1. ¹Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
2. ²INSERM, Unité 638, Nice, France
3. ³Faculté de Médecine, Université de Nice Sophia Antipolis, Nice, France
4. ⁴Department of Microbiology, University of the Pacific, Arthur A. Dugoni School of Dentistry, San Francisco, CA, USA
5. ⁵Laboratory of Pharmaceutical Technology, Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal
6. ⁶Department of Biochemistry, Faculty of Science and Technology, University of Coimbra, Coimbra, Portugal

Correspondence: Professor MC Pedroso de Lima, Department of Biochemistry: Center for Neuroscience and Cell Biology, University of Coimbra, 3000 Coimbra, Portugal. E-mail: mdelima@ci.uc.pt

Received 20 January 2008; Revised 31 March 2008; Accepted 17 May 2008; Published online 8 August 2008.

Abstract

Suicide gene therapy has been used for the treatment of a variety of cancers. We reported previously the in vitro efficacy of the Herpes Simplex Virus Thymidine kinase (HSV-tk)/ganciclovir (GCV) system to mediate cytotoxicity in oral squamous cancer cells, using transferrin (Tf)-lipoplexes, prepared from cationic liposomes composed of 1,2-dioleoyl-3-(trimethylammonium) propane (DOTAP) and cholesterol. In the present study, we evaluated the antitumoral efficacy mediated by this lipoplex formulation in two suicide gene therapy strategies, HSV-tk/GCV and cytosine deaminase (CD)/5-fluorocytosine (5-FC), using a syngeneic, orthotopic murine model for head and neck squamous cell carcinoma. The cellular and molecular events associated with the antitumoral response elicited by both the therapeutic approaches were investigated by analyzing tumor cell death, tumor-infiltrating immune cells and tumor cytokine microenvironment. Significant tumor reduction was achieved upon intratumoral delivery of HSV-tk or CD genes mediated by Tf-lipoplexes, followed by intraperitoneal injection of GCV or 5-FC, respectively. Enhanced apoptosis, the recruitment of NK cells, CD4 and CD8 T-lymphocytes and an increase in the levels of several cytokines/chemokines were observed within the tumors. These observations suggest that suicide gene therapy with lipoplexes modifies the tumor microenvironment, and leads to the recruitment of immune effector cells that can act as adjuvants in reducing the tumor size.