A novel dual-targeted lentiviral vector leads to specific transduction of prostate cancer bone metastases in vivo after systemic administration.

Targeted gene transduction to organs and tissues of interest is the ultimate goal of therapeutic gene delivery. Lentiviral vectors (LVs) are powerful tools for stable gene delivery but their integration into undesired cell types poses a serious safety concern for their use in the clinic. Here we report the development of a new dual-targeted LV that can preferentially home to and express in prostate cancer bone metastases in vivo after systemic delivery. Transductional targeting is mediated by a modified Sindbis virus envelope that interacts with the prostate stem cell antigen (PSCA) expressed by prostate cancer cells, and transcriptional targeting is mediated by a prostate cell specific promoter. Homing to prostate tumors was achieved in 70% of the animals. Importantly, tumors could be detected in some cases by molecular imaging prior to X-ray detection. The dual-targeted vector presents enhanced specificity with respect to individual transcriptional or transductional targeted vectors. Transgene expression in the liver was 190 times lower than the expression associated with solely transductionally targeted vectors, and there was 12 times less vector DNA than the amount present with solely transcriptionally targeted vectors. The LV presented here is a powerful tool for obtaining stable and site-specific gene expression and can be easily modified for its use in other diseases.