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Research Articles: Therapeutics, Targets, and Development

Suppression of cervical carcinoma cell growth by intracytoplasmic codelivery of anti-oncoprotein E6 antibody and small interfering RNA

¹ Institut Gilbert-Laustriat, UMR 7175, ESBS; ² Institut Gilbert-Laustriat, UMR 7175, Faculté de Pharmacie; ³ Institut de Génétique et de Biologie Moléculaire et Cellulaire, UMR 7104, Illkirch Cedex, France

Requests for reprints: Etienne Weiss, Institut Gilbert-Laustriat, UMR 7175, ESBS, Boulevard Sébastien Brant, BP 10413, 67412 Illkirch Cedex, France. Phone: 33-390244767; Fax: 33-390244683. E-mail: eweiss{at}esbs.u-strasbg.fr

Abstract

Cervical cancer is caused by high-risk types of human papillomaviruses (HPV) that encode the E6 and E7 oncogenes. Silencing of E6 gene expression in HPV-positive cell lines by transfection of small interfering RNA (siRNA) with cationic lipids restores the dormant p53 tumor suppressor pathway. Because cationic lipids can also be used for intracytoplasmic delivery of proteins, we tested whether the delivery of monoclonal antibodies that bind to HPV16 E6 and neutralize its biological activity in vitro could restore p53 function in tumor cells. Here, we show that the 4C6 antibody is efficiently delivered into the cell cytoplasm using a lipidic reagent used for siRNA transfection. The delivery of 4C6 resulted in the nuclear accumulation of p53 protein in CaSki and SiHa cells but not in HeLa cells. Furthermore, the antibody-mediated p53 response was dramatically increased when a peptide corresponding to the 4C6 epitope and bearing a COOH-terminal cysteine residue was added to the transduction mixture. We found that a fraction of the added peptides were dimers that allowed the formation of antibody polymers adsorbed onto the lipidic matrix. With this system, the proliferation of CaSki and SiHa cells was strongly diminished, but no apoptosis was detectable. Remarkably, cell growth was almost totally suppressed by the addition of E6-specific siRNA to the transduction complex. The results indicate that the activity of E6 oncoprotein can be down-regulated in vivo by lipid-mediated antibody delivery and that antibodies and siRNA act synergistically when codelivered. This novel targeting strategy is simple to implement and may find therapeutic applications. [Mol Cancer Ther 2007;16(5):1728–35]

Grant support: Université Louis Pasteur of Strasbourg, Centre National de la Recherche Scientifique, and Association de la Recherche contre le Cancer grant 3127.

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.

⁴ Supplementary data for this article are available at Molecular Cancer Therapeutics Online (http://mct.aacrjournals.org/).

⁵ E. Weiss, unpublished observations.

Received 12/28/06; revised 4/14/07; accepted 5/ 1/07.