This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Cuddihy, A. R. Articles by Bristow, R. G. Search for Related Content PubMed PubMed Citation Articles by Cuddihy, A. R. Articles by Bristow, R. G.

Research Articles: Therapeutics, Targets, and Development

WTp53 induction does not override MTp53 chemoresistance and radioresistance due to gain-of-function in lung cancer cells

¹ Division of Applied Molecular Oncology; ² Radiation Medicine Program, Ontario Cancer Institute, Princess Margaret Hospital (University Health Network); and Departments of ³ Radiation Oncology and ⁴ Medical Biophysics, University of Toronto, Toronto, Canada

Requests for reprints: Robert G. Bristow, Radiation Medicine Program, Princess Margaret Hospital (University Health Network), University of Toronto, 610 University Avenue, Toronto, Ontario, Canada M5G 2M9. Phone: 416-946-3936; Fax: 416-946-4586. E-mail: rob.bristow{at}rmp.uhn.on.ca

Abstract

New molecular cancer treatment strategies aim to reconstitute wild-type p53 (WTp53) function in mutant p53 (MTp53)–expressing tumors as a means of resensitizing cells to chemotherapy or radiotherapy. The success of this approach may depend on whether MTp53 proteins are acting in a dominant-negative or independent gain-of-function mode. Herein, we describe an isogenic, temperature-sensitive p53 model (p53^A138V) in p53-null human H1299 lung cancer cells in which WTp53 can be selectively coexpressed with a temperature-sensitive MTp53 allele (A138V) during initial DNA damage and subsequent DNA repair. Cells expressing MTp53 alone or coexpressing induced WTp53 and MTp53 were tested for p53 transcription, G₁ and G₂ cell cycle checkpoints, apoptosis, and long-term clonogenic survival following DNA damage. Transient transfection of WTp53 into H1299 cells, or shift-down of H1299-p53^A138V stable transfectants to 32°C to induce WTp53, led to increased p21^WAF1 expression and G₁ and G₂ arrests following DNA damage but did not increase BAX expression or apoptosis. In contrast, both transient and stable expression of the p53^A138V mutant in p53-null H1299 cells (e.g. testing gain-of-function) at 37°C blocked p21^WAF1 induction following DNA damage. Cell death was secondary to mitotic catastrophe and/or tumor cell senescence. Overexpression of WTp53 did not resensitize resistant MTp53-expressing cells to ionizing radiation, cisplatinum, or mitomycin C. Our results suggest that human MTp53 proteins can lead to resistant phenotypes independent of WTp53-mediated transcription and checkpoint control. This should be considered when using p53 as a prognostic factor and therapeutic target. [Mol Cancer Ther 2008;7(4):980–92]

Grant support: National Cancer Institute of Canada Operating Grant and Canadian Cancer Society Research Scientist Award (R.G. Bristow).

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.

Note: Present address for A.R. Cuddihy: Division of Research Immunology/BMT and GISCT Program, Children's Hospital of Los Angeles, 4650 Sunset Boulevard, Los Angeles, CA 90027.

Received 7/12/07; revised 12/20/07; accepted 2/22/08.