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  • Author: Arthur S Tischler x
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Arthur S Tischler and Ronald R deKrijger

Pathologists using their routine diagnostic tools can contribute both to the care of patients with pheochromocytoma/paraganglioma and to understanding the pathobiology of the tumors. They can document details of tissue organization and cytology that are accessible only by microscopy and can characterize admixtures of cell types that are morphologically distinct or show differential expression of immunohistochemical markers. Current roles and challenges for pathologists include differential diagnosis, identifying clues to the presence of hereditary disease, and effective communication of pathology information for clinical and research purposes. Future roles will increasingly involve risk stratification, identification of actionable targets for personalized therapies, and aiding the interpretation of molecular tests by helping characterize genetic variants of unknown significance. It remains to be determined to what extent the need for pathology input will be overshadowed by the availability of genetic testing and other molecular analyses at ever-decreasing cost, together with very effective clinical paradigms for risk stratification and patient care.

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James F Powers, Brent Cochran, James D Baleja, Hadley D Sikes, Xue Zhang, Inna Lomakin, Troy Langford, Kassi Taylor Stein and Arthur S Tischler

We describe a unique patient-derived xenograft (PDX) and cell culture model of succinate dehydrogenase-deficient gastrointestinal stromal tumor (SDH-deficient GIST), a rare mesenchymal tumor that can occur in association with paragangliomas in hereditary and non-hereditary syndromes. This model is potentially important for what it might reveal specifically pertinent to this rare tumor type and, more broadly, to other types of SDH-deficient tumors. The primary tumor and xenografts show a very high proliferative fraction, and distinctive morphology characterized by tiny cells with marked autophagic activity. It is likely that these characteristics resulted from the combination of the germline SDHB mutation and a somatic KRAS G12D mutation. The most broadly relevant findings to date concern oxygen and oxidative stress. In paragangliomas harboring SDHx mutations, both hypoxic signaling and oxidative stress are putative drivers of tumor growth. However, there are no models for SDH-deficient paragangliomas. This related model is the first from a SDHB-mutated human tumor that can be experimentally manipulated to study mechanisms of oxygen effects and novel treatment strategies. Our data suggest that tumor growth and survival require a balance between protective effects of hypoxic signaling vs deleterious effects of oxidative stress. While reduced oxygen concentration promotes tumor cell survival, a further survival benefit is achieved with antioxidants. This suggests potential use of drugs that increase oxidative stress as novel therapies. In addition, autophagy, which has not been reported as a major finding in any type of SDH-deficient tumor, is a potential target of agents that might trigger autophagic cell death.

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Lucia Martiniova, Shiromi M Perera, Frederieke M Brouwers, Salvatore Alesci, Mones Abu-Asab, Amanda F Marvelle, Dale O Kiesewetter, David Thomasson, John C Morris, Richard Kvetnansky, Arthur S Tischler, James C Reynolds, Antonio Tito Fojo and Karel Pacak

[131I]meta-iodobenzylguanidine ([131I]MIBG) is the most commonly used treatment for metastatic pheochromocytoma and paraganglioma. It enters the chromaffin cells via the membrane norepinephrine transporter; however, its success has been modest. We studied the ability of histone deacetylase (HDAC) inhibitors to enhance [123I]MIBG uptake by tumors in a mouse metastatic pheochromocytoma model. HDAC inhibitors are known to arrest growth, induce differentiation and apoptosis in various cancer cells, and further inhibit tumor growth. We report the in vitro and in vivo effects of two HDAC inhibitors, romidepsin and trichostatin A, on the uptake of [3H]norepinephrine, [123I]MIBG, and [18F]fluorodopamine in a mouse model of metastatic pheochromocytoma. The effects of both inhibitors on norepinephrine transporter activity were assessed in mouse pheochromocytoma (MPC) cells by using the transporter-blocking agent desipramine and the vesicular-blocking agent reserpine. HDAC inhibitors increased [3H]norepinephrine, [123I]MIBG, and [18F]fluorodopamine uptake through the norepinephrine transporter in MPC cells. In vivo, inhibitor treatment resulted in significantly increased uptake of [18F]fluorodopamine positron emission tomography (PET) in pheochromocytoma liver metastases (19.1±3.2% injected dose per gram of tumor (%ID/g) compared to liver metastases in pretreatment scans 5.9±0.6%; P<0.001). Biodistribution analysis after inhibitors treatment confirmed the PET results. The uptake of [123I]MIBG was significantly increased in liver metastases 9.5±1.1% compared to 3.19±0.4% in untreated control liver metastases (P<0.05). We found that HDAC inhibitors caused an increase in the amount of norepinephrine transporter expressed in tumors. HDAC inhibitors may enhance the therapeutic efficacy of [131I]MIBG treatment in patients with advanced malignant pheochromocytoma and paraganglioma.

