Figures 2b-d. present the microscopic sections taken from the rats on days 5, 9, and 
1 4. The production of the BAG enzyme in tumor cells increased with time as 
evidenced by the increase in the intensity of the blue stain in each transduced cell. 
Maximal expression was reached between 7 and 14 days following injection of the 
GINaSVBG producer cells. The injected GINaSVBG producer cells were detected in 
diminishing numbers up to 14 days when they disappeared from the injection site. 
There was a clear cut delineation between the transduced tumor cells and normal 
brain tissue (Figure 2d). Except for the possibility of a rare transduced endothelial cell 
in the vicinity of the tumor, no evidence of non-tumor brain transduction was evident in 
either cerebral hemisphere. The most mitotically active endothelial cells in the area of 
the tumor are likely to be those responding to neovascularization signal from the tumor. 
Elimination of these endothelial cells with GCV therapy is desirable. The non-producer 
control cells did not demonstrate evidence of transduction of either tumor cells or 
normal brain and they were not seen in the tumor or brain after 14 days. 
Figure 2. a. - High power magnification of a 9L brain tumor injected with the nonproducer 
cells. Note absence of X-Gal positive tumor cells. 
Recombinant DNA Research, Volume 15 
[787] 
