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Inhibition of eEF-2 kinase sensitizes human glioma cells to TRAIL and down-regulates Bcl-xL expression
Journal article   Peer reviewed

Inhibition of eEF-2 kinase sensitizes human glioma cells to TRAIL and down-regulates Bcl-xL expression

Yi Zhang, Yan Cheng, Li Zhang, Xingcong Ren, Kathryn J Huber-Keener, Sang Lee, Jong Yun, Hong-Gang Wang and Jin-Ming Yang
Biochemical and Biophysical Research Communications, Vol.414(1), pp.129-134
10/14/2011
DOI: 10.1016/j.bbrc.2011.09.038
PMCID: PMC3210449
PMID: 21945617

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Abstract

► Inhibiting eEF-2 kinase sensitizes human glioma cells to TRAIL therapy. ► The enhanced sensitivity to TRAIL is accompanied by down-regulation of Bcl-xL. ► Overexpression of Bcl-xL can abrogate this sensitizing effect on TRAIL. ► Targeting eEF-2 kinase may represent a new adjuvant therapy with TRAIL. Elongation factor-2 kinase (eEF-2 kinase, also known as calmodulin-dependent protein kinase III), is a unique calcium/calmodulin-dependent enzyme that inhibits protein synthesis by phosphorylating and inactivating elongation factor-2 (eEF-2). We previously reported that expression/activity of eEF-2 kinase was up-regulated in several types of malignancies including Gliomas, and was associated with response of tumor cells to certain therapeutic stress. In the current study, we sought to determine whether eEF-2 kinase expression affected sensitivity of glioma cells to treatment with tumor the necrosis factor-related apoptosis-inducing ligand (TRAIL), a targeted therapy able to induce apoptosis in cancer cells but causes no toxicity in most normal cells. We found that inhibition of eEF-2 kinase by RNA interference (RNAi) or by a pharmacological inhibitor (NH125) enhanced TRAIL-induced apoptosis in the human glioma cells, as evidenced by an increase in apoptosis in the tumor cells treated with eEF-2 kinase siRNA or the eEF-2 kinase inhibitor. We further demonstrated that sensitization of tumor cells to TRAIL was accompanied by a down-regulation of the anti-apoptotic protein, Bcl-xL, and that overexpression of Bcl-xL could abrogate the sensitizing effect of inhibiting eEF-2 kinase on TRAIL. The results of this study may help devise a new therapeutic strategy for enhancing the efficacy of TRAIL against malignant glioma by targeting eEF-2 kinase.
Apoptosis eEF-2 kinase Bcl-xl TRAIL Glioblastoma

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