Thalia Bei

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.

Gastrointestinal stromal tumors (GISTs) may be caused by germline mutations of the KIT and platelet-derived growth factor receptor-α (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.

Loss of expression of protein kinase A regulatory subunit 1α in pigmented epithelioid melanocytoma but not in melanoma or other melanocytic lesions

Pigmented epithelioid melanocytoma (PEM) is a recently described entity comprising most cases previously described as “animal-type melanoma” and epithelioid blue nevus (EBN) occurring in patients with the multiple neoplasia syndrome Carney complex (CNC). Mutations of the protein kinase A regulatory subunit type 1α (R1α) (coded by the PRKAR1A gene) are found in more than half of CNC patients. In this study, we investigated whether PEM and EBN are related at the molecular level, and whether changes in the PRKAR1A gene status and the expression of the R1α protein may be involved in the pathogenesis of PEM and other melanocytic lesions. Histologic analysis of hematoxylin and eosin-stained sections and immunohistochemistry (IHC) with R1α antibody were performed on 34 sporadic PEMs, 8 CNC-associated PEMs from patients with known PRKAR1A mutations, 297 benign and malignant melanocytic tumors (127 conventional sections of 10 compound nevi, 10 Spitz nevi, 5 deep-penetrating nevi, 5 blue nevi, 6 cellular blue nevi, 2 malignant blue nevi, 3 lentigo maligna, and 86 melanomas of various types); in addition, 170 tissue microarray sections consisting of 35 benign nevi, 60 primary melanomas, and 75 metastatic melanomas, and 5 equine dermal melanomas, were examined. Histologic diagnoses were based on preexisting pathologic reports and were confirmed for this study. DNA studies [loss of heterozygosity (LOH) for the 17q22-24 locus and the PRKAR1A gene sequencing] were performed on 60 melanomas and 7 PEMs. IHC showed that R1α was expressed in all but one core from tissue microarrays (169/170), and in all 127 melanocytic lesions evaluated in conventional sections. By contrast, R1α was not expressed in the 8 EBN from patients with CNC and PRKAR1A mutations. Expression of R1α was lost in 28 of 34 PEMs (82%). R1α was expressed in the 5 equine melanomas studied. DNA studies correlated with IHC findings: there were no PRKAR1A mutations in any of the melanomas studied and the rate of LOH for 17q22-24 was less than 7%; 5 of the 7 PEMs showed extensive 17q22-24 LOH but no PRKAR1A mutations. The results support the concept that PEM is a distinct melanocytic tumor occurring in a sporadic setting and in the context of CNC. They also suggest that PEM differs from melanomas in equine melanotic disease, further arguing that the term animal-type melanoma may be a misnomer for this group of lesions. Loss of expression of R1α offers a useful diagnostic test that helps to distinguish PEM from lesions that mimic it histologically.

PRKAR1A, one of the Carney complex genes, and its locus (17q22-24) are rarely altered in pituitary tumours outside the Carney complex.

The tumour suppressor gene encoding the cAMP dependent protein kinase A (PKA) type I-α regulatory subunit (RIα), PRKAR1A , has been mapped to chromosome 17q22-24 and is often mutated in the Carney complex (CNC),1,2 a multiple neoplasia and lentiginosis syndrome inherited in an autosomal dominant manner.3,4 The complex was first described as an association of lentigines, primary pigmented nodular adrenocortical disease (PPNAD), and a variety of endocrine and non-endocrine tumours (cardiac and breast myxomas).5–7 Growth hormone (GH) and prolactin (PRL) secretion abnormalities have been found in over two-thirds of patients with CNC8,9; in some cases, pituitary somatomammotrophic hyperplasia was also seen.8 GH producing adenomas (which also secrete small amounts of PRL) have been reported with increased frequency in patients with CNC; it was suggested that tumours in these patients develop in situ from precursor benign hyperplasia, following a sequence of genetic events not unlike the one described in other tissues.10,11 Genes implicated in cyclic nucleotide dependent signalling have long been considered likely candidates for pituitary tumorigenesis.12,13 Somatic activating mutations in the GNAS1 gene, which encodes the α subunit of the stimulatory G protein, lead to increased cAMP production and have been reported in approximately half of sporadic pituitary adenomas associated with acromegaly.14–16 In addition, methylation abnormalities of the GNAS1 gene are present in a significant number of pituitary tumours.17 Patients with McCune-Albright syndrome develop GH and PRL producing pituitary hyperplasia17,18 and their pituitary tissue harbours, as other affected tissues in these patients, somatic, activating mutations of the GNAS1 gene.19–21 In the present study, we investigated a large collection of sporadic pituitary adenomas (SPA) from the USA, UK, Japan, and France for loss of heterozygosity (LOH) of the 17q22-24 PRKAR1A …

Association of a COL1A1 polymorphism with lumbar disc disease in young military recruits

Background: Lumbar disc disease (LDD), one of the most common conditions for which patients seek medical care, has been associated with sequence changes of the COL genes. COL1A1, however, has not been studied in young patients with LDD; COL1A1 polymorphisms have been associated with bone mineral density (BMD) in several populations and with LDD in older adults. Objective: To study COL1A1 polymorphisms in young Greek army recruits with LDD. Subjects: These young soldiers were diagnosed with early LDD at the time of their presentation to a military training site. All patients had radiological confirmation of their disease; a control group was also studied. Methods: Sp1-binding site polymorphism of the COL1A1 gene was investigated by standard methods. Results: There was an increased frequency of the “ss” genotype (33.3%) in LDD patients; none of the controls had this genotype. In addition, a significantly smaller number of controls was heterozygotes for this allele. Conclusions: A previously studied sequence change of the regulatory region of the COL1A1 gene, the same as has previously been associated with low BMD in many populations and LDD in older adults, showed a strong association with LDD in young male soldiers who were recently diagnosed with this disease.

