Gene Summary

Gene:RET; ret proto-oncogene
Summary:This gene encodes a transmembrane receptor and member of the tyrosine protein kinase family of proteins. Binding of ligands such as GDNF (glial cell-line derived neurotrophic factor) and other related proteins to the encoded receptor stimulates receptor dimerization and activation of downstream signaling pathways that play a role in cell differentiation, growth, migration and survival. The encoded receptor is important in development of the nervous system, and the development of organs and tissues derived from the neural crest. This proto-oncogene can undergo oncogenic activation through both cytogenetic rearrangement and activating point mutations. Mutations in this gene are associated with Hirschsprung disease and central hypoventilation syndrome and have been identified in patients with renal agenesis. [provided by RefSeq, Sep 2017]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:proto-oncogene tyrosine-protein kinase receptor Ret
Source:NCBIAccessed: 31 August, 2019


What does this gene/protein do?
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Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 31 August 2019 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

Tag cloud generated 31 August, 2019 using data from PubMed, MeSH and CancerIndex

Specific Cancers (14)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Entity Topic PubMed Papers
Multiple Endocrine Neoplasia Type 2aRET mutations in Multiple Endocrine Neoplasia - type 2A View Publications715
Pheochromocytoma and ParagangliomaRET and Pheochromocytoma and Paraganglioma View Publications427
Adrenocortical CancerRET and Adrenocortical Cancer View Publications341
Thyroid CancerRET mutations in Familial Medullary Thyroid Carcinoma View Publications301
Thyroid CancerRET-PTC1 Rearangements in Papillary Thyroid Cancer
The PTC1 fusion gene is present in approximately 30% of papillary thyroid carcinomas. It involves an inversion of 10q which fuses the RET protooncogene to the D10S170 (H4) gene. High incidence of RET/PTC1 rearrangements have been reported in thyroid cancers in people living in areas adjacent to Chernobyl following the nuclear accident. SCID mice transplanted with normal human thyroid tissues and then exposed to radiation preferentially developed RET/PTC1 compared to other RET rearrangements (Mizuno,2000). A FISH study (Nikiforova, 2000) suggests that RET and PTC1 are more frequently juxtaposed in the nucleus of thyroid cells compared to other cells. This close proximity of the genes in thyroid cells may promote the PTC1 fusion since a single radiation track may be sufficient to produce a double-strand break in each gene at the same site in the nucleus.
View Publications261
Multiple Endocrine Neoplasia Type 2bRET mutations in Multiple Endocrine Neoplasia Type 2b View Publications261
Thyroid CancerRET-PTC3 (RET-ELE1) Rearangements in Papillary Thyroid Cancer
The RET gene is frequently involved in structural rearrangements with either PCT1 (CCDC6) or PCT3 (NCOA4), resulting in chimeric fusion proteins which are characteristic of Papillary Thyroid Cancer. Detection of this may aid differential diagnosis of papillary vs. follicular thyroid cancer.
View Publications182
Lung CancerRET and Lung Cancer View Publications278
Lung Cancer, Non-Small CellRET and Non-Small Cell Lung Cancer View Publications122
Thyroid CancerRET Rearrangements Following Exposure to Ionizing Radiation View Publications66
Lung CancerRET-KIF5B fusion in Adenocarcinoma Lung Cancer View Publications52
Thyroid CancerRET-NTRK1 Rearangements in Papillary Thyroid Cancer View Publications46
Thyroid Cancert(8,10) RET-HOOK Reaarangements in Papillary Thyroid Cancer View Publications2

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: RET (cancer-related)

Punda A, Bedeković V, Barić A, et al.
Acta Clin Croat. 2018; 57(4):646-652 [PubMed] Free Access to Full Article Related Publications
- The purpose of this study was to analyze the possible prognostic value of RET mutation in papillary thyroid carcinoma and its incidence in the past few decades in our population, due to the increasing incidence of papillary thyroid carcinoma. The present study included 180 patients operated for papillary thyroid carcinoma. The clinical and histopathologic characteristics were analyzed. Paraffin sections of the selected histologic slides were cut again and immunohistochemically stained by the Clone 3F8 P (HIER) from Novocastra (Vision Bio Systems Europe, Newcastle upon Tyne, UK) monoclonal antibody to RET oncoprotein. Univariate analysis indicated sex (p=0.01), histologic subtype (p=0.075) and capsular invasion (p=0.010) to be statistically significant predictors of lymph node metastases, whereas age (p=0.796), tumor size (p=0.556) and intraglandular dissemination (p=0.131) showed no such correlation. The presence of RET mutation (p=0.704) was not a statistically significant predictor of the tumor metastasizing potential. RET mutation (p=0.500) showed no statistically significant correlation with papillary thyroid carcinoma classifed into prognostic groups according to clinicopathologic features either. RET mutation was detected in 30% of 180 papillary thyroid carcinomas. This is the first large study demonstrating that RET mutation incidence in papillary thyroid carcinoma in Croatian population is consistent with the classic distribution of sporadic cases, despite the increased prevalence of papillary thyroid carcinoma in the past few decades.

An C, Li H, Zhang X, et al.
Silencing of COPB2 inhibits the proliferation of gastric cancer cells and induces apoptosis via suppression of the RTK signaling pathway.
Int J Oncol. 2019; 54(4):1195-1208 [PubMed] Free Access to Full Article Related Publications
Emerging studies have reported that coatomer protein complex subunit β2 (COPB2) is overexpressed in several types of malignant tumor; however, to the best of our knowledge, no studies regarding COPB2 in gastric cancer have been published thus far. Therefore, the present study aimed to determine the significance and function of COPB2 in gastric cancer. COPB2 expression in gastric cancer cell lines was measured using reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) analysis. In addition, lentivirus‑short hairpin RNA (shRNA) COPB2 (Lv‑shCOPB2) was generated and used to infect BGC‑823 cells to analyze the effects of COPB2 on the cancerous phenotype. The effects of shRNA‑mediated COPB2 knockdown on cell proliferation were detected using MTT, 5‑bromo‑2‑deoxyuridine and colony formation assays. In addition, the effects of COPB2 knockdown on apoptosis were analyzed by flow cytometry. Nude mice and fluorescence imaging were used to characterize the regulation of tumor growth in vivo, and qPCR and immunohistochemistry were subsequently conducted to analyze COPB2 expression in xenograft tumor tissues. Furthermore, a receptor tyrosine kinase (RTK) signaling pathway antibody array was used to explore the relevant molecular mechanisms underlying the effects of COPB2 knockdown. The results revealed that COPB2 mRNA was abundantly overexpressed in gastric cancer cell lines, whereas knockdown of COPB2 significantly inhibited cell growth and colony formation ability, and led to increased cell apoptosis in vitro. The tumorigenicity assay revealed that knockdown of COPB2 reduced tumor growth in nude mice, and fluorescence imaging indicated that the total radiant efficiency of mice in the Lv‑shCOPB2‑infected group was markedly reduced compared with the mice in the Lv‑shRNA control‑infected group in vivo. The antibody array assay revealed that the levels of phosphorylation in 23 target RTKs were significantly reduced: In conclusion, COPB2 was highly expressed in gastric cancer cell lines, and knockdown suppressed colony formation and promoted cell apoptosis via inhibiting the RTK signaling and its downstream signaling cascade molecules. Therefore, COPB2 may present a valuable target for gene silencing strategy in gastric cancer.

