The integration of transcriptional profiling, cancer cells targeting and molecular-genetic imaging into a single platform would have many biological applications and the potential to improve the practice of medicine. We have designed and validated a new hybrid viral system composed of genetic elements from adeno-associated virus (AAV) and phage (termed AAVP). These ligand-directed particles enable targeted systemic delivery and imaging of transgene reporters. Experimental non-invasive monitoring of reporter trans-activation, may be followed ex-vivo and in vivo. Targeted molecular imaging would represent a major advance in the management of prostate cancer. The overall goal in this project is to combine the homing and tumor transducing capabilities of AAVP with cancer-specific promoters, as a way to develop improved tools for tumor monitoring based on the transcriptional activity of selected markers. These promoters will be identified by the large-scale evaluation of the transcriptome of cancer cells and tumor vasculature, using extensive searches in public databases, as well as by the construction and large-scale sequencing of SAGE libraries, using modern low-cost high throughput pyrosequencing approaches. The identified upregulated genes will be validated in two independent sample sets, and the promoters of confirmed upregulated transcripts will be identified, certified and cloned into AAVPs. With the definition of a reliable set of genes we expect to have comprehensive panel of tumor markers covering most of the gene expression variability seen in distinct patient tumor samples. The concept of establishing a panel of multiple markers is in line with the much heralded era of personalized medicine, and should launch, for the first time, a system for imaging temporally and spatially, in vivo, the transcriptional profile within tumors. The combination of a vector displaying peptides designed to target tumors, which also carries a suicide/reporter transgene (HSVtk) under the control of a tumor-specific promoter should enable transcriptional imaging and tumor growth suppression in a very specific fashion. The imaging and treatment possibilities of this vector reinforce the idea of drug-diagnostic co-development that, if preceded by an individual evaluation of gene expression (in the urine of patients with prostate cancer, for instance), could lead to a personalized diagnosis/treatment based on the up-regulated markers of an individual patient. This personalized imaging test merged with a companion drug comes together with the drug-diagnostic co-development concept recently put forward by the US Food and Drug Administration. Under this vision, the transcriptional imaging provided by a specific tumor gene will also trigger tumor apoptosis, allowing imaging as well as treatment and monitoring of disease progression.
Our Specific Aims are: (i) To identify and to validate transcripts upregulated in prostate cancer using large scale transcriptome analysis. (ii) To combine ligand-directed targeting of AAVP to transcriptional targeting, and (iii) To evaluate the efficiency of imaging in vivo the expression of prostate cancer specific transcripts by using transcriptome-directed promoters cloned into RGD/GRP78-targeted AAVP constructs. The concept of establishing a panel of multiple markers is in line with the much heralded era of personalized medicine, and should launch, for the first time, a system for imaging temporally and spatially, in vivo, the transcriptional profile within tumors.
