1. ¹Division of Human Gene Therapy, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
2. ²Division of Human Gene Therapy, Department of Pathology, University of Alabama at Birmingham, Birmingham, AL, USA
3. ³Division of Human Gene Therapy, Department of Surgery, University of Alabama at Birmingham, Birmingham, AL, USA
4. ⁴The Gene Therapy Center, University of Alabama at Birmingham, Birmingham, AL, USA
5. ⁵Department of Dermatology, University Medical Center Erlangen, Erlangen, Germany

Correspondence: Dr D Nettelbeck, Department of Dermatology, University Medical Center Erlangen, Hartmannstr. 14, 91052 Erlangen, Germany

⁶Current address: Department of Experimental Diagnostic Imaging, MD Anderson Cancer Center, University of Texas, Houston, TX, USA

Received 13 January 2004; Accepted 5 July 2004; Published online 21 October 2004.

Abstract

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.