Furugaki K, Mochizuki M, Kohno M, et al.
Expression of C-terminal ALK, RET, or ROS1 in lung cancer cells with or without fusion.
BMC Cancer. 2019; 19(1):301 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Genetic alterations, including mutation of epidermal growth factor receptor or v-Ki-ras2 kirsten rat sarcoma viral oncogene homolog and fusion of anaplastic lymphoma kinase (ALK), RET proto-oncogene (RET), or v-ros UR2 sarcoma virus oncogene homolog 1 (ROS1), occur in non-small cell lung cancers, and these oncogenic drivers are important biomarkers for targeted therapies. A useful technique to screen for these fusions is the detection of native carboxy-terminal (C-terminal) protein by immunohistochemistry; however, the effects of other genetic alterations on C-terminal expression is not fully understood. In this study, we evaluated whether C-terminal expression is specifically elevated by fusion with or without typical genetic alterations of lung cancer.
METHODS: In 37 human lung cancer cell lines and four tissue specimens, protein and mRNA levels were measured by capillary western blotting and reverse transcription-PCR, respectively.
RESULTS: Compared with the median of all 37 cell lines, mRNA levels at the C-terminus of all five of the fusion-positive cell lines tested (three ALK, one RET, and one ROS1) were elevated at least 2000-, 300-, or 2000-fold, respectively, and high C-terminal protein expression was detected. In an ALK fusion-positive tissue specimen, the mRNA and protein levels of C-terminal ALK were also markedly elevated. Meanwhile, in one of 36 RET fusion-negative cell lines, RET mRNA levels at the C-terminus were elevated at least 500-fold compared with the median of all 37 cell lines, and high C-terminal protein expression was detected despite the absence of RET fusion.
CONCLUSIONS: This study of 37 cell lines and four tissue specimens shows the detection of C-terminal ALK or ROS1 proteins could be a comprehensive method to determine ALK or ROS1 fusion, whereas not only the detection of C-terminal RET protein but also other methods would be needed to determine RET fusion.

Abdullah MI, Junit SM, Ng KL, et al.
Papillary Thyroid Cancer: Genetic Alterations and Molecular Biomarker Investigations.
Int J Med Sci. 2019; 16(3):450-460 [PubMed] Free Access to Full Article Related Publications
Papillary thyroid cancer (PTC) is the most prevalent form of malignancy among all cancers of the thyroid. It is also one of the few cancers with a rapidly increasing incidence. PTC is usually contained within the thyroid gland and generally biologically indolent. Prognosis of the cancer is excellent, with less than 2% mortality at 5 years. However, more than 25% of patients with PTC developed a recurrence during a long term follow-up. The present article provides an updated condensed overview of PTC, which focuses mainly on the molecular alterations involved and recent biomarker investigations.

Cavalieri S, Platini F, Bergamini C, et al.
Genomics in non-adenoid cystic group of salivary gland cancers: one or more druggable entities?
Expert Opin Investig Drugs. 2019; 28(5):435-443 [PubMed] Related Publications
INTRODUCTION: Salivary gland cancers (SGCs) are a rare and heterogeneous group of malignant tumors arising from either major or minor salivary glands. Among SGCs patients, adenoid cystic carcinoma (ACC) is the most frequent histotype and its genetic aberrations are well known even though they are generally uncommon. Non-ACC subtypes are rarer and more heterogeneous than ACC from a histological and genomic point of view. In non-ACC, some altered molecular pathways [e.g. BRAF or RET mutations, Androgen Receptor (AR)] are potentially targetable with specific drugs.
AREAS COVERED: A literature search was performed to summarize the main druggable genomic aberrations involving non-ACC SGCs. An overview of the genomics of non-ACC salivary gland malignancies is discussed. We describe the pattern of potentially targetable genomic alterations in non-ACC salivary gland malignancies according to their frequency rather than to the single non-ACC histotype.
EXPERT OPINION/COMMENTARY: The genetic profiling through in-depth molecular analyses [e.g. Next-generation sequencing (NGS)] is advised in all patients affected by recurrent and/or metastatic non-ACC SGCs to find any potentially druggable target. Some histotypes may carry driving mutations that must be investigated and defined. For the rare cancers, access to a referral center is recommended to optimize the management of these patients.

Okamoto M, Yoshioka Y, Maeda K, et al.
Mice conditionally expressing RET(C618F) mutation display C cell hyperplasia and hyperganglionosis of the enteric nervous system.
Genesis. 2019; 57(5):e23292 [PubMed] Related Publications
Medullary thyroid carcinoma (MTC) develops from hyperplasia of thyroid C cells and represents one of the major causes of thyroid cancer mortality. Mutations in the cysteine-rich domain (CRD) of the RET gene are the most prevalent genetic cause of MTC. The current consensus holds that such cysteine mutations cause ligand-independent dimerization and constitutive activation of RET. However, given the number of the CRD mutations left uncharacterized, our understanding of the pathogenetic mechanisms by which CRD mutations lead to MTC remains incomplete. We report here that RET(C618F), a mutation identified in MTC patients, displays moderately high basal activity and requires the ligand for its full activation. To assess the biological significance of RET(C618F) in organogenesis, we generated a knock-in mouse line conditionally expressing RET(C618F) cDNA by the Ret promoter. The RET(C618F) allele can be made to be Ret-null and express mCherry by Cre-loxP recombination, which allows the assessment of the biological influence of RET(C618F) in vivo. Mice expressing RET(C618F) display mild C cell hyperplasia and increased numbers of enteric neurons, indicating that RET(C618F) confers gain-of-function phenotypes. This mouse line serves as a novel biological platform for investigating pathogenetic mechanisms involved in MTC and enteric hyperganglionosis.

Cheng X, Yin H, Fu J, et al.
Aggregate analysis based on TCGA: TTN missense mutation correlates with favorable prognosis in lung squamous cell carcinoma.
J Cancer Res Clin Oncol. 2019; 145(4):1027-1035 [PubMed] Related Publications
PURPOSE: Lung cancer prevalence with its high mortality rate is a trending topic globally. Non-small cell lung cancer (NSCLC) is the most common type of lung cancer. The human gene TTN encoding for TITIN protein is known as major mutation gene in many types of tumor including NSCLC. However, it is still controversial that TTN is a cancer-associated candidate considering tumor heterogeneity and complex genetic structure. In-depth researches on correlation between TTN mutation and NSCLC are still limited and discussable.
METHODS: Related somatic mutation profiles and attached clinical data were from The Cancer Genome Atlas (TCGA) lung project. Clinical relevance analysis of TTN mutation was evaluated using univariate analysis and a binary logistic regressive model. Survival analysis and screening of independent prognostic factors in mutation types were conducted by Cox proportional hazards models and Kaplan-Meier methods.
RESULTS: Available data covering lung adenocarcinoma (n = 517) and lung squamous cell carcinoma (n = 492) were analyzed. TTN genetic mutations exhibited significant association with lung squamous cell carcinoma. Patients with lung squamous cell carcinoma possessed favorable overall survival benefits from TTN mutant type and both favorable overall survival and disease-free survival benefits from TTN/TP53 double mutation. For patients with lung squamous cell carcinoma, about 85% of subjects with TTN mutation harbored missense variations, which was an independent indicator of good prognosis.
CONCLUSIONS: Missense mutation of TTN may act as a beneficial role in lung squamous cell carcinoma, but not in lung adenocarcinoma.

