Browsing by Author "Lopes, JM"
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- Analysis of EGFR overexpression, EGFR gene amplification and the EGFRvIII mutation in Portuguese high-grade gliomasPublication . Viana-Pereira, M; Lopes, JM; Little, S; Milanezi, F; Basto, D; Pardal, F; Jones, C; Reis, RMBACKGROUND: Patients with malignant gliomas do not respond to any current therapy. Epidermal growth factor receptor (EGFR) controls several oncogenic processes, being frequently up-regulated in gliomas due to overexpression, gene amplification and gene mutation. EGFR inhibitors are being tried in gliomas, yet the molecular determinants of therapeutic response are unclear. MATERIALS AND METHODS: EGFR overexpression, EGFRvIII mutation and EGFR amplification were determined by immunohistochemistry and chromogenic in situ hybridization (CISH) in 27 primary glioblastomas (GBM), 24 anaplastic oligodendrogliomas (AO) and four anaplastic oligoastrocytomas (AOA). RESULTS: EGFR overexpression was associated with EGFR amplification, being found in 48% and 53% GBM, 33% and 40% AO and 75% and 67% AOA, respectively. EGFRvIII was found in 22% GBM, 8% AO and was absent in AOA. No association was observed between EGFR alterations and patient survival. CONCLUSION: We characterized, for the first time, EGFR molecular alterations in Portuguese patients with malignant glioma and identified a subpopulation of patients presenting putative biomarkers for EGFR-based therapies.
- Association between functional EGF+61 polymorphism and glioma riskPublication . Costa, BM; Ferreira, P; Costa, S; Canedo, P; Oliveira, P; Silva, AI; Pardal, F; Suriano, G; Machado, JC; Lopes, JM; Reis, RMPURPOSE: Epidermal growth factor (EGF) plays a critical role in cancer. A polymorphism in the EGF gene (EGF+61) may influence its expression and contribute to cancer predisposition and aggressiveness. In the present study, we aimed to elucidate the role of EGF+61 in glioma susceptibility and prognosis. EXPERIMENTAL DESIGN: A case-control study involving 197 glioma patients and 570 controls was done. Univariate and multivariate logistic regression analyses were used to calculate odds ratio (OR) and 95% confidence intervals (95% CI). False-positive report probability was also assessed. The luciferase reporter gene assay was used to ascertain the functional consequences of this polymorphism. RESULTS: Corroborating the univariate analysis, the multivariate model showed that the G allele conferred higher risks for gliomas (OR, 1.32; 95% CI, 1.04-1.67), glioblastomas (OR, 1.47; 95% CI, 1.02-2.10), and oligodendrogliomas (OR, 1.55; 95% CI, 1.07-2.23). The GG genotypes were associated with increased risk for gliomas (OR, 1.71; 95% CI, 1.07-2.73), glioblastomas (OR, 2.03; 95% CI, 1.02-4.05), and oligodendrogliomas (OR, 2.72; 95% CI, 1.18-6.28). In addition, the AG+GG genotypes were associated with higher risk for gliomas (OR, 1.52; 95% CI, 1.03-2.23) and oligodendrogliomas (OR, 2.80; 95% CI, 1.35-5.79). No significant association was observed between the EGF+61 polymorphism and glioblastoma or oligodendroglioma patients' overall survival. The luciferase reporter gene assay exhibited a significant increased promoter activity for the G variant compared with the reference A allele. CONCLUSIONS: These findings support the role of the EGF+61 polymorphism as a susceptibility factor for development of gliomas and show its implication on EGF promoter activity.
