Cys611Ser mutation in RET proto-oncogene in a kindred with medullary thyroid carcinoma and Hirschsprung's disease

The association between Hirschsprung's disease and multiple endocrine neoplasia type 2a: a systematic review

PURPOSE

The co-occurrence of Hirschsprung's disease (HSCR) and multiple endocrine neoplasia type 2 (MEN2) is a relatively rare event. The basis for this association is the presence of a "Janus" mutation in the RET proto-oncogene--a mutation that acts simultaneously as both a gain-in-function and a loss-of-function mutation. To date, four mutations in the exon 10 region of RET that are known to cause MEN2A have been implicated in this association: C620, C618, C611 and C609. We performed a systematic review of the published literature on this association to determine its incidence, the prevalence and phenotype of HSCR associated with the 4 RET mutations mentioned above.

METHODS

A systematic literature-based search for relevant articles was conducted using three online databases. After exclusion of ineligible publications, we recorded data on all patients with a diagnosis of HSCR or MEN2A with a "Janus" RET mutation, as well as those who carried the mutation but were unaffected. Statistical analysis was performed using SPSS.

RESULTS

The literature search yielded 885 publications, of which 36 articles, incorporating data on 341 individuals, were eligible for inclusion in the final analysis. Co-occurrence of HSCR and MEN2A was recorded in 84 cases (24.6 %). HSCR occurred alone in 64 carriers of a "Janus" mutation (18.8 %) and MEN2A occurred in isolation in 173 cases (50.7 %). Twenty individuals (5.9 %) were found to carry a "Janus" mutation after screening on the basis of family history but were unaffected by either MEN2A or HSCR. The most common mutation recorded was the C620 mutation [114 cases (48.1 %)]. There was a relatively high incidence of long-segment aganglionosis (29.3 %) and total colonic aganglionosis (17.3 %) in this cohort. This trend was particularly notable in those with C620 mutations, only 33 % of whom had short-segment disease.

CONCLUSION

While the overall incidence of HSCR co-occurring with MEN2A is low, both conditions occur with a relatively high frequency in families with a RET mutation at exon 10. The proportion of cases of long-segment HSCR and total colonic aganglionosis is higher than that in the general population with HSCR in those with C620 and C618 mutations. These findings reinforce the importance of RET mutation testing in HSCR when a family history of either HSCR or MEN2 is present. In families with MEN2A and known exon 10 RET mutations, the threshold for investigation for HSCR in those with gastrointestinal symptoms should be very low. High-quality prospective longitudinal studies of large HSCR populations are required to shed greater light on this rare but important phenomenon.

A MEN2A family with two asymptomatic carriers affected by unilateral renal agenesis

Accumulating evidences suggest RET gene's involvement in development of the kidney in mice and humans. Although it is well known that RET mutation causes multiple endocrine neoplasia type 2A (MEN2A), thus far only 3 individuals have been reported to have MEN2A and renal agenesis/dysgenesis. We report a MEN2A family with RET mutation in which two asymptomatic carriers presented with unilateral renal agenesis. A 48-year-old woman underwent total thyroidectomy with regional lymph node dissection in our department for medullary thyroid carcinoma. She had earlier surgical treatment for a left adrenal pheochromocytoma at the age of 45. In the screening for MEN type 2 for her three sons, a CT scan for adrenal pheochromocytoma incidentally found unilateral renal agenesis in two of the sons, one of whom had suffered from Hirschsprung's disease (HSCR). They had contralateral kidneys exhibiting compensatory hypertrophy and normal renal function. Genetic analysis detected C618R RET mutation in the proband and her 3 sons, and no other mutations were found in RET as well as glial cell line-derived neurotrophic factor (GDNF). Our data lend support to the hypothesis that constitutive active RET mutation in MEN type 2 might partially impair RET function and thereby cause loss of function phenotype such as renal agenesis or HSCR.

