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Previous issue date: 2012-05-29 / Gastrointestinal sarcomatoid tumors (GIST) are rare malignancies, corresponding to 1 - 3% of alli GI cancers. Nevertheless, GISts are the most common GI mesenchimal malignancies. GISTs are heterogeneous in presentation, clinical course and response to therapy. Their prognosis can be roughly estimated at diagnosis by assessing tumor size, mitotic index and the topography of the primary lesion. Despite the proved utility of these prognostic factors, their limitations are well documented, and a more refined set of biological markers are much needed. The abnormal activation of the cell survival signaling pathway provided by PI3K/Akt/PTEN proteins is a well known feature in advanced epithelial and hematological malignancies, impacting the aggressiveness of the disease as well as the resistance to different traditional therapies or biological agents. Besides their multi-effect in cell survival mechanisms, the PI3K/Akt/PTEN pathway is a powerful activator of angiogenesis via VEGF protein family transcription. The different isoforms of VEGF will in turn activate the VEGF receptor (VEGFR) at the surface of endothelial cells. Therefore, VEGFR is a reliable marker of angiogenesis in human tumors. We sought to evaluate the expression of VEGFR and Akt proteins in a series of GIST patients at diagnosis, treated in a single institution, in order to correlated the levei of expression of these proteins to clinical outcomes, such as overall survival (OS) and disease free survival (DFS). The levei of expression of these proteins was also correlated to the same outcomes in a subgroup of patients with advanced disease who received more than three months of therapy with Imatinib Mesylate (GleeveC?). Methods - 48 GIST patients were evaluated. Immunohystochemistry for VEGFR and Akt was performed by tissue microarray. Results - Akt hyperexpression was statistically correlated with a shorter DFS in the group of patients with metastatic disease (ali of them receiving GleeveC?). This correlation was not observed in early cases (defined as curable disease - stages I to III). We have not observed correlation between Akt expression and OS in any clinical stage. Lower VEGFR expression was associated to a significant better OS in ali stages (including patients receiving GleeveC?). Conversely, DFS was not affected by the levei of expression of VEGFR. CONCLUSIONS - Low VEGFR expression was related to a better prognosis in any clinicalstage of GIST, reflected in larger OS. The fact that this effect was observed in GleeveC? treated patients suggests that the betler response to the drug is much more related to the biology of the tumor than to the treatment itself. Akt showed also a promising role as a prognostic marker for disease free survival in advanced disease, indicating that GISTs with hyperexpressed Akt pathway behave more aggressively or may be less sensitive to GleeveC?. / Introdu??o: GISTs s?o raros, correspondendo de 1 a 3% de todas as neoplasias do trato gastrointestinal, entretanto, s?o as neoplasias mesenquimais mais comuns desta localiza??o. Possuem uma apresenta??o, comportamento cl?nico e resposta ? terapia heterog?neos. O progn?stico pode ser grosseiramente estimado pelo tamanho tumoral ao diagn?stico, topografia e ?ndice mit?tico. Apesar da utilidade destes fatores de progn?stico de simples obten??o, a heterogeneidade da doen?a exige que marcadores mais espec?ficos sejam aplicados para uma avalia??o individual n?o apenas progn?stica ao diagn?stico, mas tamb?m preditiva ao tratamento com novas drogas dispon?veis. A ativa??o aberrante das prote?nas da via de sinaliza??o PI3K/Akt/PTEN ? um fen?meno relativamente comum em neoplasias epiteliais e hematol?gicas, com repercuss?o tanto na agressividade da neoplasia como na sua resist?ncia adquirida a tratamentos anti-neopl?sicos. Al?m da sinaliza??o para mecanismos de sobreviv?ncia, a via PI3K/Akt/PTEN est? envolvida na ativa??o de angiog?nese por meio da transcri??o de VEGF e secundariamente do seu receptor endotelial, VEGFR. O objetivo deste trabalho foi avaliar a express?o das prote?nas VEGFR, Akt e PTEN em pacientes com GIST ao diagn?stico, na tentativa de correlacionar a mesma com desfechos cl?nicos. Paralelamente acompanhamos o efeito do n?vel de express?o destas prote?nas em um subgrupo de pacientes com doen?a avan?ada que recebeu a medica??o Mesilato de Imatinib (GliveC?). M?todo: Avalia??o imunoistoqu?mica com m?todo TMA de 48 esp?cimes de GISTs utilizando os anticorpos monoclonais para Akt e VEGFR. A hiperexpress?o de Akt foi verificada em 33,3% e VEGFR em 75% das amostras. Na an?lise do grupo geral de pacientes, a hiper-express?o de Akt correlacionou-se com uma SLP (sobrevida livre de progress?o) estatisticamente encurtada (p>O.05) exclusivamente para casos com doen?a metast?tica. Esta correla??o n?o foi observada em casos com doen?a n?o inicial (est?gios I a III). No entanto, mesmo em doen?a avan?ada, a hiper-express?o de Akt n?o teve impacto na sobrevida global. Como o grupo de pacientes com doen?a avan?ada foi o grupo que recebeu GliveC?, a correla??o com SLP e hiper-express?o de Akt se manteve. A aus?ncia de express?o de VEGFR se associou com melhor sobrevida global (SG) em todos os est?gios (incluindo os pacientes que receberam GliveC?), mas n?o com sobrevida livre de doen?a (SLD). Este dado sugere que os pacientes com baixa express?o de VEGFR poderiam ter uma doen?a de biologia mais indolente, mesmo que a taxa de recorr?ncia seja id?ntica ao grupo com VEGFR hiper-expresso. Conclus?es: os resultados deste estudo sugerem que a baixa express?o de VEGFR ? um fator de progn?stico favor?vel em pacientes com doen?a em qualquer est?gio. A hiperexpress?o de Akt associa-se a uma menor SLP apenas em casos avan?ados, sugerindo que a ativa??o desta via poderia ser um mecanismo adquirido em etapas finais da doen?a que conferem resist?ncia ao GliveC?.
| Identifer | oai:union.ndltd.org:IBICT/oai:tede2.pucrs.br:tede/1694 |
| Date | 29 May 2012 |
| Creators | Carvalho, Gisele Pereira de |
| Contributors | Garicochea, Bernardo |
| Publisher | Pontif?cia Universidade Cat?lica do Rio Grande do Sul, Programa de P?s-Gradua??o em Medicina e Ci?ncias da Sa?de, PUCRS, BR, Faculdade de Medicina |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Format | application/pdf |
| Source | reponame:Biblioteca Digital de Teses e Dissertações da PUC_RS, instname:Pontifícia Universidade Católica do Rio Grande do Sul, instacron:PUC_RS |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | 7620745074616285884, 500, 600, 8624664729441623247 |
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