Gene/Protein Disease Symptom Drug Enzyme Compound
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The familial forms of pheochromocytoma have recently been demonstrated to be more frequent than believed in the past. The genes currently known to be responsible for tumor formation are RET, VHL, NF1, SDHB, SDHC and SDHD. Germline mutations of these genes increase the risk of developing pheochromocytomas and/or paragangliomas which variably associate with other neoplasms and characterize diverse clinical syndromes such as MEN 2, von Hippel-Lindau (VHL), and neurofibromatosis type 1 (NF 1), or the PGL syndromes, respectively. Although the pathogenesis of pheochromocytoma/paraganglioma formation is still largely unknown, studies of the familial forms have started to uncover some pathways that favor tumor formation, such as activation of tyrosine-kinase, induction of hypoxia-inducible factors, activation of the oncogene Ras or reduced apoptosis. These studies have also demonstrated that various gene mutations can differently affect the biological characteristics of pheochromocytoma: for example, while the tumors are mostly adrenergic (epinephrine secreting) and episodically secreting in MEN 2, they are mostly noradrenergic (norepinephrine secreting) and continuously secreting in VHL. Biological variability can also be observed in the PGL syndromes where tumors develop in the head and neck and are parasympathetic in origin and non-secreting, or in the thorax and the abdomen, where they are sympathetic in origin and catecholamine secreting. Genetic testing in patients with pheochromocytomas or paragangliomas is, at present, strongly recommended and is mandatory in young patients or in cases of multiple or recurrent tumors. The clinical picture and the biological characteristics of the tumor may suggest the priority of the genes to be tested first.
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PMID:Genetics and biology of pheochromocytoma. 1742 3

The incidence of gastrointestinal stromal tumors (GISTs) in children is exceptionally low. However, during the last decade these tumors attracted increasing attention, because they were found to express the cell surface transmembrane receptor kit (CD117) that has tyrosine kinase activity. This tyrosine kinase can be semi-selectively inhibited by signal transduction inhibitors such as imatinib mesylate (Glivec), which is a competitive inhibitor of c-kit, c-abl, platelet-derived growth factor receptor-alpha (PDGFR-alpha) and PDGFR-beta, and abl-related gene (arg). The authors present the clinical, radiographic, and pathological findings of 4 children who were diagnosed with gastric GIST. One of them had an incomplete Carney triad including GIST and mediastinal paraganglioma. All 4 patients presented with anemia and anemia-related symptoms and underwent total resection of the tumor. One patient received additional chemotherapy (in the pre-imatinib era) and 2 patients received a short course of imatinib mesylate. With a follow-up of 116, 55, 23, and 10 months all patients are alive in first complete continuous remission. In children and adolescents, particularly in female patients, GISTs should be included in the differential diagnosis of anemia secondary to gastrointestinal hemorrhage. Complete surgical resection is the mainstay of treatment for this tumor, with imatinib mesylate restricted to patients with advanced or metastatic tumors. Since late recurrences (up to 30 years following initial diagnosis) are reported, a life-long follow-up is mandatory in these patients.
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PMID:Clinical, radiological, and pathological findings in four children with gastrointestinal stromal tumors of the stomach. 1745 92

Efforts to understand the pathobiology of pheochromocytomas and extra-adrenal paragangliomas have been spurred by genetic and gene expression profiling studies showing genotype-phenotype correlations in familial pheochromocytoma/paraganglioma syndromes and in some sporadic tumors. The current challenge is to relate catalogs of genetic and phenotypic markers to cell biology. Hypothetical bases for genotype-phenotype correlations include: cell of origin, pathway dependence, and functional and anatomic context. A further consideration is phenotype plasticity. Cross talk between signaling pathways provides a general framework for understanding how mutations of apparently unrelated genes might lead to the same type of tumor, and also suggests that targeted therapies might be directed either at a specific mutated gene or a downstream signal transducer. However, precise mechanisms of tumorigenesis remain unknown. An intriguing hypothesis proposes that mutations of RET, NF1, VHL, or SDH predispose to hereditary pheochromocytoma/ paraganglioma by causing defective apoptotic culling of cells that would normally be destroyed during embryogenesis. An argument favoring survival rather than mitogenesis as a common denominator is that the same mutations are rare in sporadic pheochromocytomas/paragangliomas, suggesting they only need to act during a limited developmental window. An implication is that tumor precursors could be identified and eradicated in individuals who carry the mutations.
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PMID:Molecular and cellular biology of pheochromocytomas and extra-adrenal paragangliomas. 1752 80

