Procaspase-3 enhances the in vitro effect of cytosine deaminase-thymidine kinase disuicide gene therapy on human ovarian cancer

Abstract

Because the efficacy of genetic prodrug activation therapy (GPAT) using herpes simplex virus thymidine kinase (tk)/ganciclovir (GCV) or Escherichia coli cytosine deaminase (cd)/5-fluorocytosine (5-FC) is not satisfied in early clinical trials and the mechanism of both the GPATs have been shown to lead to the activation of cell apoptotic pathway, we hypothesized that coexpression of procaspase-3, a central downstream executioner of apoptotic pathways, with cd-tk gene leads to enhanced cell death in ovarian cancer cells in vitro. Following transfection with the vectors encoding cd and tk, 5-FC and GCV treatments lead to greater cell death in procaspase-3-expressing clones of 3AO (3AO-caspase-3) than control cells (3AO-pcDNA3), as well as more rapid activation of caspase-3 and more rapid cleavage of poly (adenosine diphosphate-ribose) polymerase (PARP). There is a greater degree of cell apoptotic rate in the procaspase-3-expressing clones than in control cells following the treatment with cd-tk/5-FC + GCV, and apoptosis is the main cell death form. None of these effects is seen following transfection with a control vector that does not encode tk and cd (pBTdel-279). The results strongly suggest that coexpression of procaspase-3 may lead to a significant enhancement of the efficacy of cd-tk/5-FC + GCV, and this strategy would be a novel and promising approach for the treatment of ovarian cancer.

Reprogramming Cellular Behavior with RNA Controllers Responsive to Endogenous Proteins

“…There was a slight reduction in survival in cells expressing our devices in the absence of pathway stimulation, which may reflect effects of high GCV concentrations on cell viability (fig. S4D) (30) and basal expression of HSV-TK from our devices. Possible therapeutic utility and safety of these targeted-cell-death devices is supported by effective cell-killing efficacy in the presence of both inputs and minimal background activity in the absence of one or both inputs.…”

Gene therapy for ovarian cancer

“…Additionally, as a result of ambient apoptotic vesicle uptake and unregulated immune response, there is a significant lateralization, whereby only a fraction of cells need to be originally transduced to obtain widespread apoptosis [4]. Whereas others have combined both apoptotic path- ways in a "double-suicide gene therapy system" [23], Song et al [24] recently reported that the efficacy of inducing ovarian cancer cell death in vitro by cd-tk/5-FC + GCV treatment was enhanced by the coexpression of caspase-3, a downstream protein responsible for the execution of apoptosis. Another promising use of the HSV-tk construct is as a safety mechanism to induce death of tumor cells used in a dendritic-tumor cell vaccine [25].…”

Suicide gene strategies applied in ovarian cancer studies

“…They showed that the cancerselective killing effect was more efficient than that of each suicide gene alone. In addition, enhancement of OC cell apoptosis, about 20% has been achieved when CD-TK was co-expressed with procaspase-3 [42]. Sher et al exploited lipid vectors encapsulating another fusion gene consisting of endostatin, one of the most potent inhibitors of angiogenesis and CD, which is governed by cancer-specific promoter survivin.…”