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Sahakian N, Castinetti F, Romanet P. Molecular Basis and Natural History of Medullary Thyroid Cancer: It is (Almost) All in the RET. Cancers (Basel) 2023; 15:4865. [PMID: 37835559 PMCID: PMC10572078 DOI: 10.3390/cancers15194865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 09/20/2023] [Accepted: 09/29/2023] [Indexed: 10/15/2023] Open
Abstract
Medullary thyroid cancer (MTC) is a rare disease, which can be either sporadic (roughly 75% of cases) or genetically determined (multiple endocrine neoplasia type 2, due to REarranged during Transfection RET germline mutations, 25% of cases). Interestingly, RET pathogenic variants (mainly M918T) have also been reported in aggressive forms of sporadic MTC, suggesting the importance of RET signalling pathways in the pathogenesis of MTC. The initial theory of RET codon-related MTC aggressiveness has been recently questioned by studies suggesting that this would only define the age at disease onset rather than the aggressiveness of MTC. Other factors might however impact the natural history of the disease, such as RET polymorphisms, epigenetic factors, environmental factors, MET (mesenchymal-epithelial transition) alterations, or even other genetic alterations such as RAS family (HRAS, KRAS, NRAS) genetic alterations. This review will detail the molecular bases of MTC, focusing on RET pathways, and the potential mechanisms that explain the phenotypic intra- and interfamilial heterogeneity.
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Affiliation(s)
- Nicolas Sahakian
- Aix Marseille Univ, APHM, INSERM, MMG, La Conception University Hospital, Department of Endocrinology, Marseille, France; (N.S.); (F.C.)
| | - Frédéric Castinetti
- Aix Marseille Univ, APHM, INSERM, MMG, La Conception University Hospital, Department of Endocrinology, Marseille, France; (N.S.); (F.C.)
| | - Pauline Romanet
- Aix Marseille Univ, APHM, INSERM, MMG, La Conception University Hospital, Laboratory of Molecular Biology, Marseille, France
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2
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Verrienti A, Grani G, Sponziello M, Pecce V, Damante G, Durante C, Russo D, Filetti S. Precision oncology for RET-related tumors. Front Oncol 2022; 12:992636. [PMID: 36091144 PMCID: PMC9449844 DOI: 10.3389/fonc.2022.992636] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Accepted: 07/29/2022] [Indexed: 12/05/2022] Open
Abstract
Aberrant activation of the RET proto-oncogene is implicated in a plethora of cancers. RET gain-of-function point mutations are driver events in multiple endocrine neoplasia 2 (MEN2) syndrome and in sporadic medullary thyroid cancer, while RET rearrangements are driver events in several non-medullary thyroid cancers. Drugs able to inhibit RET have been used to treat RET-mutated cancers. Multikinase inhibitors were initially used, though they showed modest efficacy and significant toxicity. However, new RET selective inhibitors, such as selpercatinib and pralsetinib, have recently been tested and have shown good efficacy and tolerability, even if no direct comparison is yet available between multikinase and selective inhibitors. The advent of high-throughput technology has identified cancers with rare RET alterations beyond point mutations and fusions, including RET deletions, raising questions about whether these alterations have a functional effect and can be targeted by RET inhibitors. In this mini review, we focus on tumors with RET deletions, including deletions/insertions (indels), and their response to RET inhibitors.
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Affiliation(s)
- Antonella Verrienti
- Department of Translational and Precision Medicine, Sapienza University of Rome, Rome, Italy
| | - Giorgio Grani
- Department of Translational and Precision Medicine, Sapienza University of Rome, Rome, Italy
- *Correspondence: Giorgio Grani,
| | - Marialuisa Sponziello
- Department of Translational and Precision Medicine, Sapienza University of Rome, Rome, Italy
| | - Valeria Pecce
- Department of Translational and Precision Medicine, Sapienza University of Rome, Rome, Italy
| | | | - Cosimo Durante
- Department of Translational and Precision Medicine, Sapienza University of Rome, Rome, Italy
| | - Diego Russo
- Department of Health Sciences, University “Magna Graecia” of Catanzaro, Catanzaro, Italy
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3
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Bai Y, Niu D, Yao Q, Lin D, Kakudo K. Updates in the advances of sporadic medullary thyroid carcinoma: from the molecules to the clinic. Gland Surg 2020; 9:1847-1856. [PMID: 33224860 DOI: 10.21037/gs-2019-catp-21] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Medullary thyroid carcinoma (MTC) is a rare neuroendocrine malignancy that originates in parafollicular cells. It is well-known that a quarter of MTC are involved in hereditary multiple endocrine neoplasia type 2 syndromes, whereas most MTC are sporadic. Unlike the commonly encountered gastrointestinal or pulmonary neuroendocrine tumors, most sporadic MTCs have distinct genetic alterations featured by somatic changes of either Rearranged during Transfection (RET) or RAS point mutation. The increasing application of next-generation sequencing, whole-exome sequencing, and other molecular detection techniques enables us to understand MTC comprehensively concerning its detailed molecular changes and their clinical correlations. This article reviews the advances in genetic alterations and their prognostic impact in sporadic MTC among different populations and discusses the associated tumor immune microenvironments and the potential role of immunotherapy targeting PD-L1/PD-1 in treating MTC. Furthermore, the current multikinase inhibitor targeting therapy for sporadic MTC has been summarized here and its efficacy and drug toxicity are discussed. Updates in advance of the role of calcitonin/procalcitonin/calcitonin-related polypeptide alpha (CALCA) gene transcripts in diagnosing and handling MTC are also mentioned. The treatment of advanced MTC is still challenging and might require a combination of several modalities.