Carney triad is a rare non-hereditary condition affecting young females and characterized by metachronous or synchronous occurrence of epithelioid gastrointestinal stromal tumours (GISTs), pulmonary chondroma and extra-adrenal paraganglioma. The genetic alterations in Carney triad-related GISTs have not been well studied. We evaluated GISTs from three females with incomplete Carney triad for KIT and PDGFRA mutations and studied the DNA by comparative genomic hybridization (CGH). All GISTs originated in the antrum and had a monotonous epithelioid morphology. Two patients had GISTs and pulmonary chondroma and one had GISTs and paraganglioma. Initial manifestation was GIST (n=1), pulmonary chondroma (n=1) and bladder paraganglioma (n=1). Time to the second component was 2-13 years. Two patients were alive at 108 and 168 months (one with metastases) and one died of the disease 3 years later. All cases were wild-type for KIT exons 9, 11, 13, 17 and PDGFRA exons 12 and 18. CGH revealed 14 aberrations (mean, 4.7/tumour) including 11 gains (X, 1q, 5p, 8q, 9p, 12p, 13q, 18p, 19q), 2 amplifications (1q, 19p) and one loss (13q). Carney triad-related GISTs do not only lack conventional KIT and PDGFRA mutations, but they also lack the non-random loss of 14q and 22q characteristic of their sporadic counterparts, suggesting an origin through a distinct pathogenetic pathway.
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PMID:Epithelioid gastric stromal tumours of the antrum in young females with the Carney triad: a report of three new cases with mutational analysis and comparative genomic hybridization. 1754 39

Gastrointestinal stromal tumors (GISTs) may be caused by germline mutations of the KIT and platelet-derived growth factor receptor-alpha (PDGFRA) genes and treated by Imatinib mesylate (STI571) or other protein tyrosine kinase inhibitors. However, not all GISTs harbor these genetic defects and several do not respond to STI571 suggesting that other molecular mechanisms may be implicated in GIST pathogenesis. In a subset of patients with GISTs, the lesions are associated with paragangliomas; the condition is familial and transmitted as an autosomal-dominant trait. We investigated 11 patients with the dyad of 'paraganglioma and gastric stromal sarcoma'; in eight (from seven unrelated families), the GISTs were caused by germline mutations of the genes encoding subunits B, C, or D (the SDHB, SDHC and SDHD genes, respectively). In this report, we present the molecular effects of these mutations on these genes and the clinical information on the patients. We conclude that succinate dehydrogenase deficiency may be the cause of a subgroup of GISTs and this offers a therapeutic target for GISTs that may not respond to STI571 and its analogs.
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PMID:Clinical and molecular genetics of patients with the Carney-Stratakis syndrome and germline mutations of the genes coding for the succinate dehydrogenase subunits SDHB, SDHC, and SDHD. 1766 67

Hyalinizing trabecular tumor (HTT) is a rare thyroid tumor of follicular cell origin with a trabecular pattern of growth and marked intratrabecular hyalinization. This tumor is known to share morphological and architectural similarities with paraganglioma and medullary thyroid carcinoma, as well as the nuclear features and RET/PTC1 translocations of papillary thyroid carcinoma. These tumors are not associated with RAS or BRAF mutations. Whether the presence of RET alterations in HTT are sufficient molecular proof of its relationship with papillary thyroid carcinoma (PTC) is still to be defined. Of great interest is the characteristic strong peripheral cytoplasmic and membranous staining of the tumor cells with MIB1 immunostain, not seen in any other thyroid neoplasm. Although cases of malignant HTT have been recorded, HTT should be considered a benign neoplasm or, at most, a neoplasm of extremely low malignant potential.
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PMID:Hyalinizing trabecular tumor of the thyroid: an update. 1796 May

von Hippel-Lindau disease, which is characterized by an increased risk of hemangioblastomas, clear cell renal carcinomas, and pheochromocytomas, is caused by inactivating mutations of the VHL tumor suppressor gene. The VHL gene product, pVHL, has multiple functions, but the best documented, and the one most clearly linked to tumor development, relates to its role as the substrate recognition module of a ubiquitin ligase complex that targets hypoxia-inducible factor (HIF) for destruction. pVHL function is often compromised in sporadic kidney cancers, and inhibitors of the HIF-responsive growth factor (vascular endothelial growth factor) are active against this disease. pVHL, by inhibiting atypical protein kinase C and hence JunB, also affects neuronal survival, as do the products of the other genes linked to familial pheochromocytoma or paraganglioma (NF1, RET, SDHB, SDHC, and SDHD). It is hypothesized that tumor-associated alleles of these genes allow primitive sympathoadrenal precursors to escape developmental culling, and that such cells are at increased risk of forming tumors.
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PMID:Von Hippel-Lindau disease. 1803 96

