Stephen J. Marx

Menin Interacts with the AP1 Transcription Factor JunD and Represses JunD-Activated Transcription

MEN1 is a tumor suppressor gene that encodes a 610 amino acid nuclear protein (menin) of previously unknown function. Using a yeast two-hybrid screen with menin as the bait, we have identified the transcription factor JunD as a direct menin-interacting partner. Menin did not interact directly with other Jun and Fos family members. The menin-JunD interaction was confirmed in vitro and in vivo. Menin repressed transcriptional activation mediated by JunD fused to the Gal4 DNA-binding domain from a Gal4 responsive reporter, or by JunD from an AP1-responsive reporter. Several naturally occurring and clustered MEN1 missense mutations disrupted menin interaction with JunD. These observations suggest that menins tumor suppressor function involves direct binding to JunD and inhibition of JunD activated transcription.

HRPT2, encoding parafibromin, is mutated in hyperparathyroidism-jaw tumor syndrome.

We report here the identification of a gene associated with the hyperparathyroidism–jaw tumor (HPT–JT) syndrome. A single locus associated with HPT–JT (HRPT2) was previously mapped to chromosomal region 1q25–q32. We refined this region to a critical interval of 12 cM by genotyping in 26 affected kindreds. Using a positional candidate approach, we identified thirteen different heterozygous, germline, inactivating mutations in a single gene in fourteen families with HPT–JT. The proposed role of HRPT2 as a tumor suppressor was supported by mutation screening in 48 parathyroid adenomas with cystic features, which identified three somatic inactivating mutations, all located in exon 1. None of these mutations were detected in normal controls, and all were predicted to cause deficient or impaired protein function. HRPT2 is a ubiquitously expressed, evolutionarily conserved gene encoding a predicted protein of 531 amino acids, for which we propose the name parafibromin. Our findings suggest that HRPT2 is a tumor-suppressor gene, the inactivation of which is directly involved in predisposition to HPT–JT and in development of some sporadic parathyroid tumors.

Diagnosis of Asymptomatic Primary Hyperparathyroidism: Proceedings of the Third International Workshop

BACKGROUND At the Third International Workshop on Asymptomatic Primary Hyperparathyroidism (PHPT) in May 2008, recent data on the disease were reviewed. We present the results of a literature review on issues arising from the clinical presentation and natural history of PHPT. METHODS Questions were developed by the International Task Force on PHPT. A comprehensive literature search for relevant studies was reviewed, and the questions of the International Task Force were addressed by the Consensus Panel. CONCLUSIONS 1) Data on the extent and nature of cardiovascular involvement in those with mild disease are too limited to provide a complete picture. 2) Patients with mild PHPT have neuropsychological complaints. Although some symptoms may improve with surgery, available data remain inconsistent on their precise nature and reversibility. 3) Surgery leads to long-term gains in spine, hip, and radius bone mineral density (BMD). Because some patients have early disease progression and others lose BMD after 8-10 yr, regular monitoring (serum calcium and three-site BMD) is essential in those followed without surgery. Patients may present with normocalcemic PHPT (normal serum calcium with elevated PTH concentrations; no secondary cause for hyperparathyroidism). Data on the incidence and natural history of this phenotype are limited. 4) In the absence of kidney stones, data do not support the use of marked hypercalciuria (>10 mmol/d or 400 mg/d) as an indication for surgery for patients. 5) Patients with bone density T-score -2.5 or less at the lumbar spine, hip, or distal one third radius should have surgery.

NANETS treatment guidelines: Well-differentiated neuroendocrine tumors of the stomach and pancreas

Well-differentiated neuroendocrine tumors (NETs) of the stomach and pancreas represent 2 major subtypes of gastrointestinal NETs. Historically, there has been little consensus on the classification and management of patients with these tumor subtypes. We provide an overview of well-differentiated NETs of the stomach and pancreas and describe consensus guidelines for the treatment of patients with these malignancies.

