1,721,031 research outputs found
Minireview: RET/PTC rearrangements and braf mutations in thyroid tumorigenesis
No full textThyroid papillary carcinoma is the most common type of endocrine cancer. It is frequently associated with genetic alterations leading to activation of the MAPK signaling pathway. The two most frequently affected genes, BRAF and RET, are activated by either point mutation or as a result of chromosomal rearrangement. These mutations are tumorigenic in thyroid follicular cells and correlate with specific phonotypical features and biological properties of papillary carcinomas, including tumor aggressiveness and response to radioiodine therapy. Molecular inhibitors that block RET/PTC or BRAF kinase activity have shown substantial therapeutic effects in the experimental systems and are currently being tested in clinical trial
Alterations of the BRAF gene in thyroid tumors
No full textBRAF belongs to the RAF family of protein kinases that are important components of the MAPK signaling pathway mediating cell growth, differentiation and survival. Activating point mutation of the BRAF gene resulting in V600E (previously designated as V599E) is a common event in thyroid papillary carcinoma, being found in approx 40% of this tumor. It has strong association with classical papillary carcinoma and tall cell and possibly Warthin-like variants. This mutation also occurs in thyroid poorly differentiated and anaplastic carcinomas, usually those containing areas of papillary carcinoma. Alterations in the BRAF gene do not overlap with RAS mutations and RET/PTC rearrangement, indicating that activation of one of the effectors of the MAPK pathway is sufficient for papillary thyroid carcinogenesis. Recently, another mechanism of BRAF activation has been identified, which involves chromosome 7q inversion that results in the AKAP9-BRAF fusion. It is rare in sporadic papillary carcinomas and is more common in tumors associated with radiation exposure. Yet another mechanism of BRAF activation may involve copy number gain, which is seen in a significant portion of thyroid follicular tumors of both conventional and oncocytic (Hürthle cell) types
BRAF copy number gains in thyroid tumors detected by fluorescence in situ hybridization
No full textPoint mutation of the BRAF gene is a common genetic event in papillary thyroid carcinomas. More recently, it has been found that BRAF can also participate in chromosomal rearrangement. In this study, we explore yet another possible mechanism of BRAF alteration, which involves copy number gain. Using fluorescence in situ hybridization with BRAF specific and chromosome 7 centromeric probes, we studied 62 follicular thyroid tumors and 32 papillary carcinomas. We found that numerical changes in BRAF copy number were rare in papillary thyroid carcinomas, while they occurred in 16-45% of follicular tumors of conventional and oncocytic (Hürthle cell) types. They were due to amplification of the gene or gain of one or more copies of chromosome 7. Tetrasomy for chromosome 7 was overall the most common finding. The changes in BRAF copy number did not overlap with RAS mutations in follicular tumors. In a group of follicular carcinomas, tumors with BRAF copy number gain were significantly more often widely invasive (67%) compared to tumors with no copy number change (18%). By Western blotting, the tumors carrying four copies of the gene revealed higher expression of BRAF protein, suggesting that copy number gain may represent another mechanism of BRAF activation in thyroid tumors
A comprehensive overview of the role of the RET proto-oncogene in thyroid carcinoma
No full textThe rearranged during transfection (RET) proto-oncogene was identified in 1985 and, very soon thereafter, a rearrangement named RET/PTC was discovered in papillary thyroid carcinoma (PTC). After this discovery, other RET rearrangements were found in PTCs, particularly in those induced by radiation. For many years, it was thought that these genetic alterations only occurred in PTC, but, in the past couple of years, some RET/PTC rearrangements have been found in other human tumours. 5 years after the discovery of RET/PTC rearrangements in PTC, activating point mutations in the RET proto-oncogene were discovered in both hereditary and sporadic forms of medullary thyroid carcinoma (MTC). In contrast to the alterations found in PTC, the activation of RET in MTC is mainly due to activating point mutations. Interestingly, in the past year, RET rearrangements that were different to those described in PTC were observed in sporadic MTC. The identification of RET mutations is relevant to the early diagnosis of hereditary MTC and the prognosis of sporadic MTC. The diagnostic and prognostic role of the RET/PTC rearrangements in PTC is less relevant but still important in patient management, particularly for deciding if a targeted therapy should be initiated. In this Review, we discuss the pathogenic, diagnostic and prognostic roles of the RET proto-oncogene in both PTC and MTC
