Development of an inducible suicide gene system based on human caspase 8

Suicide gene-therapy strategies are promising approaches in treating various diseases such as cancers, atherosclerosis, and graft-versus-host-disease. Here, we describe the development of a new effector gene based on inducing functional caspase 8, the initiator caspase in the death-receptor pathway. We constructed vectors encoding a constitutively active form of human caspase 8 (CC8), and demonstrated the efficient killing of a variety of cell types in transfection and lentivirus-transduction assays. We then analyzed the ability to control the apoptotic activity of a caspase 8-derived construct through the ARIADtrade mark homodimerization system (FKC8), a system shown to be extremely effective in several cellular models upon retroviral and lentiviral gene transfer. Similarly, two transcription-regulation systems, muristerone-regulated and Tet-On, were tested to control the expression of CC8. The homodimerization-regulated system FKC8 was shown to be the most efficient system with low background activity in noninduced conditions. In the presence of a dimerizer, it was as active as the activated Tet-On system. From our data, we conclude that the dimerizer-dependent human caspase 8 represents a highly inducible and very powerful system to eradicate transduced cell populations. In addition to its application in experimental gene therapy, this variant may be highly useful for mechanistic research related to apoptosis.