PMAIP1 and neoplasm: However, our results indicated that disassembly of the outer capsid proteins by the cathepsins and the subsequent penetration into the cytoplasm occurred even in reovirus-refractory tumor cells, resulting in induction of type-I IFN and Noxa expression mainly via RIG-I/IPS-1 signaling, although the amounts of virus genomes penetrating the cytoplasm in reovirus-refractory tumor cells would be lower than those in reovirus-susceptible tumor cells.