1
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Zheng ZZ, Xia L, Hu GS, Liu JY, Hu YH, Chen YJ, Peng JY, Zhang WJ, Liu W. Super-enhancer-controlled positive feedback loop BRD4/ERα-RET-ERα promotes ERα-positive breast cancer. Nucleic Acids Res 2022; 50:10230-10248. [PMID: 36124682 PMCID: PMC9561272 DOI: 10.1093/nar/gkac778] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 08/23/2022] [Accepted: 08/30/2022] [Indexed: 12/22/2022] Open
Abstract
Estrogen and estrogen receptor alpha (ERα)-induced gene transcription is tightly associated with ERα-positive breast carcinogenesis. ERα-occupied enhancers, particularly super-enhancers, have been suggested to play a vital role in regulating such transcriptional events. However, the landscape of ERα-occupied super-enhancers (ERSEs) as well as key ERα-induced target genes associated with ERSEs remain to be fully characterized. Here, we defined the landscape of ERSEs in ERα-positive breast cancer cell lines, and demonstrated that bromodomain protein BRD4 is a master regulator of the transcriptional activation of ERSEs and cognate ERα target genes. RET, a member of the tyrosine protein kinase family of proteins, was identified to be a key ERα target gene of BRD4-regulated ERSEs, which, in turn, is vital for ERα-induced gene transcriptional activation and malignant phenotypes through activating the RAS/RAF/MEK2/ERK/p90RSK/ERα phosphorylation cascade. Combination therapy with BRD4 and RET inhibitors exhibited additive effects on suppressing ERα-positive breast cancer both in vitro and in vivo, comparable with that of standard endocrine therapy tamoxifen. Furthermore, combination therapy re-sensitized a tamoxifen-resistant ERα-positive breast cancer cell line to tamoxifen treatment. Taken together, our data uncovered the critical role of a super-enhancer-associated positive feedback loop constituting BRD4/ERα–RET–ERα in ERα-positive breast cancer, and suggested that targeting components in this loop would provide a new therapeutic avenue for treating ERα-positive breast cancer in the clinic.
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Affiliation(s)
- Zao-Zao Zheng
- State Key Laboratory of Cellular Stress Biology, School of Pharmaceutical Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiang'an South Road, Xiamen, Fujian 361102, China.,Fujian Provincial Key Laboratory of Innovative Drug Target Research, School of Pharmaceutical Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiang'an South Road, Xiamen, Fujian 361102, China
| | - Lin Xia
- State Key Laboratory of Cellular Stress Biology, School of Pharmaceutical Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiang'an South Road, Xiamen, Fujian 361102, China.,Fujian Provincial Key Laboratory of Innovative Drug Target Research, School of Pharmaceutical Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiang'an South Road, Xiamen, Fujian 361102, China
| | - Guo-Sheng Hu
- State Key Laboratory of Cellular Stress Biology, School of Pharmaceutical Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiang'an South Road, Xiamen, Fujian 361102, China.,Fujian Provincial Key Laboratory of Innovative Drug Target Research, School of Pharmaceutical Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiang'an South Road, Xiamen, Fujian 361102, China
| | - Jun-Yi Liu
- State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, National Institute of Diagnostics and Vaccine Development in Infectious Diseases, School of Public Health, Faculty of Medicine and Life Sciences, Xiamen University, Xiang'an South Road, Xiamen, Fujian 361102, China
| | - Ya-Hong Hu
- State Key Laboratory of Cellular Stress Biology, School of Pharmaceutical Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiang'an South Road, Xiamen, Fujian 361102, China.,Fujian Provincial Key Laboratory of Innovative Drug Target Research, School of Pharmaceutical Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiang'an South Road, Xiamen, Fujian 361102, China
