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The aggressive behavior of Glioblastoma multiforme (GBM) is mainly due to high invasiveness and proliferation rate as well as to high resistance to standard chemotherapy. Several chemotherapeutic agents like temozolomide (TMZ), carmustine (BCNU) or doxorubicin (DOXO) have been employed for treatment of GBM, but they display limited efficacy. Therefore, it is important to identify new treatment modalities to improve therapeutic effects and enhance GBM chemosensitivity. Recently, activation of the transient receptor potential vanilloid type 2 (TRPV2) has been found to inhibit human GBM cell proliferation and overcome BCNU resistance of GBM cells. Herein, we evaluated the involvement of cannabidiol (CBD)-induced TRPV2 activation, in the modulation of glioma cell chemosensitivity to TMZ, BCNU and DOXO. We found that CBD increases TRPV2 expression and activity. CBD by triggering TRPV2-dependent Ca2+ influx increases drug uptake and synergizes with cytotoxic agents to induce apoptosis of glioma cells, whereas no effects were observed in normal human astrocytes. Moreover, as the pore region of transient receptor potential (TRP) channels is critical for ion channel permeation, we demonstrated that deletion of TRPV2 poredomain inhibits CBD-induced Ca2+ influx, drug uptake and cytotoxic effects. Overall, we demonstrated that co-administration of cytotoxic agents together with the TRPV2 agonist CBD increases drug uptake and parallelly potentiates cytotoxic activity in human glioma cells. [ABSTRACT FROM PUBLISHER]

The aim of this study was to investigate the expression and function of the transient receptor potential vanilloid 2 (TRPV2) in human glioma cells. By Real-Time–PCR and western blot analysis, we found that TRPV2 messenger RNA (mRNA) and protein were expressed in benign astrocyte tissues, and its expression progressively declined in high-grade glioma tissues as histological grade increased (n = 49 cases), and in U87MG cells and in MZC, FCL and FSL primary glioma cells. To investigate the function of TRPV2 in glioma, small RNA interfering was used to silence TRPV2 expression in U87MG cells. As evaluated by RT-Profiler PCR array, siTRPV2-U87MG transfected cells displayed a marked downregulation of Fas and procaspase-8 mRNA expression, associated with upregulation of cyclin E1, cyclin-dependent kinase 2, E2F1 transcriptor factor 1, V-raf-1 murine leukemia viral oncogene homolog 1 and Bcl-2-associated X protein (Bcl-XL) mRNA expression. TRPV2 silencing increased U87MG cell proliferation as shown by the increased percentage of cells incorporating 5-bromo-2-deoxyuridine expressing βIII-tubulin and rescued glioma cells to Fas-induced apoptosis. These events were dependent on extracellular signal-regulated kinase (ERK) activation: indeed inhibition of ERK activation in siTRPV2-U87MG transfected cells by treatment with PD98059, a specific mitogen-activated protein kinase/extracellular signal-regulated kinase kinase inhibitor, reduced Bcl-XL protein levels, promoted Fas expression, and restored Akt/protein kinase B pathway activation leading to reduced U87MG cell survival and proliferation, and increased sensitivity to Fas-induced apoptosis. In addition, transfection of TRPV2 in MZC glioma cells, by inducing Fas overexpression, resulted in a reduced viability and an increased spontaneous and Fas-induced apoptosis. Overall, our findings indicate that TRPV2 negatively controls glioma cell survival and proliferation, as well as resistance to Fas-induced apoptotic cell death in an ERK-dependent manner. [ABSTRACT FROM PUBLISHER]

Capsaicin (CPS) has been found to exhibit either tumor promoting or suppressing effects, many of which are mediated by the specific transient receptor potential vanilloid type-1 (TRPV1). Herein, we provide evidence that CPS treatment induced a more aggressive gene phenotype and invasiveness in 5637 cells-lacking TRPV1 receptor. CPS treatment of 5637 cells induced upregulation of pro-angiogenetic (angiopoietin 1, angiopoietin 2 and vascular endothelial growth factor), pro-invasive and pro-metastatic genes (MMP1, MMP9, TIMP1, TIMP3, granzyme A (GZMA), NM23A and S100A) with a downregulation of apoptotic genes (Fas/CD95 and tumor necrosis factor receptor superfamily member 1A). CPS increased the invasiveness of 5637 cells by triggering IGF (insulin-like growth factor)-1 release, GZMA and MMP9 activation, α-tubulin disassembly and cytoskeleton degradation. Finally, in order to evaluate the relationship between the lack of TRPV1 expression and increased CPS-induced invasiveness, we transfected 5637 cells with the TRPV1 complementary DNA (cDNA) sequence. We found that TRPV1-expressing cells show CPS-mediated calcium level increase, growth inhibition and apoptosis. Moreover, CPS-induced migration and MMP9 activation were reverted, suggesting an inhibitory role played by TRPV1 in urothelial cancer cell invasion and metastasis. [ABSTRACT FROM AUTHOR]