Understanding apoptotic signaling pathways in cytosine deaminase-uracil phosphoribosyl transferase-mediated suicide gene therapy in vitro.

Cytosine deaminase-uracil phosphoribosyl transferase (CD-UPRT) fusion gene is known to exhibit therapeutic effect by inducing apoptosis in vitro. However, bystander effects of 5-flurocytosine (5-FC)/CD-UPRT and the molecular mechanism for apoptosis are yet to be established. In the present study, we have generated BHK21 cell line expressing both CD-UPRT and green fluorescent protein (GFP) from two separate transcripts, where GFP was used as a noninvasive probe to monitor the therapeutic effect of CD-UPRT. Enzyme activity of CD-UPRT in the stable cell line was measured by the reverse phase high-performance liquid chromatography analysis. Inhibition of cell growth and strong bystander effects of 5-FC/CD-UPRT were established, whereas characteristic surface morphology of apoptotic cell death was identified by AFM analysis. Involvement of various apoptotic signaling genes using semi-quantitative RT-PCR has been explored to substantiate the potential application of 5-FC/CD-UPRT suicide gene in therapy.