study is to identify specific DNA copy number changes in olfactory neuroblastoma. Thirteen dissected tissue samples were analyzed using array comparative genomic hybridization. Our results show that gene copy number profiles of olfactory neuroblastoma samples are complex. The most frequent changes included gains at 7q11.22-q21.11, 9p13.3, 13q, 20p/q, and Xp/q, and losses at 2q31.1, 2q33.3, 2q37.1, 6q16.3, 6q21.33, 6q22.1, 22q11.23, 22q12.1, and Xp/q. Gains were more frequent than losses, and high-stage tumors showed more alterations than low-stage olfactory neuroblastoma. Frequent changes in high-stage tumors were gains at 13q14.2-q14.3, 13q31.1, and 20q11.21-q11.23, and loss of Xp21.1 (in 66% of cases). Gains at 5q35, 13q, and 20q, and losses at 2q31.1, 2q33.3, and 6q16-q22, were present in 50% of cases. The identified regions of gene copy number change have been implicated in a variety of tumors, especially carcinomas. In addition, our results indicate that gains in 20q and 13q may be important in the progression of this cancer, and that these regions possibly harbor genes with functional relevance in olfactory neuroblastoma.

Molecular profiles of gastroenteropancreatic endocrine tumors

Neuroendocrine tumors of the gastroenteropancreatic system are defined by their endocrine phenotype and share many histopathological and clinical features. However, the fact that the hormone production of tumors depends on their site of origin, that the tumors differ in their biology, and that the association with familial syndromes is nonrandom suggests heterogeneity. It is therefore conceivable that the gastroenteropancreatic neuroendocrine tumors also differ in their molecular profile. This review summarizes and discusses the available data in this field.

Pancreatic endocrine tumors

Incidental, nonfunctional pancreatic endocrine tumors (PET) are observed with increasing frequency. Most are insulinomas. Endoscopic ultrasound with fine-needle aspiration plays a significant role in the localization and tissue diagnosis of PET. Establishing PET behavior as aggressive or indolent remains challenging especially preoperatively. Newer techniques including DNA and micro-RNA analysis may play a role in this arena. Small benign PET may be enucleated or removed laparoscopically. Surgery is the mainstay of treating advanced disease including those with metastases and Zollinger-Ellison syndrome. The management of multiple endocrine neoplasia type 1 continues to be a challenge, including treating symptoms, targeted resections, and close observation. Diagnosis, management, and prognostication of PET are under evolution and a number of changes in these fronts are anticipated.

Gene expression patterns in pancreatic tumors, cells and tissues

Background

Cancers of the pancreas originate from both the endocrine and exocrine elements of the organ, and represent a major cause of cancer-related death. This study provides a comprehensive assessment of gene expression for pancreatic tumors, the normal pancreas, and nonneoplastic pancreatic disease.

Methods/Results

DNA microarrays were used to assess the gene expression for surgically derived pancreatic adenocarcinomas, islet cell tumors, and mesenchymal tumors. The addition of normal pancreata, isolated islets, isolated pancreatic ducts, and pancreatic adenocarcinoma cell lines enhanced subsequent analysis by increasing the diversity in gene expression profiles obtained. Exocrine, endocrine, and mesenchymal tumors displayed unique gene expression profiles. Similarities in gene expression support the pancreatic duct as the origin of adenocarcinomas. In addition, genes highly expressed in other cancers and associated with specific signal transduction pathways were also found in pancreatic tumors.

Conclusion

The scope of the present work was enhanced by the inclusion of publicly available datasets that encompass a wide spectrum of human tissues and enabled the identification of candidate genes that may serve diagnostic and therapeutic goals.

