Optimization of an E1A Gene Expression Cassette in an Oncolytic Adenovirus for Efficient Tumor Cell Killing Activity.

Abstract

Oncolytic adenoviruses (OAds) have attracted much attention as novel anticancer therapeutics. The proper design of an expression cassette containing the E1A gene, which is indispensable for self-replication of the Ad genome, is crucial for efficient tumor cell-specific infection of an OAd. Various types of oncolytic adenoviruses (OAds) possessing different types of the E1A gene expression cassettes have been developed, but their oncolytic activities and safety profiles have not been systematically evaluated. Herein we examined the oncolytic activities and safety profiles of five types of OAds possessing different types of the E1A gene expression cassette in order to optimize the E1A gene expression cassette for development of an efficient and safe OAd. We prepared five types of OAds containing different types of E1 gene expression cassettes, and examined the oncolytic activities and safety profiles of the OAds. Among the OAds examined, OAd-Δ24, which had a 24-bp deletion in the E1A gene, mediated the most efficient oncolytic activities against the human tumor cell lines, although OAd-Δ24 showed slightly higher cytotoxicity to normal human cells than the other OAds. These results provide important clues for the development of safe and efficient OAds.