289. Highly Inducible and Prostate Specific Oncolytic Adenovirus with E1A-AR Chimera

Top of pageAbstract Previously, we demonstrated prostate-specific replication and passive cell lysis using E1A driven by a prostate-specific antigen promoter (PSA) and enhancer (PSE). However, the expression of E1A relies on promoters that utilize the androgen receptor (AR) for optimal function. Recently we have discovered that E1A and AR are mutually antagonistic in their transcriptional regulation. We demonstrate that a chimeric fusion of AR with the E1A converts an androgen receptor repressor to a co-activator. Here, we describe the features of conditionally replication-competent adenoviruses (CRADs) with E1A-AR chimeric expression in prostate cancer cells and non-prostate cancer cells. We constructed a series of recombinant chimeric E1A-AR viruses including wild type AR (E1A-ARwt), transactivation domain (E1A-TAD), and a full-length AR with a point mutation in the ligand binding domain (E1A-ARC685Y), under the control of the prostate-specific enhancer (PSE) and rat probasin promoter (PBN). The E1A function of these viruses was evaluated in prostate cancer cells and non-prostate cancer cells using an adenovirus with Fiber-IRES-GFP lacking E1A as a reporter. The wild type Ad5 with an E3-deletion replicates in both prostate cancer cells and non-prostate cancer cells. Replication of this virus is decreased by 50% by activated androgen receptors in the LNCaP cell line. The CRAD Ad5PSE-PBN-E1A displayed a rapidly inducible replication in prostate cancer cells in the presence of R1881, however, it had a delayed and relatively high expression in the absence of R1881. The chimeric CRADs Ad5PSE-PBN-E1A-AR and Ad5PSE-PBN-E1A-C685Y displayed marked induction of E1A in LNCaP (AR+), no induction in PC3 (AR-), and non-prostate cancer cells Hela in the presence of hormone, and no expression in any cell line in the absence of hormone. The cytopathic effect (CPE) of these chimeric viruses was also confirmed using crystal violet staining. Our highly engineered E1A-AR chimeras not only convert a negative regulatory process into a positive regulatory process, but also greatly enhance the tissue specificity and the regulation of viral replication in the prostate. This strategy dramatically reduces toxicity in non-prostate tissue, while maintaining prostate specificity.