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Targeting a Novel Vector for Breast Cancer Gene Therapy

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Final rept. 15 Jul 1999-14 Jul 2002

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We are testing the hypothesis that a model parasite gene therapy vector can be genetically altered to safely, specifically and effectively target breast cancer cells in vitro and in vivo. The primary purpose and scope of this IDEA award project is to experimentally examine approaches to safely target the Toxoplasma gondii parasite gene therapy vector to breast cancer tissue using in vitro and in vivo models. We found that cytosine deaminase CD and thymidine kinase TK markers expressed in T gondii produce a significant bystander killing effect on both human fibroblasts and SKBR3 tumor cells in vitro. We report the construction of a highly attenuated uracil auxotrophic T gondii parasite strain for safely targeting gene therapy to breast cancer. Using trifunctional enzyme expression plasmids we co-expressed TK and CD markers in transgenic T gondii. An approach for selectively targeting the TK and CD transgenes to HEK2neu overexpressing cells was examined. We found that a bi-specific antibody with specificity to Mer2neu and a mjor T gondii surface antigen provided a small but detectable increase in the fraction of Her2neu cells infected by the targeting parasite, and sensitization of tumors cells to killing by ganciclovir or 5-fluorocytosine therapy. Improved technology will need to be developed to improve the specificity of the targeting strategy in this model.

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  • Medicine and Medical Research

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