A p53-derived apoptotic peptide derepresses p73 to cause tumor regression in vivo
Helen S. Bell, Christine Dufes, Jim O’Prey, Diane Crighton, Daniele Bergamaschi, Xin Lu, Andreas G. Schätzlein, Karen H. Vousden, Kevin M. Ryan
Helen S. Bell, Christine Dufes, Jim O’Prey, Diane Crighton, Daniele Bergamaschi, Xin Lu, Andreas G. Schätzlein, Karen H. Vousden, Kevin M. Ryan
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Research Article Oncology

A p53-derived apoptotic peptide derepresses p73 to cause tumor regression in vivo

Abstract

The tumor suppressor p53 is a potent inducer of tumor cell death, and strategies exist to exploit p53 for therapeutic gain. However, because about half of human cancers contain mutant p53, application of these strategies is restricted. p53 family members, in particular p73, are in many ways functional paralogs of p53, but are rarely mutated in cancer. Methods for specific activation of p73, however, remain to be elucidated. We describe here a minimal p53-derived apoptotic peptide that induced death in multiple cell types regardless of p53 status. While unable to activate gene expression directly, this peptide retained the capacity to bind iASPP — a common negative regulator of p53 family members. Concordantly, in p53-null cells, this peptide derepressed p73, causing p73-mediated gene activation and death. Moreover, systemic nanoparticle delivery of a transgene expressing this peptide caused tumor regression in vivo via p73. This study therefore heralds what we believe to be the first strategy to directly and selectively activate p73 therapeutically and may lead to the development of broadly applicable agents for the treatment of malignant disease.

Authors

Helen S. Bell, Christine Dufes, Jim O’Prey, Diane Crighton, Daniele Bergamaschi, Xin Lu, Andreas G. Schätzlein, Karen H. Vousden, Kevin M. Ryan

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Figure 4

Expression of iASPP or interference with p73 inhibits 37AA-mediated cell death.

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Expression of iASPP or interference with p73 inhibits 37AA-mediated cell...
(A) Saos-2 cells were transfected with the indicated plasmids and then infected with an adenovirus (Ad) expressing ΔN-p73α or empty virus control (Con). After 48 hours, cells were analyzed for cell death by flow cytometry or for expression of transfected plasmids by Western blotting. (B) Saos-2 cells that had been infected with a retrovirus expressing either an shRNA directed against TA-p73 (pRS-p73) or a scrambled control (pRS-Scr) were transfected with the indicated plasmids. After 48 hours, cells were analyzed for cell death by flow cytometry or for expression of transfected plasmids by Western blotting. (C) Saos-2 cells were transiently cotransfected with the indicated amounts of 37AA and iASPP. After 48 hours, cells were analyzed for cell death by flow cytometry and for expression of transfected plasmids by Western blotting. (D) The effects of iASPP knockdown by RNA interference in p53-null cells were determined. Saos-2 cells were transfected with plasmids expressing 2 different shRNAs that target iASPP or a scrambled shRNA control. The effects of the shRNAs on transfected iASPP expression were determined by Western blotting after 24 hours, and the effects on long-term survival were determined by assessing the clonogenic capacity of the cells. G418 con, control for drug activity; cells were mock-transfected and selected with G418. Original magnification, ×1.