| | - Yu-Jie Chen
- State Key Laboratory of Cellular Stress Biology, School of Pharmaceutical Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiang'an South Road, Xiamen, Fujian 361102, China.,Fujian Provincial Key Laboratory of Innovative Drug Target Research, School of Pharmaceutical Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiang'an South Road, Xiamen, Fujian 361102, China
| | - Jia-Yin Peng
- State Key Laboratory of Cellular Stress Biology, School of Pharmaceutical Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiang'an South Road, Xiamen, Fujian 361102, China.,Fujian Provincial Key Laboratory of Innovative Drug Target Research, School of Pharmaceutical Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiang'an South Road, Xiamen, Fujian 361102, China
| | - Wen-Juan Zhang
- Department of Laboratory Medicine, First Affiliated Hospital of Gannan Medical University, No. 23, Qingnian Road, Ganzhou, Jiangxi 341000, China
| | - Wen Liu
- State Key Laboratory of Cellular Stress Biology, School of Pharmaceutical Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiang'an South Road, Xiamen, Fujian 361102, China.,Fujian Provincial Key Laboratory of Innovative Drug Target Research, School of Pharmaceutical Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiang'an South Road, Xiamen, Fujian 361102, China
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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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Harris KL, Myers MB, McKim KL, Elespuru RK, Parsons BL. Rationale and Roadmap for Developing Panels of Hotspot Cancer Driver Gene Mutations as Biomarkers of Cancer Risk. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2020; 61:152-175. [PMID: 31469467 PMCID: PMC6973253 DOI: 10.1002/em.22326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 08/23/2019] [Accepted: 08/26/2019] [Indexed: 05/24/2023]
Abstract
Cancer driver mutations (CDMs) are necessary and causal for carcinogenesis and have advantages as reporters of carcinogenic risk. However, little progress has been made toward developing measurements of CDMs as biomarkers for use in cancer risk assessment. Impediments for using a CDM-based metric to inform cancer risk include the complexity and stochastic nature of carcinogenesis, technical difficulty in quantifying low-frequency CDMs, and lack of established relationships between cancer driver mutant fractions and tumor incidence. Through literature review and database analyses, this review identifies the most promising targets to investigate as biomarkers of cancer risk. Mutational hotspots were discerned within the 20 most mutated genes across the 10 deadliest cancers. Forty genes were identified that encompass 108 mutational hotspot codons overrepresented in the COSMIC database; 424 different mutations within these hotspot codons account for approximately 63,000 tumors and their prevalence across tumor types is described. The review summarizes literature on the prevalence of CDMs in normal tissues and suggests such mutations are direct and indirect substrates for chemical carcinogenesis, which occurs in a spatially stochastic manner. Evidence that hotspot CDMs (hCDMs) frequently occur as tumor subpopulations is presented, indicating COSMIC data may underestimate mutation prevalence. Analyses of online databases show that genes containing hCDMs are enriched in functions related to intercellular communication. In its totality, the review provides a roadmap for the development of tissue-specific, CDM-based biomarkers of carcinogenic potential, comprised of batteries of hCDMs and can be measured by error-correct next-generation sequencing. Environ. Mol. Mutagen. 61:152-175, 2020. Published 2019. This article is a U.S. Government work and is in the public domain in the USA. Environmental and Molecular Mutagenesis published by Wiley Periodicals, Inc. on behalf of Environmental Mutagen Society.
