136. The Oncolytic Adenovirus Targeting to TERT and Rb Pathway Induced Specific Cytotoxicity to Tumor Cells

Overexpression of human telomerase reverse transcriptase (hTERT) and dysfunction of retinoblastoma (Rb) have been implicated in the most types of malignancies. Oncolytic viruses have been used widely for therapy of cancers. In order to develop specific recombinant adenovirus with strict tumor specificity, we engineered oncolytic adenovirus to target both of TERT and Rb pathways. The CR2 region of adenoviral E1a protein interacts with Rb and allows virus replication. Therefore, we have constructed double-controlled recombinant adenovirus with CR2 deleted E1a driven by hTERT promoter (AdTC). As control vectors, we generated single-controlled recombinant adenovirus with either CR2 deleted E1a (AdC) or wild-type of E1a driven by hTERT promoter (AdT). Firstly, different length and modification of hTERT promoter have been studied to find out the appropriated hTERT promoter with better tumor specificity. With this modified hTERT promoter, we found that double-controlled oncolytic adenovirus AdTC has strictly tumor-specific cytotoxicity, as compared with single-controlled oncolytic adenoviruses of either AdC or AdT. This cytotoxicity was observed in the different types of tumor cells. There was dramatic reduction of cytotoxicity in normal cell infected with AdTC. Production of viral particles in tumor cells infected with AdTC as measured by progeny assay was similar as cells infected either with AdC or AdT. This dada indicated that oncolytic adenovirus to target both of TERT and Rb pathways provides safe and potent vector for therapy cancers.