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Research Articles: Therapeutics, Targets, and Development

Modulation of drug resistance by artificial transcription factors

¹ Department of Molecular Biology and The Skaggs Institute for Chemical Biology and ² Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California and ³ Department of Clinical Research, Medical Oncology/Hematology, University of Bern; ⁴ Novartis Institutes for Biomedical Research, Novartis Pharma AG, Basel, Switzerland

Requests for reprints: Carlos F. Barbas III, Department of Molecular Biology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037. Phone: 858-784-9098; Fax: 858-784-2583. E-mail: carlos{at}scripps.edu

Abstract

The efficiency of chemotherapeutic treatments in cancer patients is often impaired by the acquisition of drug resistance. Cancer cells develop drug resistance through dysregulation of one or more genes or cellular pathways. To isolate efficient regulators of drug resistance in tumor cells, we have adopted a genome-wide scanning approach based on the screening of large libraries of artificial transcription factors (ATFs) made of three and six randomly assembled zinc finger domains. Zinc finger libraries were linked to a VP64 activation domain and delivered into a paclitaxel-sensitive tumor cell line. Following drug treatment, several ATFs were isolated that promoted drug resistance. One of these ATFs, 3ZF-1-VP, promoted paclitaxel resistance in cell lines having mutated or inactivated p53, such as MDA-MB-435 and Kaposi's sarcoma cell lines. 3ZF-1-VP also induced strong resistance to etoposide, vincristine, and cisplatinum. Linkage of a repression domain to the selected ATF resulted in enhanced sensitivity to multiple drugs, particularly vincristine, cisplatinum, and 5-fluorouracil. Small interfering RNA–mediated inhibition of p53 revealed that 3ZF-1-VP activated both p53-dependent and p53-independent mechanisms to promote survival, whereas other ATF required intact p53. Real-time expression analysis and DNA microarrays showed that several ATFs up-regulated targets of p53, such as the cyclin-dependent kinase inhibitor p21^WAF1/CIP1, and genes participating in the p14^ARF-MDM2-p53 tumor suppressor pathway, such as hDMP1. Thus, ATF can be used to map genes and pathways involved in drug resistance phenotypes and have potential as novel therapeutic agents to inhibit drug resistance. [Mol Cancer Ther 2008;7(3):688–97]

Grant support: NIH grant R21GM075110 (C.F. Barbas III) and grants DK54938 and AI49165 (B.E. Torbett and M.P. Tschan) and Swiss Federation against Cancer fellowship BIL OCS-01198-09-2001 (M.P. Tschan).

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: Current address for P. Blancafort: Department of Pharmacology and the Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.

This work describes the isolation of ATF able to modulate resistance to multiple drugs in tumor cells; these proteins hold promise in cancer therapeutics as modulators of acquired drug resistance.

⁵ Supplementary material for this article is available at Molecular Cancer Therapeutics Online (http://mct.aacrjournals.org/).

Received 6/ 7/07; revised 11/ 9/07; accepted 1/24/08.