Abstract #3798: Telomerase-specific oncolytic adenovirus armed with wild-type p53 gene (CGCT-04) efficiently induces apoptosis in human cancer cells
Authors: Yasumoto Yamasaki, Hideki Onimatsu, Yuuri Hashimoto, Toru Kojima, Hiroshi Tazawa, Shunsuke Kagawa, Hiroyuki Mizuguchi, Yasuo Urata, Noriaki Tanaka, Toshiyoshi Fujiwara
Journal: Cancer Research (2009)

Background:Replication-competent oncolytic viruses are being developed for human cancer therapy. An attenuated adenovirus OBP-301 (Telomelysin), in which the human telomerase reverse transcriptase (hTERT) promoter element drives expression of E1A and E1B genes, could replicate in and causes selective lysis of a variety of human cancer cells. Upon the US FDA approval, a phase I dose-escalation study of intratumoral injection of OBP-301 for various solid tumors has been completed. We have also completed a phase I trial of intratumoral injection of a replication-deficient adenovirus expressing the tumor suppressor p53 gene (Advexin) in non-small cell lung cancer patients in Japan. In the present study, we developed a novel telomerase-specific p53-armed oncolytic virus CGCT-04 and examined whether this virus can induce apoptosis in human cancer cell lines. Methods: We constructed the telomerase-specific replication-competent adenovirus CGCT-04 that expresses the wild-type p53 by inserting the human p53 cDNA under the control of Egr-1 promoter at the deleted E3 region of OBP-301.We first confirmed exogenous p53 gene expression in human cancer cell lines after CGCT-04 infection by Western blot analysis. We also compared antitumor effect of CGCT-04 and OBP-301 in a variety of human cancer cells by XTT assay. Induction of apoptosis after CGCT-04 infection was also compared with those after OBP-301 and Advexin infection by FACS analysis measuring active caspase-3 expression. Moreover, downstream p53-targeted gene expression was assessed after CGCT-04 infection by Western blotting. Results: CGCT-04 infection resulted in a strong p53 protein expression within 24 hours after infection in various human cancer cell lines. Moreover, in vitro cytotoxicity analysis by XTT assay demonstrated that CGCT-04 infection could more efficiently induce cell death in all cell lines we used compared to OBP-301 infection. Calculated ID50 values confirmed that all cell lines could be more sensitive to CGCT-04 than OBP-301. FACS analysis demonstrated that CGCT-04 infection at 10 multiplicity of infections (MOI) induced 23.5% of apoptosis in H358 human lung cancer cells, whereas only 6.1% was observed after 10 MOI of OBP-301 infection. Advexin at 100 MOI was also required to induce 24.4% of apoptosis. In addition, 11.8% apoptosis was observed in T.Tn human esophageal cancer cells after 100 MOI of CGCT-04 infection; however, OBP-301 and Advexin at 100 MOI induced 2.3% and 1.9% apoptosis, respectively. CGCT-04 infection efficiently induced Bax expression and cleavage of PARP and caspase 3.Conclusions: Our data indicated that a novel telomerase-specific p53-armed oncolytic virus CGCT-04 induced functional p53 expression, which showed a profound antitumor effect by inducing p53-mediated apoptosis.  Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 3798.