Molecular genetics of neuroendocrine tumors

Neuroendocrine tumors can develop either sporadically or in association with familial syndromes such as multiple endocrine neoplasia type 1 (MEN1), multiple endocrine neoplasia type 2 (MEN2) or von Hippel-Lindau (VHL). A variety of genetic approaches has been utilized to dissect the underlying molecular pathogenesis of these distinctive tumors, including genome-wide screens such as comparative genomic hybridization, loss of heterozygosity and DNA microarray analysis as well as targeted investigations into specific tumor suppressor gene and oncogene candidates. The identification of the MEN1 tumor suppressor gene that underlies the MEN1 syndrome has provided important new insights into tumor pathogenesis. In addition, a number of independent approaches has converged on a pivotal role for regulators of the cell cycle. However, our understanding of the molecular biology of these tumors remains far from complete. In this review we highlight some of the key approaches, findings and implications of these genetic studies.

Nonductal neoplasms of the pancreas

Although the majority of pancreatic neoplasms are infiltrating ductal adenocarcinomas or other neoplasms with ductal differentiation, neoplasms with acinar, endocrine, mixed, or uncertain differentiation constitute a diverse and distinctive group. The most common and best-characterized nonductal neoplasms are pancreatic endocrine neoplasm, acinar cell carcinoma, pancreatoblastoma, and solid pseudopapillary neoplasm. This review details the clinical and pathologic features of these nonductal neoplasms, highlighting diagnostic criteria including the use of specific immunohistochemical stains to define the cellular differentiation of the neoplasms.

Endoscopic ultrasound-guided fine needle aspirate microsatellite loss analysis and pancreatic endocrine tumor outcome

BACKGROUND & AIMS

The clinical course of pancreatic endocrine tumor (PET) varies depending on tumor aggressiveness, disease extent, and possibly accumulated molecular alterations. Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) results, although accurate in diagnosing PET, correlate poorly with PET outcome. The role of detecting key molecular abnormalities in predicting PET behavior and clinical outcome from EUS-FNA material remains unknown.

METHODS

Patients with confirmed PET who underwent EUS-FNA during a 32-month period were included. Patient demographics and clinical data were recorded and follow-up information was obtained by contacting their physician to evaluate disease progression. Representative tumor cells were microdissected from the FNA material. DNA was harvested and amplified, targeting a panel of 17 polymorphic microsatellite markers on chromosomes 1p, 3p, 5q, 9p, 10q, 11q, 17p, 17q, 21q, and 22q. The polymerase chain reaction products were subjected to fluorescent capillary gel electrophoresis to detect microsatellite loss. The fractional allelic loss (FAL) was calculated.

RESULTS

Twenty-five patients were studied. Thirteen were classified histologically as benign PET limited to the pancreas and 12 as malignant PET (invasive or metastatic). The mean FAL in the benign and malignant PET was 0.03 and 0.37 (P<.0001), respectively. In addition, the mean FAL was significantly greater in those with disease progression as compared with patients with stable disease (0.45 vs 0.09 respectively, P<.0001).

CONCLUSIONS

Microsatellite loss analysis of EUS-FNA material from PET can be performed reliably and an FAL value of more than 0.2 is associated with disease progression. This technique may have value in the preoperative assessment and risk stratification of patients with PET.

The molecular genetics of gastroenteropancreatic neuroendocrine tumors

The pathobiology of neuroendocrine tumors (NETs) is hampered by the lack of scientific tools that define their mechanisms of secretion, proliferation, and metastasis; and, currently, there are no accurate means to assess tumor behavior and disease prognosis. Molecular biologic techniques and genetic analysis may facilitate the delineation of the molecular pathology of NETs and provide novel insights into their cellular mechanisms. The current status and recent advances in assessment of the molecular basis of tumorigenesis of gastroenteropancreatic neuroendocrine tumors (GEP-NETs) were reviewed (1981-2004). The objectives of this retrospective study were to provide a cohesive overview of the current state of knowledge and to develop a molecular understanding of these rare tumor entities to facilitate the establishment of therapeutic targets and rational management strategies. Multiple differences in chromosomal aberration patterns were noted between gastrointestinal (GI) neuroendocrine and pancreatic endocrine tumors (PETs). Divergence in gene expression patterns in the development of GI carcinoids and PETs was identified, whereas examination of the PET and GI carcinoid data demonstrated only few areas of overlap in the accumulation of genetic aberrations. These data suggest that the recent World Health Organization classification of GEP-NETs may require updating. In addition, previous assumptions of tumor similarity (pancreatic vs. GI) may be unfounded when they are examined at a molecular level. On the basis of the evolution of genetic information, enteric neuroendocrine lesions (carcinoids) and PETs may need to be classified as two distinct entities rather than grouped together as the single entity "GEP-NETs."

