Evidence for Two Modes of Development of Acquired Tumor Necrosis Factor-related Apoptosis-inducing Ligand Resistance
INVOLVEMENT OF Bcl-xL*
- ‡Department of Surgery and Pharmacology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213 and §Center for Pharmacogenetics and Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
- 1 To whom correspondence should be addressed: Dept. of Surgery, University of Pittsburgh, Hillman Cancer Center, 5117 Centre Ave., Rm. 1.46C, Pittsburgh, PA 15213. Tel.: 412-623-3268; Fax: 412-623-7709; E-mail: leeyj{at}upmc.edu.
Abstract
Previous studies have shown that repeated application of TRAIL induces acquired resistance to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Using human prostate adenocarcinoma DU-145 and human pancreatic carcinoma MiaPaCa-2 cells as a model, we now demonstrate for the first time that two states of acquired TRAIL resistance can be developed after TRAIL treatment. Data from survival assay and Western blot analysis show that acquired TRAIL resistance was developed within 1 day and gradually decayed within 6 days after TRAIL treatment in both cell lines. After TRAIL treatment, the level of Bcl-xL increased and reached a maximum within 2 days and gradually decreased in both cell lines. Bcl-xL-mediated development of acquired TRAIL resistance was suppressed by knockdown of Bcl-xL expression. Protein interaction assay revealed that during the development of TRAIL resistance, Bcl-xL dissociated from Bad and then associated with Bax. Overexpression of mutant-type Bad (S136A), which prevents this dissociation, partially suppressed the development of acquired TRAIL resistance. Thus, our results suggest that (a) dissociation of Bad from Bcl-xL and (b) an increase in the intracellular level of Bcl-xL are responsible for development of acquired TRAIL resistance.
Footnotes
-
↵2 The abbreviations used are: TRAIL, tumor necrosis factor-related apoptosis-inducing ligand; DISC, death-inducing signaling complex; DR, death receptor; IAP, inhibitor of apoptosis; PARP, poly(ADP-ribose) polymerase; PBS, phosphate-buffered saline; siRNA, small interfering RNA; BH, Bcl-2 homology.
-
↵* This work was supported by NCI, National Institutes of Health Grants CA95191, CA96989, and CA121395, Department of Defense Prostate Cancer Research Program Fund PC020530 Grant, and by the Susan G. Komen Breast Cancer Foundation. 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.
-
- Received August 22, 2006.
- Revision received November 13, 2006.
- The American Society for Biochemistry and Molecular Biology, Inc.
