Figure 4(A): Bystander cell killing was evaluated in a PC-3 tumor xenograft model in vivo. NOD/SCID animals were inoculated with mixed tumors comprised of 1:1 ratio of LV/eGFP-transduced and LV/TMPK-F105Ytransduced PC-3 cells, and treated with 10 mg/kg/day of AZT for 7 consecutive days. Percentage change in the ratio of eGFP-positive (bystander) to TMPKF105Y- positive (effector) cells from the starting 1:1 ratio in the tumors extracted at the end of treatment was determined by flow cytometry.