Barletta Carrillo CF, Poterico Rojas JA, Barrionuevo Cornejo C, et al.
[Familial medullary thyroid carcinoma: case report and literature review.]
Rev Fac Cien Med Univ Nac Cordoba. 2018; 75(4):303-309 [PubMed] Related Publications
Medullary thyroid carcinoma (MTC) is a malignant tumour of the calcitonin-secreting parafollicular C cells of the thyroid gland. Up to 25% of MTC are associated to pathogenic germinal variants on the proto-oncogene RET (locus 10q11.2), which cause Familial Medullary Thyroid Carcinoma (FMTC) or Multiple Endocrine Neoplasia type 2 (MEN2); genetic conditions inherited with autosomal dominant pattern. We present the first report of a Peruvian family with FMTC and a germinal pathogenic variant on RET proto-oncogene, identified with Sanger sequencing. This manuscript also shows a literature review of this hereditary cancer syndrome, where we highlight the relevance of primary prevention and the potential effect on public health in healthy carriers of germinal pathogenic variants.

Wang Y, Xu Y, Wang X, et al.
RET fusion in advanced non-small-cell lung cancer and response to cabozantinib: A case report.
Medicine (Baltimore). 2019; 98(3):e14120 [PubMed] Free Access to Full Article Related Publications
RATIONALE: Lung cancer is a series of gene-driven disease. EGFR, ALK, and ROS1 are 3 major driver genes that play an important role in lung cancer development and precision management. Additionally, rare genetic alterations continue to be discovered and may become novel targets for therapy. The RET gene is one of such rare genetic alteration of non-small cell lung cancer (NSCLC). In this report, we present a RET-positive case that benefited from cabozantinib treatment.
PATIENT CONCERN: A 50-year-old male patient was diagnosed with lung adenocarcinoma 2 years ago, at that time he received palliative surgery of pulmonary carcinoma and completed 4 cycles of chemotherapy with gemcitabine and cisplatin. Six months later, he was hospitalized in our cancer center due to the disease recurrence, presenting with pleural metastasis.
DIAGNOSIS: Gene alteration was examined using the intraoperative specimen by PCR method, and KIF5B/RET gene fusion was detected. Therefore, the patient was diagnosed with late-stage lung adenocarcinoma with RET gene mutation.
INTERVENTIONS: The patient received treatment with cabozantinib from June 2017.
OUTCOMES: Cabozantinib was administered (140 mg orally, once daily) for approximate 9 months, and his disease achieved stable disease (SD). During that period, there were no severe adverse events (AE), except for a grade II rash (CTCAE 4.0).
LESSONS: We found that the RET fusion gene is a novel driver molecular of lung adenocarcinoma in patients without common mutations in such genes as EGFR, ALK, and ROS1. This case report supports a rationale for the treatment of lung adenocarcinoma patients with a RET fusion and provides alternative treatment options for these types of NSCLC patients.

Høxbroe Michaelsen S, Ornstrup MJ, Poulsen MM, et al.
Long-term follow-up of RET Y791F carriers in Denmark 1994-2017: A National Cohort Study.
J Surg Oncol. 2019; 119(6):687-693 [PubMed] Related Publications
BACKGROUND AND OBJECTIVES: Recently, a comprehensive study presented evidence that a long-disputed REarranged during Transfection (RET) variant, RET Y791F, should be classified as nonpathogenic. In spite of this, several subsequently published papers, including the revised American Thyroid Association guidelines for medullary thyroid carcinoma, refer to the variant as pathogenic. This study presents data from a unique national Danish cohort of RET Y791F carriers who have been followed by watchful waiting instead of being subjected to early thyroidectomy, to determine if any carrier shows evidence of multiple endocrine neoplasia 2A (MEN2A) at long-term follow-up.
METHODS: A national cohort of all patients tested for RET mutations in Denmark from September 1994 to October 2017 was searched for carriers of RET Y791F. Medical records and laboratory reports of carriers were reviewed for signs of MEN2A at latest follow-up (medullary thyroid carcinoma, primary hyperparathyroidism, pheochromocytoma, cutaneous lichen amyloidosis, or Hirschsprung's disease).
RESULTS: In total, twenty RET Y791F-carriers were identified, none of whom showed any evidence of MEN2A, despite an age range from 7 to 87 years.
CONCLUSIONS: Our national cohort study of all Danish RET Y791F carriers substantiates the claim that the RET Y791F variant is nonpathogenic.

Martins-Costa MC, Lindsey SC, Cunha LL, et al.
A pioneering RET genetic screening study in the State of Ceará, Brazil, evaluating patients with medullary thyroid cancer and at-risk relatives: experience with 247 individuals.
Arch Endocrinol Metab. 2018; 62(6):623-635 [PubMed] Related Publications
OBJECTIVE: Initial diagnosis of medullary thyroid carcinoma (MTC) is frequently associated with advanced stages and a poor prognosis. Thus, the need for earlier diagnoses and detection in relatives at risk for the disease has led to increased use of RET genetic screening.
SUBJECTS AND METHODS: We performed RET screening in 247 subjects who were referred to the Brazilian Research Consortium for Multiple Endocrine Neoplasia (BRASMEN) Center in the State of Ceará. Direct genetic sequencing was used to analyze exons 8, 10, 11, and 13-16 in MTC index cases and specific exons in at risk relatives. Afterward, clinical follow-up was offered to all the patients with MTC and their affected relatives.
RESULTS: RET screening was performed in 60 MTC index patients and 187 at-risk family members. At the initial clinical assessment of the index patients, 54 (90%) were diagnosed with apparently sporadic disease and 6 (10%) diagnosed with hereditary disease. After RET screening, we found that 31 (52%) index patients had sporadic disease, and 29 (48%) had hereditary disease. Regarding at-risk relatives, 73/187 were mutation carriers. Mutations in RET codon 804 and the rare p.M918V mutation were the most prevalent.
CONCLUSIONS: Performing RET screening in Ceará allowed us to identify a different mutation profile in this region compared with other areas. RET screening also enabled the diagnosis of a significant number of hereditary MTC patients who were initially classified as sporadic disease patients and benefited their relatives, who were unaware of the risks and the consequences of bearing a RET mutation.

Mechera R, Soysal SD, Piscuoglio S, et al.
Expression of RET is associated with Oestrogen receptor expression but lacks prognostic significance in breast cancer.
BMC Cancer. 2019; 19(1):41 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: The Rearranged during Transfection (RET) protein is overexpressed in a subset of Estrogen Receptor (ER) positive breast cancer, with both signalling pathways functionally interacting. This cross-talk plays a pivotal role in the resistance of breast cancer cells to anti-endocrine therapies, and RET expression is assumed to correlate with poor prognosis based on findings in small patient cohorts. The aim of our study was to investigate the impact of RET expression on patient outcome in human breast cancer.
METHODS: We performed an immunohistochemical analysis of RET protein expression on a tissue microarray encompassing 990 breast cancer patients and correlated its expression with clinicopathological parameters and survival data.
RESULTS: Expression of RET was detected in 409 out of 990 cases (41.3%). RET and ER expression significantly correlated (p < 0.0001). The Luminal B HER2-positive subtype showed the highest expression rate (48.9%). In univariate and multivariate survival analyses, RET expression had no impact on overall survival.
CONCLUSION: We confirmed the co-expression of RET and ER, but we did not find RET expression to be an independent prognostic factor in human breast cancer. Clinical trials with newly developed RET inhibitors are needed to evaluate if RET inhibition has a beneficial impact on patient survival in ER positive breast cancer.