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Affiliation(s)
- Yanhua Bai
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Pathology, Peking University Cancer Hospital & Institute, Beijing, China
| | - Dongfeng Niu
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Pathology, Peking University Cancer Hospital & Institute, Beijing, China
| | - Qian Yao
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Pathology, Peking University Cancer Hospital & Institute, Beijing, China
| | - Dongmei Lin
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Pathology, Peking University Cancer Hospital & Institute, Beijing, China
| | - Kennichi Kakudo
- Department of Pathology and Thyroid Disease Center, Izumi City General Hospital, Izumi, Japan
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4
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Abstract
The pathogenesis of the development and progression of thyroid cancer (TC) is far from being clear at present. Accumulated evidence suggests that it is a complex polygenic disorder for which genetic factors play an important role in disease aetiology. Here we review the literature to report the genetic variations and alterations that have been described in the aetiology of TC. The functional effects of some mutations and single nucleotide polymorphisms on TC are validated, establishing the role of sequence variations in this cancer. However, large prospective studies are still required to evaluate the diagnostic and prognostic value of these genetic determinants in clinical practice.
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5
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Shih AJ, Telesco SE, Radhakrishnan R. Analysis of Somatic Mutations in Cancer: Molecular Mechanisms of Activation in the ErbB Family of Receptor Tyrosine Kinases. Cancers (Basel) 2011; 3:1195-231. [PMID: 21701703 PMCID: PMC3119571 DOI: 10.3390/cancers3011195] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Revised: 02/28/2011] [Accepted: 03/01/2011] [Indexed: 01/02/2023] Open
Abstract
The ErbB/EGFR/HER family of kinases consists of four homologous receptor tyrosine kinases which are important regulatory elements in many cellular processes, including cell proliferation, differentiation, and migration. Somatic mutations in, or over-expression of, the ErbB family is found in many cancers and is correlated with a poor prognosis; particularly, clinically identified mutations found in non-small-cell lung cancer (NSCLC) of ErbB1 have been shown to increase its basal kinase activity and patients carrying these mutations respond remarkably to the small tyrosine kinase inhibitor gefitinib. Here, we analyze the potential effects of the currently catalogued clinically identified mutations in the ErbB family kinase domains on the molecular mechanisms of kinase activation. Recently, we identified conserved networks of hydrophilic and hydrophobic interactions characteristic to the active and inactive conformation, respectively. Here, we show that the clinically identified mutants influence the kinase activity in distinctive fashion by affecting the characteristic interaction networks.
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Affiliation(s)
- Andrew J. Shih
- Department of Bioengineering, University of Pennsylvania, 210 S. 33 Street, 240 Skirkanich Hall, Philadelphia, PA 19104, USA; E-Mails: (A.J.S.); (S.E.T)
| | - Shannon E. Telesco
- Department of Bioengineering, University of Pennsylvania, 210 S. 33 Street, 240 Skirkanich Hall, Philadelphia, PA 19104, USA; E-Mails: (A.J.S.); (S.E.T)
| | - Ravi Radhakrishnan
- Department of Bioengineering, University of Pennsylvania, 210 S. 33 Street, 240 Skirkanich Hall, Philadelphia, PA 19104, USA; E-Mails: (A.J.S.); (S.E.T)
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6
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Abstract
Multiple endocrine neoplasia syndrome type 1 (MEN-1) consists of endocrine tumors of the parathyroid, the endocrine pancreas-duodenum, and the pituitary. Surveillance and screening for the endocrinopathies is recommended in gene carriers. Surgery for MEN-1-related hyperparathyroidism is generally performed as radical subtotal parathyroidectomy, because less surgery is likely to result in persistent or recurrent disease. Multiple endocrine neoplasia syndrome type 2 (MEN-2) consists of medullary thyroid carcinoma, pheochromocytoma, and hyperparathyroidism. Prophylactic thyroidectomy based on DNA testing in the MEN-2 syndrome is considered one of the greater achievements in cancer treatment, because it may be performed before thyroid carcinoma development and provides cure for the patient.
