This invention describes a genetic system for targeting the EVI1 gene in mammalian cells. The EVI1 gene is an oncogenic transcription factor that, when expressed, accelerates cell division and inhibits death of cells. Nucleotide sequences that block the expression of EVI1 and drug delivery systems for them are described. These nucleotide sequences cause a block in cell growth and division and trigger death of mammalian cells, including lung and ovarian cancer cells.