Banizs AB, Silverman JF
The utility of combined mutation analysis and microRNA classification in reclassifying cancer risk of cytologically indeterminate thyroid nodules.
Diagn Cytopathol. 2019; 47(4):268-274 [PubMed] Related Publications
OBJECTIVES: Real-world clinical results of (1) Bethesda categorization, (2) mutation analysis, and (3) a microRNA classifier were correlated to show the utility of molecular analysis in assessing malignancy risk of indeterminate thyroid nodules.
METHODS: Cytology and molecular results of clinically tested thyroid nodules were compared. An additional microRNA threshold was determined based on nodules with known disease status, establishing a 3-tiered microRNA approach to clinical risk assessments. Expected rate of malignancy given mutation panel and 3-tiered microRNA approach was validated in an independent cohort of atypia of undetermined significance or follicular lesion of undetermined significance (AUS/FLUS) and follicular neoplasm or suspicious for follicular neoplasm (FN/SFN) nodules with surgically derived outcomes.
RESULTS: In 2685 patients clinically tested, PIK3CA, PAX8/PPARγ, and RET/PTC mutations occurred in less than 1%. Of note, 2% had BRAFV600E mutation and 82% lacked mutations. The maximum expected risk of malignancy in nodules lacking mutations was 9% and 17% for AUS/FLUS and FN/SFN nodules, respectively. Positive microRNA status further increased risk, with the most worrisome status (level-3) elevating risk to 36% and 54%, respectively. RAS mutations occurred in 15% of nodules tested clinically, including in 8% of those that were cytologically benign. The maximum expected risk of malignancy in nodules with RAS or PAX8/PPARγ mutations was 49% and 65% for AUS/FLUS and FN/SFN nodules, respectively. Positive microRNA status further increased risk, with the most worrisome microRNA status (level-3) elevating risk to 85% and 91%, respectively.
CONCLUSIONS: Mutation panels alone do not sufficiently risk stratify thyroid nodular disease. microRNA classification complements cytology and mutation analysis with the capacity to better differentiate nodules at high risk of malignancy.

Chen Y, Huang W, Sun W, et al.
LncRNA MALAT1 Promotes Cancer Metastasis in Osteosarcoma via Activation of the PI3K-Akt Signaling Pathway.
Cell Physiol Biochem. 2018; 51(3):1313-1326 [PubMed] Related Publications
BACKGROUND/AIMS: LncRNAs have been reported to be vital regulators of the progression of osteosarcoma, although the underlying mechanisms are not completely understood.
METHODS: The levels of MALAT1 and miR-129-5p expression were measured using qRT-PCR. Cell growth was determined using the CCK-8 and colony formation assays. Cell migration and invasion were detected using the wound healing and Transwell invasion assays, respectively. Tumor growth was determined with a xenograft model.
RESULTS: MALAT1 was significantly up-regulated in osteosarcoma tissues compared with adjacent non-tumor soft tissues. Overexpression of MALAT1 promoted osteosarcoma cell proliferation, migration, and invasion in vitro and enhanced tumor growth in a tumor xenograft mouse model. MALAT1 promoted osteosarcoma progression by modulating stem cell-like properties. Moreover, rescue experiment and luciferase reporter assay results indicated that MALAT1 modulates RET expression by sponging miR-129-5p in osteosarcomas. Furthermore, MALAT1 augmented the expression of downstream proteins of the RET-Akt pathway. MALAT1 was consistently significantly increased in osteosarcoma tissues and MALAT1 expression was positively correlated with tumor size and metastasis. High expression of MALAT1 was significantly associated with poor outcomes in patients with osteosarcomas. MALAT1 expression was positively related to RET and negatively related to miR-129-5p in osteosarcoma samples and xenograft tumors. MALAT1 functioned as an oncogenic lncRNA in osteosarcomas and was as an independent prognostic indicator.
CONCLUSION: Our data revealed for the first time that MALAT1 increases stem cell-like properties by up-regulating RET via sponging miR-129-5p, and thus activates the PI3K-Akt signaling pathway and provides potential therapeutic targets for osteosarcoma treatment.

Staubitz JI, Schad A, Springer E, et al.
Novel rearrangements involving the RET gene in papillary thyroid carcinoma.
Cancer Genet. 2019; 230:13-20 [PubMed] Related Publications
BACKGROUND: In the field of gene fusions driving tumorigenesis in papillary thyroid carcinoma (PTC), rearrangement of the proto-oncogene RET is the most frequent alteration. Apart from the most common rearrangement of RET to CCDC6, more than 15 partner genes are yet reported. The landscape of RET rearrangements in PTC ("RET-PTC") can notably be enlarged by modern targeted next-generation sequencing, indicating similarities between oncogenic pathways in other cancer types with identical genetic alterations.
METHODS: Targeted next-generation sequencing was performed for two cases of BRAF-wild type PTC with confirmation of the results by Sanger sequencing. A "UniProt" database research was performed to assess protein alterations resulting from RET rearrangements.
RESULTS: RUFY2-RET and KIAA1468-RET were detected. The fusion genes were not present in normal tissue of the index patients. The rearrangement RUFY2-RET lead to a fusion of the RET tyrosine kinase domain to a RUN domain and a coiled-coil domain. For KIAA1468-RET, a fusion to a LisH domain and two coiled-coil domains resulted.
CONCLUSIONS: RUFY2-RET and KIAA1468-RET are novel RET/PTC rearrangements. The fusions were previously described in non-small cell lung cancer. The rearrangement results in a fusion of the RET tyrosine kinase to regulatory domains of RUFY2 and KIAA1468.

Meng K, Chen W, Tian W, et al.
Medullary thyroid carcinoma with breast metastasis: Two case reports.
Medicine (Baltimore). 2018; 97(47):e13193 [PubMed] Free Access to Full Article Related Publications
RATIONALE: Medullary thyroid carcinoma (MTC) is an aggressive subtype of thyroid cancer with frequent hematogenous metastasis. While its metastasis is usually observed in the lung, liver, or bone, it rarely migrates to the breast.
PATIENT CONCERNS: Here we report 2 cases with a complaint of breast lump after initial treatment of MTC.
DIAGNOSES: In both patients, the MTC characteristics of breast nodules were confirmed by pathologic analysis of biopsy specimens.
INTERVENTIONS: The genetic mutations within the metastatic breast lesion were evaluated. Wide local excision was thus performed to 1st case, while no therapeutic intervention for another patient due to the wide-spread presence of the disease.
OUTCOMES: No sign of relapse or metastasis was found in 1st case during a 14-month follow-up. For 2nd case, the breast nodule grew to 14 mm within 3 months before remaining stable for 10 months.
LESSONS: MTC can be a very indolent disease despite its aggressiveness. Reoperation should be considered for patients with local recurrence or resectable distant metastasis of MTC. The findings for both cases supported serum calcitonin as an important marker for the evaluation of disease. Future studies are needed to advance our understanding of its molecular features and improve strategies for its diagnosis and treatment.