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Affiliation(s)
- Göran Akerström
- Department of Surgery, University Hospital, Uppsala, 751 85 Sweden.
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Dvorakova S, Vaclavikova E, Sykorova V, Vcelak J, Novak Z, Duskova J, Ryska A, Laco J, Cap J, Kodetova D, Kodet R, Krskova L, Vlcek P, Astl J, Vesely D, Bendlova B. Somatic mutations in the RET proto-oncogene in sporadic medullary thyroid carcinomas. Mol Cell Endocrinol 2008; 284:21-7. [PMID: 18282654 DOI: 10.1016/j.mce.2007.12.016] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2007] [Revised: 12/19/2007] [Accepted: 12/22/2007] [Indexed: 12/19/2022]
Abstract
The frequency and prognostic relevance of RET proto-oncogene somatic mutations in sporadic medullary thyroid carcinoma (MTC) remain controversial. In order to study somatic mutations in the RET proto-oncogene in sporadic MTCs found in the Czech population and to correlate these mutations with clinical and pathological characteristics, we investigated 48 truly sporadic MTCs by sequencing classical risk exons 10, 11, 13, 14, 15 and 16. From the 48 tumors studied, 23 (48%) had somatic mutation in the RET proto-oncogene in exons 10, 11, 15 or 16. The classical somatic mutation Met918Thr in exon 16 was only found in 13 tumors (27%). In five cases, multiple somatic mutations and deletions were detected. A statistically significant correlation between the presence of somatic mutation with more advanced pathological TNM stages was observed. Other clinical and pathological characteristics did not show any statistical significant association with the presence or absence of somatic mutation.
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Affiliation(s)
- S Dvorakova
- Department of Molecular Endocrinology, Institute of Endocrinology, Prague, Czech Republic.
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de Groot JWB, Links TP, Plukker JTM, Lips CJM, Hofstra RMW. RET as a diagnostic and therapeutic target in sporadic and hereditary endocrine tumors. Endocr Rev 2006; 27:535-60. [PMID: 16849421 DOI: 10.1210/er.2006-0017] [Citation(s) in RCA: 227] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The RET gene encodes a receptor tyrosine kinase that is expressed in neural crest-derived cell lineages. The RET receptor plays a crucial role in regulating cell proliferation, migration, differentiation, and survival through embryogenesis. Activating mutations in RET lead to the development of several inherited and noninherited diseases. Germline point mutations are found in the cancer syndromes multiple endocrine neoplasia (MEN) type 2, including MEN 2A and 2B, and familial medullary thyroid carcinoma. These syndromes are autosomal dominantly inherited. The identification of mutations associated with these syndromes has led to genetic testing to identify patients at risk for MEN 2 and familial medullary thyroid carcinoma and subsequent implementation of prophylactic thyroidectomy in mutation carriers. In addition, more than 10 somatic rearrangements of RET have been identified from papillary thyroid carcinomas. These mutations, as those found in MEN 2, induce oncogenic activation of the RET tyrosine kinase domain via different mechanisms, making RET an excellent candidate for the design of molecular targeted therapy. Recently, various kinds of therapeutic approaches, such as tyrosine kinase inhibition, gene therapy with dominant negative RET mutants, monoclonal antibodies against oncogene products, and nuclease-resistant aptamers that recognize and inhibit RET have been developed. The use of these strategies in preclinical models has provided evidence that RET is indeed a potential target for selective cancer therapy. However, a clinically useful therapeutic option for treating patients with RET-associated cancer is still not available.