Thyroid cancer and co-occurring RET mutations in Hirschsprung disease

The objective of this study was to assess the occurrence of thyroid cancer and co-occurring RET mutations in a population-based cohort of adult Hirschsprung disease (HD) patients. All 156 patients operated for HD in a tertiary center during 1950-1986 were followed for thyroid malignancies up to 2010 through the nationwide Finnish Cancer Registry. Ninety-one individuals participated in clinical and genetic screening, which included serum calcitonin and thyroid ultrasound (US) with cytology. Exons 10, 11, 13, and 16 were sequenced in all, and all exons of RET in 43 of the subjects, including those with thyroid cancer, RET mutations, suspicious clinical findings, and familial or long-segment disease. Through the cancer registry, two cases (aged 35 and 37 years) of medullary thyroid cancer (MTC) were observed; the incidence for MTC was 340-fold (95% CI 52-1600) compared with average population. These individuals had C611R and C620R mutations in exon 10. One papillary thyroid cancer without RET mutations was detected by clinical screening. Four subjects (aged 31-50 years) with co-occurring RET mutations in exons 10 (C609R; n=1) and 13 (Y791F, n=3) had sporadic short-segment HD with normal thyroid US and serum calcitonin. Three novel mutations and five single-nucleotide polymorphisms were found outside exons 10 and 13 without associated signs of thyroid cancer. MTC-associated RET mutations were restricted to exons 10 and 13 affecting ∼5% of unselected adults with HD. Clinical thyroid assessment did not improve accuracy of genetic screening, which should not be limited to patients with familial or long-segment disease.

RET haplotype, not linked to the C620R activating mutation, associated with Hirschsprung disease in a novel MEN2 family

Hirschsprung disease is a congenital form of aganglionic megacolon that results from cristopathy. Hirschsprung disease usually occurs as a sporadic disease, although it may be associated with several inherited conditions, such as multiple endocrine neoplasia type 2. The rearranged during transfection (RET) proto-oncogene is the major susceptibility gene for Hirschsprung disease, and germline mutations in RET have been reported in up to 50% of the inherited forms of Hirschsprung disease and in 15-20% of sporadic cases of Hirschsprung disease. The prevalence of Hirschsprung disease in multiple endocrine neoplasia type 2 cases was recently determined to be 7.5% and the cooccurrence of Hirschsprung disease and multiple endocrine neoplasia type 2 has been reported in at least 22 families so far. It was initially thought that Hirschsprung disease could be due to disturbances in apoptosis or due to a tendency of the mutated RET receptor to be retained in the Golgi apparatus. Presently, there is strong evidence favoring the hypothesis that specific inactivating haplotypes play a key role in the fetal development of congenital megacolon/Hirschsprung disease. In the present study, we report the genetic findings in a novel family with multiple endocrine neoplasia type 2: a specific RET haplotype was documented in patients with Hirschsprung disease associated with medullary thyroid carcinoma, but it was absent in patients with only medullary thyroid carcinoma. Despite the limited number of cases, the present data favor the hypothesis that specific haplotypes not linked to RET germline mutations are the genetic causes of Hirschsprung disease.

Multiple endocrine neoplasia syndromes, children, Hirschsprung's disease and RET

Multiple endocrine neoplasia (MEN) type 2 syndromes are autosomal dominant clinical associations characterized by a common clinical feature, medullary thyroid carcinoma (MTC). The ability to accurately predict the risk by genetic RET proto-oncogene analysis has resulted in the active follow-up of children at risk for developing early metastatic tumours and which can be prevented by prophylactic thyroidectomy. The C634 and M918T mutations (associated with MEN2A and MEN2B, respectively) are particularly associated with early aggressive behavior and distant metastatic spread requiring early intervention. RET is known to be involved in cellular signalling processes during development and controls the survival, proliferation, differentiation and migration of the enteric nervous system (ENS) progenitor cells, as well as the survival and regeneration of sympathetic neural and kidney cells. The centrality of RET in the etiology of both MEN2 and HSCR is now well established with fairly consistent associations existing between RET genotype and phenotype in MEN2. The relationship between Hirschsprung's disease (HSCR) MEN2 syndromes appears to be a highly significant one, sharing a common etiological factor in the RET proto-oncogene. It is now well accepted that most HSCR arises from loss of function, RET mutations, RET haploinsufficiency or RET polymorphisms and haplotypes of the RET promotor region. MEN2 syndromes result from gene up regulation due to germline activating mutations in the RET proto-oncogene (1:500,000). MTC is mostly associated with variations in the 5 cysteine RET radicals and codon-risk management protocols are of considerable value but not infallible. Oncogenic RET mutations may, however, vary between specific population groups. RET analysis in MEN has revolutionized the management of children of MEN2 and allowed surgical prediction and prophylaxis to take place. We discuss the role of genetic testing and possible guidelines for the management of patients from MTC families. The future appears full of promise and the current evaluation of RET-targeting tyrosine kinase and other inhibitors are of considerable interest in the management of these conditions.

