A functional genetic screen identifies retinoic acid signaling as a target of histone deacetylase inhibitors

doi:10.1073/pnas.0702518104

A functional genetic screen identifies retinoic acid signaling as a target of histone deacetylase inhibitors

*Division of Molecular Carcinogenesis and Center for Biomedical Genetics, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX, Amsterdam, The Netherlands;
^‡Centre for Oncology and Applied Pharmacology, University of Glasgow, Cancer Research United Kingdom Beatson Laboratories, Garscube Estate, Glasgow G61 1BD, United Kingdom; and
^§Department of Cell Biology and Signal Transduction, Institut de Genetique et de Biologie Moleculaire et Cellulaire/Centre National de la Recherche Scientifique/Institut National de la Santé et de la Recherche Médicale/Université Louis Pasteur, BP 163, 67404 Illkirch Cedex Strasbourg, France

Edited by Ed Harlow, Harvard Medical School, Boston, MA and approved September 24, 2007 (received for review March 17, 2007)

Abstract

Understanding the pathways that are targeted by cancer drugs is instrumental for their rational use in a clinical setting. Inhibitors of histone deacetylases (HDACI) selectively inhibit proliferation of malignant cells and are used for the treatment of cancer, but their cancer selectivity is understood poorly. We conducted a functional genetic screen to address the mechanism(s) of action of HDACI. We report here that ectopic expression of two genes that act on retinoic acid (RA) signaling can cause resistance to growth arrest and apoptosis induced by HDACI of different chemical classes: the retinoic acid receptor α (RARα) and preferentially expressed antigen of melanoma (PRAME), a repressor of RA signaling. Treatment of cells with HDACI induced RA signaling, which was inhibited by RARα or PRAME expression. Conversely, RAR-deficient cells and PRAME-knockdown cells show enhanced sensitivity to HDACI in vitro and in mouse xenograft models. Finally, a combination of RA and HDACI acted synergistically to activate RA signaling and inhibit tumor growth. These experiments identify the RA pathway as a rate-limiting target of HDACI and suggest strategies to enhance the therapeutic efficacy of HDACI.

Footnotes

^¶To whom correspondence should be addressed. E-mail: R.Bernards{at}nki.nl
Author contributions: R. Bernards designed research; M.T.E., L.W., J.A.P., and M.L. performed research; H.G. and R. Brown contributed new reagents/analytic tools; M.T.E., L.W., J.A.P., R. Brown, and R. Bernards analyzed data; and M.T.E. and R. Bernards wrote the paper.
↵ ^†Present address: Urology Department of Changzheng Hospital, Fengyang Road 415, 200003 Shanghai, People's Republic of China.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0702518104/DC1.
Abbreviations:

AD,

activation domain;

HDAC,

histone deacetylase;

HDACI,

HDAC inhibitor;

KD,

knockdown;

luc,

luciferase;

MEF,

mouse embryonic fibroblast;

NR,

nuclear receptor;

PRAME,

preferentially expressed antigen of melanoma;

RA,

retinoic acid;

RAR,

retinoic acid receptor;

RARE,

retinoic acid-responsive element;

tk,

thymidine kinase;

TKO,

triple knockout;

SAHA,

suberoylanilide hydroxamic acid;

TSA,

trichostatin A.
Freely available online through the PNAS open access option.