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Affiliation(s)
- Jan Willem B de Groot
- Department of Endocrinology, University Medical Center Groningen, University of Groningen, The Netherlands
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Dvoráková S, Václavíková E, Sýkorová V, Dusková J, Vlcek P, Ryska A, Novák Z, Bendlová B. New multiple somatic mutations in the RET proto-oncogene associated with a sporadic medullary thyroid carcinoma. Thyroid 2006; 16:311-6. [PMID: 16571096 DOI: 10.1089/thy.2006.16.311] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Medullary thyroid carcinoma (MTC) occurs mostly as a sporadic tumor or in connection with inherited cancer syndromes-multiple endocrine neoplasia (MEN) types 2A and 2B and familial MTC. Germline mutations in the RET proto-oncogene are found in most of the familial cases. Somatic mutations in the RET proto-oncogene are detected in 23%-69% of patients with sporadic MTC. The most frequent somatic mutation is Met918Thr in exon 16 and only a small percentage of mutations in other RET exons have been observed. In a very few cases double mutations were found. Genetic screening for somatic mutations in RET exons 10, 11, 13, 14, 15, and 16 in Czech patients with sporadic MTC was carried out by DNA sequencing. This study presents a new triplesomatic mutation Gly911Asp, Met918Thr, and Glu921Lys in exon 16 of the RET proto-oncogene detected in an 18-year-old Czech male patient. In the second case, a new double-somatic mutation Val591Ile in exon 10 with a concomitant somatic mutation Met918Thr in exon 16 was found in a 77-year-old Czech female patient. These both newly described somatic multiple mutations were revealed in a hemizygous status, the loss of heterozygosity in tumor tissues in comparison with germline DNA was confirmed.
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Affiliation(s)
- S Dvoráková
- Department of Molecular Endocrinology, Institute of Endocrinology, Nárdoní 8, Prague 1, 11694, Czech Republic.
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10
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Kouvaraki MA, Shapiro SE, Perrier ND, Cote GJ, Gagel RF, Hoff AO, Sherman SI, Lee JE, Evans DB. RET proto-oncogene: a review and update of genotype-phenotype correlations in hereditary medullary thyroid cancer and associated endocrine tumors. Thyroid 2005; 15:531-44. [PMID: 16029119 DOI: 10.1089/thy.2005.15.531] [Citation(s) in RCA: 176] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
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.
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Affiliation(s)
- Maria A Kouvaraki
- Department of Surgical Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77230-1402, USA
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11
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Jindrichova S, Kodet R, Krskova L, Vlcek P, Bendlova B. The newly detected mutations in the RET proto-oncogene in exon 16 as a cause of sporadic medullary thyroid carcinoma. J Mol Med (Berl) 2003; 81:819-23. [PMID: 14618242 DOI: 10.1007/s00109-003-0501-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2003] [Accepted: 09/30/2003] [Indexed: 10/26/2022]
Abstract
Medullary thyroid carcinoma (MTC) occurs as a sporadic form or, less frequently, as an autosomal dominant inherited familial disorder. Germline mutations in the RET proto-oncogene in exons 10, 11, 13, 14, 15, and 16 are found in most of the familial cases (nearly 95%). Somatic mutations in sporadic MTC are detected in 23-69% of patients. The most frequent somatic mutation is located in exon 16 at codon 918, and only a small percentage of mutations are found in exons 10, 11, 13, and 15. We have searched for somatic mutations in Czech MTC patients using direct sequencing. We report here two new somatic missense mutations in exon 16 of the RET proto-oncogene associated with the sporadic MTC detected in two Czech men. A homozygous mutation at codon 922 TCC(Ser)-->CCC(Pro) as a result of loss of heterozygosity was revealed in the first patient. In the second one a heterozygous mutation at codon 930 ACG(Thr)-->ATG(Met) was found.
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Affiliation(s)
- S Jindrichova
- Department of Molecular Endocrinology, Institute of Endocrinology, Narodni 8, 11694 Prague 1, Czech Republic.
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12
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Gimm O, Marsh DJ. Does a somatic deletion in RET clarify the sporadic nature of medullary thyroid carcinoma? J Endocrinol Invest 2003; 26:381-3. [PMID: 12841548 DOI: 10.1007/bf03345188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Abstract
The multiple endocrine neoplasia syndromes form a distinct group of genetic tumor syndromes. They include multiple endocrine neoplasia types 1 and 2, von Hippel Lindau syndrome, neurofibromatosis, and Carney complex. Research over the past decade has identified a molecular basis for each of these syndromes. This knowledge has revolutionized not only the clinical management but also has illuminated the field of human cancer research by the identification of new and important genes critical for regulation of cell growth, differentiation, and death. This review focuses on the structure, physiologic function, and molecular abnormalities of the genes involved in these syndromes.
