Figure 5.

Combination of TK expression driven by the reactive oxygen species-responsive chimeric promoter, and GCV, with or without chemotherapy, inhibited the in vivo growth of established tumors. (a,b) Nude mice harboring established LoVo and A375N tumors were distributed into four groups (n = 5 per group): control (C), Dx, GCV, and GCV+Dx. All mice received six intratumoral injections of 50 µg of naked plasmid by electroporation, every 2 days. GCV (50 mg/kg) or PBS was administrated i.p from day 0 to 15, as indicated. Dx (5 mg/kg) was administrated i.p 1 hour prior to electroporation, when indicated. Growth curves represent the growths of individual tumors, relative to tumor size at the beginning of the treatment (V/V₀). Black arrows indicate the times of E6(40)VE-TK plasmid electrogene transfer; “d” indicates Dx administration, the line in the x-axis is the duration of PBS or GCV administration. (c) Photographs of LoVo and A375N mice obtained at 20 days of treatment. (*P < 0.0001 control versus GCV; *P < 0.008 control versus Dx and ^#P < 0.0001 GCV versus GCV+Dx). Dx, doxorubicin; GCV, gancyclovir; i.p., intraperitoneal; PBS, phosphate buffered saline; TK, thymidine kinase.