Paratala BS, Chung JH, Williams CB, et al.
RET rearrangements are actionable alterations in breast cancer.
Nat Commun. 2018; 9(1):4821 [PubMed] Free Access to Full Article Related Publications
Fusions involving the oncogenic gene RET have been observed in thyroid and lung cancers. Here we report RET gene alterations, including amplification, missense mutations, known fusions, novel fusions, and rearrangements in breast cancer. Their frequency, oncogenic potential, and actionability in breast cancer are described. Two out of eight RET fusions (NCOA4-RET and a novel RASGEF1A-RET fusion) and RET amplification were functionally characterized and shown to activate RET kinase and drive signaling through MAPK and PI3K pathways. These fusions and RET amplification can induce transformation of non-tumorigenic cells, support xenograft tumor formation, and render sensitivity to RET inhibition. An index case of metastatic breast cancer progressing on HER2-targeted therapy was found to have the NCOA4-RET fusion. Subsequent treatment with the RET inhibitor cabozantinib led to a rapid clinical and radiographic response. RET alterations, identified by genomic profiling, are promising therapeutic targets and are present in a subset of breast cancers.

Zhang Q, Xu C, Wang W, et al.
Comparison of Rearranged During Transfection (RET) Gene Rearrangements in Primary Versus Metastatic Non-Small Cell Lung Cancer (NSCLC).
Med Sci Monit. 2018; 24:8207-8212 [PubMed] Free Access to Full Article Related Publications
BACKGROUND RET rearrangements have been reported in 30% of papillary thyroid carcinomas and 1-2% of non-small cell lung cancer (NSCLC). In these tumors, RET gene fusion product provides a constitutively active tyrosine kinase (TKR), leading to uncontrolled cellular proliferation, differentiation, and migration. In this investigation we assessed the positivity rate of RET gene rearrangement in primary and metastatic non-small cell lung cancer and explored their relationships. MATERIAL AND METHODS Between January 2013 and May 2015, we collected 384 cases of primary metastatic non-small cell lung cancer, which included 246 matched metastatic tumors cases from multiple centers. The RET rearrangement uniformity in metastatic lymph nodes and tumor specimens were contrasted and the relationships between RET rearrangement and patients' clinical features were investigated. RESULTS For those 384 cases, 7 (1.82%) cases had tumors with identified RET rearrangement. Among the 246 paired cases, 3 (1.22%) cases of primary tumor had identified RET rearrangement and 2 (0.81%) cases of metastases had identified RET rearrangement. The sensitivity was 66.67% (2/3) and the specificity was 100% (243/243). CONCLUSIONS The results of this research indicate that the metastases of non-small cell lung cancer can predict RET rearrangement of the primary tumor tissue in the majority of cases. Testing for RET rearrangement in metastases can be used as an alternative to testing of primary tumor tissue if it is inaccessible.

Febrero B, Rodríguez JM, Ríos A, et al.
Prophylactic thyroidectomy in multiple endocrine neoplasia 2 (MEN2) patients with the C634Y mutation: A long-term follow-up in a large single-center cohort.
Eur J Surg Oncol. 2019; 45(4):625-630 [PubMed] Related Publications
BACKGROUND: Medullary thyroid carcinoma (MTC) is the main cause of death in multiple endocrine neoplasia 2A (MEN2A) patients. It is therefore important to treat this disease at an early stage. The mutation in codon 634 is considered to be associated with an aggressive clinical course, whereas the C634Y mutation may result in a more indolent course. Prophylactic thyroidectomy is performed before thyroid disease occurs. However, controversy surrounds this disease regarding levels of calcitonin (Ct) and age. In this context, few studies have investigated this mutation over a long period.
OBJECTIVE: To analyze a large cohort of patients with the C634Y mutation who received prophylactic thyroidectomy.
MATERIALS AND METHODS: In a group of 110 MEN2 patients, we analyzed those with the C634Y mutation who had received prophylactic thyroidectomy (absence of clinical and radiological thyroid disease) treated in a tertiary referral hospital between 1983 and 2016. MTC is related to age and Ct. Statistical analysis was performed using the χ
RESULTS: Fifty patients with a mean age of 12 ± 9 years were analyzed; 56% of these had MTC (100% stage I). There was no case of hypoparathyroidism or permanent recurrent damage. MTC was associated mainly with age (OR 1.38). One 5-year-old patient presented with MTC. Mean follow-up time was 16 ± 6 years, and no cases of recurrence were observed.
CONCLUSIONS: Performing prophylactic thyroidectomy in patients with the C634Y mutation allows us to cure the disease without causing long-term complications. Our results support the notion that age <5 years should be a criterion for carrying out prophylactic thyroidectomy in these patients.

Zhu YC, Wang WX, Zhang QX, et al.
The KIF5B-RET Fusion Gene Mutation as a Novel Mechanism of Acquired EGFR Tyrosine Kinase Inhibitor Resistance in Lung Adenocarcinoma.
Clin Lung Cancer. 2019; 20(1):e73-e76 [PubMed] Related Publications

Remon J, Hendriks LE, Cabrera C, et al.
Immunotherapy for oncogenic-driven advanced non-small cell lung cancers: Is the time ripe for a change?
Cancer Treat Rev. 2018; 71:47-58 [PubMed] Related Publications
Immune checkpoint inhibitors (ICIs) have been incorporated in the treatment strategy of advanced non-small cell lung cancer (NSCLC) in first- and second-line setting improving the prognosis of these patients. However, the treatment landscape has been also drastically overturned with the advent of targeted therapies in oncogenic-addicted advanced NSCLC patients. Despite ICIs represent an active and new treatment option for a wide range of advanced NSCLC patients, the efficacy and the optimal place of ICI in the treatment strategy algorithm of oncogenic-addicted tumors remains still controversial, as only a minority of trials with ICI enrol oncogenic-addicted NSCLC patients previously treated with standard therapy. Therefore, there are still several open questions about ICI in oncogenic-driven NSCLC, such as the efficacy and toxicities, which need to be addressed before considering treatment with ICI as a standard approach in this population. It is in this framework, we provide a thorough overview on this currently controversial topic.

Pecce V, Sponziello M, Damante G, et al.
A synonymous RET substitution enhances the oncogenic effect of an in-cis missense mutation by increasing constitutive splicing efficiency.
PLoS Genet. 2018; 14(10):e1007678 [PubMed] Free Access to Full Article Related Publications
Synonymous mutations continue to be filtered out from most large-scale cancer genome studies, but several lines of evidence suggest they can play driver roles in neoplastic disease. We investigated a case of an aggressive, apparently sporadic medullary thyroid carcinoma (MTC) harboring a somatic RET p.Cys634Arg mutation (a known MTC driver). A germ-line RET substitution (p.Cys630=) had also been found but was considered clinically irrelevant because of its synonymous nature. Next generation sequencing (NGS) of the tumor tissues revealed that the RET mutations were in cis. There was no evidence of gene amplification. Expression analysis found an increase of RET transcript in p.Cys630=;p.Cys634Arg patient compared with that found in 7 MTCs harboring p.Cys634 mutations. Minigene expression assays demonstrated that the presence of the synonymous RET mutation was sufficient to explain the increased RET mRNA level. In silico analyses and RNA immunoprecipitation experiments showed that the p.Cys630 = variant created new exonic splicing enhancer motifs that enhanced SRp55 recruitment to the mutant allele, leading to more efficient maturation of its pre-mRNA and an increased abundance of mature mRNA encoding a constitutively active RET receptor. These findings document a novel mechanism by which synonymous mutations can contribute to cancer progression.

