A p53-derived apoptotic peptide derepresses p73 to cause tumor regression in vivo
Helen S. Bell, … , Karen H. Vousden, Kevin M. Ryan
Helen S. Bell, … , Karen H. Vousden, Kevin M. Ryan
Published April 2, 2007
Citation Information: J Clin Invest. 2007;117(4):1008-1018. https://doi.org/10.1172/JCI28920.
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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 5

37AA does not transactivate directly, but causes secondary activation through p73.

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37AA does not transactivate directly, but causes secondary activation th...
(A) Saos-2 cells were transiently transfected with 5 μg PUMA luciferase plasmid and 200 ng each of the indicated expression constructs. After 72 hours, cells were assayed for luciferase activity, and the data were normalized against transfected β-gal activity. Values represent fold activation relative to the activity of GFP alone, which was assigned as 1. (B) Saos-2 cells were infected as indicated with adenoviruses expressing tr105, 37AA, ΔN-p73 adenovirus, or control empty adenovirus. At the indicated time points, RNA was isolated from the cells and subjected to RT-PCR for PUMA and GAPDH. (C) At the same time cells were harvested and assessed for changes in cell death by flow cytometry. (D) Cells were infected with the indicated adenoviruses for 48 hours. The mRNA levels for PUMA, DR5, Bax, and p21 were determined by qPCR. Samples were normalized to the levels of 18S ribosomal RNA. (E) Schematic of the mode of action of 37AA. Introduction of 37AA into p53-null cells sequesters iASPP and thereby derepresses p73. TA-p73 subsequently activates apoptotic target genes such as PUMA to bring about programmed cell death. In line with this model, cell death from 37AA can be inhibited by decreasing p73 activity or increasing iASPP.