- Expression, mutation and copy number analysis of platelet-derived growth factor receptor A (PDGFRA) and its ligand PDGFA in gliomasPublication . Martinho, O; Longatto-Filho, A; Lambros, MB; Martins, A; Pinheiro, C; Silva, AI; Pardal, F; Amorim, J; Mackay, A; Milanezi, F; Tamber, N; Fenwick, K; Ashworth, A; Reis-Filho, J; Lopes, JM; Reis, RMBACKGROUND: Malignant gliomas are the most prevalent type of primary brain tumours but the therapeutic armamentarium for these tumours is limited. Platelet-derived growth factor (PDGF) signalling has been shown to be a key regulator of glioma development. Clinical trials evaluating the efficacy of anti-PDGFRA therapies on gliomas are ongoing. In this study, we intended to analyse the expression of PDGFA and its receptor PDGFRA, as well as the underlying genetic (mutations and amplification) mechanisms driving their expression in a large series of human gliomas. METHODS: PDGFA and PDGFRA expression was evaluated by immunohistochemistry in a series of 160 gliomas of distinct World Health Organization (WHO) malignancy grade. PDGFRA-activating gene mutations (exons 12, 18 and 23) were assessed in a subset of 86 cases by PCR-single-strand conformational polymorphism (PCR-SSCP), followed by direct sequencing. PDGFRA gene amplification analysis was performed in 57 cases by quantitative real-time PCR (QPCR) and further validated in a subset of cases by chromogenic in situ hybridisation (CISH) and microarray-based comparative genomic hybridisation (aCGH). RESULTS: PDGFA and PDGFRA expression was found in 81.2% (130 out of 160) and 29.6% (48 out of 160) of gliomas, respectively. Its expression was significantly correlated with histological type of the tumours; however, no significant association between the expression of the ligand and its receptor was observed. The absence of PDGFA expression was significantly associated with the age of patients and with poor prognosis. Although PDGFRA gene-activating mutations were not found, PDGFRA gene amplification was observed in 21.1% (12 out of 57) of gliomas. No association was found between the presence of PDGFRA gene amplification and expression, excepting for grade II diffuse astrocytomas. CONCLUSION: The concurrent expression of PDGFA and PDGFRA in different subtypes of gliomas, reinforce the recognised significance of this signalling pathway in gliomas. PDGFRA gene amplification rather than gene mutation may be the underlying genetic mechanism driving PDGFRA overexpression in a portion of gliomas. Taken together, our results could provide in the future a molecular basis for PDGFRA-targeted therapies in gliomas.
- Impact of EGFR genetic variants on glioma risk and patient outcomePublication . Costa, BM; Viana-Pereira, M; Fernandes, R; Costa, S; Linhares, P; Vaz, R; Pinheiro, C; Lima, J; Soares, P; Silva, A; Pardal, F; Amorim, J; Nabiço, R; Almeida, R; Alegria, C; Pires, MM; Pinheiro, C; Carvalho, E; Oliveira, P; Lopes, JM; Reis, RMBACKGROUND: The epidermal growth factor receptor (EGFR) regulates important cellular processes and is frequently implicated in human tumors. Three EGFR polymorphisms have been described as having a transcriptional regulatory function: two single-nucleotide polymorphisms in the essential promoter region, -216G/T and -191C/A, and a polymorphic (CA)(n) microsatellite sequence in intron 1. We aimed to elucidate the roles of these EGFR polymorphisms in glioma susceptibility and prognosis. METHODS: We conducted a case-control study with 196 patients with glioma and 168 cancer-free controls. Unconditional multivariate logistic regression models were used to calculate ORs and 95% confidence intervals. A Cox regression model was used to evaluate associations with patient survival. False-positive report probabilities were also assessed. RESULTS: None of the EGFR -216G/T variants was significantly associated with glioma risk. The -191C/A genotype was associated with higher risk for glioma when the (CA)(n) alleles were classified as short for ≤16 or ≤17 repeats. Independently of the (CA)(n) repeat cutoff point used, shorter (CA)(n) repeat variants were significantly associated with increased risk for glioma, particularly glioblastoma and oligodendroglioma. In all tested models with different (CA)(n) cutoff points, only -191C/A genotype was consistently associated with improved survival of patients with glioblastoma. CONCLUSIONS: Our findings implicate EGFR -191C/A and the (CA)(n) repeat polymorphisms as risk factors for gliomas, and suggest -191C/A as a prognostic marker in glioblastoma. IMPACT: Our data support a role of these EGFR polymorphisms in determining glioma susceptibility, with potential relevance for molecularly based stratification of patients with glioblastoma for individualized therapies
- Molecular alterations of PDGA and PDGFRA in GliomasPublication . Martinho, O; Longatto-Filho, A; Lambros, MB; Martins, A; Pinheiro, C; Silva, AI; Pardal, F; Amorim, J; Mackay, A; Milanezi, F; Tamber, N; Fenwick, K; Ashworth, A; Reis-Filho, JS; Lopes, JM; Reis, RM
