Exogenous gene induction of therapeutic, diagnostic and safety mechanism could be a considerable improvement in oncolytic virotherapy. Here, we introduced a doxycycline-inducible promoter system (comprised of a tetracycline-repressor, several promoter constructs and a tet-operator sequence) into oncolytic recombinant vaccinia viruses (rVACV), which was further characterized in detail. Experiments in cell culture as well as in tumor bearing mice were analyzed to determine the role of the inducible system components. To accomplish this, we took advantage of the optical reporter construct, which resulted in the production of click-beetle luciferase as well as a red fluorescent protein. The results indicated that e... More
Exogenous gene induction of therapeutic, diagnostic and safety mechanism could be a considerable improvement in oncolytic virotherapy. Here, we introduced a doxycycline-inducible promoter system (comprised of a tetracycline-repressor, several promoter constructs and a tet-operator sequence) into oncolytic recombinant vaccinia viruses (rVACV), which was further characterized in detail. Experiments in cell culture as well as in tumor bearing mice were analyzed to determine the role of the inducible system components. To accomplish this, we took advantage of the optical reporter construct, which resulted in the production of click-beetle luciferase as well as a red fluorescent protein. The results indicated that each of the system components could be used to optimize the induction rates and had influence on the background expression levels. Depending on a given gene to be induced in rVACV colonized tumors of patients, we discuss the doxycycline-inducible promoter system adjustment and further optimization. IMPORTANCE:Oncolytic virotherapy of cancer can greatly benefit from the expression of heterologous genes. It is reasonable that some of those heterologous gene products could have detrimental effects on either the cancer patient or on the oncolytic virus itself if expressed at the wrong time or if the expression levels are too high. Therefore, exogenous control of gene expression levels by administration of a non-toxic inducer will have positive effects on the safety as well as the therapeutic outcome of oncolytic virotherapy. In addition, it paves the way for introduction of new therapeutic genes into the genome of oncolytic viruses that could not have been tested otherwise.
