1. ¹Division of Human Gene Therapy, Department of Medicine, Department of Pathology, Department of Surgery, Gene Therapy Center, University of Alabama at Birmingham, Birmingham, AL 35294, USA
2. ²Department of Obstetrics and Gynecology, Duesseldorf University Medical Center, Heinrich-Heine University, 40225 Duesseldorf, Germany
3. ³Rational Drug Design Program, Biomedicum Helsinki, University of Helsinki, 00014 Helsinki, Finland
4. ⁴Department of Oncology, Helsinki University Central Hospital, 00029 Helsinki, Finland
5. ⁵Department of Obstetrics and Gynecology, Helsinki University Central Hospital, 00029 Helsinki, Finland
6. ⁶Comprehensive Cancer Center, Biostatistics and Bioinformatics Unit, University of Alabama at Birmingham, Birmingham, AL 35294, USA
7. ⁷Department of Dermatology, University Medical Center Erlangen, 91052 Erlangen, Germany
8. ⁸Department of Biotechnology and Molecular Medicine, University of Kuopio, 70211 Kuopio, Finland

Correspondence: Akseli Hemminki, Cancer Gene Therapy Group, Biomedicum Helsinki, Haartmaninkatu 8, 00290 Helsinki, Finland. Fax: +358 9 1912 5465. E-mail: Akseli.Hemminki@Helsinki.fi

Received 20 June 2005; Revised 12 January 2006; Accepted 30 January 2006.

Abstract

Conditionally replicating adenoviruses (CRAd's) feature selective replication in and killing of tumor cells. Initial clinical studies with relatively attenuated early generation agents have resulted in promising safety and efficacy data. Nevertheless, increased specificity may be advantageous for an emerging generation of infectivity-enhanced CRAd's. Further, increased specificity could translate into a larger tolerated dose. An approach for increasing specificity is dual control of E1A expression. We constructed six CRAd's featuring two variants of the cyclo-oxygenase 2 (cox2) promoter, combined with three versions of E1A. Transcriptional targeting was supplemented with transductional targeting utilizing the serotype 3 knob. In vivo and in vitro results suggest that cox2 can be utilized for enhancing the specificity of E1A deletion mutants and that combination with the Delta24 mutation increases specificity without reducing potency. Combination with Delta2–Delta24 was specific but somewhat attenuated. The promoter variants behaved similarly, although the longer 1554-bp version displayed a trend for improved specificity. Transcriptional modifications were compatible with transductional targeting and resulted in up to 100,000-fold increase in the therapeutic window for Ad5/3cox2Ld24 vs wild-type adenovirus. Thus, the proposed triple-targeting strategy may be useful for increasing the safety and efficacy of adenoviral gene therapy for ovarian cancer.