2. Anti-tumor Effect of In Situ Injection with an HS-tk Vector Producer Cell 
Line on the In Vivo Growth of the 9L Gliosarcoma in Rats 
9L is a rat gliosarcoma cell line derived from the Fisher 344 strain. This 
brain tumor model has been well characterized (16). Injection of 4x1 0 4 9L tumor cells 
into the the cerebral white matter of a rat results in 100% lethality by 4 weeks. 
Therefore, we have used this brain tumor model to evaluate in vivo HS-tk transduction 
and the subsequent anti-tumor response to GCV treatment . 
Fisher 344 male rats weighing 250-350 grams were anesthetized and 
placed in a stereotaxic apparatus. On day 0, we implanted 4x1 0 4 9L tumor cells in a 
volume of 50pL into the right cerebral hemisphere. 5 days later, the same stereotaxic 
coordinates were used to introduce either saline or 3x1 0 6 STK producer line cells in 
50|jJ directly into the growing tumor. 5 days later, the rats began treatment with GCV at 
1 50mg/kg/dose twice daily. On the 5th day (10 days since inoculation of the tumor), the 
rats brains were examined for the extent of tumor growth. As seen in figure 6, the rats 
treated with the STK producer cell line and GCV are the only animals that experienced 
complete macroscopic elimination of the tumor (14 of 14 rats). Microscopic analysis 
revealed either no evidence of tumor (11 of 14 rats) or some residual, mostly necrotic, 
tumor in the tumor bed (3 of 14 rats). There was no evidence of vasculitis or destruction 
of normal tissues due to spread of the vector. This experiment further supports the data 
obtained with the G1 NaSVBG vector, that this in vivo transduction method appears to 
be without significant side effects and has substantial efficacy. 
Recombinant DNA Research, Volume 15 
[797] 
