Expression of growth factor peptides and their receptors in neuroendocrine tumors of the digestive system

Clinical and In vitro Studies of Imatinib in Advanced Carcinoid Tumors

PURPOSE

Effective systemic therapy options for carcinoid tumors are lacking. We conducted in vitro studies and a phase II clinical trial to explore the activity of imatinib in carcinoid tumors.

EXPERIMENTAL DESIGN

Cells of the human bronchial carcinoid cell line NCI-H727 and the human pancreatic carcinoid cell line BON-1 were treated with increasing concentrations of imatinib using standard procedures to assess in vitro growth-inhibitory activity. A clinical trial using a two-stage phase II design to assess the response rate and safety profile of imatinib at a dose of 400 mg given twice daily in patients with advanced carcinoid tumors was completed.

RESULTS

In both cell lines, there was a dose- and time-dependent cytotoxic effect. The clinical trial enrolled 27 evaluable patients. Median duration on trial was 16 weeks. One patient had a partial response, 17 had stable disease, and 9 had progressive disease by the Response Evaluation Criteria in Solid Tumors criteria. Median progression-free survival time was 24 weeks. Median overall survival is 36 months. Seven patients who achieved a biochemical response had a superior progression-free survival time compared with patients without biochemical response (115 weeks compared with 24 weeks; P = 0.003). An increase in plasma basic fibroblast growth factor was associated with a shorter progression-free survival duration (P = 0.02).

CONCLUSIONS

Our data suggest that imatinib is active in vitro and has a modest clinical activity in carcinoid patients. Changes in tumor markers may help select patients who are likely to benefit from therapy.

Sunitinib malate for the treatment of solid tumours: a review of current clinical data

Receptor tyrosine kinases (RTKs) play important roles in the regulation of cellular growth, and mutated or overexpressed RTKs have been implicated in various human cancers. Sunitinib malate is an oral multitargeted tyrosine kinase inhibitor with antitumour and antiangiogenic activity that recently received approval from the FDA for the treatment of advanced renal cell carcinoma and of gastrointestinal stromal tumours after disease progression on or intolerance to imatinib mesilate therapy. Sunitinib has also demonstrated promising clinical activity in the treatment of other advanced solid tumours. The present review provides an updated summary of emerging clinical experience with this promising new anticancer agent.

Current status of gastrointestinal carcinoids

Gastrointestinal (GI) carcinoids are ill-understood, enigmatic malignancies, which, although slow growing compared with adenocarcinomas, can behave aggressively. Carcinoids are classified based on organ site and cell of origin and occur most frequently in the GI (67%) where they are most common in small intestine (25%), appendix (12%), and rectum (14%). Local manifestations--mass, bleeding, obstruction, or perforation--reflect invasion or tumor-induced fibrosis and often result in incidental detection at emergency surgery. Symptoms are protean (flushing, sweating, diarrhea, bronchospasm), usually misdiagnosed, and reflect secretion of diverse amines and peptides. Biochemical diagnosis is established by elevation of plasma chromogranin A (CgA), serotonin, or urinary 5-hydroxyindoleacetic acid (5-HIAA), while topographic localization is by Octreoscan, computerized axial tomography (CAT) scan, or endoscopy/ultrasound. Histological identification is confirmed by CgA and synaptophysin immunohistochemistry. Primary therapy is surgical excision to avert local manifestations and decrease hormone secretion. Hepatic metastases may be amenable to cytoreduction, radiofrequency ablation, embolization alone, or with cytotoxics. Hepatic transplantation may rarely be beneficial. Chemotherapy and radiotherapy have minimal efficacy and substantially decrease quality of life. Intravenously administered receptor-targeted radiolabeled somatostatin analogs are of use in disseminated disease. Local endoscopic excision for gastric (type I and II) and rectal carcinoids may be adequate. Somatostatin analogues provide the most effective symptomatic therapy, although interferon has some utility. Overall 5-year survival for carcinoids of the appendix is 98%, gastric (types I/II) is 81%, rectum is 87%, small intestinal is 60%, colonic carcinoids is 62%, and gastric type III/IV is 33%.

