RESUMEN
Unmethylated O6-methylguanine-DNA-methyltransferase (MGMT) promoter leads to Temozolomide (TMZ) resistance in most of the glioblastoma multiforme (GBM) patients. We previously investigated the synergistic effect of Olea europaea leaf extract (OLE) on TMZ cytotoxicity through modulating microRNA expression. To date, knowledge about the effect of OLE on MGMT methylation is insufficient. The aim of the current study was to evaluate the potential modulating effect of OLE on the TMZ response of GBM tumors through MGMT methylation. Exposure to 1 mg/mL OLE caused a significant induction of CpG island methylation in the MGMT gene using Methyl quantitative PCR assay (P < 0.001). In WST-1 analysis, the use of 350 µM TMZ plus 1 mg/mL OLE significantly increased the TMZ response of MGMT unmethylated cells (P = 0.003). Using the comet assay, the impact of 1 mg/mL OLE plus 350 µM TMZ on the formation of DNA strand breaks was significantly higher than that of 450 µM TMZ alone (P < 0.001) and Western blot analysis revealed that, when cells are treated with 1-mg/mL OLE, the total p53 protein levels tended to decrease. The results presented in this study uniquely demonstrated that OLE synergistically increased the TMZ response of GBM tumors by regulating MGMT gene methylation and p53 expression. However, further studies to validate our findings are required.
Asunto(s)
Metilación de ADN , Metilasas de Modificación del ADN/metabolismo , Enzimas Reparadoras del ADN/metabolismo , Dacarbazina/análogos & derivados , Glioblastoma/tratamiento farmacológico , Extractos Vegetales/farmacología , Proteína p53 Supresora de Tumor/metabolismo , Proteínas Supresoras de Tumor/metabolismo , Anciano , Línea Celular Tumoral , Ensayo Cometa , Islas de CpG , Daño del ADN , Metilasas de Modificación del ADN/genética , Enzimas Reparadoras del ADN/genética , Dacarbazina/uso terapéutico , Relación Dosis-Respuesta a Droga , Resistencia a Antineoplásicos/genética , Femenino , Humanos , Concentración 50 Inhibidora , Masculino , Persona de Mediana Edad , Olea/química , Hojas de la Planta/química , Regiones Promotoras Genéticas , Temozolomida , Proteína p53 Supresora de Tumor/genética , Proteínas Supresoras de Tumor/genéticaRESUMEN
Patients with glioblastoma multiforme (GBM) that are cancer stem-cell-positive (GSC [+]) essentially cannot benefit from anti-angiogenic or anti-invasive therapy. In the present study, the potential anti-angiogenic and anti-invasive effects of Olea europaea (olive) leaf extract (OLE) were tested using GSC (+) tumours. OLE (2mg/mL) caused a significant reduction in tumour weight, vascularisation, invasiveness and migration (p=0.0001, p<0.001, p=0.004; respectively) that was associated with reducing the expression of VEGFA, MMP-2 and MMP-9. This effect was synergistically increased in combination with bevacizumab. Therefore, our current findings may contribute to research on drugs that inhibit the invasiveness of GBM.