Geeta N. Eick

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.” Cancer 2005.

Gastrointestinal Carcinoids: The Evolution of Diagnostic Strategies

Carcinoid tumors are rare, often insidious neoplasms arising from neuroendocrine cells. The majority arise in the gastrointestinal system, and are often incidentally found during investigation, although some may present as an emergency bleed or perforation. The prosaic symptoms of flushing, diarrhea, and sweating are often overlooked; thus, the diagnosis is usually much delayed and the tumor is advanced at presentation. This diagnostic delay renders effective management difficult and adversely affects outcome. This overview provides a current assessment of the evolution of the diagnostic techniques available to establish an accurate biochemical (5-hydroxyindole-3-acetic acid and chromogranin A) and topographic diagnosis (octreoscan, radio-labeled metaidobenzylguanidine, computerized tomography, magnetic resonance imaging, positron emission tomography, enteroclysis, endoscopic ultrasound, enteroscopy, capsule endoscopy, and angiography) of carcinoid tumors. The utility and shortcomings of the respective modalities available are evaluated. Although considerable advances have been made in establishing the diagnosis of carcinoid tumors and in defining the topography of metastatic disease, the major limitation is the inability to establish an early and timely diagnosis before the advent of metastatic disease.

The Role of Genetic Markers— NAP1L1, MAGE-D2, and MTA1—in Defining Small-Intestinal Carcinoid Neoplasia

BackgroundStandard clinical and immunohistochemical methods cannot reliably determine whether a small intestinal carcinoid (SIC) is indolent or aggressive. We hypothesized that carcinoid malignancy could be defined by using quantitative reverse transcriptase-polymerase chain reaction (QRT-PCR) and immunohistochemical approaches that evaluate potential marker genes.MethodsCandidate marker gene expression (nucleosome assembly protein 1–like 1 [NAP1L1], melanoma antigen D2 [MAGE-D2], and metastasis-associated protein 1 [MTA1]) identified by Affymetrix transcriptional profiling was examined by QRT-PCR in SIC, liver, and lymph node (LN) metastases, colorectal carcinomas, and healthy tissues. Immunohistochemical expression levels of MTA1 were analyzed quantitatively by a novel automated quantitative analysis in a tissue microarray of 102 gastrointestinal carcinoids and in a breast/prostate carcinoma array.ResultsAffymetrix transcriptional profiling identified three potentially useful malignancy-marker genes (out of 1709 significantly altered genes). By QRT-PCR, NAP1L1 was significantly (P < .03) overexpressed in SIC compared with colorectal carcinomas and healthy tissue. Increased levels (P < .05) were identified in both liver and LN metastases. Levels in colorectal carcinomas were the same as in healthy mucosa. MAGE-D2 and MTA1 were increased (P < .05) in primary tumors and metastases and overexpressed in carcinomas. Automated quantitative analysis demonstrated the highest levels of MTA1 immunostaining in malignant primary SICs and in metastases to the liver and LN. These were significantly increased (P < .02) compared with nonmetastatic primary tumors. MTA1 was overexpressed in breast and prostate carcinomas (P < .05).ConclusionsSICs overexpress the neoplasia-related genes NAP1L1 (mitotic regulation), MAGE-D2 (adhesion), and MTA1 (estrogen antagonism). The ability to determine the malignant potential of these tumors and their propensity to metastasize provides a biological rationale for the management of carcinoids and may have prognostic utility.

Microsatellite instability and gene mutations in transforming growth factor-beta type II receptor are absent in small bowel carcinoid tumors

Microsatellite instability (MSI) with concomitant mutations in the coding region of transforming growth factor‐beta type II receptor (TGFβRII) results in an aberrant growth‐regulatory phenotype in colorectal carcinomas. The authors postulated that a similar mechanism occurred during the malignant evolution of small bowel carcinoid tumors.

Small bowel carcinoid (enterochromaffin cell) neoplasia exhibits transforming growth factor-β1-mediated regulatory abnormalities including up-regulation of C-myc and MTA1

Although it is known that small intestinal carcinoids are derived from enterochromaffin (EC) cells, these cells remain poorly characterized and little is known of the growth regulatory mechanisms of these neuroendocrine cells. Down‐regulation or loss of the transforming growth factor‐β1 (TGFβ1) cytostatic program and activation of TGFβ‐mediated transcriptional networks is associated with uncontrolled growth and metastasis in other neural tumors, glioblastomas. Whether this phenomenon is common to small intestinal carcinoid tumors was investigated.

