Experimental study for development of microbubble applicable to clinical use in oral cancer chemotherapy

在本研究中，我们已经开发了一种微成像系统，使用微泡作为一种有效的类型的超声造影剂，和口腔癌治疗使用微泡和超声的分子传递系统。结果表明，通过使用高分辨率超声显微成像系统（最高频率：80 MHz），可以可视化直径为200 nm的微泡（流动的血管）。此外，当直径小于200 nm的纳米尺寸的气泡用作超声造影剂时，增强的渗透性和保留效果，即气泡倾向于在肿瘤组织中比在正常组织中更多地积聚的性质，也被超声显微成像系统可视化。另一方面，为了测试微泡和超声的组合使用是否具有将一些治疗材料递送到癌细胞中的潜力，我们检查了5-FU和顺铂以及自杀基因单纯疱疹病毒胸苷激酶（HSVtk）基因的递送效率。根据使用癌细胞系和实验小鼠的体外和体内研究结果，超声微泡产生了单独超声或药物所未见的显著细胞毒性。此外，HSVtk基因转染癌细胞，使用微泡和超声显示了潜在的细胞毒性敏感性更昔洛韦。这些结果表明，同时使用微成像系统和分子递送系统，通过使用微泡和超声方法结合抗癌药物和/或自杀基因治疗具有治疗口腔癌的潜力。

In the present study, we have developed a micro-imaging system using microbubbles as an effective type of ultrasound contrast agent, and a molecular delivery system for oral cancer therapy using microbubbles and ultrasound. As a result, it was clarified that microbubbles of 200nm in diameter, flowing blood vessels, could be visualized by using high-resolution ultrasound micro-imaging system (the highest frequency : 80MHz). In addition, when the nanosized bubbles less than a diameter of 200nm were used as an ultrasound contrast agent, the enhanced permeability and retention effect, that is the property by which the bubbles tend to accumulate in tumor tissue much more than they do in normal tissues, was also visualized by the ultrasound micro-imaging system. On the other hand, to test whether the combined use of microbubbles and ultrasound has a potential to deliver some therapeutic materials into cancer cells, we examined the delivery efficiency of 5-FU and cisplatin, and a suicide gene, herpes simplex virus thymidine kinase (HSVtk) gene. From results of in vitro and in vivo studies using cancer cell lines and experimental mice, microbubbles with ultrasound produced significant cytotoxicity not seen with either ultrasound or drug alone. Moreover, HSVtk gene transfection to cancer cells using microbubbles and ultrasound showed a potential of cytotoxic sensitivity by ganciclovir. These results suggests that simultaneous use of the micro-imaging system and the molecular delivery system by using the microbubbles and ultrasound method combined with anti-cancer agents and/or suicide gene therapy has a potential to treat oral cancer.