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Program No.: 849
Targeting Retrovirus Replication to Prostate Tumors
Aki Logg, Christopher Logg, Robert J. Matusikô, Bernard H. Bochner, Nori Kasahara
Department of Biochemistry and Molecular Biology,
Institute for Genetic Medicine,
Department of Pathology,
Department of Urology, University of Southern California School of Medicine
ôDepartments of Urologic Surgery and Cell Biology, Vanderbilt University School of Medicinee ww
Keywords:
Special Text: Prostate replication-competent
Hitherto, the inability of standard replication-defective retroviral vectors to achieve effective transduction of tumors in vivohas been a major obstacle to gene therapy for cancer. The use of replication-competent retroviral vectors would be more efficient, as each tumor cell that is transduced by the vector would itself become a vector-producing cell. We have previously described a replication-competent vector derived from murine leukemia virus that is capable of transducing solid tumors in vivowith very high efficiency. The use of such a vector as a therapeutic agent, however, would not be feasible unless there were some means to confine its replication to targeted tissues. The U3 region of the murine leukemia virus (MLV) long terminal repeat (LTR) contains the enhancer and promoter sequences for transcription of the provirus from the 5' LTR. We have replaced these sequences in the replication-competent retroviral vector with those from the prostate-specific probasin promoter to target viral replication to prostate tumor cells. The viral enhancer/promoter sequences up to the CAAT box, TATA box or R region were substituted with approximately 400 bp from the proximal probasin promoter. Replacement of the viral sequences up to the R region were found to strongly inhibit viral replication, whereas replacement up to the CAAT box resulted in a vector with only moderate cell type specificity. Retention of the retroviral TATA box in the probasin-targeted vector, however, allowed replication to high titers with a high degree of specificity for prostate epithelial cells. Our results demonstrate the feasibility of targeting retroviral spread using hybrid viral-cellular promoters. |