1. Recent clinical and fundamental research studies have revolutionized our understanding of the genetics of phaeochromocytoma (PH) and functional paraganglioma (FPGL). It was widely thought that only 10% of PH patients had familial disease and that the malignant phenotype of PH could not be diagnosed before occurrence of the first metastasis. 2. Human genetic studies have now shown that 25-30% of patients have hereditary PH due to a germline mutation in the SDHB, SDHD, VHL, RET or NF1 gene and that the identification of a germline SDHB mutation is associated with a high risk of malignancy and a poor prognosis in PH/PGL patients. 3. Fundamental research studies have shown that SDH genes are tumour suppressor genes and that succinate dehydrogenase inactivation induces abnormal stimulation of the hypoxia-angiogenesis pathway. 4. Finally various fundamental research studies, conducted through the Cortico and Medullo-surrenale: les Tumeurs Endocrines (COMETE) network in France and by other groups worldwide, have produced new recommendations for genetic counselling and testing and for the management of PH patients. They have also improved our understanding of the molecular mechanisms involved in PH tumorigenesis.
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PMID:Recent advances in the genetics of phaeochromocytoma and functional paraganglioma. 1830 24

Familial renal cell carcinoma (RCC) is a heterogeneous disorder that is most commonly caused by germline mutations in the VHL, MET, and FLCN genes or by constitutional chromosome 3 translocations. However, for many patients with familial RCC, the genetic basis of the disease is undefined. We investigated whether germline mutations in fumarate hydratase (FH) or succinate dehydrogenase subunit genes (SDHB, SDHC, SDHD) were associated with RCC susceptibility in 68 patients with no clinical evidence of an RCC susceptibility syndrome. No mutations in FH, SDHC, or SDHD were identified in probands, but 3 of the 68 (4.4%) probands had a germline SDHB mutation. Patients with a germline SDHB mutation presented with familial RCC (n = 1) or bilateral RCC (n = 2) and no personal or family history of pheochromocytoma or head and neck paraganglioma. Age at diagnosis of RCC in SDHB mutation carriers ranged from 24 to 73 years. These findings 1) demonstrate that patients with suspected inherited RCC should be examined for germline SDHB mutations, 2) suggest that all identified SDHB mutation carriers should be offered surveillance for RCC, and 3) provide a further link between familial RCC and activation of hypoxic-gene response pathways.
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PMID:Germline SDHB mutations and familial renal cell carcinoma. 1872 80

Hereditary susceptibility to pheochromocytoma (PCC) and paraganglioma (PGL) represents a very complex genetic scenario. It has been reported that the absence of familial antecedents of the disease does not preclude the existence of a mutation affecting any of the five major susceptibility genes. In fact, 11-24% of apparently sporadic cases (without familial or syndromic antecedents) harbor an unexpected germline mutation, but we do not know what is happening in "truly apparently" sporadic patients (i.e., apparently sporadic cases diagnosed with only one tumor). In the present study, we have analyzed 135 apparently sporadic patients developing a single tumor for the five major susceptibility genes: VHL, RET, SDHB, SDHC, and SDHD. Fourteen percent of cases were found to harbor a germline mutation, and only 2.2% of patients were older than 45 years at onset. By taking into account the tumor location and a threshold age at onset of 45 years, we propose a rational scheme for genetic testing. Analyzing VHL and RET genes would be recommended only in young patients developing a single PCC. On the other hand, genetic testing of SDHD should be done in all patients developing an extra-adrenal tumor before the age of 45, and SDHC could be the responsible gene in cases developing a single head and neck tumor, independently of age. Finally, the analysis of SDHB should always be performed because of its association to malignancy and the low penetrance of mutations affecting this gene.
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PMID:Rationalization of genetic testing in patients with apparently sporadic pheochromocytoma/paraganglioma. 1934 21


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