Figure 4(B): Magnitude of bystander cell killing was evaluated following the delivery of the TMPK-F105Y suicide gene by direct intratumoral injection of LV/TMPK into established tumors in NOD/SCID mice. Reduction in tumor mass was assessed at the end of 6-day AZT treatment regimen (at 50 mg/kg/ day) by extraction of tumors and measurement of wet tumor weight. Statistical significance is indicated by an asterisk (* p<0.05).