Cyclooxygenase-2 expression correlates with phaeochromocytoma malignancy: evidence for a Bcl-2-dependent mechanism

Imaging pheochromocytoma in small animals: preclinical models to improve diagnosis and treatment

Pheochromocytomas (PCCs) and paragangliomas (PGLs), together referred to as PPGLs, are rare chromaffin cell-derived tumors. They require timely diagnosis as this is the only way to achieve a cure through surgery and because of the potentially serious cardiovascular complications and sometimes life-threatening comorbidities that can occur if left untreated. The biochemical diagnosis of PPGLs has improved over the last decades, and the knowledge of the underlying genetics has dramatically increased. In addition to conventional anatomical imaging by CT and MRI for PPGL detection, new functional imaging modalities have emerged as very useful for patient surveillance and stratification for therapy. The availability of validated and predictive animal models of cancer is essential for translating molecular, imaging and therapy response findings from the bench to the bedside. This is especially true for rare tumors, such as PPGLs, for which access to large cohorts of patients is limited. There are few animal models of PPGLs that have been instrumental in refining imaging modalities for early tumor detection, as well as in identifying and evaluating novel imaging tracers holding promise for the detection and/or treatment of human PPGLs. The in vivo PPGL models mainly include xenografts/allografts generated by engrafting rat or mouse cell lines, as no representative human cell line is available. In addition, there is a model of endogenous PCCs (i.e., MENX rats) that was characterized in our laboratory. In this review, we will summarize the contribution that various representative models of PPGL have given to the visualization of these tumors in vivo and we present an example of a tracer first evaluated in MENX rats, and then translated to the detection of these tumors in human patients. In addition, we will illustrate briefly the potential of ex vivo biological imaging of intact adrenal glands in MENX rats.

Targeting Cyclooxygenase-2 in Pheochromocytoma and Paraganglioma: Focus on Genetic Background

Cyclooxygenase 2 (COX-2) is a key enzyme of the tumorigenesis-inflammation interface and can be induced by hypoxia. A pseudohypoxic transcriptional signature characterizes pheochromocytomas and paragangliomas (PPGLs) of the cluster I, mainly represented by tumors with mutations in von Hippel–Lindau (VHL), endothelial PAS domain-containing protein 1 (EPAS1), or succinate dehydrogenase (SDH) subunit genes. The aim of this study was to investigate a possible association between underlying tumor driver mutations and COX-2 in PPGLs. COX-2 gene expression and immunoreactivity were examined in clinical specimens with documented mutations, as well as in spheroids and allografts derived from mouse pheochromocytoma (MPC) cells. COX-2 in vivo imaging was performed in allograft mice. We observed significantly higher COX-2 expression in cluster I, especially in VHL-mutant PPGLs, however, no specific association between COX-2 mRNA levels and a hypoxia-related transcriptional signature was found. COX-2 immunoreactivity was present in about 60% of clinical specimens as well as in MPC spheroids and allografts. A selective COX-2 tracer specifically accumulated in MPC allografts. This study demonstrates that, although pseudohypoxia is not the major determinant for high COX-2 levels in PPGLs, COX-2 is a relevant molecular target. This potentially allows for employing selective COX-2 inhibitors as targeted chemotherapeutic agents and radiosensitizers. Moreover, available models are suitable for preclinical testing of these treatments.

Expression and Molecular Regulation of the Cox2 Gene in Gastroenteropancreatic Neuroendocrine Tumors and Antiproliferation of Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)

Background

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) has had a significant increase over the past 4 decades. The pathophysiological role of the cyclooxygenase-2 (cox-2) gene and factors responsible for the expression in GEP-NETs is of clinical value. Current study determined the expression of cox-2 gene in human GEP-NET tissues and corresponding cell lines, investigated the molecular mechanisms underlying the regulation of cox-2 gene expression and assessed the effect of nonsteroidal anti-inflammatory drugs (NSAIDs) on both anchorage-dependent and independent growth of GEP-NET cells.

