O papel da proteína supressora de tumor p53 na indução de ciclooxigenase-2 em Carcinoma de Pulmão de Células Não Pequenas: aspectos moleculares e clínicos

• Autor(a) principal: Duarte, Mariana Lemos
• Data de Publicação: 2009
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/7825
• topic: Cyclooxygenase-2; p53; Chemotherapy; Lung cancer; Ciclooxigenase 2; p53; Quimioterapia; Câncer de pulmão; CNPQ::CIENCIAS BIOLOGICAS::MORFOLOGIA

Non-Small Cell Lung Cancer (NSCLC) is a lethal disease and highly resistant to conventional chemotherapeutic agents, like cisplatin and paclitaxel. Overexpression of cyclooxygenase-2 (COX-2) is frequently found in NSCLC, and is associated with a bad prognosis. High COX-2 expression is thought to exert antiapoptotic effects in cancer, but little is known about COX-2 regulation. Many signals that activate COX-2 also induce the tumor suppressor protein p53, which is believed to play a pivotal role in controlling proliferation and apoptosis. Recent data indicate the tumor suppressor protein p53 as an important regulator of COX-2. The main objective of this work was to analyze the effect of chemotherapy on the expression of COX-2 according to TP53 status and also evaluate the relationship between COX-2 expression and TP53 mutational status, according to clinic pathological features in NSCLC patients. As experimental tools techniques of cell and molecular biology such as RNA interference, real time PCR, mutational analysis and immunohistochemistry were used. We report herein that lung cancer cell lines expressing wild-type p53 when exposed to cisplatin treatment induced COX-2 (mRNA and protein), with concurrent synthesis of prostaglandins (PGE2). In contrast, COX-2 expression was not detected or changed after cisplatin treatment of cells containing an inactive form of p53. For paclitaxel treatment, an increase in COX-2 mRNA expression was observed in H460 and A549 (wild-type p53 cell lines), although the same was not observed on PGE2 production. Moreover, paclitaxel treatment increased COX-2 expression in ACC-LC-319 cell lines (p53 null). Further, after silencing wild-type p53 expression in A549 cells by RNA interference, cisplatin was no longer able to induce COX-2 mRNA and protein expression. While in treatment with paclitaxel the silencing of wild type TP53 did not change COX-2 expression, showing a p53-independent effect. Therefore, we suggest that induction of COX-2 by cisplatin in NSCLC cell lines is dependent on p53. In the NSCLC patients analysis, the results showed a COX-2 positive staining in 54% patients. TP53 mutations were found in 57% of the patients, including 56% in current smokers and 37% in former smokers. There was an association between COX-2 expression and wild-type TP53. Among COX-2 positive patients, 80% were wild-type TP53. A higher number of patients are necessary to increase statistical power and confirm the tendencies observed in this study