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Affiliation(s)
- Kelly L. Harris
- Division of Genetic and Molecular ToxicologyNational Center for Toxicological Research, US Food and Drug AdministrationJeffersonArkansas
| | - Meagan B. Myers
- Division of Genetic and Molecular ToxicologyNational Center for Toxicological Research, US Food and Drug AdministrationJeffersonArkansas
| | - Karen L. McKim
- Division of Genetic and Molecular ToxicologyNational Center for Toxicological Research, US Food and Drug AdministrationJeffersonArkansas
| | - Rosalie K. Elespuru
- Division of Biology, Chemistry and Materials ScienceCDRH/OSEL, US Food and Drug AdministrationSilver SpringMaryland
| | - Barbara L. Parsons
- Division of Genetic and Molecular ToxicologyNational Center for Toxicological Research, US Food and Drug AdministrationJeffersonArkansas
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4
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Halperin DM, Phan AT, Hoff AO, Aaron M, Yao JC, Hoff PM. A phase I study of imatinib, dacarbazine, and capecitabine in advanced endocrine cancers. BMC Cancer 2014; 14:561. [PMID: 25086465 PMCID: PMC4125701 DOI: 10.1186/1471-2407-14-561] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 07/22/2014] [Indexed: 12/11/2022] Open
Abstract
Background Patients with advanced endocrine cancers, such as adrenocortical carcinoma and medullary thyroid carcinoma, have few well-validated therapeutic options. Pre-clinical studies have suggested potential activity of imatinib in these tumors. We therefore sought to establish a safe, novel treatment regimen combining imatinib with cytotoxic chemotherapy for future study in endocrine cancers. Methods A standard 3 + 3 dose-escalation design was used with a 21-day cycle, including imatinib on days 1–21, dacarbazine on days 1–3, and capecitabine on days 1–14. Results Twenty patients were treated. The most frequent toxicities were edema and fatigue, with dose-limiting fatigue and dyspnea. The recommended phase II regimen is dacarbazine 250 mg/m2 daily on day 1–3, capecitabine 500 mg/m2 twice daily on days 1–14, and imatinib 300 mg daily on days 1–21 of a 21-day cycle. Interestingly, responses were seen in patients with adrenocortical carcinoma, with 1 of 6 patients experiencing a partial response and a second experiencing a minor response, with progression-free survival of 8.8 and 6.4 months, respectively. Conclusions The regimen of imatinib, dacarbazine, and capecitabine is well-tolerated. It may have some activity in adrenocortical carcinoma, and further study of this combination or its components may be beneficial for this disease with limited treatment options. Trial registration ClinicalTrials.gov identifier NCT00354523, registered July 18, 2006.
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Affiliation(s)
| | | | | | | | - James C Yao
- Department of Gastrointestinal Medical Oncology, The University of Texas M, D, Anderson Cancer Center, Houston, Texas, USA.
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5
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Santos MACGD, Nunes AB, Abelin N, Ezabella MCL, Toledo RDA, Lourenço D, Hayashida CY, Fonseca IIMD, Toledo SPDA. [Genetic screening of multiple endocrine neoplasia type 2: experience of the USP Endocrine Genetics Unit]. ACTA ACUST UNITED AC 2006; 50:7-16. [PMID: 16628270 DOI: 10.1590/s0004-27302006000100003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Multiple endocrine neoplasia type 2 (MEN-2) is an inherited tumor syndrome that includes medullary thyroid carcinoma (MTC), primary hyperparathyroidism, pheochromocytoma and other non-endocrine diseases. Since the first RET missense mutations in association with MEN-2 were identified, RET mutation analysis had a great impact in the clinical management of MEN-2, such as in early diagnosis and treatment of MTC. Presently, early total thyroidectomy provides real cure of MTC for cases in which molecular diagnosis has been performed at early ages. After RET mutation identification, family members should be screened for this mutation by using methods as DGGE, SSCP, restriction enzyme, genetic sequencing or mini-sequencing. In this paper, we briefly review our experience with the direct RET gene sequencing and DGGE approaches. In 50 typical MEN-2 patients analyzed using both methods, we found no false results suggesting that DGGE is a reliable screening method for RET proto-oncogene mutation analysis.
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Affiliation(s)
- Marcelo A C G dos Santos
- Unidade de Endocrinologia Genética, Clínica Médica, Faculdade de Medicina, Universidade de São Paulo, SP
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6
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Abstract
The activation of the RET proto-oncogene contributes to the development of human cancers in two different ways. Somatic rearrangements of RET with a variety of activating genes, which contribute to unscheduled expression and constitutive dimerization of the chimeric RET/PTC oncoproteins in thyroid follicular cells, are frequently found in radiation-induced papillary thyroid carcinomas. Germ-line mutations, mainly point mutations, that lead to constitutive activation of RET tyrosine kinase activity are responsible for the development of the inherited cancer syndrome, multiple endocrine neoplasia type 2. There appears to be a correlation between specific types of RET mutation and clinical phenotypes of the cancers involved. The biological effects and the signaling pathways induced by different forms of RET activation have been investigated in a variety of cultured cells as well as in genetically engineered animal models. The identification of RET mutations in most MEN 2 families (95%) has translated into improved care for MEN 2 patients. However, further investigation of the signaling pathways contributing to tumorigenesis in relevant tissues will eventually help us to develop novel strategies to prevent or to treat human papillary thyroid carcinomas, MEN 2 disease, as well as the sporadic cancers relevant to MEN 2 disease.
