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Research Articles: Therapeutics, Targets, and Development

Caspase-, cathepsin-, and PERK-dependent regulation of MDA-7/IL-24-induced cell killing in primary human glioma cells

Departments of ¹ Biochemistry, ² Medicine, and ³ Neurosurgery, Virginia Commonwealth University, Richmond, Virginia; Departments of ⁴ Pathology, ⁵ Neurosurgery, and ⁶ Urology, Herbert Irving Comprehensive Cancer Center, Columbia University Medical Center, College of Physicians and Surgeons, New York, New York; ⁷ Division of Human Gene Therapy, Departments of Medicine, Pathology and Surgery, and the Gene Therapy Center, University of Alabama at Birmingham, Birmingham, Alabama; and ⁸ Department of Radiation Oncology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania

Requests for reprints: Paul Dent, Department of Biochemistry, Virginia Commonwealth University, 401 College Street, Massey Cancer Center, Box 980035, Richmond, VA 23298-0035. Phone: 804-628-0861; Fax: 804-827-1309. E-mail: pdent{at}vcu.edu

Abstract

Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) is a novel cytokine displaying selective apoptosis-inducing activity in transformed cells without harming normal cells. The present studies focused on defining the mechanism(s) by which a GST-MDA-7 fusion protein inhibits cell survival of primary human glioma cells in vitro. GST-MDA-7 killed glioma cells with diverse genetic characteristics that correlated with inactivation of ERK1/2 and activation of JNK1-3. Activation of JNK1-3 was dependent on protein kinase R–like endoplasmic reticulum kinase (PERK), and GST-MDA-7 lethality was suppressed in PERK–/– cells. JNK1-3 signaling activated BAX, whereas inhibition of JNK1-3, deletion of BAX, or expression of dominant-negative caspase-9 suppressed lethality. GST-MDA-7 also promoted a PERK-, JNK-, and cathepsin B–dependent cleavage of BID; loss of BID function promoted survival. GST-MDA-7 suppressed BAD and BIM phosphorylation and heat shock protein 70 (HSP70) expression. GST-MDA-7 caused PERK-dependent vacuolization of LC3-expressing endosomes whose formation was suppressed by incubation with 3-methyladenine, expression of HSP70 or BiP/GRP78, or knockdown of ATG5 or Beclin-1 expression but not by inhibition of the JNK1-3 pathway. Knockdown of ATG5 or Beclin-1 expression or overexpression of HSP70 reduced GST-MDA-7 lethality. Our data show that GST-MDA-7 induces an endoplasmic reticulum stress response that is causal in the activation of multiple proapoptotic pathways, which converge on the mitochondrion and highlight the complexity of signaling pathways altered by mda-7/IL-24 in glioma cells that ultimately culminate in decreased tumor cell survival. [Mol Cancer Ther 2008;7(2):297–313]

Grant support: Public Health Service grants P01-CA104177, R01-CA108325, and R01-DK52825, Jim Valvano "V" Foundation, and Department of Defense award DAMD17-03-1-0262 (P. Dent); Public Health Service grants R01-CA63753 and R01-CA77141 and a Leukemia Society of America grant 6405-97 (S. Grant); Public Health Service grants P01-CA104177, R01-CA097318, R01-CA098172, and P01-NS031492, Samuel Waxman Cancer Research Foundation, and Michael and Stella Chernow Endowment (P.B. Fisher); and Public Health Service grant P01-CA104177 (D.T. Curiel).

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Note: P. Dent is The Universal, Inc. Professor in Signal Transduction Research. P.B. Fisher is The Michael and Stella Chernow Urological Cancer Research Scientist and a SWCRF Investigator.

⁹ Supplementary material for this article is available at Molecular Cancer Therapeutics Online (http://mct.aacrjournals.org/).

¹⁰ Unpublished observation.

Received 10/ 4/07; revised 11/26/07; accepted 12/26/07.

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