RAIDYNAMIC INACTIVATION WITH ACRIDINE ORANGE ON MOUSE OSTEOSARCOMA

Kusuzaki K, Hashiguchi S, Hirata M, Murata H, Takeshita H, Ashihara T*, Hirasawa Y. (Department of Orthopaedic Surgery and Pathology*. Kyoto Prefectural University of Medicine. Kamigyo-ku Kawaramachi Hirokoji, Kyoto 602-8566 Japan)

We lately revealed that acridine orange (AO) was useful for photodynamic therapy (PDT) against a mouse osteosarcoma, however, photoexcitation is not effective against a tumor localized at deep site such as muscle or bone. Therefore, we undertook to clarify a cytocidal effect of AO excited by radiation against osteosarcoma. Mouse osteosarcoma cell (MOS) line supplied by Massachusetts General Hospital was used. The 10⁵ cells of MOS were cultured in DMEM medium containing 10% FBS in 5% CO2 atmosphere at 37^oC. After 48 hours, medium was replaced with new medium containing 0.05, 0. 1 µ g/ml of AO and X-ray was simultaneously irradiated to cultured cells. X-ray irradiation was performed by linear accelerator (Lineac: Mitsubishi Elec. Co.). Various doses of X-ray as 1, 5, 10, 20, 30 Gy were applied to cells. Cells without AO and irradiation or cells with AO alone showed a logarithmic growth. In cells with radiation alone, cell growth was inhibited, depending on X-ray dose. In contrast with these results, cells treated with AO and radiation showed strong growth inhibition, even at 0. 1 µ g/ml of AO and 1 Gy or at 0.05 µ g/ml of AO and 5 Gy. Because low concentration AO at 0.1 or 0.05 µ g/ml, or low dose of X-ray at 1 or 5 Gy does not have a cytocidal effect, it is evident that AO can be excited by radiation and the excited AO, even by low dose X-ray radiation, has strong effect of cell growth inhibition against the mouse osteosarcoma. Therefore, we concluded that combination with low concentration AO and low dose radiation has mostly same effect as PDT with AO, and this may be useful for unresectable or multiple pulmonary metastatic osteosarcoma.