Genetic Differentiation of Appendiceal Tumor Malignancy: A Guide for the Perplexed

Objective:To use differential gene expression of candidate markers to discriminate benign appendiceal carcinoids (APCs) from malignant and mixed cell APCs. Summary Background Data:Controversy exists in regard to the appropriate surgical management of APCs since it is sometimes difficult to predict tumor behavior using traditional pathologic criteria. We have identified 5 differentially expressed genes (a mitosis-regulatory gene NAP1L1, an adhesin MAGE-D2, an estrogen-antagonist, the metastasis marker MTA1, the apoptotic marker NALP, and chromogranin A) that define gut neuroendocrine cell behavior. Methods:Total RNA was isolated using TRIzol reagent from 42 appendiceal samples, including appendiceal carcinoids identified at exploration for appendicitis (no evidence of metastasis; n = 16), appendicitis specimens (n = 11), malignant appendiceal tumors (>1.5 cm, evidence of metastatic invasion; n = 7), and mixed (goblet) cell appendiceal adenocarcinoids (n = 3), normal appendiceal tissue (n = 5), and 5 colorectal cancers. Gene expression (CgA, NAP1L1, MAGE-D2, MTA1, and NALP1) was examined by Q-RT PCR (Applied Biosystems) and quantified against GAPDH. Results:CgA message was elevated (>1000-fold, P < 0.05) in all tumor types. NAP1L1 was elevated (>10-fold, P < 0.03) in both malignant and goblet cell adenocarcinoids compared with normal and incidental lesions (P < 0.006). MAGE-D2 and MTA1 message were significantly elevated (>10-fold, P < 0.01) in the malignant and goblet cell adenocarcinoid tumors but not in the appendicitis-associated carcinoids or normal mucosa. The apoptotic marker, NALP1, was overexpressed (>50-fold, P < 0.05) in the appendicitis-associated and malignant appendiceal carcinoids but was significantly decreased (>10-fold, P < 0.05) in the goblet cell adenocarcinoids. Elevated CgA transcript and protein levels indicative of a carcinoid tumor were identified in one acute appendicitis sample with no histologic evidence of a tumor. Conclusions:These data demonstrate that malignant APCs and goblet cell adenocarcinoids have elevated expression of NAP1L1, MAGE-D2, and MTA1 compared with appendiceal carcinoids identified at surgery for appendicitis. This and the differences in NALP1 gene expression (decreased in goblet cell adenocarcinoids) provide a series of molecular signatures that differentiate carcinoids of the appendix. CgA identified all appendiceal tumors as well as covert lesions, which may be more prevalent than previously recognized. The molecular delineation of malignant appendiceal tumor potential provides a scientific basis to define the appropriate surgical management as opposed to morphologic assessment alone.

Utility of molecular genetic signatures in the delineation of gastric neoplasia

Current techniques to define gastric neoplasia are limited but molecular genetic signatures can categorize tumors and provide biological rationale for predicting clinical behavior. We identified three gene signatures: Chromogranin A (CgA), MAGE‐D2 (adhesion), and MTA1 (metastasis) that define gastrointestinal (GI) carcinoids and hypothesize that their expression can delineate gastric neoplasia. This strategy provides a molecular basis to define neuroendocrine gastric carcinoids (GCs), neuronal stromal tumors (GISTs), or epithelial cell (gastric adenocarcinomas [GCAs])‐derived tumors.

Friedrich Feyrter: A Precise Intellect in a Diffuse System

Prior to the contributions of Friedrich Feyrter (1895–1973), the regulation of gastrointestinal function was an ill-understood field that was polarized by a combination of the inability of clinical scientists to perceive the relationship between the cellular elements of ‘nervism’ and the newly recognized chemical messenger system. Feyrter, an Austrian pathologist of luminescent intellect and possessed of rigorous analytic capacity, recognized the interface of the divergent elements (neural and endocrine) and established the concept of the diffuse neuroendocrine system. His pathological descriptions of the specialized neuroendocrine cells producing biologically active substances and regulating homeostasis by a network functioning via endocrine, paracrine, and neuracrine mechanisms laid the basis for contemporary understanding of gut function. In 1938, Feyrter identified Helle Zellen (clear cells) of the pancreas and gastrointestinal tract, which was later incorporated into the amine precursor uptake decarboxylation concept of endocrine cells by A.G.E. Pearse (1916–2003). Feyrter proposed a diffuse network as a functional regulatory system as opposed to the then current doctrine of ‘organ’ regulation in his 1938 manuscript Über diffuse endokrine epitheliale Organe. In addition to this seminal contribution, the prodigious intellect of Feyrter produced an array of novel observations including benign and malignant tumors of the skin, gastrointestinal tract, and eyes, carcinoid tumors and the carcinoid syndrome, the genesis of the nevus, the transformation of lipids and disorders of cellular metabolism. Sadly, the contributions of Feyrter were obscured in the catastrophe of wartime Germany and his accomplishments little recognized. We describe the life and times of this gifted scientist, teacher, and pathologist, often referred to as the ‘Father of Neuroendocrinology’.