- mTOR pathway overactivation in BRAF mutated papillary thyroid carcinomaPublication . Faustino, A; Couto, JP; Pópulo, H; Rocha, AS; Pardal, F; Cameselle-Teijeiro, JM; Lopes, JM; Sobrinho-Simões, M; Soares, PCONTEXT: There are several genetic and molecular evidences suggesting dysregulation of the mammalian target of rapamycin (mTOR) pathway in thyroid neoplasia. Activation of the phosphatidylinositol-3-kinase/AKT pathway by RET/PTC and mutant RAS has already been demonstrated, but no data have been reported for the BRAF(V600E) mutation. OBJECTIVE: The aim of this study was to evaluate the activation pattern of the mTOR pathway in malignant thyroid lesions and whether it may be correlated with known genetic alterations, as well as to explore the mechanisms underlying mTOR pathway activation in these neoplasias. RESULTS: We observed, by immunohistochemical evaluation, an up-regulation/activation of the mTOR pathway proteins in thyroid cancer, particularly in conventional papillary thyroid carcinoma (cPTC). Overactivation of the mTOR signaling was particularly evident in cPTC samples harboring the BRAF(V600E) mutation. Transfection assays with BRAF expression vectors as well as BRAF knockdown by small interfering RNA revealed a positive association between BRAF expression and mTOR pathway activation, which appears to be mediated by pLKB1 Ser428, and emerged as a possible mechanism contributing to the association between BRAF mutation and mTOR pathway up-regulation. When we evaluated the rapamycin in the growth of thyroid cancer cell lines, we detected that cell lines with activating mutations in the MAPK pathway show a higher sensitivity to this drug. CONCLUSIONS: We determined that the AKT/mTOR pathway is particularly overactivated in human cPTC harboring the BRAF(V600E) mutation. Moreover, our results suggest that the mTOR pathway could be a good target to enhance therapy effects in certain types of thyroid carcinoma, namely in those harboring the BRAF(V600E) mutation.
- Mutation analysis of B-RAF gene in human gliomas.Publication . Basto, D; Trovisco, V; Lopes, JM; Martins, A; Pardal, F; Soares, P; Reis, RMThe RAS/RAF/MEK/ERK kinase pathway is pivotal in the transduction of mitogenic stimuli from activated growth factor receptors, which regulates cell proliferation, survival, and differentiation. Up-regulation of this pathway due to RAS mutations is found in approximately 30% of human tumors. Recently, activating mutations of B-RAF were identified in a large proportion of human cancers. Gliomas are the most frequent primary central nervous system tumors and the molecular mechanisms that underlie the development and progression of these tumors are far from being completely understood. The purpose of this study was to clarify the incidence of B-RAF mutations and their possible relation with tumor progression in a series of 82 human gliomas, including 49 astrocytic and 33 oligodendroglial tumors. The analysis of B-RAF hotspot regions, exons 11 and 15, showed presence of B-RAF mutations in only 2 out of 34 (6%) glioblastomas, and absence in the remaining histological types. Both mutations were located in the hotspot residue 600 (V600E) at exon 15, which leads to constitutive B-RAF kinase activity. These data suggest that activating mutations of B-RAF are not a frequent event in gliomas; nevertheless, when present they are associated with high-grade malignant lesions.
- Prognostic value of MGMT promoter methylation in glioblastoma patients treated with temozolomide-based chemoradiation: a Portuguese multicentre studyPublication . Costa, BM; Caeiro, C; Guimarães, I; Martinho, O; Jaraquemada, T; Augusto, I; Castro, l; Osório, L; Linhares, P; Honavar, M; Resende, M; Nabiço, R; Almeida, R; Alegria, C; Pires, M; Pinheiro, C; Carvalho, E; Lopes, JM; Costa, P; Damasceno, M; Reis, RMGlioblastoma (GBM) is the most common and aggressive primary brain tumor. The identification of novel molecular prognostic markers of GBM has recently been an area of great interest in neuro-oncology. The methylation status of the MGMT gene promoter is currently a promising molecular prognostic marker, but some controversial data have precluded its clinical use. We analyzed MGMT methylation by methylation-specific PCR in 90 GBM patients from four Portuguese hospitals, uniformly treated with radiotherapy combined with concomitant and adjuvant temozolomide (Stupp protocol). The Kaplan-Meier method was used to construct survival curves, and the log-rank test and a Cox-regression model were used to analyze patient survival. The methylation status of MGMT was successfully determined in 89% (80/90) of the tumors. The frequency of tumoral MGMT promoter methylation was 47.5%. The median overall survivals (OSs) were 16 months (95% CI 12.2-19.8) and 13 months (95% CI 13.3-18.7) for patients whose tumors had a methylated or unmethylated MGMT, respectively. Univariate and multivariate analyses did not show any statistically significant association between MGMT methylation status and patient OS (P=0.583 by the log-rank test; P=0.617 by the Cox-regression test) or progression-free survival (P=0.775 by the log-rank test; P=0.691 by the Cox-regression test). None of the patient clinical features were significantly correlated with survival. This is the first study to report the frequency of MGMT methylation among Portuguese GBM patients. Our data did not show statistically significant associations between MGMT promoter methylation and the outcome of GBM patients treated with temozolomide. Additional robust prospective studies are warranted to clarify whether the MGMT status should be used in clinical decisions.
