Effect of temozolomide on the U-118 glioma cell line

Abstract

Abstract. Glioblastomas (GBM) are the most lethal subtype of astrocytomas, with a mean patient survival rate of 12 months after diagnosis. The gold standard treatment of GBM, which includes surgery followed by the combination of radiotherapy and chemotherapy with temozolomide (TMZ), increases the survival rate to 14.6 months. The success of TMZ appears to be limited by the occurrence of chemoresistance that allows glioma cells to escape from death signaling pathways. However, the mechanism of TMZ action is yet to be clarified although some controversial results have been reported. Therefore, our aim was to evaluate the occurrence of apoptosis and autophagy in glioma cells treated with TMZ and to correlate TMZ action with the survival pathways Pi3K/ Akt and ERK1/2 MAP kinase. Cell proliferation was evaluated by incorporation of bromodeoxyuridine. Apoptosis was studied by flow cytometry as well as by fluorescence confocal microscopy in order to evaluate the sub G0/G1 percentage of cells and chromatin condensation. The expression of the autophagy-associated protein, LC3, as well as Akt and ERK1/2 was performed by Western blotting. In TMZ-treated GBM cells the expression of LC3, the autophagy-associated protein was increased and only a reduced percentage of cells underwent apoptosis. In addition, we showed that the phosphorylation status of Pi3K/Akt and ERK1/2 MAP kinase was maintained during the treatment with TMZ, suggesting that glioma cells escape from TMZ-induced cell death due to these signaling pathways. The chemoresistance of U-118 cells to TMZ was partially eradicated when cells were simultaneously treated with specific inhibitors of Pi3K/Akt and ERK1/2 MAP kinase signaling pathways and TMZ. Therefore, we hypothesized that in order to induce glioma cell death it is essential to evaluate the activation of the survival pathways and establish a combined therapy using TMZ and inhibitors of those signaling pathways.

Autophagy inhibition improves the efficacy of curcumin/temozolomide combination therapy in glioblastomas

“…JNK1/2 and p38 are known to promote G2/M checkpoint and survival of TMZ [21,22,30]. Here, we showed that JNK/p38 also controls TMZ, but not curcumin, induced autophagy.…”

Pine (Pinus morrisonicola Hayata) Needle Extracts Sensitize GBM8901 Human Glioblastoma Cells to Temozolomide by Downregulating Autophagy and O6-Methylguanine-DNA Methyltransferase Expression

“…24 Moreover the autophagy-associated protein, LC3, and Akt were maintained during the treatment with TMZ, suggesting that glioblastoma cells escape from TMZ-induced cell death because of Akt signaling pathways. 25 Our results demonstrated that chrysin induces apoptosis and downregulates Akt of GBM8901 cells significantly, suggesting that chrysininduced apoptotic signaling serves to inhibit autophagy. This result is consistent with those of previous studies, which have shown that pharmacologic inhibition of stress-induced autophagy was reported to promote chemotherapeutic response.…”

Mechanism of temozolomide-induced antitumour effects on glioma cells

“…[11][12][13] However, the specific mechanisms of action of temozolomide remain elusive. The aim of this present study was to evaluate the effect of temozolomide on U251 cells in vitro and explore the possible pharmacological mechanisms of action.…”