Material/Methods

GEP-NET tissues and QGP-1, BON, and LCC-18 GEP-NET cell lines were used. The expression of cox-2 gene was analyzed by immunohistochemistry, western blot, RT-PCR, and enzyme immunoassay. Transient transfection and luciferase assays along with electrophoretic mobility shift assays were conducted to explore the regulation of cox-2 gene expression. The effect of COX-inhibitors on GEP-NET cell growth was determined by proliferation assays and colony growth assessment.

Results

We found 87.8% of GEP-NET tissues stained positive for COX-2. QGP-1 and LCC-18 cells expressed cox-2 gene. PGE2 (prostaglandin E2) amounts quantified in the supernatants of NET cells matched to cox-2 expression level. The CRE-E-box element (−56 to −48 bp) and binding of USF1, USF2, and CREB transcription factors to this proximal promoter element were essential for cox-2 promoter activity in GEP-NET cells. COX-2-specific inhibitor NS-398 potently and dose-dependently inhibited PGE2 release from QGP-1 cells. Interestingly, both NS-398 and acetylic salicylic acid effectively suppressed proliferation of QGP-1 and BON cells in a dose-dependent manner.

Conclusions

The majority of GEP-NETs over express cox-2 gene. The binding of CREB and USF-1/-2 transcription factors to a proximal, overlapping CRE-Ebox element is the underlying mechanism for cox-2 gene expression. NSAIDs potently suppressed the proliferations and may offer a novel approach for chemoprevention and therapy of GEP-NETs.

Neuroendocrine Differentiation in Breast Cancer: Clinicopathological Significance of Bcl-2 Positive Solid Papillary Carcinoma

Solid papillary carcinoma (SPC) is considered a rare malignant breast tumor. Maluf and Koerner first reported this disease entity as a special type of ductal carcinoma in situ with several characteristic histopathological features, including low-grade cellular atypia, intracellular or extracellular mucin deposition, and solid papillary growth pattern, as well as neuroendocrine differentiation. The present paper describes a case of SPC with bcl-2 expression, which is known as a marker for malignancy of neuroendocrine tumors. Interestingly, despite bcl-2 expression being a poor prognostic indicator of neuroendocrine tumors, the patient with this tumor has achieved long-term survival (approximately 6 years) at the time of writing this report. Because previous investigators reported that bcl-2 expression might play a role in the inhibition of the development of breast cancer, we suggest that bcl-2 expression might reflect a good prognosis in patients with SPC, rather than being a poor prognostic indicator, as it is in several types of neuroendocrine tumor. However, to confirm this hypothesis, further investigation is required.

Surgical treatment of potentially primary malignant adrenal tumors: an unresolved issue

Although the great majority of incidentalomas are adrenocortical adenomas, a number of them, depending on the size and radiological characteristics of the lesions, will turn out to be carcinomas. These tumors may present as suspicious on initial evaluation and potentially malignant or malignant on histology. Adrenocortical carcinoma is a rare and aggressive malignancy with evolving diagnostic and therapeutic approaches. Laparoscopic surgery has become the gold standard for surgery of benign adrenal tumors. Despite the extensive experience gained in laparoscopic adrenalectomy, controversy still remains in the management of adrenal tumors with high suspicion or evidence of malignancy. The aim of this review is to update the existing information regarding the diagnostic approach and surgical management of suspicious and potentially malignant primary adrenal tumors.The interpretation of radiologic characteristics is a cornerstone in pre-operative assessment of large adrenal masses, since open surgery remains the preferred procedure when malignancy is suspected in large tumors with possible local invasion. Despite the improvement of imaging techniques, they lack sufficient accuracy to exclude primary malignancy in tumors from 4 cm to 10 cm in size. An initial laparoscopic approach can be used in this group of patients, but early conversion to open technique is mandatory if curative resection cannot be performed. Adrenal tumors >10 cm of malignant potential should be treated by the open approach from the start. Solitary adrenal metastasis from another primary malignancy is usually amenable to laparoscopic surgery. Patients with suspected adrenal cancer should be referred to tertiary centers that perform laparoscopic and open adrenal surgery with minimal morbidity and mortality.

