Selectivity and efficiency of late transgene expression by transcriptionally targeted oncolytic adenoviruses are dependent on the transgene insertion strategy.

Key challenges facing cancer therapy are the development of tumor-specific drugs and potent multimodal regimens. Oncolytic adenoviruses possess the potential to realize both aims by restricting virus replication to tumors and inserting therapeutic genes into the virus genome, respectively. A major effort in this regard is to express transgenes in a tumor-specific manner without affecting virus replication.

Transgene expression by oncolytic adenoviruses is modulated by E1B19K deletion in a cell type-dependent manner.

Major strategies to increase oncolytic adenovirus efficacy, as required for clinical applications, are enhancing oncolysis by acceleration of virus release/spread and "arming" by insertion of therapeutic genes. We investigated whether these strategies can be effectively combined as it has been speculated that the arming approach rather benefits from delayed cell lysis and extended time for protein synthesis. We report that deleting adenoviral E1B19K results in an apoptosis-dependent early viral release and thus enhanced oncolysis in several tumor cells, but inhibits virus replication in others.

Insulated hsp70B' promoter: stringent heat-inducible activity in replication-deficient, but not replication-competent adenoviruses.

Background: Key to the realization of gene therapy is the development of efficient and targeted gene transfer vectors. Therapeutic gene transfer by replication-deficient or more recently by conditionally replication-competent/oncolytic adenoviruses has shown much promise. For specific applications, however, it will be advantageous to provide vectors that allow for external control of gene expression.