title: Loss of ganciclovir sensitivity by exclusion of thymidine kinase gene from transplanted proinsulin-producing fibroblasts as a gene therapy model for diabetes.
abstract: To establish a practical method of somatic gene therapy, we aimed to develop a regulatory system at the cellular level using a suicide vector. We introduced the herpes simplex virus type 1 thymidine kinase (HSV-tk) gene into the human proinsulin-producing Ltk-cells and examined whether ganciclovir (GCV) administration could control proinsulin production in vivo. The cells transfected with the HSV-tk gene showed more than 100-fold increase in sensitivity to GCV compared with the parent cells. Analysis of blood glucose in diabetic nude mice with transplanted cells showed that proinsulin production by these cells was strongly suppressed by GCV treatment in vivo as reflected by the reversal to hyperglycemia. However, in the in vivo experiment, the plasmid containing the HSV-tk gene was spontaneously lost from the transplanted cells in one of six cases resulting in the resistance to GCV as reflected by the persistent hypoglycemia and increased tumor size. This system of HSV-tk and administration of GCV may be applicable to gene therapy as a suicide vector, but the system of stable expression of the HSV-tk gene must be established.
authors.affiliation: Otsuka Department of Clinical and Molecular Nutrition, School of Medicine, University of Tokushima, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Yoshimoto
authors.forename: R
authors.initials: R
authors.lastname: Murakami
authors.forename: M
authors.initials: M
authors.lastname: Moritani
authors.forename: M
authors.initials: M
authors.lastname: Ohta
authors.forename: H
authors.initials: H
authors.lastname: Iwahana
authors.forename: H
authors.initials: H
authors.lastname: Nakauchi
authors.forename: M
authors.initials: M
authors.lastname: Itakura
mesh_terms: D000818:Animals; D002460:Cell Line; D003921:Diabetes Mellitus, Experimental / Q000139:chemically induced / Q000628:therapy*; D004195:Disease Models, Animal; D005347:Fibroblasts / Q000378:metabolism / Q000637:transplantation; D015774:Ganciclovir / Q000494:pharmacology*; D015316:Genetic Therapy; D006564:Herpesviridae / Q000201:enzymology / Q000235:genetics; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008819:Mice, Nude; D011384:Proinsulin / Q000096:biosynthesis*; D013311:Streptozocin; D013937:Thymidine Kinase / Q000235:genetics*
chemical_list: D013311:Streptozocin; D011384:Proinsulin; D013937:Thymidine Kinase; D015774:Ganciclovir