Angiogenesis inhibitors, such as sunitinib, represent a promising strategy to improve glioblastoma (GBM) tumor response. In this study, we used the O(6)-methylguanine methyltransferase (MGMT)-negative GBM cell line U87MG stably transfected with MGMT (U87/MGMT) to assess whether MGMT expression affects the response to sunitinib. We showed that the addition of sunitinib to standard therapy (temozolomide [TMZ] and radiation therapy [RT]) significantly improved the response of MGMT-positive but not of MGMT-negative cells. Gene expression profiling revealed alterations in the angiogenic profile, as well as differential expression of several receptor tyrosine kinases targeted by sunitinib. MGMT-positive cells displayed higher levels of vascular endothelial growth factor receptor 1 (VEGFR-1) compared with U87/EV cells, whereas they displayed decreased levels of VEGFR-2. Depleting MGMT using O(6)-benzylguanine suggested that the expression of these receptors was directly related to the MGMT status. Also, we showed that MGMT expression was associated with a dramatic increase in the soluble VEGFR-1/VEGFA ratio, thereby suggesting a decrease in bioactive VEGFA and a shift towards an antiangiogenic profile. The reduced angiogenic potential of MGMT-positive cells is supported by: (i) the decreased ability of their secreted factors to induce endothelial tube formation in vitro and (ii) their low tumorigenicity in vivo compared with the MGMT-negative cells. Our study is the first to show a direct link between MGMT expression and decreased angiogenicity and tumorigenicity of GBM cells and suggests the combination of sunitinib and standard therapy as an alternative strategy for GBM patients with MGMT-positive tumors.

This study investigated the role of the glutamatergic system on the antinociception caused by Polygala sabulosa hydroalcoholic extract (HE). The systems mediated by substance P, capsaicin, interleukin-1 β (IL-1 β ) and tumour necrosis factor-α (TNF-α ) were also investigated. P. sabulosa HE given orally produced a significant inhibition of glutamateinduced paw licking ) mg/kg and inhibition of 79 ± 6% at 1000 mg/kg]. The plant derivatives α -spinasterol, scopoletin and styryl-2-pyrones (compound 1 and 3) (10 mg/kg, intraperitoneally) inhibited 80 ± 7%, 46 ± 11%, 45 ± 11% and 35 ± 13% the nociceptive response caused by glutamate, respectively. Furthermore, P. sabulosa HE (500 mg/kg, orally) caused marked inhibition of nociceptive response induced by intrathecal injection of glutamate, N-methyl-d -aspartic acid, α -amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, kainate, TNF-α and IL-1 β , with inhibitions of 44 ± 7%, 55 ± 4%, 38 ± 10%, 61 ± 7%, 76 ± 9% and 100%, respectively. In contrast, P. sabulosa HE (500 mg/kg, orally) did not affect the biting response induced by the metabotropic glutamatergic receptor agonist (±)-1-aminocyclopentanetrans -1,3-dicarboxylic acid, substance P and capsaicin. The locomotor activity was altered only in mice treated with a very high dose (1000 mg/kg) of P. sabulosa HE. Our results showed that the antinociceptive effects of P. sabulosa HE are associated with an inhibition of glutamatergic transmission and an inhibition of pathways dependent on pro-inflammatory cytokines. The plant derivatives α -spinasterol, scopoletin and styryl-2-pyrones play an important role on the antinociceptive effects of P. sabulosa HE.The plants of genus Polygala are widely distributed in Santa Catarina state, Brazil, and have been employed to treat disorders of the bowel and kidney, as a topical anaesthetic and expectorant [1]. Scientific studies in isolated cells and in animals have confirmed the biological activities of the plants from genus Polygala [2-10]. The chemical constituents of Polygala , coumarins, steroids, saponins, lignans, flavonoids and xanthones confer to these plants valuable pharmacological properties [7][8][9][10][11][12][13].Recently, we have demonstrated that Polygala sabulosa hydroalcoholic extract (HE) A. W. Bennett (Polygalaceae) produced antinociceptive action against the acetic acidinduced visceral nociception. The presence of styryl-2-pyrones, coumarin (scopoletin) and steroid ( α -spinasterol) gives to the plant a potent antinociceptive effect [9]. However, the model of nociception previously employed did not allow to clearly identify the mechanism of the antinociceptive action of the plant extract. Indeed, the acetic acid-induced visceral nociception involves a chain of inflammatory mediators that are released into the abdominal cavity and in the central nervous system [14][15][16].In this concern, the aim of this study was to identify the mechanism by which P. sabulosa HE exerts its antinociceptive effect. For this purpose, the effects of the P. sabulosa HE we...