The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and oncolytic virus vectors have recently been investigated extensively for cancer therapy. However, preclinical and clinical studies have revealed that the clinical application of these two agents is hampered either by their weak anticancer activity or by their possible systemic toxicity. Therefore, strategies to maximize their anticancer activity and minimize their systemic toxicity are essential to the success of these agents in the treatment of cancers. The goal of this proposal is to determine the efficacy and safety of a tumor-specific replication-competent (oncolytic) adenovector expressing the TRAIL gene for the treatment of cancer. The hypothesis to be tested is that integration of virotherapy and TRAIL gene therapy into a single agent will enhance its in vivo transduction efficiency and apoptosis-induction capacity and that an oncolytic adenovector expressing both the TRAIL and E1A genes from the human telomerase reverse transcriptase (hTERT) promoter will target both virotherapy and TRAIL gene therapy to cancer, destroying tumor tissue but sparing normal tissue. Our preliminary studies showed that incorporating the TRAIL gene into an oncolytic adenovector enhanced viral replication and oncolysis in cancer cells, whether they were susceptible or resistant to the TRAIL gene, both in vitro and in vivo, with minimal replication activity and cytotoxic effects in normal human fibroblasts. Intralesional administration of the TRAIL-expressing oncolytic adenovector eliminated all subcutaneous xenograft tumors established from a human non-small cell lung cancer cell line in nu/nu mice, resulting in long-term tumor-free survival. To further test the hypothesis, we will determine the optimal adenovector systems for the delivery of hTERT-TRAIL to human and syngeneic Syrian hamster tumors by evaluating the therapeutic and side effects of hTERT-TRAIL delivered by an E1-deleted vector, an oncolytic vector, and a fiber-modified oncolytic vector in vitro and in vivo. We will also determine whether an immune response triggered by an adenovector will have any effect on either antitumor activity or side effects. Finally, we will determine the antitumor activity of the TRAIL-expressing oncolytic vector in both human and Syrian hamster syngeneic metastatic models established in both immunocompromised and immunocompetent animals. Completing the proposed studies will allow us to determine the optimal methods for delivery of hTERT- TRAIL and develop strategies for the treatment of metastasis. The results of these preclinical studies will also provide a solid scientific basis for future integration of TRAIL therapy and oncolytic virotherapy and may lead to new therapeutic agents for cancer therapy.
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