Olea europaea leaf extract and bevacizumab synergistically exhibit beneficial efficacy upon human glioblastoma cancer stem cells through reducing angiogenesis and invasion in vitro

Abstract 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 (2 mg/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.