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Permanent URL to this publication: http://dx.doi.org/10.5167/uzh-23534

Dubois, L; Magagnin, M G; Cleven, A H G; Weppler, S A; Grenacher, B; Landuyt, W; Lieuwes, N; Lambin, P; Gorr, T A; Koritzinsky, M; Wouters, B G (2009). Inhibition of 4E-BP1 sensitizes U87 glioblastoma xenograft tumors to irradiation by decreasing hypoxia tolerance. International Journal of Radiation Oncology, Biology and Physics, 73(4):1219-1227.

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Abstract

PURPOSE: Eukaryotic initiation factor 4E (eIF4E) is an essential rate-limiting factor for cap-dependent translation in eukaryotic cells. Elevated eIF4E activity is common in many human tumors and is associated with disease progression. The growth-promoting effects of eIF4E are in turn negatively regulated by 4E-BP1. However, although 4E-BP1 harbors anti-growth activity, its expression is paradoxically elevated in some tumors. The aim of this study was to investigate the functional role of 4E-BP1 in the context of solid tumors. METHODS AND MATERIALS: In vitro and in vivo growth properties, hypoxia tolerance, and response to radiation were assessed for HeLa and U87 cells, after stable expression of shRNA specific for 4E-BP1. RESULTS: We found that loss of 4E-BP1 expression did not significantly alter in vitro growth but did accelerate the growth of U87 tumor xenografts, consistent with the growth-promoting function of deregulated eIF4E. However, cells lacking 4E-BP1 were significantly more sensitive to hypoxia-induced cell death in vitro. Furthermore, 4E-BP1 knockdown cells produced tumors more sensitive to radiation because of a reduction in the viable fraction of radioresistant hypoxic cells. Decreased hypoxia tolerance in the 4E-BP1 knockdown tumors was evident by increased cleaved caspase-3 levels and was associated with a reduction in adenosine triphosphate (ATP). CONCLUSIONS: Our results suggest that although tumors often demonstrate increases in cap-dependent translation, regulation of this activity is required to facilitate energy conservation, hypoxia tolerance, and tumor radioresistance. Furthermore, we suggest that targeting translational control may be an effective way to target hypoxic cells and radioresistance in metabolically hyperactive tumors.

Item Type:Journal Article, refereed, original work
Communities & Collections:05 Vetsuisse Faculty > Institute of Veterinary Physiology
04 Faculty of Medicine > Center for Integrative Human Physiology
DDC:570 Life sciences; biology
610 Medicine & health
Language:English
Date:2009
Deposited On:02 Nov 2009 14:13
Last Modified:28 Nov 2013 00:41
Publisher:Elsevier
ISSN:0360-3016
Publisher DOI:10.1016/j.ijrobp.2008.12.003
PubMed ID:19251093
Citations:Web of Science®. Times Cited: 12
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