Tumor necrosis factor-related apoptosis-inducing
ligand (TRAIL) has been shown to induce apoptosis in neoplastic cells. While many previous studies have been performed in cell culture, the delivery and efficiency of TRAIL variants in vivo is less well established. Using dual substrate/reporter bioluminescence imaging (Fluc:
firefly luciferase-
luciferin and Rluc:
Renilla luciferase-
coelenterazine), we tested the efficacy of TRAIL using replication-deficient herpes simplex virus (HSV) type 1 amplicon vectors in
gliomas. The
cDNA for complete TRAIL and the extracellular domain of TRAIL (aa 114-281) were cloned into HSV amplicons and packaged into helper virus-free vectors. Both forms of TRAIL induced similar degrees of apoptosis in human
glioma cells (Gli36) in culture within 24 h of
infection with TRAIL amplicon vectors. Growth of
tumors stably transfected with Fluc (Gli36fluc+) was readily monitored in vivo by bioluminescence imaging following
luciferin administration. HSV amplicon vectors bearing the genes for TRAIL and Rluc injected directly into Gli36fluc(+)-expressing subcutaneous
gliomas revealed peak Rluc activity 36 h after intratumoral injection as determined by
coelenterazine injection followed by imaging. TRAIL-treated
gliomas regressed in size over a period of 4 weeks as compared to the mock-injected
gliomas. These results show the efficacy of vector delivered TRAIL in treating
tumors in vivo and offer a unique way to monitor both gene delivery and efficacy of TRAIL-induced apoptosis in
tumors in vivo in real time by dual
enzyme substrate (Rluc/Fluc) imaging.