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 spec ific targeting of gene expression. Here we describe a new approach based on the development of dual-specificity promoters that are both cell type spec ific and cell cycle regulated. The gene of interest is driven by an artific ial heterodimeric transcription factor, whose DNA-binding subunit is expres sed from a tissue-specific promoter, whereas the transactivating subunit is transcribed from a cell cycle-regulated promoter, As a result gene express ion 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 cyc lin A and tyrosinase promoter elements. We also show that the level of expr ession that can be achieved by this system is sufficient to induce a clear biological effect in a TNF-alpha cytotoxicity assay.