RET proto-oncogene testing in infants presenting with Hirschsprung disease identifies 2 new multiple endocrine neoplasia 2A kindreds

BACKGROUND

Multiple endocrine neoplasia 2A (MEN 2A) is a genetic syndrome manifesting as medullary thyroid carcinoma (MTC), hyperparathyroidism, and pheochromocytoma. Multiple endocrine neoplasia 2A results from mutations in the RET proto-oncogene. Hirschsprung disease (HSCR) is a rare manifestation of MEN 2A and has been described in known MEN 2A families.

METHODS

Here we describe 2 MEN 2A families that were only identified after the diagnosis of HSCR.

RESULTS

Kindred 1: A boy presented in infancy with HSCR. Genetic screening revealed a C609Y mutation, which is consistent with MEN 2A. Evaluation of his sister, father, and grandmother revealed the same mutation. All 3 had thyroidectomies demonstrating C-cell hyperplasia. The grandmother had a microscopic focus of MTC. Kindred 2: An infant boy and his sister were diagnosed with HSCR as neonates. Genetic testing demonstrated a C620R gene mutation consistent with MEN 2A. Total thyroidectomies revealed metastatic MTC in the father and C-cell hyperplasia in both children.

CONCLUSIONS

Hirschsprung disease can be the initial presentation of MEN 2A. We strongly recommend that genetic screening be performed in patients presenting with HSCR, looking for the known RET mutations associated with MEN 2A. If a mutation consistent with MEN 2A is detected, genetic screening of all first-degree relatives in the kindred is recommended.

RET tyrosine kinase signaling in development and cancer

The variety of diseases caused by mutations in RET receptor tyrosine kinase provides a classic example of phenotypic heterogeneity. Gain-of-function mutations of RET are associated with human cancer. Gene rearrangements juxtaposing the tyrosine kinase domain to heterologous gene partners have been found in sporadic papillary carcinomas of the thyroid (PTC). These rearrangements generate chimeric RET/PTC oncogenes. In the germline, point mutations of RET are responsible for multiple endocrine neoplasia type 2 (MEN 2A and 2B) and familial medullary thyroid carcinoma (FMTC). Both MEN 2 mutations and PTC gene rearrangements potentiate the intrinsic tyrosine kinase activity of RET and, ultimately, activate the RET downstream targets. Loss-of-function mutations of RET cause Hirschsprung's disease (HSCR) or colonic aganglionosis. A deeper understanding of the molecular signaling of normal versus abnormal RET activity in cancer will enable the development of potential new treatments for patients with sporadic and inherited thyroid cancer or MEN 2 syndrome. We now review the role and mechanisms of RET signaling in development and carcinogenesis.

RET proto-oncogene: a review and update of genotype-phenotype correlations in hereditary medullary thyroid cancer and associated endocrine tumors

Hereditary medullary thyroid carcinoma (MTC) is caused by autosomal dominant gain-of-function mutations in the RET proto-oncogene. Associations between specific RET mutations (genotype) and the aggressiveness of MTC and presence or absence of other endocrine neoplasms (phenotype) are well documented. Mutations in six exons (10, 11, 13, 14, 15, and 16) located in either cysteine-rich or tyrosine kinase domains cause one of three distinctive clinical subtypes: familial MTC, multiple endocrine neoplasia (MEN) type 2A (including variants with Hirschsprung's disease and cutaneous lichen amyloidosis), and MEN 2B. Hallmarks of MEN 2A include MTC, pheochromocytoma, and hyperparathyroidism. MEN 2B is associated with an earlier onset of MTC and pheochromocytoma, the absence of hyperparathyroidism, and the presence of striking physical stigmata (e.g., coarse facies, ganglioneuromatosis, and marfanoid habitus). Familial MTC is not associated with other endocrine neoplasms; however, the accurate distinction between familial MTC and MEN 2A may be difficult in kindreds with small size, incomplete histories, or a predominance of young individuals who may not have yet fully manifested the syndrome. Genetic testing detects greater than 95% of mutation carriers and is considered the standard of care for all first-degree relatives of patients with newly diagnosed MTC. Recommendations on the timing of prophylactic thyroidectomy and the extent of surgery are based upon a model that utilizes genotype- phenotype correlations to stratify mutations into three risk levels.

A novel Czech kindred with familial medullary thyroid carcinoma and Hirschsprung's disease

PURPOSE

The RET proto-oncogene is involved in neural crest disorders. Activating germline mutations in the RET proto-oncogene cause the development of familial medullary thyroid carcinoma (FMTC) or medullary thyroid carcinoma (MTC) as a part of multiple endocrine neoplasia type 2 (MEN2) syndrome. Inactivating germline mutations in the RET proto-oncogene are detected in Hirschsprung's disease (HSCR). Only in a very small number of families are these 2 diseases expressed together.