Tumour biology of gastroenteropancreatic neuroendocrine tumours

Neuroendocrine tumours of the gastroenteropancreatic tract (GEP NETs) represent a rare and heterogeneous group of tumours. Based on their ontogenetic origin, GEP NETs are classified into foregut, midgut and hindgut tumours. Although they have many features in common, their molecular backgrounds are obviously different. Elucidation of the key factors determining tumour biology has been hampered by the low incidence and high variability of these tumours in terms of origin, morphology and growth. However, recent years have shed some light on molecular genetics of these tumours, revealing important genetic factors as the RET proto-oncogene and the tumour suppressor menin as well as knowledge about the role of growth factors like IGF-1, TGF-beta, VEGF and PDGF for the regulation of differentiation, growth and secretion. In the future, emerging molecular tools in rapid individual genome analysis and in proteomic and array technologies may help to delineate common patterns of NET disease.

From basic to clinical research in gastroenteropancreatic neuroendocrine tumor disease -- the clinician-scientist perspective

Patients with rare tumors represent a diagnostic and therapeutic challenge for non-specialized physicians, surgeons and other medical doctors. Whereas several specialized centers have gathered data for an improved diagnosis and therapy of neuroendocrine tumor disease, numerous clinical issues have not been resolved on an evidence-based medicine level. Furthermore, the evaluation of new treatment options has been overshadowed by the low incidence of the disease. In this article, a major medical challenge for the diagnosis and therapy of neuroendocrine tumor disease is addressed. As well, new therapeutic treatment options translated from current findings in the fields of molecular and tumor biology are discussed.

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.

Immunohistochemical detection of fibroblast growth factor receptors in normal endocrine cells and related tumors of the digestive system

Endocrine tumors (ETs) of the digestive system produce several growth factors including acidic and basic fibroblast growth factors (aFGF and bFGF, respectively), which are thought to be involved in the growth of tumor cells and in the proliferation of tumor stromal cells. Their actions depend on binding to four specific receptors--FGFR1, FGFR2, FGFR3, and FGFR4--whose distribution in normal endocrine cells and related tumors of the gastroenteropancreatic (GEP) system has previously been examined. Formalin-fixed, paraffin-embedded normal tissues and 60 well-characterized GEP endocrine tumors were immunostained using specific antibodies directed against various GEP hormones, aFGF, FGFR1, FGFR2, FGFR3, and FGFR4. Acidic FGF immunoreactivity (IR) was found in gut EC cells; FGFR1 immunoreactivity in rare duodenal endocrine cells and in pancreatic A cells; FGFR2 immunoreactivity in gastric and duodenal G cells, pancreatic B cells, and rectal EC cells; FGFR3 immunoreactivity in duodenal G cells; and FGFR4 immunoreactivity in rectal L cells and in pancreatic B, PP, and A cells. Immunoreactivity for at least one of the four FGFRs was found in all tumors, independently of FGFR expression in the putative cell of origin. EC cell tumors, which were all positive for aFGF, were found to express at least three different FGFRs. FGFRs also were localized in the stromal cells of all the tumors examined. The tumor stroma was more abundant in EC cell tumors than in other types of neoplasms. The results suggest that aFGF-FGFR interaction may be involved in the modulation of normal endocrine cell functions and in the regulation of tumor growth and stromal proliferation of EC cell carcinoids.

Gastrointestinal carcinoid tumors and second primary malignancies

The development of second primary malignancies (SPM) in patients with gastrointestinal carcinoid tumors is a well-described phenomenon, with reported rates as high as 55%. There is a predilection for gastrointestinal and genitourinary adenocarcinomas, but a variety of other malignancies have been reported as well. The etiology of this malignant predisposition may be rooted in the tumorigenic properties of the various neuroendocrine peptides elaborated and secreted by neuroendocrine cells. Peptides such as secretin, gastrin, bombesin, cholecystokinin (CCK), and vasoactive intestinal peptide (VIP) are believed to promote the growth of tumor cells. As many as 30 peptides and amines identified in neuroendocrine cells may have similar properties. This review of the literature on carcinoid-associated second primary malignancies is accompanied by a case report of metastatic carcinoid identified during surgical exploration for a perforating colon adenocarcinoma.

