Browsing by Author "Oliveira, Maria José"
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- Loss of WNK2 expression by promoter gene methylation occurs in adult gliomas and triggers Rac1-mediated tumour cell invasivenessPublication . Moniz, Sónia; Martinho, Olga; Pinto, Filipe; Sousa, Bárbara; Loureiro, Cláudia; Oliveira, Maria José; Moita, Luís Ferreira; Honavar, Mrinalini; Pinheiro, Célia; Pires, Manuel; Lopes, José Manuel; Jones, Chris; Costello, Joseph F; Paredes, Joana; Reris, Rui Manuel; Jordan, PeterThe gene encoding protein kinase WNK2 was recently identified to be silenced by promoter hypermethylation in gliomas and meningiomas, suggesting a tumour-suppressor role in these brain tumours. Following experimental depletion in cell lines, WNK2 was further found to control GTP-loading of Rac1, a signalling guanosine triphosphatase involved in cell migration and motility. Here we show that WNK2 promoter methylation also occurs in 17.5% (29 out of 166) of adult gliomas, whereas it is infrequent in its paediatric forms (1.6%; 1 out of 66). Re-expression of WNK2 in glioblastoma cells presenting WNK2 gene silencing reduced cell proliferation in vitro, tumour growth in vivo and also cell migration and invasion, an effect correlated with reduced activation of Rac1. In contrast, when endogenous WNK2 was depleted from glioblastoma cells with unmethylated WNK2 promoter, changes in cell morphology, an increase in invasion and activation of Rac1 were observed. Together, these results validate the WNK2 gene as a recurrent target for epigenetic silencing in glia-derived brain tumours and provide first mechanistic evidence for a tumour-suppressing role of WNK2 that is related to Rac1 signalling and tumour cell invasion and proliferation.
- Mixed lineage kinase 3 gene mutations in mismatch repair deficient gastrointestinal tumours.Publication . Velho, Sérgia; Oliveira, Carla; Paredes, Joana; Sousa, Sónia; Leite, Marina; Matos, Paulo; Milanezi, Fernanda; Ribeiro, Ana Sofia; Mendes, Nuno; Licastro, Danilo; Karhu, Auli; Oliveira, Maria José; Ligtenberg, Marjolijn; Hamelin, Richard; Carneiro, Fátima; Lindblom, Annika; Peltomaki, Paivi; Castedo, Sérgio; Schwartz, Simó Jr; Jordan, Peter; Aaltonen, Lauri A.; Hofstra, Robert M.W.; Suriano, Gianpaolo; Stupka, Elia; Fialho, Arsenio M; Seruca, RaquelMixed lineage kinase 3 (MLK3) is a serine/threonine kinase, regulating MAPkinase signalling, in which cancer-associated mutations have never been reported. In this study, 174 primary gastrointestinal cancers (48 hereditary and 126 sporadic forms) and 7 colorectal cancer cell lines were screened for MLK3 mutations. MLK3 mutations were significantly associated with MSI phenotype in primary tumours (P = 0.0005), occurring in 21% of the MSI carcinomas. Most MLK3 somatic mutations identified were of the missense type (62.5%) and more than 80% of them affected evolutionarily conserved residues. A predictive 3D model points to the functional relevance of MLK3 missense mutations, which cluster in the kinase domain. Further, the model shows that most of the altered residues in the kinase domain probably affect MLK3 scaffold properties, instead of its kinase activity. MLK3 missense mutations showed transforming capacity in vitro and cells expressing the mutant gene were able to develop locally invasive tumours, when subcutaneously injected in nude mice. Interestingly, in primary tumours, MLK3 mutations occurred in KRAS and/or BRAF wild-type carcinomas, although not being mutually exclusive genetic events. In conclusion, we have demonstrated for the first time the presence of MLK3 mutations in cancer and its association to mismatch repair deficiency. Further, we demonstrated that MLK3 missense mutations found in MSI gastrointestinal carcinomas are functionally relevant.
- Silencing of the tumor suppressor gene WNK2 is associated with upregulation of MMP2 and JNK in gliomasPublication . Costa, Ângela; Pinto, Filipe; Martinho, Olga; Oliveira, Maria José; Jordan, Peter; Reis, Rui ManuelMatrix metalloproteinases (MMPs) are proteolytic enzymes that degrade extracellular matrix (ECM), thus assisting invasion. Upregulation of MMPs, frequently reported in gliomas, is associated with aggressive behavior. WNK2 is a tumor suppressor gene expressed in normal brain, and silenced by promoter methylation in gliomas. Patients without WNK2 exhibited poor prognosis, and its downregulation was associated with increased glioma cell invasion. Here we showed that MMP2 expression and activity are increased in glioma cell lines that do not express WNK2. Also, WNK2 inhibited JNK, a process associated with decreasing levels of MMP2. Thus, WNK2 promoter methylation and silencing in gliomas is associated with increased JNK activation and MMP2 expression and activity, thus explaining in part tumor cell invasion potential.