302. Herpes Simplex Virus Thymidine Kinase/Ganciclovir Therapy Mediated by Transferrin-Associated Lipoplexes in a Murine Model for Oral Cancer

Abstract

Current treatments of oral cancer are largely unsatisfactory, and the five-year survival rate has not improved over the last two decades. In fact, despite recent advances, the present therapeutic approaches such as surgery, radiation and chemotherapy have significant limitations both in terms of efficacy and ability to prolong survival in patients with advanced cancer disease. Although viral vectors are generally efficient in transducing cells, the drawbacks associated with their use, namely those related with safety problems, have prompted investigators to develop alternative methods for gene delivery. Cationic lipid-based systems (lipoplexes) have been extensively used, both in vitro and in vivo, despite their limited efficiency of delivery and gene expression. Our previous studies have shown that transferrin-associated lipoplexes composed of DOTAP:cholesterol constitute a promising tool for delivering Herpes Simplex Virus thymidine kinase (HSV-tk) gene to the squamous cell carcinoma cells, including human squamous cells (HSC-3) and murine squamous carcinoma cells (SCC VII). High cytotoxicity (95 %) was achieved for both types of cells upon treatment with 100 |[mu]|M ganciclovir (GCV) following transfection with 1 |[mu]|g pCMVtk. In this study, we evaluated the in vivo efficiency of the transferrin-associated lipoplexes to deliver a reporter gene in an orthotopic model of oral cancer established in C3H/HeJ immunocompetent mice (upon injection of 1 |[times]| 105 of SCC VII cells into the floor of the mouth). Our results show that DOTAP:cholesterol/transferrin-complexes, when prepared at 3/2 lipid/DNA (+/-) charge ratio (40 |[mu]|g pCMVlacZ), are able to efficiently transfect the tumor cells in vivo, as assessed by scoring the percentage of cells expressing |[beta]|-galactosidase, using both immunohistochemistry and X-gal staining. In addition, we will investigate the efficacy of this formulation to mediate tumor cell killing and tumor size reduction, upon delivery of the HSV-tk gene followed by GCV treatment. Since our in vitro studies have shown that SCC-VII cells are very sensitive to this therapy and significantly transfected in vivo, a regression of the tumor is expected to be achieved. Our results suggest that DOTAP:cholesterol/transferrin-complexes can be promising for the gene therapy of oral cancer in animal models.