Makri A, Akshintala S, Derse-Anthony C, et al.
Multiple Endocrine Neoplasia Type 2B Presents Early in Childhood but Often Is Undiagnosed for Years.
J Pediatr. 2018; 203:447-449 [PubMed] Free Access to Full Article Related Publications
We describe the presenting symptoms and signs of multiple endocrine neoplasia type 2B in a cohort of children. Improved awareness of the early nonendocrine signs of multiple endocrine neoplasia type 2B could lead to earlier diagnosis before the development of medullary thyroid cancer and possibly its metastasis.

Weng Y, Li F, Zhang S, et al.
[Study of RET proto-oncogene mutations in two pedigrees affected with multiple endocrine neoplasia type 2A].
Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 2018; 35(5):648-652 [PubMed] Related Publications
OBJECTIVE: To study the pattern of RET proto-oncogene mutations in two pedigrees affected with multiple endocrine neoplasia type 2A (MEN2A).
METHODS: Peripheral blood samples were collected from members of the two pedigrees, with total genomic DNA extracted for polymerase chain reaction (PCR). PCR products of 7 exons of the RET proto-oncogene (including exons 8, 10, 11, 13, 14, 15, 16) which have higher mutation rates were purified and subjected to direct sequencing. Suspected mutations in the 2 probands were verified in other members of the pedigrees. To exclude other mutations, PCR products of remaining 14 exons were sequenced in the proband from pedigree 1.
RESULTS: A novel heterozygous mutation, 1893-1895delCGA, was detected in exon 11 of the RET proto-oncogene among 3 patients and 2 unaffected members from pedigree 1, while a heterozygous mutation, Cys634Arg, was detected in exon 11 among 2 patients and 1 unaffected family member from pedigree 2.
CONCLUSION: The heterozygous 1893-1895delCGA and Cys634Arg mutations of the RET proto-oncogene probably underlie the disease in the two pedigrees. Above discovery has enriched the human gene mutation database.

Asao T, Takahashi F, Takahashi K
Resistance to molecularly targeted therapy in non-small-cell lung cancer.
Respir Investig. 2019; 57(1):20-26 [PubMed] Related Publications
The discovery of oncogenic driver gene mutations, including epidermal growth factor receptor (EGFR) mutation, anaplastic lymphoma kinase (ALK) fusion, ROS proto-oncogene 1 (ROS1) fusion, and ret proto-oncogene (RET) fusion, has led to the development of molecularly targeted therapy for non-small-cell lung cancer (NSCLC). This therapy has changed the standard of care for NSCLC. Despite the dramatic response to molecularly targeted therapy, almost all patients ultimately develop resistance to the drugs. To understand the mechanisms of resistance to molecularly targeted agents, it is essential to understand the molecular pathways of NSCLC. Here, we review the mechanisms of resistance to molecularly targeted therapy and discuss strategies to overcome drug resistance.

Miller TE, Yang M, Bajor D, et al.
Clinical utility of reflex testing using focused next-generation sequencing for management of patients with advanced lung adenocarcinoma.
J Clin Pathol. 2018; 71(12):1108-1115 [PubMed] Related Publications
AIMS: The growing number of genomically targeted therapies has made genomic testing an important part of the care for patients with non-small cell lung cancer. However, limited tissue availability, cost and long turnaround times can create barriers to efficient genomic testing and subsequent treatment. Effective approaches to reduce these barriers are needed.
METHODS: 302 advanced lung adenocarcinomas from consecutive patients seen at University Hospitals Cleveland Medical Center (UHCMC) were tested inhouse using a hybrid DNA/RNA next-generation sequencing (NGS) panel. Sample testing was reflexed from pathology for all stage III or IV tumours. Genomic alterations were tiered according to their clinical relevance and reported with guideline-recommended therapies. Clinical implications of genomic testing results were assessed by manual chart review.
RESULTS: With a sample cohort consisting of 64% biopsies, 16% excisions/resections and 20% fine needle aspirations, the assay was reliable with a 95% success rate. The average turnaround time from receipt of unstained formalin-fixed paraffin embedded slides to reporting was 4.8±2.1 days, half of the recommended 10 days and similar to single-gene testing. Alterations with Food and Drug Administration-approved or the National Cancer Center Network guideline-recommended targeted therapies were found in 18% of cases. Within this group, 60% of patients went on genomically driven therapies.
CONCLUSIONS: We found our reflexed inhouse NGS assay to be reliable, cost-effective and efficient. Incorporation of reflex testing with our NGS assay led to an expansion of successful genomic profiling for all guideline-recommended alterations, and by including an expanded number of alterations within our panel we obtained clinically useful information outside the guidelines without changing cost or efficiency. This approach has enabled UHCMC clinicians to efficiently initiate genomically driven therapies for patients with lung adenocarcinoma.

Machens A, Elwerr M, Schneider R, et al.
Disease impacts more than age on operative morbidity in children with Graves' disease after total thyroidectomy.
Surgery. 2018; 164(5):993-997 [PubMed] Related Publications
BACKGROUND: In pediatric Graves' disease, operative morbidity after total thyroidectomy remains ill defined. The present study aimed to clarify whether total thyroidectomy entails greater operative morbidity in children with Graves' disease, in particular when they are very young, as compared with an age-matched reference group of children with hereditary C-cell disease who underwent total thyroidectomy at the same time.
METHODS: Operative morbidity after total thyroidectomy for Graves' disease was determined in relation to the child's age and in comparison with a reference group of age-matched children with hereditary C-cell disease.
RESULTS: Included in the study were 58 children with Graves' disease (51 girls and 7 boys) and 108 children with hereditary C-cell disease (59 girls and 49 boys). When children with Graves' disease and children with hereditary C-cell disease were compared across and within the 4 age increments (≤ 3, 4-6, 7-12, and 13-18 years), operative mortality did not differ significantly among and within age increments. Children with Graves' disease had a 1.7-fold greater overall risk of transient hypoparathyroidism (29% versus 17%; P = .073) than children with hereditary C-cell disease. Permanent hypoparathyroidism was nil in either group. Transient recurrent laryngeal nerve palsy, wound hemorrhage, and wound infections were infrequent (≤ 3% each), resolving spontaneously and after reoperation, respectively.
CONCLUSION: Disease impacts more than age on operative morbidity in children with Graves' disease after total thyroidectomy but is fairly low overall and rarely permanent in experienced hands.