Chromosome 1q loss of heterozygosity frequently occurs in sporadic insulinomas and is associated with tumor malignancy

The pathogenesis of sporadic insulinomas is not clear, and there are no reliable genetic determinants that are useful to distinguish malignant and benign forms of this tumor. It was reported that 1q LOH might contribute to pathogenesis in gastrinomas and was correlated with tumor progression. However, little data are available on 1q LOH in sporadic insulinomas. In our study, we determine whether 1q LOH occurs in sporadic insulinomas and is associated with tumor malignancy by performing 1q allelotyping with 17 markers in 40 tumors and pair normal DNA. Thirty-five (88%) insulinomas had 1q LOH. Of the 35 insulinomas with 1q LOH, 14 (40%) had 1q21.3-23.2 LOH over a 7.5 cM region (SRO-1), whereas LOH in 21 tumors (60%) occurred at 1q31.3 over an 11.4 cM area (SRO-2). Of 24 tumors without MEN1 LOH, 20 had either SRO-1 or SRO-2 LOH (83%), whereas in 16 tumors with MEN1 LOH, 9 were shown to have LOH at either SRO-1 or SRO-2 (56%) (p = 0.065). This result suggests that LOH at 2 SRO might be MEN1 gene independent and may contribute to the pathogenesis in a subset of insulinomas without MEN1 gene LOH. The presence of 1q21.3-23.2 LOH is significantly associated with malignancy of insulinomas (p = 0.014). The high frequency of LOH at 1q 21.3-23.2 and 1q31.3 suggests these 2 areas may harbor putative tumor suppressor genes that may play an important role in the tumorigenesis of a subset of insulinomas. LOH at 1q21.3-23.2, which was associated with tumor malignancy, could be one of the genetic markers for identifying malignancy in sporadic insulinomas.

Historical, current and future perspectives on gastrointestinal and pancreatic endocrine tumors

Gastrointestinal and pancreatic endocrine tumors are neoplasms of which the pathogenesis is not completely understood and of which the clinical behavior is difficult to predict. Originally, Masson suggested that the cell of origin was an endocrine cell derived from the gastrointestinal epithelium. However, Pearse showed that the endocrine cells throughout the body shared various features, among others the amine precursor uptake and decarboxylation (APUD) capacity, and postulated the neural crest as the common origin for all APUD cells, a hypothesis that received support from the scientific community for many years. Now, biologists start to elucidate the various transcription factors that drive gastrointestinal development, and it has become evident that Masson was presumably right. Transcription factors relevant for development may also operate during tumorigenesis, and their expression may determine tumor biology. With other genetic factors, they may play a role in the pathogenesis of gastrointestinal and pancreatic endocrine tumors, and perhaps, their expression will turn out to be of prognostic or therapeutic value. In this review, current knowledge on the development of endocrine cells, hypotheses on the origin of endocrine tumors, genetic alterations, and prognostic factors are discussed. It is suggested that the increasing understanding of the normal development of gastrointestinal and pancreatic endocrine cells, the accumulating data on genetic alterations in endocrine tumors and the reappraisal of the hypotheses on their pathogenesis formulated in the past may help in elucidating their pathogenesis and in more accurately predicting prognosis.

