Targeting and killing of prostate cancer cells using lentiviral constructs containing a sequence recognized by translation factor eIF4E and a prostate-specific promoter

To develop a gene therapy that would selectively kill prostate cancer cells while sparing normal cells, we have constructed lentiviral vectors that contain a therapeutic gene with a short DNA sequence in the 5'-untranslated region (UTR) that is recognized by the translation initiation factor, eIF4E, which is often overexpressed in malignant cells. Infection of cancer (LNCaP, PC-3M, DU145, and MCF-7 cells) and noncancer cell lines (BPH-1, 267-B1, Plat-E, and Huvec-c cells) with lentivirus having a CMV-promoter and EGFP reporter resulted in high levels of EGFP expression in all cells, whereas, inclusion of the eIF4E UTR recognition sequence restricted high expression to cancer cells and Plat-E cells, which also express substantial levels of eIF4E. Infection of the cells with lentiviral vectors having this UTR in front of the HSV thymidine kinase suicide gene resulted in differential sensitivity to the killing effects of ganciclovir, with at least 100-fold more drug required to kill noncancer cells than cancer cells. Furthermore, in experiments where the CMV promoter was replaced by the prostate-specific ARR(2)PB promoter, the killing effects of ganciclovir were restricted to prostate cancer cells and not seen in nonprostate cancer cells. Our results indicate that combined translational regulation, by incorporation of an eIF4E-UTR recognition sequence into a therapeutic gene, together with transcriptional regulation with a prostate-specific promoter, may provide a means to selectively destroy prostate cancer cells while sparing normal prostate cells.