Background: Oncolytic adenoviral therapy is a promising new approach for cancer treatment. The aim of this study was to improve the conditionally replicative adenoviruses (CRAds) for gallbladder cancer therapy by modifying the fiber-knob region for infectivity enhancement and by incorporating tumor-specific promoters (TSPs) for enhanced specificity.
Methods: For promoter-controlled replication, in vitro efficacy of eight TSPs was investigated in two gallbladder cancer cell lines (NOZ and OCUG-1). Infectivity enhancement was analyzed by two different fiber modifications: Arg-Gly-Asp (RGD) incorporation into the HI loop (RGD modification) and a chimeric construct with a serotype 5 shaft and a serotype 3 knob (5/3 fiber modification). Comparisons were made by infectivity analysis and cytotoxicity assays in vitro, followed by tumor suppressive effects tested in vivo.
Results: Among TSPs, highest potency was exhibited by the cyclooxygenase-2 (COX-2), Midkine, and vascular endothelial growth factor promoters in both cell lines tested. Fiber chimera (Ad5/3Luc1) conferred significant enhancement of Ad infectivity in comparison with unmodified and RGD-modified vectors. COX-2 CRAds demonstrated selective cytocidal effect in gallbladder cancer cells in vitro. COX-2 promoter-based Ad5/3 CRAds showed significantly enhanced tumor-suppressive effect compared with nonreplicative and RGD-modified CRAd vectors in vivo.
Conclusions: The 5/3 fiber-modified, COX-2 promoter-driven CRAds may prove to be a new agent for the treatment of gallbladder carcinoma.