Tissue-Specific,Cell Cycle-Regulated Chimeric Transcription Factors for the Targeting of Gene Expression to Tumor Cells

A major challenge in the gene therapy of proliferative diseases is the specific targeting of gene expression. Here we describe a new approach based on the development of dual-specificity promoters that are both cell type specific and cell cycle regulated. The gene of interest is driven by an artificial heterodimeric transcription factor, whose DNA-binding subunit is expressed from a tissue-specific promoter, whereas the trans-activating subunit is transcribed from a cell cycle-regulated promoter. As a result gene expression occurs preferentially in the proliferating cells of a specific type of tissue. The selectivity of this strategy is demonstrated for the expression of a transgene in proliferating melanoma cells, using a combination of cyclin A and tyrosinase promoter elements. We also show that the level of expression that can be achieved by this system is sufficient to induce a clear biological effect in a TNF-α cytotoxicity assay.

Overview summary

Cell proliferation is one of the hallmarks of cancer cells that can be exploited for the targeting of malignant tumors by gene therapy. A frequently employed strategy, the thymidine kinase/ganciclovir system, makes use of effector systems whose efficacy is dependent on cell division. A limiting factor of this approach is the fact that nonproliferating cells will not be affected. It would therefore be advantageous to achieve cell cycle dependence by means of the expression vector rather than by means of the therapeutic gene. One way to accomplish this goal would be to combine cell type-specific and cell cycle-regulated gene expression from the same promoter. Here, we establish a generally applicable strategy for the construction of such dual-specificity promoters.