Tumor-selective gene transduction and cell killing with an oncotropic autonomous parvovirus-based vector

A recombinant MVMp of the fibrotropic strain of minute virus of mice (MVMp) expressing the chloramphenicol acetyltransferase reporter gene was used to infect a series of biologically relevant cultured cells, normal or tumor-d erived, including normal melanocytes Versus melanoma cells, normal mammary epithelial cells versus breast adenocarcinoma cells, and normal neurons or astrocytes versus glioma cells. As a reference cell system we used normal h uman fibroblasts versus the SV40-transformed fibroblast cell line NB324K. A fter infection, we observed good expression of the reporter gene in the dif ferent tumor cell types, but only poor expression if any in the correspondi ng normal cells. We also constructed a recombinant MVMp expressing the gree n fluorescent protein reporter gene and assessed by flow cytometry the effi ciency of gene transduction into the different target cells. At a multiplic ity of infection of 30, we observed substantial transduction of the gene in to most of the tumor cell types tested, but only marginal transduction into normal cells under the same experimental conditions. Finally, we demonstra ted that a recombinant MVMp expressing the herpes simplex virus thymidine k inase gene can, in vitro, cause efficient killing of most tumor cell types in the presence of ganciclovir, whilst affecting normal proliferating cells only marginally if at all. However, in the same experimental condition, br east tumor cells appeared to be resistant to GCV-mediated cytotoxicity, pos sibly because these cells are not susceptible to the bystander effect. Our data suggest that MVMp-based vectors could prove useful as selective vehicl es for anticancer gene therapy, particularly for in vivo delivery of cytoto xic effector genes into tumor cells.