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Affiliation(s)
- S M Jhiang
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, Ohio, OH 43210, USA
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7
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Hansford JR, Mulligan LM. Multiple endocrine neoplasia type 2 and RET: from neoplasia to neurogenesis. J Med Genet 2000; 37:817-27. [PMID: 11073534 PMCID: PMC1734482 DOI: 10.1136/jmg.37.11.817] [Citation(s) in RCA: 179] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Multiple endocrine neoplasia type 2 (MEN 2) is an inherited cancer syndrome characterised by medullary thyroid carcinoma (MTC), with or without phaeochromocytoma and hyperparathyroidism. MEN 2 is unusual among cancer syndromes as it is caused by activation of a cellular oncogene, RET. Germline mutations in the gene encoding the RET receptor tyrosine kinase are found in the vast majority of MEN 2 patients and somatic RET mutations are found in a subset of sporadic MTC. Further, there are strong associations of RET mutation genotype and disease phenotype in MEN 2 which have led to predictions of tissue specific requirements and sensitivities to RET activity. Our ability to identify genetically, with high accuracy, subjects with MEN 2 has revolutionised our ability to diagnose, predict, and manage this disease. In the past few years, studies of RET and its normal ligand and downstream interactions and the signalling pathways it activates have clarified our understanding of the roles played by RET in normal cell survival, proliferation, and differentiation, as well as in disease. Here, we review the current knowledge of the normal functions of RET and the effects of mutations of this gene in tumorigenesis and in normal development.
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Affiliation(s)
- J R Hansford
- Department of Pathology, Queen's University, Kingston, Ontario K7L 3N6, Canada
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8
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Li QX, Robbins JM, Welch PJ, Wong-Staal F, Barber JR. A novel functional genomics approach identifies mTERT as a suppressor of fibroblast transformation. Nucleic Acids Res 2000; 28:2605-12. [PMID: 10871412 PMCID: PMC102704 DOI: 10.1093/nar/28.13.2605] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2000] [Revised: 05/10/2000] [Accepted: 05/10/2000] [Indexed: 11/12/2022] Open
Abstract
As a tool for functional genomics, a hairpin ribozyme gene library with randomized target recognition sequences was constructed in a retroviral vector. This library has the potential to target and cleave any possible RNA substrate. Mouse fibroblasts transduced with this ribozyme gene vector library were selected in a focus formation assay to isolate in vivo functional ribozymes that promote cell transformation in tissue culture. After two successive rounds of selection by focus formation assay, a transforming ribozyme (Rz007) was identified. The sequence of this ribozyme was used to identify the putative target genes responsible for the transformation. A candidate gene target for Rz007 encodes telomerase reverse transcriptase (mTERT). Both mRNA level and enzymatic activity of mTERT were down-regulated in Rz007-transformed cells. Furthermore, newly designed ribozymes, recognizing other potential ribozyme cleavage sites unique to the mTERT mRNA, also cause cell transformation, thus validating the role of mTERT in suppressing the transformation phenotype. These surprising results suggest that the commonly accepted role of telomerase in maintaining cellular immortalization is more complicated than previously thought. These studies also demonstrate the utility of this novel 'reverse' functional genomics approach, enabling the targeted discovery of genes, whether previously known or not, that are involved in any selectable phenotype.
