We have demonstrated earlier that the replacement of the plasma membrane components of Erlich adenocarcinoma cells by the ones of thymocytes facilitates induced apoptosis in the tumor cells. Here we questioned whether similar effect can be achieved by transfection of thymocyte DNA. Lyposome transfer of normal DNA did not change the basal level of the programmed cell death. However, transfection activated apoptosis induced by Roentgen irragiation or glucocorticoids. Probably, this effect was due to restoration suppressor genes, which had been lost during the process malignant transformation. These experiments may be useful for the development of gene therapy approaches for tumor sensibilisation.