Carcinoid-related angiomatous polyposis simulating Crohn disease

Polyposis associated with ileal carcinoid tumors is a rarely described pathologic mucosal transformation that may simulate inflammatory or neoplastic polyps. We describe a case with innumerable sessile polyps and groups of large filiform-like polyps of the terminal ileum associated with submucosal carcinoid tumors and a large mesenteric carcinoid tumor mass. The clinical, radiographic, and endoscopic presentation of the polyposis, together with the presence of multiple small bowel stenotic lesions, simulated Crohn disease. We propose the descriptive terminology angiomatous polyposis to describe the striking microscopic vascular proliferation that characterizes these polyps. The distribution of these lesions, with the most profuse polyposis in the immediate proximity of the carcinoid nests, and the immunohistochemical demonstration of growth factor substances, such as transforming growth factor alpha within neoplastic cells and adjacent polyps, suggest a tumor factor-mediated stromal proliferation.

Site-specific epithelial-mesenchymal interactions in digestive neuroendocrine tumors. An experimental in vivo and in vitro study

Little is known about the functional interactions between digestive neuroendocrine tumor cells and their stromal microenvironment. The focus of our study is whether mesenchymal cells modulate peptide expression, cell proliferation, and invasiveness in digestive neuroendocrine tumor cells. We designed an experimental in vivo and in vitro study using the mouse enteroendocrine cell line STC-1. In vivo, STC-1 cells were injected subcutaneously in 18 immunosuppressed newborn rats. At day 21, all animals presented poorly differentiated neuroendocrine tumors with lung metastases. Subcutaneous tumors were usually limited by a capsule containing basement membrane components and myofibroblasts that presented a low mitotic index. Lung tumors were devoid of capsule and poor in myofibroblasts, and their mitotic index was high. The profile of peptide expression in STC-1 tumors was different from that of cultured STC-1 cells. In vitro, STC-1 cells were cultured with fibroblasts of different origins, including dermis, lung, digestive tract, and liver. Based on their origin, myofibroblasts differentially modulated hormone synthesis, proliferation, spreading, and adhesion of STC-1 cells. In conclusion, our results show that site-specific functional interactions between mesenchymal and neuroendocrine cells may contribute to modulating the behavior of digestive neuroendocrine tumors, depending on their growth site.

Growth factor receptor expression in human gastroenteropancreatic neuroendocrine tumours

BACKGROUND

Human gastroenteropancreatic neuroendocrine tumours are functionally and biologically heterogeneous, but their exact growth factor receptor expression pattern, important for onco- and carcinogenesis, remains unknown.

METHODS

This study searched for the mRNA expression pattern of six tyrosine- and serine/threonine kinase receptors [hepatocyte growth factor (HGFR), fibroblast growth factor (FGFR), epidermal growth factor (EGFR), insulin-like growth factor (IGF)-1R, transforming growth factor (TGF)-betaR1, TGF-betaR2] together with the five somatostatin receptors in human gastroenteropancreatic neuroendocrine tumours (gastrinomas, insulinomas, tumours with carcinoid syndrome, functionally inactive neuroendocrine tumours) using reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS

EGF receptor was expressed almost exclusively in gastrinomas. Among the four tumour subtypes, expression frequencies of the somatostatin receptors 1 and 5, HGF-, IGF-1-, TGF-betaR1, TGF-betaR2 and the EGF-receptor varied significantly.

CONCLUSIONS

In spite of the common cellular origin of these tumours, differences in growth factor receptor expression suggest the existence of different pathways during tumour subtype development.

Molecular mechanisms of enteroendocrine differentiation

Passing through a complex series of developmental steps, the visceral endoderm differentiates into four intestinal epithelial lineages comprising enterocytes, goblet cells, paneth cells, and enteroendocrine cells. The intestinal enteroendocrine system consists of at least 15 different cell types, which can be classified on the basis of morphological criteria, expression of secretory products, and abundance of specific marker molecules. During intestinal development and in the adult gut, neuroendocrine subpopulations display strictly controlled differences in their geographical distribution that go along with dramatic differences in cell type-specific gene expression. Identification to transcription factors and regulatory DNA elements responsible for cell-specific gene expression in different neuroendocrine cell types as well as various transgenic and "knock-out" mouse models have largely added to our understanding of mechanisms controlling appropriate special and temporal activation of enteroendocrine differentiation programs. This article reviews current in vitro and in vivo studies analyzing different molecular aspects of enteroendocrine differentiation. In addition, the influence of intestinal diseases including malignant transformation on enteroendocrine differentiation and the underlying mechanisms will be discussed.

