A new double substitution mutation in the MEN1 gene: a limited penetrance and a specific phenotype

Comprehensive Analysis of MEN1 Mutations and Their Role in Cancer

Simple Summary

Cancers are characterized by accumulation of genetic mutations in key cell cycle regulators that alter or disable the function of these genes. Such mutations can be inherited or arise spontaneously during the life of the individual. The MEN1 gene prevents uncontrolled cell division and it is considered a tumor suppressor. Inherited MEN1 mutations are associated with certain parathyroid and pancreatic syndromes while spontaneous mutations have been detected in cancer cells. We investigated whether inherited mutations appear in cancer cells which would suggest that patients with parathyroid and pancreatic syndromes have a predisposition to develop cancer. We find a weak correlation between the spectrum of inherited mutations and those appearing spontaneously. Thus, inherited MEN1 mutations may not be a good predictor of tumorigenesis.

Abstract

MENIN is a scaffold protein encoded by the MEN1 gene that functions in multiple biological processes, including cell proliferation, migration, gene expression, and DNA damage repair. MEN1 is a tumor suppressor gene, and mutations that disrupts MEN1 function are common to many tumor types. Mutations within MEN1 may also be inherited (germline). Many of these inherited mutations are associated with a number of pathogenic syndromes of the parathyroid and pancreas, and some also predispose patients to hyperplasia. In this study, we cataloged the reported germline mutations from the ClinVar database and compared them with the somatic mutations detected in cancers from the Catalogue of Somatic Mutations in Cancer (COSMIC) database. We then used statistical software to determine the probability of mutations being pathogenic or driver. Our data show that many confirmed germline mutations do not appear in tumor samples. Thus, most mutations that disable MEN1 function in tumors are somatic in nature. Furthermore, of the germline mutations that do appear in tumors, only a fraction has the potential to be pathogenic or driver mutations.

Diagnosis and Management of Hereditary Carcinoids

Carcinoid tumours arise in cells of the diffuse neuroendocrine system and can develop in a number of anatomical sites including the lungs and the gastrointestinal tract. There has been a move away from the use of the term carcinoid tumour to the more appropriate use of neuroendocrine tumour (NET) to highlight the potential for invasion and metastasis associated with some NETs. Although most cases are sporadic, 15-20% of cases are related to a hereditary syndrome, the most common of these being multiple endocrine neoplasia 1 (MEN1). Other hereditary syndromes include the following: von Hippel-Lindau (VHL), neurofibromatosis 1 and tuberous sclerosis complex (TSC), which are all associated with a germline mutation of the associated tumour suppressor gene and an autosomal dominant inheritance pattern. Familial small intestinal NET (SI NET) is a recently described condition which is also inherited in an autosomal dominant manner. There appears to be more than one causative gene; thus far, only the IPMK gene has been identified as a causative germline mutation. This was identified by carrying out whole-exome sequencing of germline and tumour DNA in a family with multiple members diagnosed with SI NET. Identification of NET predisposition genes in other families via these methods will allow the development of dedicated NET gene panels which can be used to screen NET patients and at-risk relatives for hereditary mutations. Close surveillance of at-risk individuals is important to detect NETs early when curative surgery can be offered and the morbidity and mortality of metastatic NETs can be avoided.

Genetic test in multiple endocrine neoplasia type 1 syndrome: An evolving story

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant inherited tumour syndrome expressing various endocrine and non-endocrine lesions and tumours. Since the identification of the causative gene, the oncosuppressor gene MEN1, in 1997, genetic testing has revealed an important approach for the early and differential diagnosis of the disease. The finding of a MEN1 mutation in a patient has important clinical implications for relatives since it allows very early disease diagnosis and identification of carriers, even before biochemical and/or clinical manifestation, permitting their inclusion in a specific program of surveillance and subsequent praecox therapy. Currently, genetic testing for MEN1 consists principally of the sequencing of coding regions and intron-exon junctions of the MEN1 gene. However, the recent acquisition of novel high throughput technologies will allow the design of innovative, accurate, complete and rapid genetic diagnosis. These new tools are able to increase the strength of the analysis and almost completely eliminate the possibility of false negative results. This review aims to give an overview on genetic testing of MEN1 syndrome, reporting the positive aspects of performing the analysis and the future perspectives for improving the performance of the test, as well as its application in clinical practice.

Early-onset, severe, and recurrent primary hyperparathyroidism associated with a novel CDC73 mutation

Hyperparathyroidism-jaw tumor syndrome (HPT-JT) is a rare autosomal dominant hereditary tumor syndrome characterized by synchronous or metachronous occurrence of primary hyperparathyroidism (PHPT), ossifying fibroma of the maxilla and/or mandible, renal tumor and uterine tumors. Early diagnosis of this syndrome is essential because it is associated with increased risk of parathyroid cancer. A 30-year-old man with urolithiasis had severe hypercalcemia (15.0 mg/dL after correction) induced by inappropriate parathyroid hormone (PTH) secretion (intact PTH 1390 pg/mL), indicating severe PHPT. An underlying parathyroid tumor was surgically removed and was histologically confirmed to be an adenoma. However, PHPT due to another parathyroid tumor reoccurred two years after the surgery. Although no HPT-JT-associated manifestations other than PHPT were detected, HPT-JT was strongly suspected based on the exclusion of multiple endocrine neoplasia (MEN) and the young age of disease occurrence. Genetic analysis revealed a novel nonsense mutation (p.Arg91X; c.271C>T) in exon 3 of the causative gene, CDC73, which encodes the tumor suppressor protein parafibromin. The residual parathyroid glands were all removed without autotransplantation of parathyroid gland taking into consideration prospective parathyroid carcinogenesis. The resected parathyroid tumor was also an adenoma. The present case highlights that HPT-JT should be considered and CDC73 mutation analysis should be performed, especially in cases of early-onset PHPT, recurrent PHPT, PHPT with polyglandular parathyroid involvement, and PHPT presenting with severe hypercalcemia even if there is no positive family history.

Standards of care intended for multiple endocrine neoplasia families

In the past, the medical expenditure for multiple endocrine neoplasia families was high and the course of their disease not predictable. In a couple of decades, the prospects changed completely. The genetic origin of the diseases is well known and prevention is possible, whereas in advanced stages target-directed treatment is coming within reach. The most important change is the responsibility for these families. Initially, this was completely the task of the attending physician, whereas at this moment patients and disease gene carriers themselves have the central responsibility with respect to these diseases. Unfortunately, for them information about the disease is insufficiently available.