Transduction of human pancreatic tumor cells with vesicular stomatitis virus G-pseudotyped retroviral vectors containing a herpes simplex virus thymidine kinase mutant gene enhances bystander effects and sensitivity to ganciclovir

We examined the suitability of Moloney murine leukemia virus (MLV) 4070A-, cat endogenous virus (CEV) RD114-, or vesicular stomatitis virus G (VSV-G)- pseudotyped retroviruses containing the humanized enhanced green fluorescen t protein (hEGFP) or one of two herpes simplex virus thymidine kinase (HSV- TK) genes to transduce and provide gene expression in human pancreatic tumo r cells. Fluorescence-activated cell sorter analysis demonstrated that VSV- G-pseudotyped hEGFP vector infected a greater percentage of cells and gener ated more robust gene expression than MLV 4070A- or CEV RD114-pseudotyped v ectors. Dot blot and Southern blot analysis of genomic DNA revealed up to 1 0-fold more gene copies in G418-selected VSV-G hEGFP vector-transduced cell s compared with genomic DNA from cells transduced with MLV 4070A or CEV RD1 14 pseudotypes. Cells transduced with VSV-G pseudotypes of HSV-TKWT or the HSV-TK30 vectors were 5- to 10-fold more sensitive to ganciclovir (GCV) tha n other pseudotype-transduced cells. A 40- to 61-fold difference in sensiti vity to GCV was observed between cells transduced with VSV-G HSV-TK30 vecto r and cells transduced with MLV 4070A HSV-TKWT vector in vitro. A 13-fold r eduction in tumor volume was observed in severe combined immunodeficient mi ce inoculated with PancTulTK(30) cells compared with mice inoculated with P ancTulTK(WT) cells during GCV treatment. We conclude that the choice of gly coprotein envelope and the potency of a particular suicide gene were therap eutically additive and increased the number of HSV-TK-positive cells and se nsitivity toward GCV in human pancreatic tumors cells for prodrug gene ther apy.