Paragangliomas: update on differential diagnostic considerations, composite tumors, and recent genetic developments

Recent developments in molecular genetics have expanded the spectrum of disorders associated with pheochromocytomas (PCCs) and extra-adrenal paragangliomas (PGLs) and have increased the roles of pathologists in helping to guide patient care. At least 30% of these tumors are now known to be hereditary, and germline mutations of at least 10 genes are known to cause the tumors to develop. Genotype-phenotype correlations have been identified, including differences in tumor distribution, catecholamine production, and risk of metastasis, and types of tumors not previously associated with PCC/PGL are now considered in the spectrum of hereditary disease. Important new findings are that mutations of succinate dehydrogenase genes SDHA, SDHB, SDHC, SDHD, and SDHAF2 (collectively "SDHx") are responsible for a large percentage of hereditary PCC/PGL and that SDHB mutations are strongly correlated with extra-adrenal tumor location, metastasis, and poor prognosis. Further, gastrointestinal stromal tumors and renal tumors are now associated with SDHx mutations. A PCC or PGL caused by any of the hereditary susceptibility genes can present as a solitary, apparently sporadic, tumor, and substantial numbers of patients presenting with apparently sporadic tumors harbor occult germline mutations of susceptibility genes. Current roles of pathologists are differential diagnosis of primary tumors and metastases, identification of clues to occult hereditary disease, and triaging of patients for optimal genetic testing by immunohistochemical staining of tumor tissue for the loss of SDHB and SDHA protein. Diagnostic pitfalls are posed by morphological variants of PCC/PGL, unusual anatomic sites of occurrence, and coexisting neuroendocrine tumors of other types in some hereditary syndromes. These pitfalls can be avoided by judicious use of appropriate immunohistochemical stains. Aside from loss of staining for SDHB, criteria for predicting risk of metastasis are still controversial, and "malignancy" is diagnosed only after metastases have occurred. All PCCs/PGLs are considered to pose some risk of metastasis, and long-term follow-up is advised.

Overexpression of the insulin-like growth factor 1 receptor (IGF-1R) is associated with malignancy in familial pheochromocytomas and paragangliomas

CONTEXT

Pheochromocytomas and paragangliomas (pheo/pgl) are neuroendocrine tumours derived from chromaffin cells. Although mostly benign, up to 26% of pheo/pgl will undergo malignant transformation. Reliable histological signs to differentiate benign pheo/pgl from malignant tumours are currently lacking. Increased IGF-1R expression has been shown during progression to metastatic phenotypes of several types of cancer.

OBJECTIVE

To analyse the distribution and expression of the IGF-1R in pheo/pgl of different genetic origin and degree of malignancy.

MEASUREMENTS

We studied the expression of the IGF-1R protein by immunohistochemistry, in 40 primary tumours from patients with pheo/pgl from different genetic aetiology (11 of 29 metastatic/nonmetastatic diseases).

RESULTS

We found a strong association between increased expression of IGF-1R and malignant behaviour regardless of the age at diagnosis and the genetic aetiology. IGF-1R labelling was mostly weak in primary tumours from patients with nonmetastatic pheo/pgl. Conversely, intense IGF-1R labelling was predominant in cases of pheo/pgl with confirmed metastatic disease. The risk of metastases was 11·7 times higher if tumour IGF-1R labelling was intense independently of age at diagnosis. The probability of remaining free of metastases was higher in patients with pheo/pgl scored weak for IGF-1R at 60 months and more than twofold higher at 120 months of follow-up than in patients with intense IGF-1R labelling in their primary tumours.

CONCLUSIONS

Our results strongly suggest that IGF-1R is associated with malignancy in familial pheo/pgl and that IGF-1R expression in the primary tumour might be a useful tool to detect those patients harbouring pheo/pgl who have an increased risk of metastasis.

Literature survey on epidemiology and pathology of gangliocytic paraganglioma

BACKGROUND

Although gangliocytic paraganglioma (GP) has generally been regarded as a neuroendocrine tumor, its origin remains unclear. We therefore aimed to investigate the details of this disease by carefully analyzing and extracting common features of the disease as presented in selected publications.