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MESH Headings
- 3T3 Cells
- Animals
- Base Sequence
- Binding Sites
- Cell Line, Transformed
- Cell Size
- Cell Transformation, Neoplastic/genetics
- Cell Transformation, Neoplastic/metabolism
- Cell Transformation, Neoplastic/pathology
- DNA-Binding Proteins
- Down-Regulation/genetics
- Gene Expression Regulation, Enzymologic
- Gene Library
- Genetic Vectors/genetics
- Genome
- Humans
- Mice
- Molecular Sequence Data
- Nucleic Acid Conformation
- Phenotype
- RNA
- RNA, Catalytic/chemistry
- RNA, Catalytic/genetics
- RNA, Catalytic/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Regulatory Sequences, Nucleic Acid/genetics
- Reproducibility of Results
- Retroviridae/genetics
- Telomerase/biosynthesis
- Telomerase/genetics
- Telomerase/metabolism
- Transduction, Genetic
- Tumor Stem Cell Assay
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Affiliation(s)
- Q X Li
- Immusol Inc., San Diego, CA 92121, USA
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9
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Hoff AO, Cote GJ, Fritsche HA, Qiu H, Schultz PN, Gagel RF. Calcium-induced activation of a mutant G-protein-coupled receptor causes in vitro transformation of NIH/3T3 cells. Neoplasia 1999; 1:485-91. [PMID: 10935495 PMCID: PMC1508117 DOI: 10.1038/sj.neo.7900072] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The calcium-sensing receptor (CaR) is a G-protein-coupled receptor that is widely expressed, has tissue-specific functions, and regulates cell growth. Activating mutations of this receptor cause autosomal dominant hypocalcemia, a syndrome characterized by hypocalcemia and hypercalciuria. The identification of a family with an activating mutation of the CaR (Thr151Met) in which hypocalcemia cosegregates with several unusual neoplasms led us to examine the transforming effects of this mutant receptor. Transfection of NIH/3T3 cells with the mutant but not the normal receptor supported colony formation in soft agar at subphysiologic calcium concentrations. The mutant CaR causes a calcium-dependent activation of the extracellular signal-regulated protein kinase (ERK) 1/2 and Jun-N-terminal kinase/stress-activated (JNK/ SAPK) pathways, but not P38 MAP kinase. These findings contribute to a growing body of information suggesting that this receptor plays a role in the regulation of cellular proliferation, and that aberrant activation of the mutant receptor in this family may play a role in the unusual neoplastic manifestations.
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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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10
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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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11
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Abstract
Progress in the characterization of gap junctions and their constituent connexin sub-units is leading to a greater understanding of the structure, function, and regulation of this cell-cell communication channel. Although much of the experimental evidence generated to date is correlative, recent work utilizing reverse genetic approaches to manipulate connexin gene function has provided direct evidence that intercellular communication via gap junctions plays key roles in development, cellular differentiation, and organogenesis. Pathogenic mutations in human connexin genes have now been identified. Furthermore, a considerable body of experimental evidence correlates a loss of junctional communication with progression to a malignant phenotype. Although the cell biology of the mammary gland has been extensively studied, the role(s) of gap junctions in the development, differentiation, and maintenance of this tissue are unknown. Gap junctions were first reported in the mammary gland following freeze-fracture and electron microscopic analyses. The development of anti-connexin antibodies and the cloning of individual connexin isoforms have enabled this work to be extended, but there are contradictory reports in the temporal expression patterns of these proteins within mammary epithelium. In addition, a recent report in this Journal has implied by immunocytochemistry that there is up-regulation of connexin protein in some human breast tumours, a novel observation which may be inconsistent with the proposed tumour suppressor role for gap junctions.
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Affiliation(s)
- D Locke
- Institute of Cancer Research, Sutton, Surrey, U.K.
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12
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Mayr B, Pötter E, Goretzki P, Rüschoff J, Dietmaier W, Hoang-Vu C, Dralle H, Brabant G. Expression of Ret/PTC1, -2, -3, -delta3 and -4 in German papillary thyroid carcinoma. Br J Cancer 1998; 77:903-6. [PMID: 9528832 PMCID: PMC2150093 DOI: 10.1038/bjc.1998.149] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Ret/PTC oncogene has been described with a frequency of 2.5-30% in papillary thyroid carcinomas. We examined the expression of ret/PTC in 99 German papillary thyroid carcinomas, including two recently described new variants of ret/PTC3 and identified eight ret/PTC-positive tumours (8%) but none with the new variants.
