Abstract 4778: Identification of promoters for targeted gene expression in tumors

Abstract

Abstract A variety of novel therapeutic approaches to cancer have been proposed in the past several decades. One of the most compelling is the use of gene therapy to treat tumors. Restricting the expression of these genes to tumor avoids toxicity in normal cells and the concurrent side effects that this activity engenders. Promoter sequences can be used as a tool for transcriptional targeting, by restricting the expression of the therapeutic genes, or, in the case of oncolytic virotherapy, the replication of the viral agent. Several tumor-upregulated promoters have been identified in a wide variety of human tumors. Given the recognition of the validity of canine tumors as comparative models of human disease, it is critical to determine the activities of these promoters in the canine system. To achieve this goal, endogenous cSurvivin, cTERT, and cCXCR4 promoter activity was evaluated in a panel of canine normal and tumor cell lines/tissues and primary tumors by RT-Q-PCR. These three promoters, along with an E2F modified Canine Adenovirus 2 E1a promoter (E2F-E1a), were also assessed for their activity when supplied exogenously to tumor cells in an in vitro GFP reporter transfection assay. Endogenous expression of cTERT showed negligible differences between normal canine cells/tissues and tumor cell/tissues. cSurvivin showed elevated endogenous activity in non-hematopoietic tumor cells and moderately elevated activity in some normal tissues and hematopoietic tumors. cCXCR4 activity was elevated exclusively in a T-lymphoma cell line and a primary T-cell lymphoma. Exogenous expression in most cancer cell lines showed enhanced activity with most of the promoters tested. The percentage of cells expressing GFP was elevated in tumor compared to normal with all four tested promoters, when normalized to CMV-GFP expression. However, the relative fluorescence intensity varied significantly between cell lines, while the fluorescence intensity varied less between promoters within a specific cell line. Exogenous expression results did not correlate well with endogenous expression in tumor cells, but they did correlate well in normal cells. This disparity implies that promoter selection for transcriptional targeting of tumors should account for both endogenous and exogenous expression patterns. Additionally, these findings indicate that identification of a pan-cancer promoter is complex and that expression targeting may need to rely on selecting patient-specific promoters to drive the activity of therapeutic genes. Citation Format: Abdul Mohin Sajib, Maninder Sandey, Samantha Morici, Bradley Schuler, Payal Agarwal, Bruce Smith. Identification of promoters for targeted gene expression in tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4778.