Florid angiogenesis in mucosa surrounding an ileal carcinoid tumor expressing transforming growth factor-alpha

Carcinoid tumors of the gastrointestinal tract are known to be associated with fibrosis and vascular elastosis, either within the tumor or at distant sites. The current report describes prominent vascular proliferation in the villi extending 38 cm proximal and 15 cm distal to an ileal carcinoid tumor. These villi were expanded by vessels, producing a segmental carpet of multiple small polypoid protrusions around the tumor. Immunohistochemical analysis suggested that the major stromal components were of endothelial and myofibroblastic cell origin. The stroma of the tumor itself had minimal fibrosis and vascularity. To our knowledge, this is the first description of vascular proliferation in the vicinity but distinct from a carcinoid tumor. The demonstration of transforming growth factor-alpha (TGF-alpha) synthesis by tumor cells supports the possibility of a field effect by angiogenic factor(s) secreted by the tumor.

Immunohistochemical localization of acidic fibroblast growth factor in normal human enterochromaffin cells and related gastrointestinal tumours

Acidic fibroblast growth factor (aFGF) is a member of the structurally related heparin-binding growth factor family. The best studied members of this family are aFGF and basic FGF (bFGF), which are potent mitogens and differentiation factors for mesoderm-derived cells, including fibroblasts. This study was designed to verify the immunohistochemical expression of aFGF in normal human endocrine cells of the gut and in related endocrine tumours. We examined normal gastrointestinal mucosa from seven different subjects and 41 gut endocrine tumours from different sites, including stomach, duodenum, and small and large intestine, using an aFGF polyclonal antibody with no cross-reactivity for bFGF. We localized aFGF in a fraction of serotonin-producing enterochromaffin (EC) cells of the normal gut, while it was absent in gastrin (G), CCK, secretion (S), somatostatin (D) and glicentin (L) cells. aFGF immunoreactivity was also expressed in serotonin producing EC cell tumours, but not in other functional types of gut endocrine neoplasms investigated, including gastric ECL cell, duodenal somatostatin and gastrin cell, and rectal L cell tumours. A positive correlation was found between expression of aFGF and the amount of tumour fibrous stroma, suggesting that aFGF may be involved in proliferation and activity of stromal fibroblasts.

Surgical management of gastrointestinal endocrine tumours

The surgical management of gastrointestinal endocrine tumours must involve a multidisciplinary approach. The importance of accurate diagnosis, rendering the patient safe, and, in our opinion, localizing the tumour(s) before embarking on surgery cannot be overemphasized. Surgery is the only available treatment for cure. Occult primary tumours are now rarely a problem with novel imaging techniques, which can also improve detection and hence clearance of local spread. Surgical management in extensive metastatic or multicentric disease is less rigidly defined, and is dependent on the endocrine syndrome. A better understanding of tumour pathology, for example in MEN 1, has not always simplified matters. An appreciation of the benefit of chemotherapy, use of somatostatin analogues and hepatic artery embolization are vital to target appropriate palliative surgery. Hepatic transplantation may have an increasing role in the future. Surgical strategies must adapt to new medical treatments. If therapeutically relevant, advances in tumour biology (for example somatostatin receptor subtypes and growth factors) will influence surgical strategies in the future.

Vascular endothelial growth factor (VEGF) expression in prostatic tumours and its relationship to neuroendocrine cells

