Enhanced oncolysis by a tropism-modified telomerase-specific replication-selective adenoviral agent OBP-405 (‘Telomelysin-RGD’)

Abstract

Replication-competent oncolytic viruses are being developed for human cancer therapy. We previously reported that an attenuated adenovirus (OBP-301, 'Telomelysin'), in which the hTERT promoter element drives expression of E1A and E1B genes linked with an IRES, could replicate in cancer cells, and causes selective lysis of cancer cells. We further constructed OBP-405 ('Telomelysin-RGD') that contains an RGD motif in the HI loop of the fiber knob. We examined whether OBP-405 could be effective in overcoming the limitations of OBP-301, specifically their inefficient infection into cells lacking the primary receptor, the coxsackievirus and adenovirus receptor (CAR). By flow cytometric analysis, H1299 (lung) and SW620 (colorectal) tumor cells showed high levels of CAR expression, whereas LN444 (glioblastoma), LNZ308 (glioblastoma), and H1299-R5 (lung) tumor cells were negative for CAR expression. A quantitative realtime PCR analysis demonstrated that fiber-modified OBP-405 infected more efficiently than OBP-301, although the intracellular replication rate of both viruses was consistent. The comparative antitumor effect of fibermodified OBP-405 and unmodified OBP-301 for human cancer cells was evaluated in vitro by XTT assay as well as in vivo by using athymic mice carrying xenografts. OBP-405 had a profound oncolytic effect on human cancer cell lines compared to OBP-301, in particular on cells with low CAR expression. Intratumoral injection of 10 7 plaque-forming units of OBP-405 into CAR-negative H1299-R5 lung tumor xenografts in nu/nu mice resulted in a significant inhibition of tumor growth and long-term survival in all treated mice. Moreover, selective replication of OBP-405 in the distant, uninjected H1299-R5 tumors was demonstrated. Our results suggest that fiber-modified replication-competent adenovirus OBP-405 exhibits a broad target range by increasing infection efficiency, an outcome that has important implications for the treatment of human cancers.

Virus-mediated oncolysis induces danger signal and stimulates cytotoxic T-lymphocyte activity via proteasome activator upregulation

“…The recombinant replication-selective, tumor-specific adenovirus vector OBP-301 (Telomelysin), in which the hTERT promoter element drives the expression of E1A and E1B genes linked with an IRES, was constructed and characterized previously Umeoka et al, 2004;Taki et al, 2005;Watanabe et al, 2006). Onyx-015 (dl1520) is an E1B 55 kDa-deleted adenovirus engineered to selectively replicate in and lyse p53-deficient cancer cells, and kindly provided by Dr Frank McCormick (UCSF Comprehensive Cancer Center and Cancer Research Institute).…”

“…We reported previously that telomerase-specific replication-competent adenovirus (Telomelysin,, in which the human telomerase reverse transcriptase (hTERT) promoter element drives the expression of E1A and E1B genes linked with an internal ribosome entry site (IRES), induced selective E1 expression and efficiently killed human cancer cells, but not normal human fibroblasts Umeoka et al, 2004;Taki et al, 2005;Watanabe et al, 2006). Although the precise molecular mechanism of OBP-301-induced cell death is still unclear, the process of oncolysis is morphologically distinct from apoptosis and necrosis.…”

Comparison of herpes simplex virus- and conditionally replicative adenovirus-based vectors for glioblastoma treatment

“…[33][34][35][36][37] Previously, it has been demonstrated that the oncolytic efficacy of adenoviral vectors critically depends on their infection efficiency of the targeted tumor cells. 31,32 Since CD46 is overexpressed by malignant glioma cells, 40 we analyzed the fiber chimeric Ad5/35, which uses CD46 as primary receptor to bypass the dependence on CAR for adenoviral entry and replication.…”

“…Several groups demonstrated that controlling the expression of E1A and E4 genes simultaneously will provide a significantly tighter control over virus replication than just transcriptionally targeting of E1A. [25][26][27][28][29][30] Because the anti-neoplastic efficacy of oncolytic adenoviral vectors is critically dependent on the expression of the primary adenovirus receptor on the tumor cells 31,32 and the capacity of Ad5-based vectors to infect human glioblastoma cells has been questioned by several groups, [33][34][35][36][37] we bypassed the dependence on coxsackie adenovirus receptor (CAR) for adenoviral entry by using the fiber chimeric Ad5/35, which uses CD46 as primary receptor 38,39 which is overexpressed by malignant glioma. 40 We named the conditionally replicative adenovirus for glioblastoma therapy Ad5/35.GD Á Ki.…”

“…37 The vector was generated via homologous recombination in E. coli using pAdEasy-1/F35, 61 rescued and propagated in 293 cells. Analogous the replicationdefective GFP encoding Ad5/35.GFP vector was generated using the previously described shuttle plasmid.…”