Greek BRCA1 and BRCA2 mutation spectrum: two BRCA1 mutations account for half the carriers found among high-risk breast/ovarian cancer patients

Abstract127 Greek breast/ovarian cancer families were screened for germline BRCA1/2 mutations by dHPLC followed by direct sequencing. Our results indicated 16 and 5 breast/ovarian cancer families bearing deleterious mutations in the BRCA1 and BRCA2 genes, respectively. Two novel BRCA2 germline mutations (G4X and 3783del10) are reported here for the first time. Subsequent compilation of our present findings with previously reported mutation data reveals that in a total of 287 Greek breast/ovarian cancer families, 46 and 13 carry a deleterious mutation in BRCA1 and BRCA2, respectively. It should be noted that two BRCA1 mutations, 5382insC and G1738R, both located in exon 20, account for 46% of the families found to carry a mutation. Based on our mutation analysis results, we propose here a hierarchical, cost-effective BRCA1/2 mutation screening protocol for individuals of Greek ethnic origin. The suggested protocol can impact on the clinical management of breast-ovarian cancer families on a national healthcare system level.

A rare RET gene exon 8 mutation is found in two Greek kindreds with familial medullary thyroid carcinoma: implications for screening

Objective  Familial medullary thyroid carcinoma (FMTC) is caused by germ‐line mutations in the RET proto‐oncogene. These mutations concern mainly cysteine residues in exons 10 and 11, whereas noncysteine mutations in exons 13–16 are rare. Mutations in other exons have been reported only in isolated families. In this study we have analysed the RET gene in two FMTC families negative for mutations in the above exons.

Molecular cloning, chromosomal localization of human peripheral-type benzodiazepine receptor and PKA regulatory subunit type 1A (PRKAR1A)-associated protein PAP7, and studies in PRKAR1A mutant cells and tissues

A mouse protein that interacts with the peripheral‐type benzodiazepine receptor (PBR) and cAMP‐dependent protein kinase A (PKA) regulatory subunit RIα (PRKAR1A), named PBR and PKA‐associated protein 7 (PAP7), was identified and shown to be involved in hormone‐induced steroid biosynthesis. We report the identification of the human PAP7 gene, its expression pattern, genomic structure, and chromosomal mapping to 1q32–1q41. Human PAP7 is a 60‐kDa protein highly homologous to the rodent protein. PAP7 is widely present in human tissues and highly expressed in seminal vesicles, pituitary, thyroid, pancreas, renal cortex, enteric epithelium, muscles, myocardium and in steroidogenic tissues, including the gonads and adrenal cortex. These tissues are also targets of Carney complex (CNC), a multiple neoplasia syndrome caused by germline inactivating PRKAR1A mutations (PRKAR1A‐mut) and associated with primary pigmented nodular adrenocortical disease (PPNAD) and increased steroid synthesis. PAP7 and PRKAR1A expression were studied in PPNAD and in lymphoblasts from patients bearing PRKARlA‐mut. Like PRKAR1A, PAP7 was decreased in CNC lymphocytes and PPNAD nodules, but not in the surrounding cortex. These studies showed that, like in the mouse, human PAP7 is highly expressed in steroidogenic tissues, where it follows the pattern of PRKAR1A expression, suggesting that it participates in PRKAR1A‐mediated tumorigenesis and hypercortisolism.

Functioning paraganglioma and gastrointestinal stromal tumor of the jejunum in three women: Syndrome or coincidence

Functioning paraganglioma and gastrointestinal stromal tumor (GIST) are uncommon tumors that occur mostly in a sporadic and isolated form, occasionally as components of multiple neoplasia syndromes, either separately or together. Separately, they occur in several inherited syndromes including multiple endocrine neoplasia 2, and the GIST, lentigines, and mast cell tumor syndrome. Together, they are variably prominent components of three syndromes: the familial paraganglioma and gastric GIST syndrome, neurofibromatosis type 1, and the Carney triad. The two former conditions are inherited as autosomal dominant traits; the latter does not appear to be inherited and affects young women predominantly. This article reports the nonfamilial occurrence of functioning paraganglioma and GIST of the jejunum in 3 women, 1 young (22 years) at initial presentation. The occurrences were unexpected because of the infrequency of the tumors. The neoplasms, respectively, did not show germline SDHA, SDHB, SDHC, and SDHD, and KIT mutations associated with familial paraganglioma and familial GIST. The paraganglioma-jejunal GIST combination may be the harbinger of a rare genetic syndrome, a variant of the Carney triad or the paraganglioma-gastric stromal sarcoma syndrome, or be coincidental.