Oncolytic adenoviruses constitute a new and promising tool for cancer treatment that has been rapidly translated into clinical trials. However, minimal or absent expression of the adenovirus serotype 5 (Ad5) receptor CAR (coxsackievirus and adenovirus receptor) on cancer cells represents a major limitation for Ad5-based oncolysis. Here, we report on the resistance of CAR-negative primary melanoma cells to cell killing by wild-type Ad5 (Ad5wt) even after high titer infection, thus underlining the need for tropism-modification of oncolytic adenoviruses. We engineered a new generation of oncolytic adenoviruses that exhibit both efficient target cell infection by swapping Ad5 fiber domains with those of Ad serotype 3, which binds to a receptor distinct from CAR, and targeted virus replication. Fiber chimerism resulted in efficient cytopathicity to primary melanoma cells, which was at least 104-fold increased relative to Ad5wt. Since viral infectivity mediated by such modified viral capsids was not cell type-specific, it was pivotal to carefully restrict adenoviral replication to target cells. Towards this end, we replaced both E1A and E4 promoters of fiber chimeric viruses by tyrosinase enhancer/promoter constructs. The resulting viruses showed melanoma-specific expression of E1A and E4 and combined efficient virus replication and cell killing in melanoma cell lines and primary melanoma cells with a remarkable specificity profile that implements strong attenuation in nonmelanoma cells, including normal fibroblasts and keratinocytes.
Bibliographical noteFunding Information:
This work was supported by the Deutsche Forschungs-gemeinschaft (grant NE832/1 to DMN, and Graduier-tenkolleg 592 to SS), the Deutsche Krebshilfe (grant 10-2186-Ne 1 to DMN) and the National Cancer Institute (grants R01 CA83821, P50 CA83591, R01 CA93796, and R01 CA94084). We are grateful to Dr D Dieckmann, Dr IJ Fidler, Dr F Noya, Dr J Price, L Rivera, Dr J Schlom, and Dr T Strong for cell lines and primary cells, to Dr J Chrobozcek for providing plasmid pBR.Ad3Fib, Dr Ruben Hernandez-Alcoceba for plasmid pUC19-E4P-, Dr Gary Ketner for the E4 antibody, and to T Uil for plasmid pNEB.PK.SnaBI.
- Conditionally replicative adenovirus
- Fiber chimerism
- Tyrosinase enhancer/promoter
- Viral oncolysis