CASP9 and neoplasm: We did not observe any significant activation of the intrinsic caspase pathway (as measured by caspase-3 and caspase-9 expression) in tumors of mice injected with HepG2 cells infected with UV-treated HCMV, indicating that active viral replication is required at least at some stages to restrict tumor formation in vivo. These findings are consistent with the previous published study22 where inactivated murine CMV virions failed to suppress the growth of lymphoma in murine model.