Nagaoka R, Sugitani I, Sanada M, et al.
The Reality of Multiple Endocrine Neoplasia Type 2B Diagnosis: Awareness of Unique Physical Appearance Is Important.
J Nippon Med Sch. 2018; 85(3):178-182 [PubMed] Related Publications
BACKGROUND: Multiple endocrine neoplasia type 2B (MEN2B) is an extremely rare syndrome mainly caused by RET918 germline mutations. MEN2B typically causes medullary thyroid carcinoma (MTC), pheochromocytoma, and unique physical characteristics including mucosal neuroma, distinctive facial appearance, and Marfanoid habitus. Most patients have abdominal symptoms such as bloating, intermittent constipation, and diarrhea. MTC is the most important determinant of mortality in patients with MEN2B. Establishing the diagnosis of MEN2B at a curative stage of MTC is crucial.
CASE PRESENTATION: We have encountered four patients with MEN2B. Two were hereditary cases from the same family, and two were considered de novo cases with phenotypically normal parents. Mean age at diagnosis was 25.5 years (range, 13-39 years). Although all patients had shown mucosal neuroma on the lips and tongue, in addition to gastrointestinal symptoms from infancy, diagnoses were made from symptomatic MTC even for the hereditary patients (our index case was a 14-year-old girl, whose mother was subsequently diagnosed with advanced MTC). Genetic tests for RET mutations revealed the M918T mutation in all patients. Two patients developed pheochromocytoma, two died from distant metastases of MTC, and two received treatment for multiple metastases of MTC (one with vandetanib).
CONCLUSIONS: In our patients with MEN2B, prophylactic or early thyroidectomy could not be performed. The characteristic phenotype associated with MEN2B is almost always seen prior to detection of MTC or pheochromocytoma. Knowledge about the non-endocrine manifestations of MEN2B needs to be shared among pediatricians and gastroenterologists.

Zhang K, Chen H, Wang Y, et al.
Clinical Characteristics and Molecular Patterns of
Oncol Res. 2019; 27(5):575-582 [PubMed] Related Publications

Wu K, Zhang Y, Zhang H, et al.
[Germline gene testing of the RET, VHL, SDHD and SDHB genes in patients with pheochromocytoma/paraganglioma].
Beijing Da Xue Xue Bao Yi Xue Ban. 2018; 50(4):634-639 [PubMed] Related Publications
OBJECTIVE: To analyze the germline variations of genes RET, VHL, SDHD and SDHB in patients with pheochromocytoma and/or paraganglioma and to evaluate variations of these genes in Chinese patients.
METHODS: Patients who were treated in Peking University First Hospital from September 2012 to March 2014 and diagnosed with pheochromocytoma and/or paraganglioma by pathologists were included in this study. Twelve patients were included in total, of whom 11 had pheochromocytoma, and 1 had paraganglioma. Deoxyribonucleic acid (DNA) was extracted from the leukocytes of peripheral blood of the patients. The exons 10, 11, 13-16 of the RET gene, and all exons of VHL, SDHB and SDHD genes and their nearby introns (±20 bp) were amplified with polymerase chain reactions, and the products were sent to a biotechnology company for sequencing. The sequencing results were compared with wildtype sequences of these genes to identify variations. One of the patients was diagnosed with multiple endocrine neoplasia type 2A. A family analysis was performed in his kindred, and his family members received genetic tests for the related variations.
RESULTS: Three patients were found to have germline gene variations. A c.136C>T (p.R46X) variation of the SDHB gene was found in a patient with malignant pheochromocytoma. A c.1901G>A (C634Y) variation, as well as c.2071G>A (p.G691S) and c.2712C>G (p.S904S) variations of the RET gene were found in a patient with multiple endocrine neoplasia type 2A. After a family analysis, five family members of this patient were found to have the same variations. c.2071G>A (p.G691S) and c.2712C>G (p.S904S) variations of the RET gene were also found in a clinical sporadic patient without evidence of malignancy. A patient with congenital single ventricle malformation and pheochromocytoma was included in this study, and no variation with clinical significance was found in the four genes of this patient.
CONCLUSION: 25% (3/12) patients with pheochromocytoma or paraganglioma were found to have missense or nonsense germline gene variations in this study, including the c.136C>T (p.R46X) variation of the SDHB gene, the c.1901G>A (C634Y) variation of the RET gene, and c.2071G>A (p.G691S) and c.2712C>G (p.S904S) variations of the RET gene. The former two variations have already been confirmed to be pathogenic. The existence of these variations in Chinese patients with pheochromocytoma and/or paraganglioma was validated in this study, which supports the conclusion that genetic testing is necessary to be generally performed in patients with pheochromocytoma and/or paraganglioma.

Further References

Mulligan LM, Kwok JB, Healey CS, et al.
Germ-line mutations of the RET proto-oncogene in multiple endocrine neoplasia type 2A.
Nature. 1993; 363(6428):458-60 [PubMed] Related Publications
Multiple endocrine neoplasia type 2A (MEN 2A) is a dominantly inherited cancer syndrome that affects tissues derived from neural ectoderm. It is characterized by medullary thyroid carcinoma (MTC) and phaeochromocytoma. The MEN2A gene has recently been localized by a combination of genetic and physical mapping techniques to a 480-kilobase region in chromosome 10q11.2 (refs 2,3). The DNA segment encompasses the RET proto-oncogene, a receptor tyrosine kinase gene expressed in MTC and phaeochromocytoma and at lower levels in normal human thyroid. This suggested RET as a candidate for the MEN2A gene. We have identified missense mutations of the RET proto-oncogene in 20 of 23 apparently distinct MEN 2A families, but not in 23 normal controls. Further, 19 of these 20 mutations affect the same conserved cysteine residue at the boundary of the RET extracellular and transmembrane domains.

Donis-Keller H, Dou S, Chi D, et al.
Mutations in the RET proto-oncogene are associated with MEN 2A and FMTC.
Hum Mol Genet. 1993; 2(7):851-6 [PubMed] Related Publications
Multiple endocrine neoplasia type 2A (MEN 2A) and familial medullary thyroid carcinoma (FMTC) are dominantly inherited conditions which predispose to the development of endocrine neoplasia. Evidence is presented that sequence changes within the coding region of the RET proto-oncogene, a putative transmembrane tyrosine kinase, may be responsible for the development of neoplasia in these inherited disorders. Single strand conformational variants (SSCVs) in exons 7 and 8 of the RET proto-oncogene were identified in eight MEN 2A and four FMTC families. The variants were observed only in the DNA of individuals who were either affected or who had inherited the MEN2A or FMTC allele as determined by haplotyping experiments. The seven variants identified were sequenced directly. All involved point mutations within codons specifying cysteine residues, resulting in nonconservative amino acid changes. Six of the seven mutations are located in exon 7. A single mutation was found in exon 8. Variants were not detected in four MEN 2B families studied for all exon assays available, nor were they detectable in 16 cases of well documented sporadic medullary thyroid carcinoma or pheochromocytoma that were tested for exon 7 variants. Coinheritance of the mutations with disease and the physical and genetic proximity of the RET proto-oncogene provide evidence that RET is responsible for at least two of the three inherited forms of MEN 2. Neither the normal function, nor the ligand of RET are yet known. However, its apparent involvement in the development of these inherited forms of neoplasia as well as in papillary thyroid carcinoma suggest an important developmental or cell regulatory role for the protein.

