Tài liệu Báo cáo khoa học: Upregulation of DR5 by proteasome inhibitors potently sensitizes glioma

Upregulation of DR5 by proteasome inhibitors potently

sensitizes glioma cells to TRAIL-induced apoptosis

Holger Hetschko1

, Valerie Voss1

, Volker Seifert1

, Jochen H. M. Prehn2 and Donat Ko¨ gel1

1 Department of Neurosurgery, Centre for Neurology and Neurosurgery, Johann Wolfgang Goethe University Clinics, Frankfurt ⁄ Main,

Germany

2 Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland

Gliomas are the most common and malignant primary

brain tumors in humans. Glioblastoma multiforme is

the highest-grade as well as the most aggressive and

frequent glioma [1]. Because gliomas are characterized

by a diffuse infiltrative growth into the surrounding

brain tissue, complete surgical resection of glioblas￾toma multiforme tumors is virtually impossible [2]. In

addition, high-grade gliomas exhibit only limited sensi￾tivity to ensuing multimodal treatment with radio￾therapy and chemotherapy [2], which in large part is

Keywords

apoptosis; astrocytoma; death receptor;

proteasome; stress kinase

Correspondence

D. Ko¨gel, Experimental Neurosurgery,

Johann Wolfgang Goethe University Clinics,

Theodor-Stern-Kai 7, Neuroscience Centre,

D-60590 Frankfurt am Main, Germany

Fax: +49 69 6301 5575

Tel: +49 69 6301 6940

E-mail: [email protected]

(Received 28 January 2008, revised 19

February 2008, accepted 21 February 2008)

doi:10.1111/j.1742-4658.2008.06351.x

This study was undertaken to explore the potential of new therapeutic

approaches designed to reactivate cell death pathways in apoptosis-refrac￾tory gliomas and to characterize the underlying molecular mechanisms of

this reactivation. Here we investigated the sensitivity of a panel of glioma

cell lines (U87, U251, U343, U373, MZ-54, and MZ-18) to apoptosis

induced by the death receptor ligand tumor necrosis factor-related apopto￾sis-inducing ligand (TRAIL), TRAIL in combination with gamma irradia￾tion, and TRAIL in combination with proteasome inhibitors (MG132 and

epoxomicin). Analysis of these six glioma cell lines revealed drastic differ￾ences in their sensitivity to these treatments, with two of the six cell lines

revealing no significant induction of cell death in response to TRAIL

alone. Interestingly, the proteasome inhibitors MG132 and epoxomicin

were capable of potentiating TRAIL-induced apoptosis in TRAIL-sensitive

U87 and U251 cells and of reactivating apoptosis in TRAIL-resistant U343

and U373 cells. In contrast, gamma irradiation had no synergistic effects

with TRAIL in the two TRAIL-resistant cell lines. RNA interference

against death receptor 5 (DR5) revealed that reactivation of TRAIL￾induced apoptosis by proteasome inhibitors depended on enhanced tran￾scription and surface expression of DR5. Transient knockdown of the

transcription factor GADD153 ⁄ C ⁄EBP homologous protein and applica￾tion of the synthetic c-Jun N-terminal kinase inhibitor SP600125 indicated

that enhanced DR5 expression occurred independently of GADD153 ⁄

C ⁄EBP homologous protein, but required activation of the c-Jun N-termi￾nal kinase ⁄ c-Jun signaling pathway. Novel therapeutic approaches using

TRAIL or agonistic TRAIL receptor antibodies in combination with pro￾teasome inhibitors may represent a promising approach to reactivate apop￾tosis in therapy-resistant high-grade gliomas.

Abbreviations

Ac-DEVD-AMC, acetyl-DEVD-7-amido-4-methylcoumarin; CHOP, C ⁄ EBP homologous protein; DR4, death receptor 4; DR5, death receptor 5;

FACS, fluorescence-activated cell sorting; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; JNK, c-Jun N-terminal kinase; NF-jB,

nuclear factor kappa B; PI, proteasome inhibitor; siRNA, small interfering RNA; TRAIL, tumor necrosis factor-related apoptosis-inducing

ligand.

FEBS Journal 275 (2008) 1925–1936 ª 2008 The Authors Journal compilation ª 2008 FEBS 1925