In control mice, the injection of LNL6 producer cells alone produces a 
transient tumor, that is rejected in 7-10 days. Since the evaluation of tumors in the 
experimental group was performed at 4 weeks, it is very unlikely that these G418 
resistant cells are the producer line cells. The lack of G41 8-resistance in group 2 and 
the lack of vector production by the recovered G418-selected cells in group 3 suggests 
that the PA317 producer line is not responsible for the G41 8-resistance in group 3. 
2. In Vivo Transduction of the E. Coli LacZ (p-galactosidase gene) Vector 
(GINaSVBG) into the 9L Rat Brain Tumor 
To evaluate the in vivo transduction dynamics within brain tumors, we have 
used the G1 NaSVBG vector. G1 NaSVBG (produced by Genetic Therapy Inc., GTI) has 
a titer of 1 -5X1 0 6 cfu/ml. This vector contains NeoR and the E. Coli derived gene LacZ 
which encodes for the production of the enzyme (3-galactosidase (BAG) (15). The BAG 
expression can be detected using an X-GAL histochemical stain. Staining the brain 
with X-Gal turns BAG expressing cells blue. This results when an indolyl is liberated 
from X-GAL by the action of the BAG enzyme. Subsequent oxidization and self - 
coupling forms an indigo blue derivative. The vector containing cells can thus be 
discriminated from unmodified cells and then be enumerated with light microscopy. 
Rats were inoculated with 4x1 0 4 9L gliosarcoma cells into the right 
cerebral hemisphere using stereotaxic guidance. 7 days later, 3x1 0 6 GINaSVBG 
producer cells were injected into the tumor bearing and non-tumor bearing 
hemispheres using the same stereotaxic coordinates. 5, 9, and 14 days after injection 
of the producer line cells, the rats were sacrificed by an intracardiac injection of 
formaldehyde to fix the brain. The brains were removed and stained with the X-GAL 
technique. Control rats were injected with a BAG expressing non producer cell line 
(GINaSVBG transduced, G418 selected 3T3 non-producer cells). The producer cells 
and the control GINaSVBG transduced 3T3 cells were 100% positive by X-Gal 
(\ 
staining prior to injection. 
In this experiment, we have shown that the injection of producer cells led 
to transduction of 50-79% of the tumor cells in situ (Table 2). There was no evidence 
of tumor transduction in the recipient of the non-vector producing group (Figure 2a). 
[786] 
Recombinant DNA Research, Volume 15 