Molecular genetics of multiple endocrine neoplasia types 1 and 2

Six multiple endocrine neoplasia (MEN) syndromes have received a level of attention that might seem disproportionate to their low prevalence. The attention has been given because their hormonal excesses cause striking metabolic expressions and because they might clarify pathways disrupted in more common tumours. The recent discovery of the main gene in each MEN syndrome has furthered our understanding of not only hereditary but also sporadic tumours and has fostered new avenues of research.

The tumor suppressor protein menin interacts with NF-κB proteins and inhibits NF-κB-mediated transactivation

Multiple endocrine neoplasia type 1 is an autosomal dominant tumor syndrome. Manifestations include neoplasms of the parathyroid glands, enteropancreatic neuroendocrine cells, and the anterior pituitary gland. The MEN1 tumor suppressor gene encodes menin, a 610 amino acid nuclear protein without sequence homology to other proteins. To elucidate menin function, we used immunoprecipitation to identify interacting proteins. The NF-κB proteins p50, p52 and p65 were found to interact specifically and directly with menin in vitro and in vivo. The region of NF-κB proteins sufficient for binding to menin is the N-terminus. Furthermore, amino acids 305–381 of menin are essential for this binding. Menin represses p65-mediated transcriptional activation on NF-κB sites in a dose-dependent and specific manner. Also, PMA (phorbol 12-myristate 13-acetate)-stimulated NF-κB activation is suppressed by menin. These observations suggest that menins ability to interact with NF-κB proteins and its modulation of NF-κB transactivation contribute to menins tumor suppressor function.

Resistance to multiple hormones in patients with pseudohypoparathyroidism. Association with deficient activity of guanine nucleotide regulatory protein.

Abstract Pseudohypoparathyroidism type I is characterized by resistance (defined as a deficient urinary cAMP response) to parathyroid hormone and, in most cases, hypocalcemia and hyperphosphatemia. Many patients with pseudohypoparathyroidism type I snow a peculiar somatic phenotype termed Albrights hereditary osteodystrophy, but patients without this feature who show identical parathyroid hormone resistance have been described. Parathyroid hormone resistance in pseudohypoparathyroidism type I has been attributed to a defective parathyroid hormone receptor-adenylate cyclase complex. Recent studies have demonstrated deficient activity of the guanine nucleotide regulatory protein (G unit) of adenylate cyclase in many patients with Pseudohypoparathyroidism. Since the G unit is common to all tissues, as opposed to hormone receptors, which are tissue specific, a defective G unit should lead to resistance to multiple hormones that act by stimulating adenylate cyclase. To test this hypothesis, we studied erythrocyte G unit activity and clinical endocrine function in 29 patients with pseudohypoparathyroidism type I. Thirteen patients had deficient erythrocyte G unit activity (43 ± 9 percent of control [mean ± 1 SD]); 16 patients had normal G unit activity (92 ± 8 percent of control) (p

Familial isolated hyperparathyroidism: clinical and genetic characteristics of 36 kindreds.