Comparative genomic hybridization analysis of thymic neuroendocrine tumors

Thymic neuroendocrine (carcinoid) tumors are a rare neoplasm of the anterior mediastinum. The tumors frequently exhibit a wide spectrum of histology and appear to follow a more aggressive behavior than their nonthymic counterparts. Given the differing clinicopathologic manifestations, thymic neuroendocrine tumors may also possess different cytogenetic abnormalities from those that occur in foregut carcinoid tumors. In this study, we employed comparative genomic hybridization to detect genomic instability in 10 sporadic thymic neuroendocrine tumors and one multiple endocrine neoplasia type 1 (MEN1)-associated case. Gross chromosomal imbalances were found in nine cases, including gains of chromosomal material on regions X, 8, 18 and 20p and losses on 3, 6, 9q, 13q and 11q. We did not observe deletion at locus 11q13 where the MEN1 gene is located. These findings were essentially dissimilar to those reported in sporadic and MEN1-associated foregut carcinoid tumors. Consequently, we consider that a distinctive cytogenetic mechanism is at work in the development of thymic neuroendocrine tumors, which is different from that of foregut carcinoid tumors.

Chromosomal alterations detected by comparative genomic hybridization in nonfunctioning endocrine pancreatic tumors

We have used comparative genomic hybridization to investigate changes in DNA copy number in 20 nonfunctioning endocrine pancreatic tumors. The total number of regional DNA imbalances per tumor showed variation from case to case and high genetic heterogeneity was observed. From 1 to 22 chromosomal anomalies were detected in 13 of the 20 cases evaluated. Overall gains predominated over losses with a ratio of about 3.9:1 (58 gains/15 losses). The mean total number of regions displaying imbalances increased from 1.25 per tumor for benign tumors to 5.25 for malignant tumors, although statistical significance was not reached (P=0.074).

Resolved and unresolved controversies in the surgical management of patients with Zollinger-Ellison syndrome

OBJECTIVE

Highlight unresolved controversies in the management of Zollinger-Ellison syndrome (ZES).

SUMMARY BACKGROUND DATA

Recent studies have resolved some of the previous controversies including the surgical cure rate in patients with and without Multiple Endocrine Neoplasia-type1 (MEN1), the biological behavior of duodenal and pancreatic gastrinomas, role of imaging studies to localize tumor, and gastrectomy to manage acid output.

METHODS

Review of the literature based on computer searches in Index Medicus, Pubmed and Ovid.

RESULTS

Current controversies as identified in the literature include the role of endoscopic ultrasound (EUS), surgery in ZES patients with MEN1, pancreaticoduodenectomy (Whipple procedure), lymph node primary gastrinoma, parietal cell vagotomy, reoperation and surgery for metastatic tumor, and the use of minimally invasive surgical techniques to localize and remove gastrinoma.

CONCLUSIONS

It is hoped that future studies will focus on these issues to improve the surgical management of ZES patients.

DPC4/Smad4: no mutations, rare allelic imbalances, and retained protein expression in pancreatic endocrine tumors

Several chromosomal loci involved in tumorigenesis of pancreatic endocrine tumors (PET) have been identified. To date, the only gene known to be frequently altered is the MEN1 gene. Recently, DPC4 mutations and homozygous deletions have been described in 5/9 (55%) non-functioning PET, thus representing the most frequent genetic aberration described in PET. However, these data are in discordance with comparative genomic hybridization (CGH) results that rarely show genetic losses on chromosome 18. They have also been challenged by immunohistochemical data. We performed a detailed combined DPC4 mutation and deletion analysis in 34 benign and malignant PET. Mutations of the conserved C-terminal exons were not found in all examined PET and allelic loss (LOH) was found to be rare (<6%) by combined microsatellite PCR and FISH analysis. In addition, DPC4 protein expression was retained in all PET that were examined by immunohistochemistry. Therefore, DPC4 inactivation by mutation or deletion appears to be very rare in PET, which confirms the current concept of unrelated mechanisms of tumorigenesis of endocrine versus exocrine pancreatic tumors.

Molecular genetics of gastroenteropancreatic endocrine tumors

To elucidate the molecular background of sporadic gastroenteropancreatic endocrine tumors, several investigations into chromosomal alterations and allelic imbalances have identified several chromosomal regions of interest. These regions might harbor candidate genes important in tumor development and progression. However, only a small number of genes have been thoroughly analyzed, and only very few were shown to be altered in a substantial subset of tumors. Therefore, we are far from understanding the molecular mechanisms of tumor initiation and progression in gastroenteropancreatic endocrine tumors, although some "molecular patterns" are currently emerging. In this review, chromosomal alterations, that is, allelic losses and gene mutations, identified in gastroenteropancreatic endocrine tumors are briefly summarized. Molecular differences among various subtypes of gastroenteropancreatic endocrine tumors are highlighted in view of their role as indicators of separate genetic pathways.

