• T A Tirone, S P Fagan, N S Templeton, X Wang, and F C Brunicardi.
• Departments of Molecular Biology and Center for Gene Therapy, Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, Texas, USA.
• Ann. Surg. 2001 May 1; 233 (5): 603611603-11.

Objective And Summary Background DataTumor-specific gene therapy can be achieved if a tumor-specific promoter can be identified. In this study the authors investigated the use of the rat insulin promoter (RIP) for insulinoma-specific expression of a reporter gene. Insulinoma-specific cytotoxicity using the suicide gene thymidine kinase (tk) was studied both in vitro and in vivo. RIPtk gene therapy, delivered by a nontoxic, noninflammatory liposomal delivery system, was used in an insulinoma ICR/SCID mouse model to prevent hypoglycemic death.MethodsRat insulin promoter (0.502 kb) was ligated to the reporter gene lacZ and ligated to the tk gene. These two genes were transfected into a mouse insulinoma (NIT) cell line to ascertain insulinoma-specific expression and insulinoma-specific cytotoxicity in vitro. Reverse transcriptase-polymerase chain reaction and electrophoretic mobility-shift assays were performed on NIT-1 cell RNA and nuclear extract, respectively, to determine the transcription factors present and responsible for RIP activation in NIT-1 cells. A mouse insulinoma model was created with NIT-1 cells. These mice were treated with the RIPtk gene, and both blood sugars and animal viability were monitored.ResultsOnly NIT-1 cells stained blue after X-gal staining or had detectable levels of beta-galactosidase protein. A significant decrease in cell survival was observed in NIT-1 cells transfected with RIPtk in vitro. Messenger RNA for both BETA2 and PDX-1 was found in NIT-1 cells, and a supershift was observed for both BETA2 and PDX-1. Experimental mice treated with the RIPtk gene, delivered by a liposomal gene delivery system, maintained their blood glucose levels, and the animals did not die of hypoglycemia.ConclusionsThe data suggest that the RIP is an insulinoma-specific promoter. An ICR/SCID mouse insulinoma model was used to show that insulinoma-specific cytotoxicity can be accomplished by RIP coupled to a suicide gene in vivo, preventing hypoglycemic death.

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