Browsing by Author "Pinto, Filipe"
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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.
- Protein Kinase WNK2 has a Tumour Suppressor Role in GliomasPublication . Moniz, Sonia; Martinho, Olga; Pinto, Filipe; Reis, Rui Manuel; Jordan, PeterMalignant glioblastoma is the most common and lethal adult brain tumour type. Recently, the promoter region of the protein kinaseWNK2 gene was found to be hypermethylated in 29 of 31 infiltrative gliomas and about 5 of 7 meningiomas. We have previously described that theexperimental depletion of WNK2 expression decreases RhoA activity whilst leading to increased Rac1 activity. RhoA/Rac1 activities are important forcell migration and glioblastomas are very invasive tumours so that we tested the effects of WNK2 on wound-healing assays in glioma cell lines SW1088and A172. SW1088 cells express endogenous WNK2 and we observed that wound closure was increased upon experimental depletion of endogenousWNK2. In contrast, A172 cells display complete promoter region methylation and WNK2 re-expression was found to decrease migration. Consistently,we observed an increase in Rac1 activity in SW1088 cells upon WNK2 down-regulation, but lower levels of active Rac1 in A172 cells stably expressingWNK2 cDNA when compared with an equivalent cell line stably transfected with the same empty vector. Our studies indicate that loss of WNK2expression promotes Rac1 activation and may contribute to the highly invasive phenotype that glioblastomas present.
- 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.