CASP9 and infection: Indeed, the infection of human cells with murine CMV activates the intrinsic apoptosis pathway mediated by caspase-9 in the human target cells.34 To further evaluate the role of apoptotic machinery in tumor delay, we assessed the expression of caspase-9 and caspase-3 proteins and transcripts in tumor samples using IHC, western blotting, and RT-PCR (Figure 6).