(549e) Analysis of Promoters and Expression-Targeted Gene Therapy, Optimization Based On Cell Behavior

Expression-targeting utilizes specific promoters to target transgene expression to cells that are actively expressing endogenous genes under the control of the same promoter. Correlations between expression-targeted transgene expression and transcription of corresponding endogenous genes were investigated, and it was found that cyclooxygenase-2 (Cox-2) and human epidermal growth factor receptor 2 (Her-2) had positive correlations while others, such as survivin, had no correlation at all. However, a positive correlation is not enough to implicate a promoter as a suitable target for expression-targeted gene delivery. Use of the Her-2 promoter was essentially fruitless because of the low rate of increase of transgene expression associated with increases in endogenous Her-2 expression, plus a low overall transfectability of the targeted cells. The five Cox-2-overexpressing cell lines tested were amenable to PEI-mediated gene delivery and had a greater sensitivity to changes in endogenous Cox-2 expression levels. Taking into account endogenous gene expression levels, overall cell transfectability, and cell doubling rates, a predictive model for expression-targeted gene delivery outcomes was developed. In an application which utilized expression-targeting to repeatedly deliver genes encoding pro-apoptotic caspase proteins, the model was able to predict cell survival numbers that were significantly similar to actual survivals observed.