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Affiliation(s)
- B Mayr
- Abteilung Klinische Endokrinologie, Medizinische Hochschule Hannover, Germany
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13
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Xing S, Furminger TL, Tong Q, Jhiang SM. Signal transduction pathways activated by RET oncoproteins in PC12 pheochromocytoma cells. J Biol Chem 1998; 273:4909-14. [PMID: 9478934 DOI: 10.1074/jbc.273.9.4909] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Gene alterations in the ret proto-oncogene, which encodes a receptor tyrosine kinase, have been found to associate with several human diseases. In this study, we showed that induction of the vgf promoter activity is a good molecular indicator for RET activation in PC12 cells, a rat pheochromocytoma cell line. We demonstrated that all forms of RET oncoprotein, including RET chimeric oncoproteins found in human papillary thyroid carcinomas (RET/PTC) as well as RET oncoproteins found in patients with multiple endocrine neoplasia type 2A and 2B (2A/RET and 2B/RET) can induce vgf promoter activity in PC12 cells. In contrast, a RET mutant found in a patient with Hirschsprung's disease, as well as a RET/PTC1 mutant with deletion of the dimerization domain, failed to induce vgf promoter activity in PC12 cells. We further determined that the signaling events mediated by phosphorylated Tyr294 and phosphorylated Tyr451 binding sites are essential for RET/PTC1 to induce vgf promoter activity in PC12 cells. We also showed that RET/PTC1, 2A/RET, and 2B/RET induce ELK-, cAMP-responsive element binding protein (CREB), or JUN-mediated gene expression in PC12 cells, and these three signaling events are mediated by phosphorylated Tyr294 and phosphorylated Tyr451 binding sites in RET/PTC1.
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Affiliation(s)
- S Xing
- Department of Physiology, The Ohio State University, Columbus, Ohio 43210, USA
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14
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Gagel RF. An overview of molecular abnormalities leading to thyroid carcinogenesis: a 1993 perspective. Stem Cells 1997; 15 Suppl 2:7-13. [PMID: 9368282 DOI: 10.1002/stem.5530150705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
This discussion reviews molecular abnormalities in thyroid carcinoma and points out areas where these molecular defects might be applicable to thyroid carcinogenesis induced by radiation exposure. Both medullary and papillary follicular thyroid carcinoma are discussed. The multiple endocrine neoplasia type 2 gene on chromosome 10 is one of the genes responsible for medullary thyroid carcinoma. Genes thought to be involved in papillary and follicular thyroid carcinoma include the gsp, ret, trk, ras, met, and p53 oncogenes. Research is continuing to: A) find new genes whose regulation and/or expression may be responsible for these disorders; B) determine the mechanisms by which gene mutations can lead to thyroid carcinogenesis, and C) devise methods to prevent or counter the effects of these mutational events.
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Affiliation(s)
- R F Gagel
- University of Texas, M.D. Anderson Cancer Center, Houston, USA
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Tong Q, Xing S, Jhiang SM. Leucine zipper-mediated dimerization is essential for the PTC1 oncogenic activity. J Biol Chem 1997; 272:9043-7. [PMID: 9083029 DOI: 10.1074/jbc.272.14.9043] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The PTC1 chimeric oncogene is generated by the fusion of the tyrosine kinase domain of the RET proto-oncogene to the 5'-terminal region of another gene named H4 (D10S170). This oncogene has been detected only in human papillary thyroid carcinomas. We have previously demonstrated that the putative leucine zipper in the N-terminal region of H4 can mediate oligomerization of the PTC1 oncoprotein in vitro. In this study, we further demonstrated that the PTC1 oncoprotein forms a dimer in vivo, and the leucine zipper is responsible for this dimerization. The H4 leucine zipper-mediated dimerization is essential for tyrosine hyperphosphorylation and the transforming activity of the PTC1 oncoprotein. Introducing a loss-of-function PTC1 mutant into PTC1-transformed NIH3T3 cells suppressed the transforming activity of PTC1 and reversed the transformed phenotype of these cells, presumably by forming inactive heterodimers between the two forms of PTC1. Taken together, these data indicate that constitutive dimerization of the PTC1 oncoprotein is essential for PTC1 transforming activity and suggest that constitutive oligomerization acquired by rearrangement or by point mutations may be a general mechanism for the activation of receptor tyrosine kinase oncogenes.
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Affiliation(s)
- Q Tong
- Department of Physiology and the Department of Internal Medicine, Ohio State University, Columbus, Ohio 43210, USA
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