METHODS

This study presents a novel Czech kindred with FMTC-HSCR phenotype. Two family members (mother and daughter) were tested for RET germline mutations in exons 10, 11, 13, 14, 15, and 16.

RESULTS

Direct fluorescent sequencing of genomic DNA revealed a heterozygous mutation in the RET proto-oncogene in exon 10 at codon C609Y in both persons tested. This family was reclassified, thanks to genetic screening from the apparently sporadic MTC-HSCR to FMTC-HSCR.

CONCLUSION

The germline mutation was detected because of the systematic genetic screening of the RET proto-oncogene, which is useful for genetic counseling of potential risk of HSCR and MTC in other family members. This family could be added to the small worldwide cohort of families with MEN2A/FMTC-HSCR.

Multiple endocrine neoplasia type 2

Multiple endocrine neoplasia type 2 (MEN 2) is an autosomal dominant inherited cancer syndrome. Predisposition to MEN 2 is caused by germline mutations of the RET proto-oncogene on chromosome 10q11.2 [1]. There are three clinically distinct forms of MEN 2 syndrome -- MEN 2A, familial medullary thyroid carcinoma (FMTC), and MEN 2B. In all of these subtypes, medullary thyroid carcinoma (MTC) is a key. MEN 2A is the most common subtype of MEN 2. Clinical features of the MEN 2A syndrome include medullary thyroid carcinoma (MTC) and/or C-cell hyperplasia (CCH) in almost all affected individuals, pheochromocytoma (approximately 50%) and hyperparathyroidism (HPT) (15-30%). MEN type 2B is the most aggressive of the MEN 2 variants and accounts for approximately 5% of all cases of MEN 2. MEN 2B is similar to MEN 2A but is characterized by the earlier onset of the disease and by developmental abnormalities. In FMTC, the third form of MEN 2, MTC is the only clinical feature. Introduced in recent years and still developing genetic testing of individuals at highest hereditary risk of MEN 2 syndrome holds the possibility of early detection and improved treatment and prognosis.

Mutation of RET oncogene and endo-thelin B receptor gene in Hirschpru-ng's disease

AIM: To clarify the relationship between the mutation of RET and EDNRB genes and Chinese patients with Hirschspr-ung's disease (HD), and to investigate whether the two genes mutation concurred in the disease.

METHODS: Patients with HD were divided into RET/EDNRB group (group A, 56 cases) and ENDRB group (group B, 40 cases) at random. Healthy children were use as controls (group C, 56 and 40 cases). Genomic DNA was obtained from peripheral blood, then the exons 6, 13, 15 and 17 of RET gene and the exons 4, 5 and 6 of EDNRB gene were analyzed for gene mutation. The mutation products were automatically sequenced.

RESULTS: In group A, two heterozygous mutations at exons 17 and 13 were discovered in 2 sporadic HD patients. Direct DNA sequence analysis identified gene polymorphisms, which showed CTG→CTT, and Leu769→Leu. The sporadic mutation rate was 4% (2/48). Two heterozygous mutations were discovered in 2 familial HD patients at exon 15. DNA sequence analysis displayed a missense mutation Lys889→Thr in one patient and two silent mutation at codons V906 and S909 in another (GTGAAGAGGAGCCA→GTTAAGAGGAGTCA). The familial mutation rate was 25% (2/8). One heterozygous mutation of EDNRB gene at exon 5 in a sporadic short segmental patient failed to sequence. In group B, one heterozygous mutation was discovered in a sporadic short segmental patient. DNA sequence showed a G to A transversion at nucleotide 831, which resulted in a silent mutation Leu 277→Leu. The mutation rate was 2.7%(1/37). No mutation was detected in three familial HD patients. In group C, RET and EDNRB genes were identified no mutation. The difference of the RET gene mutation between the familial and sporadic patients by statistical analysis was x² = 4.95 (P < 0.05), odds ratio (OR) = 8; 95%CI = 1.28-49.87.

CONCLUSION: The mutation of RET and EDNRB genes reliably has correlated with the pathogenesis of HD. The RET gene mutation rate in familial HD patients is 25% and majority of sporadic cases have mutation in EDNRB gene. No HD patient has the two genes mutation at the same time. The risk of familial patients to get HD is 8 times higher than that of sporadic patients, and the confidence interval is 95%.