1. ¹Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan
2. ²Department of Biopharmaceutics, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan
3. ³National Institute of Health Sciences, Osaka Branch, Fundamental Research Laboratories for Development of Medicine, 7-6-8 Asagi, Saito, Ibaraki, Osaka 567-0085, Japan
4. ⁴National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan
5. ⁵Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan

Correspondence: Dr Naoki Okada, PhD, Department of Biopharmaceutics, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan. E-mail: okada@mb.kyoto-phu.ac.jp

Received 4 October 2004; Published online 4 March 2005.

Abstract

Since RGD fiber-mutant adenovirus vector (AdRGD), which contains an v-integrin tropism, is highly efficient in gene transduction to melanoma, the AdRGD-mediated herpes simplex virus thymidine kinase (HSVtk)/ganciclovir (GCV) system is an attractive approach for melanoma treatment. However, the intratumoral injection of AdRGD causes limited transgene expression in healthy normal tissue, due to unwanted vector spread. Herein, we describe our attempt to overcome this limitation related to the safety of HSVtk/GCV treatment by using AdRGD carrying either melanoma-specific tyrosinase (Tyr) promoter or tumor-specific telomerase reverse transcriptase (TERT) promoter instead of universal cytomegalovirus promoter. Our in vitro study revealed that Tyr promoter-regulated AdRGD exhibited high transgene expression specificity for melanoma cells, and that TERT promoter-regulated AdRGD could induce efficient gene expression in tumor cells, but was relatively quiescent in normal cells. Anti-B16BL6 melanoma effects in mice injected intratumorally with AdRGD-Tyr/HSVtk or AdRGD-TERT/HSVtk, after which GCV was injected intraperitoneally for 10 days, were comparable to those in mice injected with AdRGD-CMV/HSVtk at 10 times less vector dosage. On the other hand, AdRGD-Tyr/HSVtk and AdRGD-TERT/HSVtk did not induce severe adverse effects even when they were intravenously injected into mice at 10⁹ plaque-forming units (PFU), whereas mice injected with AdRGD-CMV/HSVtk at 10⁸ PFU exhibited body weight reduction and serum level increase of biochemical enzymes for hepatotoxicity. These results indicate that AdRGD combined with transcriptional regulation using Tyr or TERT promoter is a potentially useful and safe vector system for suicide gene therapy for melanoma.