Abstract
PURPOSE: The tumor necrosis factor-alpha-related apoptosis-inducing ligand (TRAIL) and oncolytic viruses have recently been investigated extensively for cancer therapy. However, preclinical and clinical studies have revealed that their clinical application is hampered by either weak anticancer activity or systemic toxicity. We examined whether the weaknesses of the two strategies can be overcome by integrating the TRAIL gene into an oncolytic vector. EXPERIMENTAL DESIGN: We constructed a TRAIL-expressing oncolytic adenovector designated as Ad/TRAIL-E1. The expression of both the TRAIL and viral E1A genes is under the control of a synthetic promoter consisting of sequences from the human telomerase reverse transcriptase promoter and a minimal cytomegalovirus early promoter. The transgene expression, apoptosis induction, viral replication, antitumor activity, and toxicity of Ad/TRAIL-E1 were determined in vitro and in vivo in comparison with control vectors. RESULTS: Ad/TRAIL-E1 elicited enhanced viral replication and/or stronger oncolytic effect in vitro in various human cancer cell lines than a TRAIL-expressing, replication-defective adenovector or an oncolytic adenovector-expressing green fluorescent protein. Intralesional administration of Ad/TRAIL-E1 eliminated all s.c. xenograft tumors established from a human non-small cell lung cancer cell line, H1299, on nu/nu nude mice, resulting in long-term, tumor-free survival. Furthermore, we found no treatment-related toxicity. CONCLUSIONS: Viral replication and antitumor activity of oncolytic adenovirus can be enhanced by the TRAIL gene and Ad/TRAIL-E1 could become a potent therapeutic agent for cancer therapy.