Sensitivity of 293 human epithelial kidney cells transfected by human cytochrome CYP450 gene to cyclophosphamide was investigated. Transfection was carried out by plasmid DNA containing CYP2B6 gene complexed with cationic liposomes. Liposomes were prepared from mixture of cationic lipids and cholesterol at different molar ratios. Experimental protocol included the following steps: transfection of epithelial kidney cells by complexes of plasmid DNA-cationic liposomes, clone selection in the medium with antibiotic Geneticin G418, selected clone harvesting and their treatment by cyclophosphamide as following cytotoxicity evaluation. It was shown that addition of 0.25 mM of cyclophosphamide resulted in death of 40-45% transfected cell population.