Retinoic acid receptor beta2 re-expression and growth inhibition in thyroid carcinoma cell lines after 5-aza-2'-deoxycytidine treatment
No full textI CARCINOMI PAPILLARI E MIDOLLARI DELLA TIROIDE PRESENTI CONTEMPORANEAMENTE HANNO ORIGINE GENETICA INDIPENDENTE
No full textIl Carcinoma Papillare (PTC) ed il Carcinoma Midollare (MTC) della tiroide si sviluppano entrambi nella tiroide ma hanno un’origine embrionale distinta: il PTC deriva dalle cellule follicolari mentre il MTC dalle cellule C-parafollicolari. In letteratura sono riportati casi in cui questi due tipi di tumore si presentano contemporaneamente ed una possibile causa genetica comune e’ stata ipotizzata anche se i dati a disposizione rimangono tuttora controversi. Scopo di questo studio è stato quello di analizzare la presenza di alterazioni genetiche caratteristiche dei due tipi di tumore (PTC e MTC) che si presentano contemporaneamente. Allo scopo abbiamo studiato 24 pazienti (6 maschi, 18 femmine) che presentavano simultaneamente un PTC ed un MTC. Il DNA genomico è stato estratto dalle componenti tumorali e dal parenchima sano ed e’ stato analizzato con sequenziamento diretto per le mutazioni nei codoni 12, 13 e 61 dei geni H-, K- ed N-RAS, 600 del gene BRAF e 634 e 918 dell’oncogene RET. Due/24 pazienti (8.3%) erano affetti da MEN2A con mutazione germinale del gene RET (S981A, V804M). Nessuno degli altri pazienti presentava mutazioni nel tessuto sano ed in 8/24 pazienti (33.4%) non presentavano mutazioni nemmeno nelle porzioni tumorali. Negli altri pazienti: 8/24 (33.3%) MTC presentavano la mutazione somatica di RET M918T; 3/24 (12.5%) mutazioni del gene H-RAS (G13R, Q61R, D69N) ed 1/24 (4.2%) mutazioni H-RAS (Q61K) e RET (M918T) contemporanea. Nella componente PTC: 1/24 (4.2%) presentava la mutazione BRAF (V600E), 1/24 (4.2%) la mutazione H-RAS (T58A) e 1/24 (4.2%) la mutazione K-RAS (M1T). In un caso, si aveva contemporaneamente la mutazione RET (M918T) nella componente MTC e BRAF (V600E) nella componente PTC. Nessuna delle mutazioni trovate era presente su entrambe le componenti tumorali. Questi dati suggeriscono cause indipendenti nell’insorgenza di PTC ed MTC che si presentano contemporaneamente in cui si osservano mutazioni tipiche per il tipo istologico (PTC e il MTC). A conferma di questa ipotesi, uno dei pazienti mostrava contemporaneamente una mutazione di RET nella componente MTC e la mutazione di BRAF nella componente PTC. Nel pannello di mutazioni trovate, le mutazioni D69N, T58A di H-RAS e M1T di K-RAS risultano nuove e mai descritte, suggerendo che anche mutazioni al di fuori degli hot spot classici dei geni RAS potrebbero avere un ruolo nella patogenesi di questi tumori
GENETIC SCREENING OF RET CAN IDENTIFY NEW MUTATIONS EVEN AFTER 20 YEARS
No full textObjectives: In the last 20 years we performed RET genetic screening in more than 1000 hereditary or sporadic MTC patients.
Methods: RET analysis was performed in constitutive and/or somatic DNA by direct sequencing. TA cloning was performed to characterize new mutations and deletions. Site-directed mutagenesis, focus formation and soft agar assays were performed to test in vitro the activity of new mutations. The Align GVGD program was employed for the in silico analysis.
Results: we identified 3 new RET alterations. The first was a 7bp “somatic” in frame deletion in exon 11 encompassing codon 629-631. The second showed the simultaneous presence of a “somatic” E616Q mutation in exon 10 and a “somatic” C630G mutation in exon 11 on different alleles. Moreover, in the same patient, we found an alternative splicing causing the in frame skip of exon 10 in the allele carrying the C630G mutation. The third alteration was a new “germline” mutation (E632K, exon 11) and was found in an apparently sporadic MTC. According to the in vitro and in silico tests, both E616Q and E632K RET mutations were not transforming while the C630G RET mutation showed a high transforming activity.
Conclusions: 1) RET genetic screening should be performed by sequencing analysis in all MTC patients to detect also new RET mutations that would be missed when looking only at the “hot spot” mutations; 2) all new mutations must be evaluated by in silico and/or in vitro analysis to define their transforming ability since in some cases they may be inactive mutations
WHOLE EXOME SEQUENCING OF MEDULLARY THYROID CARCINOMA CASES IDENTIFIES 86 VARIATIONS IN GENES POSSIBLY INVOLVED IN TUMORAL TRANSFORMATION
No full textObjectives: About 40% of sporadic Medullary Thyroid Carcinomas (MTC) is still orphan of an oncogenic driver. Purpose of this study was to disclose novel genetic alterations leading to the pathogenesis of MTC using Whole Exome Sequencing (WES) of RET+ and RET- cases.
