Mammalian host cells for use in a cell-mediated transfection process, which contain an RNAi molecule and an expression vector for a pro-apoptotic protein. The method includes inducing apoptotic cell (AC) death in mammalian cells that contain an RNAi molecule capable of down-regulating a chosen target gene. Living cells expressing the target gene are then exposed to the ACs. The ACs are processed by the living cells, and the RNAi molecule in the ACs down-regulates the expression of the target gene in living cells.
