Sam68 is a RNA binding protein involved in various aspects of mRNA metabolism, including splicing, nuclear export and translation; its structure enables Sam68 to interact with several proteins involved in signal transduction cascades activated by growth factor receptors. Upregulation of Sam68 expression occurs in prostate, breast and renal carcinomas; although these observations strongly suggest that Sam68 supports cell transformation, its specific role in neoplastic cells have only been partially investigated. Constitutive expression and activation of Nucleophosmin/Anaplastic Lymphoma Kinase (NPM/ALK) is a key oncogenic event in Anaplastic Large Cells Lymphoma (ALCL) carrying the t(2;5)(p23;q35) chromosomal translocation. I have investigated the potential involvement of Sam68 in ALK-signalling. Results obtained indicate Sam68 as a novel regulator of ALK-mediated biological properties. Indeed: 1) ALK kinase activity strictly correlate with Sam68 phosphorylation in a p60src-dependent manner; 2) down-regulation of Sam68 severely impairs cell migration and cell growth in NPM/ALK positive cell lines; moreover, depletion of Sam68 sensitized this cells to cisplatin 3) interestingly I also observed a specific association between Sam68 and Vav1, a guanine nucleotide exchange factor, as a consequence of ALK activation. ALK kinase activity strictly correlate with Vav1 phosphorylation and depleting ALCL derived cells of Vav1 prevents ALK-induced Rac1 activation and results in impaired cell growth and migration. I have also investigated the potential involvement of Sam68 in Malignant pleural mesothelioma (MM) pathogenesis. Down-regulation of Sam68 in MM derived cells drastically impairs cell migration and reduced CD44v5 transcripts, whose expression has been correlated with enhanced malignancy and invasiveness of tumour cells. Finally, in this cells cisplatin induced relocalization of Sam68 from nucleus to cytoplasm suggesting for this protein a role in genotoxic stress response
Sam68, una proteina che lega l’RNA, è coinvolta in vari aspetti del metabolismo degli mRNA, tra cui lo splicing, l’esportazione dal nucleo e la traduzione; la sua struttura le consente di interagire con proteine coinvolte nella trasduzione del segnale attivata dai recettori per i fattori di crescita. A sostegno dell’ormai accreditato ruolo oncogenico, diversi studi ne documentano la frequente iper-espressione in carcinomi alla prostata, alla mammella e al rene; tuttavia i meccanismi molecolari attraverso i quali Sam68 promuove la trasformazione neoplastica sono ancora poco conosciuti. In questo contesto si inserisce l’attività di ricerca da me svolta: in particolare ho voluto analizzare il ruolo di Sam68 nella trasformazione mediata da ALK., la cui variante oncogenica NPM/ALK, gioca un ruolo centrale nella patogenesi del linfoma anaplastico a grandi cellule (ALCL). Ho potuto osservare che:1) l’attività di ALK è in grado di modulare la fosforilazione di Sam68 con un meccanismo p60src-dipendente 2) la down-regolazione di Sam68 determina una drastica inibizione delle capacità migratorie e proliferative, ed una sensibilizzazione al cisplatino delle cellule NPM/ALK positive derivanti da ALCL 3) in seguito ad attivazione di ALK, ho potuto osservare l’associazione tra Sam68 e Vav1, un fattore di scambio per nucleotidi, la cui attivazione è estremamente importante nella trasduzione dei segnali trasformanti ALK-mediati. Questi dati hanno trovato riscontro anche in cellule di mesotelioma maligno (MM) della pleura, in cui la down-regolazione di Sam68 è strettamente correlata ad una drastica riduzione delle capacità migratorie e dei livelli di espressione del trascritto CD44v5, la cui espressione è riscontrabile durante la fase invasiva di molti tumori. Infine, il trattamento con cisplatino induce nelle cellule derivate da MM una rilocalizzazione di Sam68 dal nucleo al citoplasma, suggerendo per questa proteina un ruolo fondamentale nella risposta allo stress genotossico.
Ruolo della proteina Sam68 nella regolazione degli eventi biologici in cellule neoplastiche / Borghetti, Giulia. - (2012 Feb 28).
Ruolo della proteina Sam68 nella regolazione degli eventi biologici in cellule neoplastiche
Borghetti, Giulia
2012-02-28
Abstract
Sam68 is a RNA binding protein involved in various aspects of mRNA metabolism, including splicing, nuclear export and translation; its structure enables Sam68 to interact with several proteins involved in signal transduction cascades activated by growth factor receptors. Upregulation of Sam68 expression occurs in prostate, breast and renal carcinomas; although these observations strongly suggest that Sam68 supports cell transformation, its specific role in neoplastic cells have only been partially investigated. Constitutive expression and activation of Nucleophosmin/Anaplastic Lymphoma Kinase (NPM/ALK) is a key oncogenic event in Anaplastic Large Cells Lymphoma (ALCL) carrying the t(2;5)(p23;q35) chromosomal translocation. I have investigated the potential involvement of Sam68 in ALK-signalling. Results obtained indicate Sam68 as a novel regulator of ALK-mediated biological properties. Indeed: 1) ALK kinase activity strictly correlate with Sam68 phosphorylation in a p60src-dependent manner; 2) down-regulation of Sam68 severely impairs cell migration and cell growth in NPM/ALK positive cell lines; moreover, depletion of Sam68 sensitized this cells to cisplatin 3) interestingly I also observed a specific association between Sam68 and Vav1, a guanine nucleotide exchange factor, as a consequence of ALK activation. ALK kinase activity strictly correlate with Vav1 phosphorylation and depleting ALCL derived cells of Vav1 prevents ALK-induced Rac1 activation and results in impaired cell growth and migration. I have also investigated the potential involvement of Sam68 in Malignant pleural mesothelioma (MM) pathogenesis. Down-regulation of Sam68 in MM derived cells drastically impairs cell migration and reduced CD44v5 transcripts, whose expression has been correlated with enhanced malignancy and invasiveness of tumour cells. Finally, in this cells cisplatin induced relocalization of Sam68 from nucleus to cytoplasm suggesting for this protein a role in genotoxic stress responseFile | Dimensione | Formato | |
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