X-chromosome loss of heterozygosity frequently occurs in gastrinomas and is correlated with aggressive tumor growth

BACKGROUND

Recent studies have shown that tumor growth, rather than hormone overproduction, is the leading cause of death among patients with gastrinomas and other malignant gastrointestinal endocrine tumors. No patient/laboratory characteristics accurately predict which tumors will exhibit aggressive growth. Furthermore, little is known regarding the molecular pathogenesis of these tumors. X-chromosome loss of heterozygosity (LOH) occurs in some nonendocrine tumors, and its presence can be associated with aggressive growth/decreased survival. Data on X-chromosome LOH in gastrointestinal endocrine tumors are conflicting. Therefore, the purpose of the current study was to determine whether X-chromosome LOH occurred in gastrinomas and, if so, whether it was correlated with tumor growth, tumor behavior, and/or prognosis.

METHODS

X chromosome allelotyping was performed using 12 microsatellite markers spaced throughout the chromosome using DNA from leukocytes and microdissected gastrinoma specimens from 16 female patients. The presence of X-chromosome LOH was analyzed for correlations with clinical and laboratory tumor characteristics as well as tumor growth characteristics.

RESULTS

Nine gastrinoma specimens (56%) had X-chromosome LOH, ranging from 6% to 23% at the 12 different loci studied. X-chromosome LOH was significantly associated with aggressive postoperative tumor growth, increased primary tumor size, and pancreatic primaries. In 6 tumor specimens, LOH occurred on Xp22.1-22.3 over a 28.4-centimorgan region.

CONCLUSIONS

X-chromosome LOH was common in gastrinoma specimens from female patients, and its presence was found to be a potentially useful molecular/genetic prognostic factor for aggressive growth.

The focal form of persistent hyperinsulinemic hypoglycemia of infancy: morphological and molecular studies show structural and functional differences with insulinoma

Paternal mutation of ATP-sensitive K(+) (K(ATP)) channel genes and loss of heterozygosity (LOH) of the 11p15 region including the maternal alleles of ABCC8, IGF2, and CDKN1C characterize the focal form of persistent hyperinsulinemic hypoglycemia of infancy (FoPHHI). We aimed to understand the actual nature of FoPHHI in comparison with insulinoma. In FoPHHI, the lesion consists in clusters of beta-cells surrounded by non-beta-cells. Compared with adjacent islets, proinsulin mRNA is similar and proinsulin production higher (P < or = 0.02), indicating regulation at a translational level, with slightly lower insulin stock and lower ABCC8 peptide labeling (P<0.05). Insulinomas, composed of beta-cell nests or cords, have similar proinsulin mRNA compared with adjacent islets, highly variable proinsulin production, lower insulin stock (P < or = 0.02), and higher ABCC8 peptide labeling (P<0.05). Proinsulin mRNA is lower than in FoPHHI (P<0.001). Islets adjacent to FoPHHI appear to be resting, in contrast to those adjacent to insulinomas, evidencing intrapancreatic regulation of islet beta-cell activity. IGF2 peptide is present inside and outside both lesions, but IGF2 mRNA is restricted to the lesions. The 11p15 LOH and absence of CDKN1C peptide staining are demonstrated in all FoPHHI but also in three of eight insulinomas. Despite some molecular similarities, FoPHHI is thus fundamentally different from insulinoma.

Molecular insights into gastrointestinal neuroendocrine tumours: importance and recent advances

A subset of gastrointestinal neuroendocrine tumours (carcinoids and pancreatic endocrine tumours) show aggressive growth. Early identification of this subset is essential for management; however, clinical, laboratory and histologic features frequently fail to achieve this. Currently, there is an increased understanding of the molecular pathogenesis/changes in neuroendocrine tumours and this may identify important prognostic factors and possibly, new treatments. Recent findings and progress in this area are briefly reviewed in this article.