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Affiliation(s)
- A O Hoff
- Department of Internal Medicine Specialties, University of Texas M.D. Anderson Cancer Center, Houston 77030, USA
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Uchino S, Noguchi S, Yamashita H, Sato M, Adachi M, Yamashita H, Watanabe S, Ohshima A, Mitsuyama S, Iwashita T, Takahashi M. Somatic mutations in RET exons 12 and 15 in sporadic medullary thyroid carcinomas: different spectrum of mutations in sporadic type from hereditary type. Jpn J Cancer Res 1999; 90:1231-7. [PMID: 10622534 PMCID: PMC5926019 DOI: 10.1111/j.1349-7006.1999.tb00701.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Germline mutations in the RET proto-oncogene are responsible for multiple endocrine neoplasia type 2 (MEN 2A and 2B) and familial medullary thyroid carcinoma (FMTC). Point mutations or in-frame deletions of exons 10, 11, 13, 14 and 16 are associated with sporadic medullary thyroid carcinoma (MTC). To understand further the role of the RET gene in sporadic MTC, we examined mutations in exons 12 and 15 of RET in patients with sporadic MTC. DNAs were extracted from 39 formalin-fixed tumor tissues and corresponding normal thyroid tissues or peripheral blood leukocytes. DNA sequencing was used to identify mutations in exons 12 and 15 of RET. In this study, one novel somatic mutation was found in exon 12 and five novel mutations or deletions were found in exon 15. Of the patients with mutations, one had an in-frame 12-bp deletion (nt. 2625-2636), one had point mutations in both codons 884 and 908, and the remaining three had point mutations in codons 748, 876 and 901, respectively. Together with our previous identification of somatic mutations in exons 10, 11, 13, 14 and 16, somatic alterations were found in 10 out of 39 (25.6%) sporadic MTCs. There was no association of RET gene mutations with tumor recurrence or prognosis. These results suggest that mutations occur frequently in the RET coding region in addition to the previously reported mutation hot spots, and there is a different spectrum of mutations between sporadic and hereditary MTC.
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Affiliation(s)
- S Uchino
- Noguchi Thyroid Clinic and Hospital Foundation, Beppu, Oita.
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Uchino S, Noguchi S, Adachi M, Sato M, Yamashita H, Watanabe S, Murakami T, Toda M, Murakami N, Yamashita H. Novel point mutations and allele loss at the RET locus in sporadic medullary thyroid carcinomas. Jpn J Cancer Res 1998; 89:411-8. [PMID: 9617347 PMCID: PMC5921821 DOI: 10.1111/j.1349-7006.1998.tb00579.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Germline mutations in the RET proto-oncogene have been shown to be the underlying cause of multiple endocrine neoplasia type 2 (MEN 2A and 2B) and familial medullary thyroid carcinoma (FMTC). Some cases of sporadic medullary thyroid carcinoma (sporadic MTC) are reported to have specific codon 918, 883 and 768 mutations of the RET gene in tumor tissues. We examined RET gene mutations in 40 Japanese cases who had previously undergone surgery for sporadic MTC. DNA extracted from formalin-fixed tumor tissues and corresponding normal thyroid tissues or peripheral blood leukocytes was analyzed for mutations of exon 10, 11, 13, 14 and 16 of the RET gene by DNA sequencing and by mutation-specific restriction enzyme analysis. Germline RET point mutations were found in six of 40 cases (15%), cysteine residues at codon 618 in two, codon 634 in three and valine residue at codon 804 in one, and were newly identified as heritable MTC. Of the remaining 34 sporadic MTC cases, four (12%) had tumor-specific RET point mutations. Two were found in exon 16; one case showed an ATG to ACG (Met to Thr) mutation at codon 918, and the other showed two point mutations, ATG to ACG (Met to Thr) at codon 918 and GCA to GTA (Ala to Val) at codon 919 with loss of the wild-type allele, suggesting that both alleles at the RET locus were altered. The other two were found in exon 13; one case showed a CCG to TCG (Pro to Ser) mutation at codon 766 and the other showed a silent mutation, GTC to GTT (Val) at codon 778 with loss of the wild-type allele. There was no association of sporadic mutations with recurrence or prognosis in patients with sporadic MTC. The low rate of somatic RET mutation at codon 918 in our sporadic MTC suggests that as yet unknown factors may be involved. Genetic alterations in both alleles may have an important role in small fraction of sporadic MTCs.
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Affiliation(s)
- S Uchino
- Noguchi Thyroid Clinic and Hospital Foundation, Oita
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