膠芽腫は最も難治性の中枢神経原発悪性腫瘍である。低線量照射に対する細胞反応は放射線高感受性であることに着目し, 基礎的検討を行った。膠芽腫細胞株に対して低線量照射を行い, 細胞生存率と細胞周期, アポトーシス誘導を測定した。コロニー形成法による検討では, 放射線超感受性を示唆する生存曲線が複数のセルラインで観察された。細胞周期やアポトーシス誘導の変化は検出困難であった。そこで低線量照射を反復して行ったところ, 照射間隔が比較的長い(30分)群で細胞生存率の低下が観察され, 照射後早期(30分)でG1期分画比率の減少とG2/M期分画の増加, アポトーシス分画の比率の増加が観察され, 有効な治療法と考えられた。
Glioblastoma is highly lethal disease. Radiotherapy plays important role but tumor recurrence is occurred in most of cases. We focused low-dose hyper-radiosensitivity phenomena as a new treatment strategy. Cell survival, cell cycle and rate of apoptosis were measured. Survival rate decreased in association with increasing dose on single low dose irradiation suggestive of hyper-radiosensitivity in some cell lines. On the other hand, the observed cell cycle change of G1/G2 ratio was less than 5%. The survival rate lowered when an interval became longer by low dose repeat irradiation (LDRR). The moderate change of the G1/G2 ratio was observed in the examination 30 minutes after irradiation only at 30 minutes interval. A rise of the apoptotic component was observed at 30 minutes interval. The LDRR at 30 minutes interval seems to be a promising approach, although, confirmation by other technique and elucidation of the further mechanism is warranted.
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