Methods: WES analysis was performed on 6 sporadic MTC cases (2 RET+, 4 RET-) using an Illumina platform. After processing and proper filtering, all non-synonymous Single Nucleotide Variations (SNV) shared by the RET- cases were listed. Validation on 135 MTC cases and 189 healthy controls by PCR and enzymatic restriction analysis was performed in one of the genes of interest identified through WES.
Results: WES analysis led to the identification of a panel of 86 non-synonymous SNV shared in the 4 RET- cases and possibly involved in tumoral transformation process. Among the 86 SNV identified, the A133S polymorphism of the RASSF1A oncosuppressor appeared to be of interest. We found A133S in 21/135 (15.6%) MTC cases and in 19/189 (10%) healthy controls (P=0.137). The incidence of A133S appeared to be slightly lower in RET mutated MTC [9/64 (14%)] than in not-mutated [12/71 (17%)], although not statistically significant.
Conclusions: Through WES analysis we were able to identify 86 non-synonymous SNV shared in RET- MTC cases. This panel represents the first list of variations containing hypothetically novel genetic drivers involved in MTC oncogenesis. The prevalence of the A133S SNP was found to be higher in MTC cases compared to healthy controls (15.6% vs 10%) although not statistically significant. Further validation of other candidate genes is on-going
Re-differentiation of thyroid carcinoma cell lines treated with 5-Aza-2'-deoxycytidine and retinoic acid
No full textL’ANALISI GENETICA DI CARCINOMI PAPILLARI E MIDOLLARI DELLA TIROIDE PRESENTI CONTEMPORANEAMENTE RIVELA LA LORO NATURA CASUALE
No full textIl Carcinoma Papillare (PTC) ed il Carcinoma Midollare (MTC) della tiroide originano rispettivamente dalle cellule follicolari e parafollicolari della ghiandola. Abbastanza frequentemente, essi possono però presentarsi contemporaneamente. Diversi studi hanno tentato di trovare una causa patogenetica comune ma i dati a disposizione sono ancora controversi. Scopo di questo studio è quello di fornire un’analisi genetica dei tumori (PTC e MTC) che si presentano contemporaneamente per capire l’origine di questo fenomeno. Allo scopo abbiamo studiato 24 pazienti (6 maschi, 18 femmine) con presenza simultanea di PTC e MTC. DNA genomico è stato estratto dalle componenti PTC, MTC e parenchima sano per essere analizzato tramite PCR e sequenziamento diretto con primer specifici per mutazioni nei codoni 12, 13 e 61 dei geni H-, K- ed N-RAS, 600 del gene BRAF e 634 e 918 dell’oncogene RET. Due/24 pazienti (8.3%) erano affetti da MEN2A con mutazione germinale del gene RET (S981A, V804M), presente quindi in tutte e tre le componenti. Nessuno degli altri pazienti presentava mutazioni nel tessuto sano ed in 8/24 pazienti (33.4%) non e’ stata trovata alcuna mutazione nemmeno nelle porzioni PTC ed MTC. Negli altri pazienti, 8/24 (33.3%) MTC presentavano la mutazione somatica di RET M918T; 3/24 (12.5%) mutazioni del gene H-RAS (G13R, Q61R, D69N) ed 1/24 (4.2%) mutazioni H-RAS (Q61K) e RET (M918T) in contemporanea. Per quanto riguarda la componente PTC: 1/24 (4.2%) presentava la mutazione BRAF (V600E), 1/24 (4.2%) la mutazione H-RAS (T58A) e 1/24 (4.2%) la mutazione K-RAS (M1T). Uno dei pazienti mostrava contemporaneamente la mutazione RET (M918T) nella componente MTC e BRAF (V600E) nella componente PTC. Nessuna delle mutazioni trovate era presente su entrambe le. Da questi dati si evidenzia che le due componenti tumorali presentano mutazioni tipiche per il tipo istologico (PTC e il MTC) ed in nessun caso sono condivise, suggerendo cause indipendenti nell’insorgenza di questi tumori. A supporto di questa osservazione, uno dei pazienti mostrava una mutazione di RET nella componente MTC e la mutazione di BRAF nella componente PTC. Nel pannello di mutazioni trovate, le mutazioni D69N, T58A di H-RAS e M1T di K-RAS risultano nuove e mai descritte, suggerendo che anche mutazioni alternative agli hot spot classici dei geni RAS potrebbero avere un ruolo nella patogenesi di questi tumori
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