TRAIL Gene-armed Oncolytic Adenovirus As Therapy For Cancer

Cancer remains one of the top causes of death. Improvement has been made in the overall survival of early stage cancer patients after the emergence of advanced diagnostic and integrated treatment techniques over the past few decades. However, it is still an obstacle for patients with advanced cancer. New approaches are urgently needed for better cancer therapy. Cancer gene therapy is one of hot spots in cancer research. cancer gene therapy is defined as the introduction of genes into target tissues or target cells via gene transfer, with the purpose of deriving a therapeutic or preventative of cancer from the function of these genes.Recently, the anti-tumor effect of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and oncolytic adenovirus were extensively studied. However, some preclinical research and clinical data shows the anti-tumor effect is not strongly enough or has system toxicity, which may effect its further clinical application. How to reinforce the anti-tumor effect and reduce system toxicity is the key point of its successfully clinical application. To overcome the weakness of both TRAIL therapy and oncolytic virotherapy when used individually, we recently constructed a TRAIL-expressing oncolytic adenoviral vector (Ad/TRAIL-E1), in which the expression of both the TRAIL and E1 A genes were under the control of a synthetic promoter consisting of sequences from the human telomerase reverse transcriptase (hTERT) promoter and a minimal cytomegalovirus (CMV) early promoter. Part one:TRAIL gene-armed oncolytic adenovirus inhibit peritoneal dissemination of human gastric cancer cellsPurpose:To evaluate antitumor effect of Ad/TRAIL-E1 in gastric cancer cells and peritoneal dissemination of xenotransplanted gastric cancer cells.Methods:The vectors were amplified in 293 cells, purified by CsCl banding; SRB assay and cell clonogenic assay were performed to determine the killing effect of the Ad/TRAIL-E1 in vitro, Flow cytometric assay and Western blot were performed to determine the transgene expression and apoptosis activation in vitro. Use tissue culture infectious dose 50 (TCID50) to detect replication titer in vitro. Finally, evaluate antitumor effects in vivo by nude mouse peritoneal dissemination model.Results:Ad/TRAIL-El exhibited significant killing effect on gastric cancer cells as compared to a TRAIL-expressing, replication-defective adenovector (Ad/gTRAIL) or an oncolytic adenovector (Ad/GFP-E1). The mechanism of this effect is due to enhanced viral replication and expresses TRAIL more effectively. The in vivo studies showed that the number and the weight of the peritoneal dissemination tumors in the Ad/TRAIL-E1 group were significantly less than those in the PBS or Ad/CMV-GFP group, and less than those in Ad/GFP-E1 and Ad/gTRAIL group. Ad/TRAIL-El also significantly prolonged animal survival when compared with that of using PBS or Ad/CMV-GFP group. Furthermore, we found no treatment-related toxicity.Conclusion: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 gastric cancer therapy.Part two:Treatment of patient tumor-derived colon cancer xenografts by a TRAIL gene-armed oncolytic adenovirusPurpose:To establish patient tumor-derived colon cancer xenografts and evaluate antitumor effect of Ad/TRAIL-E1 in this tumor model.Methods:First, we established primary colon cancer xenografts from fresh surgical specimens. We next treated these xenografts with Ad/TRAIL-El and other adenovirus vectors. Immunohistochemistry and terminal deoxyribonucleotide transferase-mediated dUTP nick end labeling (TUNEL) assay were performed to determine TRAIL expression and apoptosis in vivo. TCID50 assay was used to assess the efficacy of adenovirus replication in vivo.Results:We implanted a total of 21 surgical specimens derived from human colon tumors into nude mice. Of these 21 specimens,3 resulted in tumor growth. All xenografts revealed a high concordance with their respective original human counterparts. In these xenografts, Ad/TRAIL-E1 exhibited more significant inhibitory effects on tumor growth than Ad/gTRAIL or Ad/GFP-E1 alone. The TRAIL expression and apoptosis rate in Ad/TRAIL-E1 group were higher than other treatment groups and control groups. TCID50 assay result demonstrated that the infectious viral units in tumor treated with Ad/TRAIL-E1 were much higher than in those treated with Ad/GFP-E1. Furthermore, we did not find any obvious treatment-related toxicity in the mice.Conclusion:We established human cancer xenografts from human colon tumor surgical specimens. Our results demonstrated that Ad/TRAIL-E1 treatment improved both tumor suppression and survival in all established models. The use of an oncolytic adenoviral vector, in combination with TRAIL gene therapy, is a promising novel approach for colon cancer therapy.