Compilation of published comparative genomic hybridization studies

The power of comparative genomic hybridization (CGH) has been clearly proven since the first paper appeared in 1992 as a tool to characterize chromosomal imbalances in neoplasias. This review summarizes the chromosomal imbalances detected by CGH in solid tumors and in hemopathies. In May of 2001, we took a census of 430 articles providing information on 11,984 cases of human solid tumors or hematologic malignancies. Comparative generic hybridization has detected a number of recurrent regions of amplification or deletion that allows for identification of new chromosomal loci (oncogenes, tumor suppressor genes, or other genes) involved in the development, progression, and clonal evolution of tumors. When CGH data from different studies are combined, a pattern of nonrandom genetic aberrations appears. As expected, some of these gains and losses are common to different types of pathologies, while others are more tumor-specific.

The position of pulmonary carcinoids within the spectrum of neuroendocrine tumors of the lung and other tissues

Bronchopulmonary carcinoids comprise 25% of all human carcinoids. The World Health Organization divides them into typical (TC) and atypical forms (ATC), distinguished by differences in mitotic counts lower or higher than 2/2 mm(2) and the presence or absence of necrosis. The reproducibility of this classification with respect to the borderline cases with 1-2 mitotic counts/2 mm(2) has been questioned. We have analyzed 15 TCs and 20 ATCs by comparative genomic hybridization. Loss of 11q was the most frequent aberration in ATC (55%), but was observed only twice in TC (13%). Deletions of 3p were seen only in ATC (25%). Meta-analysis of our data and data from 218 neuroendocrine tumors and 50 non-small-cell lung carcinomas obtained from the literature revealed differences between carcinoids and carcinomas. For example, loss of 5q is frequent in lung carcinomas (75%) but is rarely seen in carcinoids (1.4%). Deletions of 11q are less frequent in neuroendocrine lung carcinomas than in ATC. To obtain a more objective survey of the relationship of pulmonary carcinoids to other neuroendocrine tumors and lung carcinomas, we created a hierarchical clustering dendrogram. This statistical approach resulted in a clear separation of carcinoids and carcinomas, which both built up different clusters. In summary, this study demonstrates the benefit of chromosomal analysis supplementary to the diagnosis of bronchopulmonary carcinoids. We also identified the feasibility of hierarchical clustering to get some clues on relationship between different tumor types. This study further argues against a transition of ATC to high-grade neuroendocrine lung carcinoma.

Sex chromosome anomalies in pancreatic endocrine tumors

We have investigated the status of sex chromosomes in 40 pancreatic endocrine tumors (PETs) using 2 complementary techniques: microsatellite and interphase FISH analysis. Twenty-five tumors were from female and 15 from male patients and included 31 nonfunctioning and 9 functioning PET (6 insulinomas, 2 glucagonomas and 1 VIPoma). Microsatellite and FISH analysis showed concordant results in all cases. PETs from females showed frequent loss of chromosome X (40%) whereas PETs from males showed relatively frequent loss of chromosome Y (36%) but never loss of the X chromosome. Statistical analysis showed significant association of sex chromosome loss with metastases (Spearman correlation test, r = 0.5, p < 0.001), local invasion (r = 0.33, p < 0.05) and high proliferation rate measured as Ki-67 index with a 5% cut-off (r = 0.42, p < 0.02). The analysis also showed that local invasion and metastases were highly correlated (r = 0.86). Multivariate survival analysis was therefore carried out including local invasion and loss of sex chromosomes. The presence of local invasion increased the risk of death almost 9 times whereas sex chromosome loss was an independent variable associated with a shorter survival period and an increased risk of death of approximately 4-fold.