Familial hyperparathyroidism (HPT) encompasses a clinically and genetically heterogeneous group of disorders. Syndromes with familial HPT include multiple endocrine neoplasia type 1 (MEN1) (Mendelian Inheritance in Man [MIM] 1311001) (63, 87), multiple endocrine neoplasia type 2A (MEN2A) (MIM 171400)(42, 79, 86), familial hypocalciuric hypercalcemia (FHH) (MIM 145980, 145981, 600740) also known as familial benign hypercalcemia (38, 64), and the hyperparathyroidism-jaw tumor syndrome (HPT-JT; HRPT2) (MIM 145001) (45). Familial isolated hyperparathyroidism2 (FIH; HRPT1) (MIM 145000) is a subgroup of familial HPT that can result from the incomplete expression of a syndromic form of familial HPT or from full expression of other entities (Figure 1). It is unknown how many as yet unrecognized clinical entities, including mutant genotypes, can also present as FIH. MEN1 is an autosomal dominant disorder characterized by endocrine and nonendocrine tumors, most strikingly involving the parathyroids, enteropancreatic endocrine system, and pituitary. Because FIH is seen less frequently than full expressions of MEN1, because HPT is the earliest and most frequent endocrinopathy in MEN1, and because even some large families with an apparent phenotype of FIH ultimately express MEN1, we (59, 67) and others (2, 61) previously speculated that most kindreds with FIH were occult expressions of MEN1. The gene responsible for MEN1 has been cloned (15), leading to powerful gene sequencing methods applicable to MEN1, FIH, and other conditions (63). MEN2A, unlike MEN1, is not typically a consideration in the differential diagnosis of FIH, because the higher penetrance of medullary thyroid carcinoma and pheochromocytoma than of HPT in MEN2A dominates the clinical presentation in a family (42, 79, 86). FHH is an autosomal dominant trait usually causing mild HPT (62) with relative hypocalciuria; hypercalcemia in FHH is highly penetrant at all ages, even in the perinatal period (64). Mild hypermagnesemia is sometimes seen in FHH but is unusual in other forms of primary HPT (53, 64). FHH cases almost always remain hypercalcemic following standard subtotal parathyroidectomy (PTX) (64). FHH always presents 0025-7974/02/8101-0001/0 MEDICINE® 81: 1-26, 2002 Vol. 81, No. 1 Copyright

Deficient activity of guanine nucleotide regulatory protein in erythrocytes from patients with pseudohypoparathyroidism

Abstract The activity in two assay systems of guanine nucleotide regulatory protein was significantly lower in red cells from pseudohypoparathyroid patients compared to that of normal subjects. The results support the hypothesis that deficient activity of the guanine nucleotide regulatory protein is the molecular basis for hormone resistance in this inherited disorder.

A prospective trial evaluating a standard approach to reoperation for missed parathyroid adenoma.

OBJECTIVES The authors evaluate the results of preoperative imaging protocols and surgical re-exploration in a series of patients with missed parathyroid adenomas after failed procedures for primary hyperparathyroidism. BACKGROUND The success rate is lower and the complication rate is increased in patients undergoing reoperation for primary hyperparathyroidism compared with initial procedures. Scarring and distortion of tissue planes plus the potential for ectopic gland location leads to this worsened outcome. METHODS Two hundred eighty-eight consecutive patients with persistent/recurrent hyperparathyroidism were treated at a single institution after a failed procedure or procedures at outside institutions. Two hundred twenty-two of these patients (77%) were believed to have a missed single adenoma, and these patients underwent 228 operations and 227 preoperative work-ups. Preoperative evaluation consisted of a combination of four noninvasive imaging studies--neck ultrasound, nuclear medicine scan, neck and mediastinal computed tomography scan, and neck and mediastinal magnetic resonance imaging. Based on the noninvasive testing alone, 27% patients underwent surgery whereas the other patients underwent invasive studies, including selective angiography (58%), selective venous sampling for parathyroid hormone (43%), or percutaneous aspiration of suspicious lesions (15%). RESULTS Abnormal parathyroid adenomas were found in 209 of 222 initial procedures and 6 of 6 second procedures, with an overall success rate in terms of resolution of hypercalcemia in 97% (215/222) of patients. The single most common site of missed adenoma glands was in the tracheal-esophageal groove in the posterior superior mediastinum (27%). The most common ectopic sites for parathyroid adenomas are thymus (17%), intrathyroidal (10%), undescended glands (8.6%), carotid sheath (3.6%), and the retroesophageal space (3.2%). The most sensitive and specific noninvasive imaging test is the sestamibi subtraction scan, with 67% true-positive and no false-positive results. The rate of true-positive and false-positive results for ultrasound, computed tomography, magnetic resonance imaging, and technetium thallium scans were 48%/21%, 52%/16%, 48%/14% and 42%/8%, respectively. The incidence of injury to the recurrent laryngeal nerve was 1.3%. CONCLUSIONS A single missed parathyroid adenoma is the most common cause for a failed initial parathyroid operation. Appropriate use of preoperative imaging tests and knowledge of the potential location or parathyroid adenomas can lead to very high cure rates with minimal morbidity.