1. ¹Department of Health Promotion, Division of Infections and Molecular Biology, Kitakyushu, Japan
2. ²Department of Oral and Maxillofacial Surgery, Division of Maxillofacial Diagnostic and Surgical Science, Kitakyushu, Japan
3. ³Department of Health Promotion, Division of Community Oral Health Science, Kyushu Dental College, Kitakyushu, Japan

Correspondence: Dr T Nishihara, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, 803-8580, Japan. E-mail: tatsujin@kyu-dent.ac.jp

Received 22 February 2006; Revised 20 August 2006; Accepted 9 October 2006; Published online 2 February 2007.

Abstract

Recently, ultrasound-targeting microbubble destruction has been employed in molecular gene therapy, and a new potent nonviral gene transfer method known as 'sonoporation' has been developed. We investigated the efficiency of sonoporation toward growth inhibition of human gingival squamous carcinoma cell line, Ca9-22, in vitro and in vivo. The cytotoxicity of bleomycin (BLM) was investigated using flow-cytometric analysis and Hoechst's staining in vitro assay systems. We found that the delivery of BLM by sonoporation induced cytotoxic effect toward Ca9-22 cells in vitro. Our in vivo results showed that tumors nearly disappeared in Ca9-22 cell-implanted nude KSN/slc mice treated with a low dose of BLM followed by sonoporation during the 4-week experimental period. Histological analysis revealed that the cytotoxic effect was mainly apoptosis. We previously reported that the cytolethal distending toxin B (cdtB) from Actinobacillus actinomycetemcomitans, a periodontopathic bacterium, is responsible for cell cycle arrest and apoptosis in vitro. Thus, we used sonoporation to transfect a cdtB-expressing plasmid into Ca9-22 cells and examined cell viability in vitro and in vivo. We found that an administration of cdtB-expressing plasmid followed by sonoporation-induced marked growth inhibition of Ca9-22 cells and apoptotic cells were also observed in vitro and in vivo. These findings suggest that local administration of cytotoxic agents with sonoporation is a useful method for molecular cancer therapy.