Thymidine Incorporation (cpm) 
positive cells were completely inhibited at 0.5 pg/ml (Appendix A, Table 1). These 
findings confirm that HS-tk gene-containing retroviral vectors can effectively transduce 
murine and rat tumor cells and stably express both the NeoR and HS-tk genes 
resulting in 100% kill of the transduced cells in vitro when exposed to GCV. All in vivo 
studies were conducted using G418-selected producer and control non-producer cell 
lines that had a similar pattern of GCV sensitivity conferred by a transferred HS-tk 
gene. 
Figure 3. a. 
GCV Sensitivity of 9L Glioma Cells +/• GITKSVNa 
[790] 
Recombinant DNA Research, Volume 15 
