In vivo enhancement of herpes simplex virus thymidine kinase/ganciclovir cancer gene therapy with polyamine biosynthesis inhibition

✍ Scribed by Tiina Wahlfors; Tanja Hakkarainen; Juhani Jänne; Leena Alhonen; Jarmo Wahlfors

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: French
• Weight: 150 KB
• Volume: 118
• Category: Article
• ISSN: 0020-7136
• DOI: 10.1002/ijc.21722

✦ Synopsis

Abstract

We have earlier demonstrated that inhibition of polyamine biosynthesis with difluoromethylornithine (DFMO) can be used to enhance the cytotoxicity of herpes simplex virus thymidine kinase/ganciclovir (HSV‐TK/GCV) gene therapy in different tumor cell lines. Here, the utility of this treatment combination was tested in vivo in a nude mouse tumor model. First, the effect of DFMO was verified by treating mice bearing subcutaneous 9L rat glioma tumors with 2% DFMO in drinking water. The drug treatment induced almost complete suppression of ornithine decarboxylase activity, and as a result, a strong decrease in intratumoral putrescine and spermidine concentrations, which were normalized 4 days after drug removal. Consequently, the tumors displayed a significant reduction in the proliferation activity that was increased to 20% higher than the normal level at day 4 and returned to normal level 7 days after DFMO removal. Next, 9L tumors with 30% of TK‐GFP fusion gene positive cells were induced and the animals were given DFMO and GCV in 2 treatment schemes, with the drug administration periods overlapping either 5 or 2 days. The analysis of tumor size at the end of the treatment revealed that DFMO can enhance HSV‐TK/GCV cytotoxicity when the overlap between DFMO and GCV was 5 days, but the result was not significant. However, the 2‐day overlap scheme yielded a significantly (p < 0.05, ANOVA) enhanced antitumor effect. In conclusion, the data here confirms that a novel combination of 2 clinically relevant treatment modalities, polyamine deprivation and HSV‐TK/GCV suicide gene therapy, can be used synergistically in vivo. © 2005 Wiley‐Liss, Inc.