Mulligan LM, Eng C, Healey CS, et al.
Specific mutations of the RET proto-oncogene are related to disease phenotype in MEN 2A and FMTC.
Nat Genet. 1994; 6(1):70-4 [PubMed] Related Publications
We have analysed 118 families with inherited medullary thyroid carcinoma (MTC) for mutations of the RET proto-oncogene. These included cases of multiple endocrine neoplasia types 2A (MEN 2A) and 2B (MEN 2B) and familial MTC (FMTC). Mutations at one of 5 cysteines in the extracellular domain were found in 97% of patients with MEN 2A and 86% with FMTC but not in MEN 2B patients or normal controls. 84% of the MEN2A mutations affected codon 634. MEN 2A patients with a Cys634 to Arg substitution had a greater risk of developing parathyroid disease than those with other codon 634 mutations. Our data show a strong correlation between disease phenotype and the nature and position of the RET mutation, suggesting that a simple, constitutive activation of the RET tyrosine kinase is unlikely to explain the events leading to MEN 2A and FMTC.

Hofstra RM, Landsvater RM, Ceccherini I, et al.
A mutation in the RET proto-oncogene associated with multiple endocrine neoplasia type 2B and sporadic medullary thyroid carcinoma.
Nature. 1994; 367(6461):375-6 [PubMed] Related Publications
Multiple endocrine neoplasia type 2 (MEN 2) comprises three clinically distinct, dominantly inherited cancer syndromes. MEN 2A patients develop medullary thyroid carcinoma (MTC) and phaeochromocytoma. MEN 2B patients show in addition ganglioneuromas of the gastrointestinal tract and skeletal abnormalities. In familial MTC, only the thyroid is affected. Germ-line mutations of the RET proto-oncogene have recently been reported in association with MEN 2A and familial MTC. All mutations occurred within codons specifying cysteine residues in the transition point between the RET protein extracellular and transmembrane domains. We now show that MEN 2B is also associated with mutation of the RET proto-oncogene. A mutation in codon 664, causing the substitution of a threonine for a methionine in the tyrosine kinase domain of the protein, was found in all nine unrelated MEN 2B patients studied. The same mutation was found in six out of 18 sporadic tumours.

Bounacer A, Wicker R, Caillou B, et al.
High prevalence of activating ret proto-oncogene rearrangements, in thyroid tumors from patients who had received external radiation.
Oncogene. 1997; 15(11):1263-73 [PubMed] Related Publications
A high frequency (about 60%) of ret rearrangements in papillary thyroid carcinomas of children exposed to radioactive fallout in Belarus after the Chernobyl accident, has been reported by three recent studies (Fugazzola et al., 1995; Ito et al., 1994; Klugbauer et al., 1995). These studies suggested that the radiation exposure may be a direct inducer of activating rearrangements in the ret gene. In order to confirm the postulated link between irradiation and the role of the ret proto-oncogene in thyroid tumorigenesis, we analysed for the presence of ret activating rearrangements using RT-PCR, XL-PCR, Southern blot and direct sequencing techniques, 39 human thyroid tumors (19 papillary carcinomas and 20 follicular adenomas), from patients who had received external radiation for benign or malignant conditions. As controls, we studied 39 'spontaneous' tumors (20 papillary carcinomas and 19 follicular adenomas). Our data concerning the radiation-associated tumors, showed that: (1) the overall frequency of ret rearrangements was 84% in papillary carcinomas (16/19) and 45% (9/20) in follicular adenomas; (2) in contrast with the results obtained in the Chernobyl tumors, the most frequently observed chimeric gene was RET/PTC1 instead of the RET/PTC3 and (3) all the tumors were negative for RET/PTC2. In the 'spontaneous' tumors, only the papillary carcinomas presented a ret rearrangement (15%:3/20): 1 RET/PTC1, 1 RET/ PTC3 and 1 uncharacterized. In conclusion, our results confirm the crucial role played by the ret proto-oncogene activating rearrangements in the development of radiation-associated thyroid tumors appearing after therapeutic or accidental ionizing irradiation, and show, for the first time, the presence of RET/PTC genes in follicular adenomas appeared after external irradiation.

Nikiforov YE, Rowland JM, Bove KE, et al.
Distinct pattern of ret oncogene rearrangements in morphological variants of radiation-induced and sporadic thyroid papillary carcinomas in children.
Cancer Res. 1997; 57(9):1690-4 [PubMed] Related Publications
In this study, we compare the morphological and genetic characteristics of 38 post-Chernobyl thyroid papillary carcinomas from Belarussian children 5-18 years old with those of 23 sporadic papillary carcinomas from the same age children without history of radiation exposure from Los Angeles and Cincinnati. Among radiation-induced tumors, solid variant of papillary carcinoma was found in 37%, follicular in 29%, typical papillary in 18%, and mixed and diffuse sclerosing variants in 8% each. In the sporadic group, a typical papillary pattern was prevalent in 70%, follicular in 17%, diffuse sclerosing variant in 9%, and solid in 4%. In both groups, the prevalence of ret rearrangements was high, but the frequency of specific types of rearrangement was significantly different. Among radiation-induced tumors, ret/PTC3 was found in 58%, ret/PTC1 in 16%, and ret/PTC2 in 3%, whereas among sporadic tumors, ret/PTC1 was found in 47% (P < 0.05), and ret/PTC3 was found in 18% (P = 0.01). The morphological variants of papillary carcinoma showed different prevalence of the specific types of ret rearrangement. Seventy-nine % of solid variant tumors had ret/PTC3, whereas only 7% had ret/PTC1 (P = 0.0007). Among typical papillary tumors, ret/PTC1 was found in 38%, ret/PTC3 in 19%, and ret/PTC2 in 5%. Thus, ret rearrangements are highly prevalent in pediatric papillary carcinomas from children exposed to radiation and in those occurring sporadically. However, the types of ret/PTC vary between these two populations, with ret/PTC3 present more commonly in post-Chernobyl tumors. Furthermore, solid variants have a high prevalence of ret/PTC3, whereas typical papillary carcinomas do not, suggesting that the different types of ret rearrangement confer neoplastic thyroid cells with distinct phenotypic properties.

Smida J, Salassidis K, Hieber L, et al.
Distinct frequency of ret rearrangements in papillary thyroid carcinomas of children and adults from Belarus.
Int J Cancer. 1999; 80(1):32-8 [PubMed] Related Publications
Rearrangements of the ret oncogene were investigated in papillary thyroid carcinomas (PTC) from 51 Belarussian children with a mean age of 3 years at the time of the Chernobyl radiation accident. For comparison, 16 PTC from exposed Belarussian adults and 16 PTC from German patients without radiation history were included in the study. ret rearrangements were detected and specified by RT-PCR and direct sequencing using specific primers for ret/PTC1, 2 and 3. Only ret/PTC1, and no ret/PTC3, was found in the adult patients, with a frequency of 69% for the Belarussian cases, but of only 19% in the German patients. In contrast, 13 ret/PTC3 (25.5%) and 12 ret/PTC1 (23.5%) rearrangements were present in PTC from Belarussian children. Thus, our study reveals about a 1:1 ratio of ret/PTC3 and ret/PTC1, in contrast to earlier studies with lower numbers of cases and exhibiting a high predominance of ret/PTC3 (ratio about 3:1). A ratio (2.5:1) similar to that in earlier investigations (diagnosed 1991-94) was obtained for cases included in our study that were diagnosed in 1993/94. The present data suggest that ret/PTC3 may be typical for radiation-associated childhood PTC with a short latency period, whereas ret/PTC1 may be a marker for later-occurring PTC of radiation-exposed adults and children.

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