- TP53 codon 72 polymorphism in susceptibility, overall survival, and adjuvant therapy response of gliomas.Publication . Lima-Ramos, V; Pacheco-Figueiredo, L; Costa, S; Pardal, F; Silva, A; Amorim, J; Lopes, JM; Reis, RMTP53 is a key tumor suppressor gene that encodes a transcriptional factor involved in several cellular mechanisms, including growth arrest, DNA repair, and induction of apoptosis. In addition to TP53 gene mutations, a common polymorphism, Arg72Pro, has been involved in the carcinogenesis process. The Pro72 variant has been associated with a slower induction of apoptosis and may influence the risk of cancer development. The role of Arg72Pro polymorphism in glioma susceptibility is poorly characterized. With the objective of analyzing the role of the TP53 Arg72Pro polymorphism in glioma risk, overall survival, and patient therapy response in a Portuguese population, we conducted a retrospective case-control study, including 171 patients with gliomas and 526 cancer-free individuals. The Arg72Pro genotype was assessed by the polymerase chain reaction-restriction fragment length polymorphism technique. No statistically significant differences were observed in the genotypic and allelic frequencies between glioma and control groups, and no statistically significant differences were observed with stratification of gliomas into distinct histological subtypes: astrocytic (n = 115), glioblastoma (n = 75), and oligodendroglial (n = 54) tumors. No significant association was observed between TP53 Arg72Pro and patient overall survival, but Kaplan-Meier analysis of glioma patients harboring the Pro72 allele showed a significantly longer survival with adjuvant therapy. In this first assessment of the role of TP53 Arg72Pro polymorphism in a large series of Portuguese glioma tumors, no association was observed with glioma susceptibility or overall survival, except for patients submitted to adjuvant therapy.
- A transcriptomic signature mediated by HOXA9 promotes human glioblastoma initiation, aggressiveness and resistance to temozolomidePublication . Pojo, M; Gonçalves, CS; Xavier-Magalhães, A; Oliveira, AI; Gonçalves, T; Correia, S; Rodrigues, AJ; Costa, S; Pinto, L; Pinto, AA; Lopes, JM; Reis, RM; Rocha, M; Sousa, N; Costa, BMGlioblastoma is the most malignant brain tumor, exhibiting remarkable resistance to treatment. Here we investigated the oncogenic potential of HOXA9 in gliomagenesis, the molecular and cellular mechanisms by which HOXA9 renders glioblastoma more aggressive, and how HOXA9 affects response to chemotherapy and survival. The prognostic value of HOXA9 in glioblastoma patients was validated in two large datasets from TCGA and Rembrandt, where high HOXA9 levels were associated with shorter survival. Transcriptomic analyses identified novel HOXA9-target genes with key roles in cancer-related processes, including cell proliferation, DNA repair, and stem cell maintenance. Functional studies with HOXA9-overexpressing and HOXA9-silenced glioblastoma cell models revealed that HOXA9 promotes cell viability, stemness and invasion, and inhibits apoptosis. Additionally, HOXA9 promoted the malignant transformation of human immortalized astrocytes in an orthotopic in vivo model, and caused tumor-associated death. HOXA9 also mediated resistance to temozolomide treatment in vitro and in vivo via upregulation of BCL2. Importantly, the pharmacological inhibition of BCL2 with the BH3 mimetic ABT-737 reverted temozolomide resistance in HOXA9-positive cells. These data establish HOXA9 as a driver of glioma initiation, aggressiveness and resistance to therapy. In the future, the combination of BH3 mimetics with temozolomide should be further explored as an alternative treatment for glioblastoma.