Vascular endothelial growth factor (VEGF) expression was examined by immunohistochemistry in 45 prostatic carcinoma specimens and ten benign prostatic tumours (BPH). The majority of carcinoma specimens exhibited cytoplasmic staining for VEGF and showed a trend of increasing expression with dedifferentiation (2p = 0.003). Immunoreactive VEGF was also seen in the prostatic carcinoma cell lines, the order of staining intensity was PC3 > DU145 > LNCaP. Intense granular cytoplasmic staining for VEGF was observed in neuroendocrine-like cells which were seen focally in many of the prostatic specimens. Consecutive sections were incubated with a chromogranin A antibody to confirm the neuroendocrine phenotype of these cells. A significant correlation (P < 0.0001) between the total number of intensely stained VEGF-positive cells and chromogranin A-positive cells was found. A subpopulation of neuroendocrine-like cells also showed intense immunoreactivity for transforming growth factor alpha (TGF-alpha). A correlation was observed (2p = 0.0092) between the intensity of VEGF and TGF-alpha immunostaining in carcinoma cells which were not of neuroendocrine differentiation. The presence of these two angiogenic factors may aid the neovascularisation of carcinomas and their increased expression in tumour-associated neuroendocrine cells may contribute to a more aggressive phenotype.

Surgery and polychemotherapy of non-functional endocrine pancreatic tumors: a case report with a dramatic clinical response

Endocrine pancreatic tumors (EPT) are a rare clinical entity, representing 5% of all pancreatic tumors. Nonfunctional subtypes (NF-EPT) often present themselves at diagnosis in a locally advanced or metastatic stage. Therapeutic planning of these neoplasias is based on a multidisciplinary integration of surgery and medical treatments. The Authors describe a case of NF-EPT with massive metastatic spread after cytoreductive surgery, with impressive response to polychemotherapy with 5-fluorouracil, epirubicin and dacarbazine. The various options concerning chemotherapic treatment of these tumors are reviewed.

Transforming growth factor-beta in GI neoplasia, wound healing and immune response

The last decade has been marked by tremendous advances in the biochemical and functional characterization of TGF-betas and their receptors in normal and transformed cells. TGF-betas have been shown to modulate proliferation, differentiation and motility of different cell types in a number of in vitro model systems and in some cases with some intriguing results. It is obvious that there is no simple pattern that explains the TGF-betas biological activity in vitro and their effects on cell behaviour need to be assessed in the context of an appropriate physiological cellular environment. Cell-cell and cell-matrix interactions, the differentiating status of the cell together with the functional activity of other soluble growth factors can influence how TGF-betas modulate cell behaviour. However, the overwhelming interest in this field shown by clinicians and basic scientists is rapidly increasing our understanding of how growth factors such as TGF-betas regulate the homeostasis of the GI mucosa and their role in gastrointestinal carcinogenesis.

Duct-acinar-islet cell tumor of the pancreas

A case of a rare pancreatic tumor, duct-acinar-islet cell tumor is presented. The tumor was incidentally found in the pancreatic body on computed tomography of a 21 year old male suffering from mumps. It was well demarcated from surrounding pancreas, and spherical in shape, measured 2.5 cm in diameter. Histologic and immunohistochemical examinations showed the tumor to consist of three distinct cell populations: duct, acinar and islet cells. Small cell nests consisting of these cellular components, either solely of one cell type or mixed of the three cell types, were separated by broad desmoplastic stroma. Islet (endocrine) cells, which were most predominant, were arranged in a trabecular pattern or small cell nests. Most of them were positive for glucagon, and a few cells expressed insulin, somatostatin, serotonin or pancreatic polypeptide. These cells were distributed randomly within the cell nests. Ducts, some of which contained goblet cells, were found among the endocrine cell nests. Duct-islet complexes were also observed. The acinar cells were the least conspicuous component. They expressed pancreatic alpha-amylase. An electron microscopic examination revealed duct cells with intercellular attachments and interdigitations, endocrine cells containing secretory granules, and acinar cells with zymogen granules. No definite evidence suggesting malignancy could be obtained.

Progressive carcinoid heart disease after resection of primary ovarian carcinoid

Primary ovarian carcinoid tumors are uncommon, and carcinoid heart disease is a rare complication. Although carcinoid syndrome and carcinoid heart disease typically occur in the setting of metastatic carcinoid tumor, particularly involving the liver, this is not necessarily the case in patients with primary ovarian carcinoid tumors. After surgical resection of an ovarian carcinoid tumor, the prognosis is excellent; however, carcinoid heart disease can continue to progress. The following is a case report of a patient who, despite having complete resection of a primary ovarian carcinoid tumor, went on to develop progressive, debilitating carcinoid heart disease. This is an important scenario to recognize, because proper management and surgical intervention in carcinoid heart disease can be lifesaving.