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Oncogene. 1998 Dec 3;17(22):2889-99.

Prostate carcinoma cell death resulting from inhibition of proteasome activity is independent of functional Bcl-2 and p53.

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The Department of Genitourinary Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston 77030, USA.


The ATP/ubiquitin-dependent 26S proteasome is a central regulator of cell cycle progression and stress responses. While investigating the application of peptide aldehyde proteasome inhibitors to block signal-induced IkappaBalpha degradation in human LNCaP prostate carcinoma cells, we observed that persistent inhibition of proteasomal activity signals a potent cell death program. Biochemically, this program included substantial upregulation of PAR-4 (prostate apoptosis response-4), a putative pro-apoptotic effector protein and stabilization of c-jun protein, a potent pro-death effector in certain cells. We also observed modest downregulation of bcl-XL, a pro-survival effector protein. However, in contrast to some recent reports stable, high level, expression of functional bcl-2 protein in prostate carcinoma cells failed to signal protection against cell death induction by proteasome inhibitors. Also in disagreement to a recent report, no evidence was found for activation of the JNK stress kinase pathway. A role for p53, a protein regulated by the proteasome pathway, was ruled out, since comparable cell death induction by proteasome inhibitors occurred in PC-3 cells that do not express functional p53 protein. These data signify that the ubiquitin/proteasome pathway represents a potential therapeutic target for prostate cancers irrespective of bcl-2 expression or p53 mutations.

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