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Graeme Eisenhofer, Stefan R Bornstein, Frederieke M Brouwers, Nai-Kong V Cheung, Patricia L Dahia, Ronald R de Krijger, Thomas J Giordano, Lloyd A Greene, David S Goldstein, Hendrik Lehnert, William M Manger, John M Maris, Hartmut P H Neumann, Karel Pacak, Barry L Shulkin, David I Smith, Arthur S Tischler and William F Young Jr

Pheochromocytomas are rare catecholamine-producing neuroendocrine tumors that are usually benign, but which may also present as or develop into a malignancy. Predicting such behavior is notoriously difficult and there are currently no curative treatments for malignant tumors. This report follows from a workshop at the Banbury Conference Center, Cold Spring Harbor, New York, on the 16th–18th November 2003, held to review the state of science and to facilitate future progress in the diagnosis and treatment of malignant pheochromocytoma. The rarity of the tumor and the resulting fragmented nature of studies, typically involving small numbers of patients, represent limiting factors to the development of effective treatments and diagnostic or prognostic markers for malignant disease. Such development is being facilitated by the availability of new genomics-based tools, but for such approaches to succeed ultimately requires comprehensive clinical studies involving large numbers of patients, stringently collected clinical data and tumor samples, and interdisciplinary collaborations among multiple specialist centers. Nevertheless, the well-characterized hereditary basis and the unique functional nature of these neuroendocrine tumors provide a useful framework that offers advantages for establishing the pathways of tumorigenesis and malignancy. Such findings may have relevance for understanding the basis of other more common malignancies where similar frameworks are not available. As the relevant pathways leading to pheochromocytoma are established it should be possible to take advantage of the new generation of drugs being developed to target specific pathways in other malignancies. Again the success of this will require well-designed and coordinated multicenter studies.

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Roland Därr, Joan Nambuba, Jaydira Del Rivero, Ingo Janssen, Maria Merino, Milena Todorovic, Bela Balint, Ivana Jochmanova, Josef T Prchal, Ronald M Lechan, Arthur S Tischler, Vera Popovic, Dragana Miljic, Karen T Adams, F Ryan Prall, Alexander Ling, Meredith R Golomb, Michael Ferguson, Naris Nilubol, Clara C Chen, Emily Chew, David Taïeb, Constantine A Stratakis, Tito Fojo, Chunzhang Yang, Electron Kebebew, Zhengping Zhuang and Karel Pacak

Worldwide, the syndromes of paraganglioma (PGL), somatostatinoma (SOM) and early childhood polycythemia are described in only a few patients with somatic mutations in the hypoxia-inducible factor 2 alpha (HIF2A). This study provides detailed information about the clinical aspects and course of 7 patients with this syndrome and brings into perspective these experiences with the pertinent literature. Six females and one male presented at a median age of 28 years (range 11–46). Two were found to have HIF2A somatic mosaicism. No relatives were affected. All patients were diagnosed with polycythemia before age 8 and before PGL/SOM developed. PGLs were found at a median age of 17 years (range 8–38) and SOMs at 29 years (range 22–38). PGLs were multiple, recurrent and metastatic in 100, 100 and 29% of all cases, and SOMs in 40, 40 and 60%, respectively. All PGLs were primarily norepinephrine-producing. All patients had abnormal ophthalmologic findings and those with SOMs had gallbladder disease. Computed tomography (CT) and magnetic resonance imaging revealed cystic lesions at multiple sites and hemangiomas in 4 patients (57%), previously thought to be pathognomonic for von Hippel–Lindau disease. The most accurate radiopharmaceutical to detect PGL appeared to be [18F]-fluorodihydroxyphenylalanine ([18F]-FDOPA). Therefore, [18F]-FDOPA PET/CT, not [68Ga]-(DOTA)-[Tyr3]-octreotate ([68Ga]-DOTATATE) PET/CT is recommended for tumor localization and aftercare in this syndrome. The long-term prognosis of the syndrome is unknown. However, to date no deaths occurred after 6 years follow-up. Physicians should be aware of this unique syndrome and its diagnostic and therapeutic challenges.

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Hartmut P Neumann, William F Young Jr, Tobias Krauss, Jean-Pierre Bayley, Francesca Schiavi, Giuseppe Opocher, Carsten C Boedeker, Amit Tirosh, Frederic Castinetti, Juri Ruf, Dmitry Beltsevich, Martin Walz, Harald-Thomas Groeben, Ernst von Dobschuetz, Oliver Gimm, Nelson Wohllk, Marija Pfeifer, Delmar M Lourenço Jr, Mariola Peczkowska, Attila Patocs, Joanne Ngeow, Özer Makay, Nalini S Shah, Arthur Tischler, Helena Leijon, Gianmaria Pennelli, Karina Villar Gómez de las Heras, Thera P Links, Birke Bausch and Charis Eng

Although the authors of the present review have contributed to genetic discoveries in the field of pheochromocytoma research, we can legitimately ask whether these advances have led to improvements in the diagnosis and management of patients with pheochromocytoma. The answer to this question is an emphatic Yes! In the field of molecular genetics, the well-established axiom that familial (genetic) pheochromocytoma represents 10% of all cases has been overturned, with >35% of cases now attributable to germline disease-causing mutations. Furthermore, genetic pheochromocytoma can now be grouped into five different clinical presentation types in the context of the ten known susceptibility genes for pheochromocytoma-associated syndromes. We now have the tools to diagnose patients with genetic pheochromocytoma, identify germline mutation carriers and to offer gene-informed medical management including enhanced surveillance and prevention. Clinically, we now treat an entire family of tumors of the paraganglia, with the exact phenotype varying by specific gene. In terms of detection and classification, simultaneous advances in biochemical detection and imaging localization have taken place, and the histopathology of the paraganglioma tumor family has been revised by immunohistochemical-genetic classification by gene-specific antibody immunohistochemistry. Treatment options have also been substantially enriched by the application of minimally invasive and adrenal-sparing surgery. Finally and most importantly, it is now widely recognized that patients with genetic pheochromocytoma/paraganglioma syndromes should be treated in specialized centers dedicated to the diagnosis, treatment and surveillance of this rare neoplasm.