Abstract

PURPOSE
To overcome the limitations of cancer gene therapy using replication-incom- petent adenovirus, we generated E1B 55 kD-deleted adenovirus (YKL-1) by polymerase chain reaction (PCR) and homologous recombination. We then investigated tumor-specific virus replication and cytotoxicity of YKL-1 in vitro and in vivo.
MATERIALS AND METHODS
YKL-1 was constructed by reintroducting E1A and E1B 19 kD into pTG-CMV El/E3-deficient adenoviral vector and inducing homologous recombination in E. coli. The recombinant vector pYKL-1 was transfected into 293 cells to generate YKL-1. The properties of newly constructed YKL-1 was defined by PCR and immuno- blotting analysis. Virus replication was examined by infecting human normal and cancer cells on 6-wells at multiplicity of infection (MOI) of 10 for 3 days. Virus was then recovered and titered. Cytopathic effect was analyzed by infecting human normal and cancer cells on 24-wells at MOIs of 10, 1 or 0.1 for 7 to 10 days and staining them with crystal violet solution. Inhibition of tumor growth was examined in human cancer cell xenografts in nu/nu mice by intratumoral injection of YKL-l.
RESULTS
PCR and immunoblotting analysis confirmed that YKL-1 contained E1A and E1B 19 kD but not E1B 55 kD. In human normal cells, virus replication and subsequent cytopathic effect of E1B 55 kD-deleted adenovirus YKL-1 was markedly attenuated by larger than 2 to 3 log in magnitude, compared to that of wild-type ad-XJ. In contrast, YKL-1 was capable of replicating and inducing cytotoxicity i.n most human cancer cells. C33A and Hep3B containing p53 mutation were much more sensitive, whereas HeLa and H460 with wild type p53 were relatively resistant to YKL-1. Finally, the tumor growth was dramatically retarded by intratumoral injection of YKL-1 in C33A cervical cancer xenograft and the histology showed significant necrosis by intratumoral injection of YKL-1.
CONCLUSION
The results here demonstrated the ability of preferential virus replication and cytotoxicity of ElB 55 kD-deleted adenovirus YKL-1 in human cancer cells. Therefore, these indicated a promising potential of YKL-1 as an antitumoral virus agent and a selective replication-competent virus vector.

• Keywords: Adenovirus;Gene therapy;El gene;pS3 gene