Malignancy-associated allelic losses on the X-chromosome in foregut but not in midgut endocrine tumours

Information on genetic changes involved in the progression of gastroenteropancreatic (GEP) endocrine tumours is scanty. On the other hand, the identification of molecular markers of malignancy could be crucial for the prognostic evaluation of these neoplasms, which is hardly predictable on the basis of conventional histological criteria. An association of X-chromosome deletions with malignancy has already been found in gastric endocrine tumours. To investigate this further, a comparative loss of heterozygosity (LOH) analysis was performed on 17 pancreatic endocrine tumours (PETs) and 17 intestinal (ten ileal, six appendiceal, and one rectal) carcinoids from female patients. The relationship of X-chromosome LOH with the ploidy status of the neoplasms was also investigated. LOH was found in six of eight malignant PETs (60% of the informative markers), but was infrequent in the nine benign ones (4.5%). In contrast, although retention of heterozygosity was consistently observed in benign midgut tumours, LOH was infrequent in malignant carcinoids (15%). No correlation was found between LOH and the ploidy status. These results indicate an association between X-chromosome LOH and malignancy in foregut endocrine tumours. The lack of such an association in midgut carcinoids suggests that different molecular mechanisms are involved in the progression of these two categories of endocrine neoplasms, which are otherwise considered to be closely related. These findings emphasize the need for further molecular studies on GEP endocrine tumours, carefully subdivided according to their anatomical site of origin.

Genomic imbalances in the progression of endocrine pancreatic tumors

Endocrine pancreatic tumors (EPTs) are neoplasms with malignant potential. To explore the molecular basis of metastatic progression in human EPTs, we analyzed 17 paired specimens of primary EPTs and their metastases and 28 nonmetastatic EPTs using comparative genomic hybridization (CGH). Genomic alterations were detected in all of the matched primary/metastatic tumors and 19 (58%) nonmetastatic EPTs. The mean number of genomic changes was 17.3 in metastases, 12.5 in their primary tumors, and 4.5 in nonmetastatic EPTs. Statistical analysis of shared genomic changes in matched pairs of primary tumors and metastases showed a high probability (>95%) of a clonal relationship in 15 of the 17 cases. A closely related genetic pattern was also demonstrated on the basis of concordance analysis of the two groups. The most striking genomic changes which were enriched in metastases included gains of chromosomes 4 and 7 and losses of 21q. Other common regions of frequent losses (>40%) identified in metastases and/or their primary tumors involved 2p, 2q, 3p, 3q, 6q, 10p, and 11p, whereas frequently detected gains (>40%) in the paired tumors involved 5p, 5q, 12q, 14q, 17q, 18q, and 20q. These chromosomal aberrations were found in significantly fewer nonmetastatic EPTs. Some of these chromosomal loci may harbor genes contributing to the progression of EPT.

A high-resolution 6.0-megabase transcript map of the type 2 diabetes susceptibility region on human chromosome 20

Recent linkage studies and association analyses indicate the presence of at least one type 2 diabetes susceptibility gene in human chromosome region 20q12-q13.1. We have constructed a high-resolution 6.0-megabase (Mb) transcript map of this interval using two parallel, complementary strategies to construct the map. We assembled a series of bacterial artificial chromosome (BAC) contigs from 56 overlapping BAC clones, using STS/marker screening of 42 genes, 43 ESTs, 38 STSs, 22 polymorphic, and 3 BAC end sequence markers. We performed map assembly with GraphMap, a software program that uses a greedy path searching algorithm, supplemented with local heuristics. We anchored the resulting BAC contigs and oriented them within a yeast artificial chromosome (YAC) scaffold by observing the retention patterns of shared markers in a panel of 21 YAC clones. Concurrently, we assembled a sequence-based map from genomic sequence data released by the Human Genome Project, using a seed-and-walk approach. The map currently provides near-continuous coverage between SGC32867 and WI-17676 ( approximately 6.0 Mb). EST database searches and genomic sequence alignments of ESTs, mRNAs, and UniGene clusters enabled the annotation of the sequence interval with experimentally confirmed and putative transcripts. We have begun to systematically evaluate candidate genes and novel ESTs within the transcript map framework. So far, however, we have found no statistically significant evidence of functional allelic variants associated with type 2 diabetes. The combination of the BAC transcript map, YAC-to-BAC scaffold, and reference Human Genome Project sequence provides a powerful integrated resource for future genomic analysis of this region.