METHODS

We searched for English and Japanese cases of GP using the PubMed and IgakuChuoZasshi databases on August 2010. We then extracted and sampled raw data from the selected publications and performed appropriate statistical analyses. Additionally, we evaluated the expression of hormone receptors based on our previously reported case.

RESULTS

192 patients with GP were retrieved from the databases. Patient ages ranged from 15 y to 84 y (mean: 52.3 y). The gender ratio was 114:76 (male to female, 2 not reported). Maximum diameter of the tumors ranged from 5.5 mm to 100 mm (mean: 25.0 mm). The duodenum (90.1%, 173/192) was found to be the most common site of the disease. In 173 patients with duodenal GP, gastrointestinal bleeding (45.1%, 78/173) was found to be the most common symptom of the disease, followed by abdominal pain (42.8%, 74/173), and anemia (14.5%, 25/173). Rate of lymph node metastasis was 6.9% (12/173). Our statistical analysis indicated that significant differences were found for gender between GP within the submucosal layer and exceeding the submucosal layer. Furthermore, our immunohistochemical evaluation showed that both epithelioid and pancreatic islet cells showed positive reactivity for progesterone receptors.

CONCLUSIONS

Our literature survey revealed that there were many more cases of GP exceeding the submucosal layer than were expected. Meanwhile, our statistical analyses and immunohistochemical evaluation supported the following two hypotheses. First, vertical growth of GP might be affected by progesterone exposure. Second, the origin of GP might be pancreatic islet cells. However, it is strongly suspected that our data have been affected by publication bias and to confirm these hypotheses, further investigation is required.

Duodenal gangliocytic paraganglioma showing lymph node metastasis: a rare case report

We describe a case of duodenal gangliocytic paraganglioma showing lymph node metastasis. A 61-year-old Japanese man underwent pylorus preserving pancreaticoduodenectomy to remove a tumor at the papilla of Vater. The section of the tumor extending from the mucosa to submucosa of the duodenum was sharply demarcated, solid, and white-yellowish. Neither necrosis nor hemorrhage was present. Histological examination confirmed the immunohistochemical identification of three components comprising epithelioid cells, spindle-shaped cells, and ganglion-like cells. Epithelioid cells showed positive reactivity for synaptophysin, somatostatin, and CD56. In contrast, spindle-shaped cells showed positive reactivity for S-100 protein, but not for synaptophysin, somatostatin or CD56. Furthermore, we found lymph node metastasis despite lack of bcl-2 and p53 expression. In addition to the rarity of the tumor, we are describing here the present case suggests the malignant potency of the tumor despite lack of acceptable prognostic indicators for neuroendocrine tumor.

Asymptomatic extra-adrenal paraganglioma masquerading as retroperitoneal sarcoma

A 41-year-old man without clinical symptoms was referred for treatment of an enlarging retroperitoneal tumor. Enhanced computed tomography showed a well-defined and heterogeneously enhanced tumor, 4 cm in size, in the dorsal portion of the pancreas. A low-density nodule was detected in the left adrenal gland, 10 mm in diameter. Retroperitoneal sarcoma and nonfunctional left adrenal tumor were suspected, and surgical treatment was performed. During excision of the retroperitoneal tumor, blood pressure was extremely elevated when the tumor was compressed. Blood pressure normalized after excision of the tumor; thus, a diagnosis of paraganglioma was favored over that of retroperitoneal sarcoma. The left adrenal gland was resected together with the adrenal tumor. Microscopically, the tumor cells of the retroperitoneum had round to oval nuclei, and abundant granular amphophilic cytoplasm proliferated in nest-like fashion. Extra-adrenal retroperitoneal paraganglioma was considered, and the adrenal tumor was diagnosed as cortical adenoma. In patients with retroperitoneal tumor, even in the absence of clinical symptoms, we should keep in mind the possibility of extra-adrenal paraganglioma.