Development of adenovirus-based oncolytic virus to induce EBV lytic reactivation.

Background: Oncolytic viruses (OVs) selectively replicate in and lyse tumor cells. Epstein-Barr virus-associated gastric carcinoma (EBVaGC), representing ~ 10% of gastric cancers globally, remains a therapeutic challenge. We developed Ad-TBZ, a novel oncolytic adenovirus engineered to selectively target EBVaGC by inducing EBV lytic reactivation.

Methods: Ad-TBZ was constructed by inserting an hTERT promoter (hTERTp)-driven E1A/IRES-E1B cassette and a CMV promoter (CMVp)-driven BZLF1 gene into the adenoviral genome. We evaluated Ad-TBZ replication, cytotoxicity, and EBV lytic reactivation in EBVaGC cell lines (SNU719, NCC24, YCCEL1, AGS-EBV, MKN1-EBV), EBV-negative cells, and normal fibroblasts (CCD-986sk). In vivo efficacy was assessed using SNU719 and MKN1-EBV xenograft mouse models. Combination effects with platinum-based drugs and ganciclovir were also investigated.

Results: Ad-TBZ selectively replicated in EBVaGC cells and demonstrated cell line-specific cytotoxic effects while sparing normal cells. It significantly upregulated EBV lytic genes (BRLF1, BMRF1, BGLF4, BXLF1, BALF4, BLLF1), increased viral genome copies, and induced cell line-specific late apoptosis. In vivo, Ad-TBZ effectively suppressed tumor growth in both xenograft models without systemic toxicity. Sequential treatment with oxaliplatin showed modest synergistic effects at specific concentrations in limited conditions, while most combination approaches showed no significant synergistic effects. These findings indicate Ad-TBZ functions optimally as a monotherapy.

Conclusions: Ad-TBZ demonstrates potent and selective antitumor activity against EBVaGC through hTERTp-mediated selective replication and BZLF1-induced EBV lytic reactivation. These findings support Ad-TBZ as a promising novel monotherapeutic strategy for EBVaGC.