Saito Hajime, Mitobe Kazutaka, Ito Aki, Sugawara Yu, Maruyama Kiyotomi, Minamiya Yoshihiro, Motoyama Satoru, Yoshimura Noboru, Ogawa Jun-ichi
Department of Surgery, Akita University, 1-1-1 Hondo, Akita City 010-8543, Japan.
Cancer Sci. 2008 Apr;99(4):805-9. doi: 10.1111/j.1349-7006.2008.00726.x. Epub 2008 Feb 21.
Hyperthermia has been used for many years to treat a variety of malignant tumors. The Curie temperature (Tc) is a transition point at which magnetic materials lose their magnetic properties, causing a cessation of current and thus heat production. The Tc enables automatic temperature control throughout a tumor as a result of the self-regulating nature of the thermosensitive material. We have developed a method of magnetically-induced hyperthermia using thermosensitive ferromagnetic particles (FMPs) with low Tc (43 degrees C), enough to mediate automatic temperature control. B16 melanoma cells were subcutaneously injected into the backs of C57BL/6 mice, after which tumors were allowed to grow to 5 mm in diameter. FMPs were then injected into the tumors, and the mice were divided into three groups: group I (no hyperthermia, control); group II (one hyperthermia treatment); and group III (hyperthermia twice a week for 4 weeks). When exposed to a magnetic field, the FMPs showed a sharp rise in heat production, reaching the Tc in tissue within 7 min, after which the tissue temperature stabilized at approximately the Tc. In groups I and II, all mice died within 30-45 days. In group III, however, 6 of 10 mice remained alive 120 days after beginning treatment. Our findings suggest that repeated treatment with magnetically-induced self-regulating hyperthermia, mediated by FMPs with a low Tc, is an effective means of suppressing melanoma growth. A key advantage of this hyperthermia system is that it is minimally invasive, requiring only a single injection for repeated treatments with automatic temperature control.
热疗已被用于治疗多种恶性肿瘤多年。居里温度（Tc）是一个转变点，在该点磁性材料会失去其磁性，导致电流停止从而产生热量。由于热敏材料的自我调节特性，居里温度能够在整个肿瘤内实现自动温度控制。我们开发了一种利用低居里温度（43摄氏度）的热敏铁磁颗粒（FMPs）进行磁诱导热疗的方法，该温度足以实现自动温度控制。将B16黑色素瘤细胞皮下注射到C57BL/6小鼠的背部，待肿瘤生长至直径5毫米后，将FMPs注射到肿瘤内，然后将小鼠分为三组：第一组（无热疗，对照组）；第二组（进行一次热疗）；第三组（每周进行两次热疗，共4周）。当暴露于磁场中时，FMPs的产热急剧上升，在7分钟内达到组织内的居里温度，之后组织温度稳定在约居里温度。在第一组和第二组中，所有小鼠在30 - 45天内死亡。然而，在第三组中，10只小鼠中有6只在开始治疗120天后仍存活。我们的研究结果表明，由低居里温度的FMPs介导的磁诱导自我调节热疗重复治疗是抑制黑色素瘤生长的有效方法。这种热疗系统的一个关键优势是微创性，仅需单次注射即可进行重复治疗并实现自动温度控制。
