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Research Articles: Therapeutics, Targets, and Development

Recombinant, refolded tetrameric p53 and gonadotropin-releasing hormone-p53 slow proliferation and induce apoptosis in p53-deficient cancer cells

¹ ProteomTech, Inc., Costa Mesa, California and ² GeneCopoeia, Inc., Germantown, Maryland

Requests for reprints: Xinli Lin, GeneCopoeia, Inc., 19520 Amaranth Drive, Germantown, MD 20874. Phone: 301-515-6982; Fax: 301-515-6983. E-mail: xllin{at}genecopoeia.com

Abstract

The p53 tumor suppressor is mutated in over 50% of human cancers. Mutations resulting in amino acid changes within p53 result in a loss of activity and consequent changes in expression of genes that regulate DNA repair and cell cycle progression. Replacement of p53 using protein therapy would restore p53 function in p53-deficient tumor cells, with a consequence of tumor cell death and tumor regression. p53 functions in a tetrameric form in vivo. Here, we refolded a wild-type, full-length p53 from inclusion bodies expressed in Escherichia coli as a stable tetramer. The tetrameric p53 binds to p53-specific DNA and, when transformed into a p53-deficient cancer cell line, induced apoptosis of the transformed cells. Next, using the same expression and refolding technology, we produced a stable tetramer of recombinant gonadotropin-releasing hormone-p53 fusion protein (GnRH-p53), which traverses the plasma membrane, slows proliferation, and induces apoptosis in p53-deficient, GnRH-receptor–expressing cancer cell lines. In addition, we showed a time-dependent binding and internalization of GnRH-p53 to a receptor-expressing cell line. We conclude that the GnRH-p53 fusion strategy may provide a basis for constructing an effective cancer therapeutic for patients with tumors in GnRH-receptor–positive tissue types. [Mol Cancer Ther 2008;7(6):1420–9]

Grant support: ProteomTech, Inc.

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.

³ Supplementary data for this article are available at Molecular Cancer Therapeutics Online (http://mct.aacrjournals.org/).

Received 3/ 5/08; revised 4/18/08; accepted 4/18/08.