Mack Philip C, Jones Angela A, Gustafsson Matthew H, Gandara David R, Gumerlock Paul H, Goldberg Zelanna
Cancer and Molecular Research Laboratory, Division of Hematology/Oncology, Department of Internal Medicine, Sacramento, California 95817, USA.
Radiat Res. 2004 Dec;162(6):623-34. doi: 10.1667/rr3253.
Thoracic ionizing radiation is a standard component of combined-modality therapy for locally advanced non-small cell lung cancer. To improve low 5-year survival rates (5- 15%), new strategies for enhancing the effectiveness of ionizing radiation are needed. The kinase inhibitor UCN-01 has multiple cell cycle effects, including abrogation of DNA damage-induced S- and G(2)-phase arrest, which may limit DNA repair prior to mitosis. To test the hypothesis that therapy-induced cell cycle effects would have an impact on the efficacy of a combination of UCN-01 plus ionizing radiation, the cell cycle responses of the non-small cell lung cancer cell lines Calu1 (TP53-null) and A549 (wild-type TP53) to 2 Gy ionizing radiation were correlated with clonogenic survival after irradiation plus UCN-01. Irradiated cells were exposed to UCN-01 simultaneously and at 3-h increments after irradiation. In Calu1 cells but not A549 cells, sequence-dependent potentiation of radiation by UCN-01 was observed, with maximal interaction occurring when UCN-01 was administered 6 h after irradiation. This coincided with the postirradiation time with the greatest depletion of cells from G(1). Abrogation of G(2) arrest was observed regardless of TP53 status. The role of TP53 was investigated using siRNA to achieve gene silencing. These studies demonstrated that radiation plus UCN-01 was more effective in cells with diminished TP53 activity, associated with a reduced G(1) checkpoint arrest. These studies indicate that simultaneous elimination of multiple DNA damage-induced checkpoints in G(1), S and G(2) may enhance the effects of radiation and that drug scheduling may have an impact on clinical efficacy.
胸部电离辐射是局部晚期非小细胞肺癌综合治疗的标准组成部分。为提高较低的5年生存率（5%-15%），需要新的策略来增强电离辐射的有效性。激酶抑制剂UCN-01具有多种细胞周期效应，包括消除DNA损伤诱导的S期和G2期阻滞，这可能会限制有丝分裂前的DNA修复。为了验证治疗诱导的细胞周期效应会影响UCN-01联合电离辐射疗效的假设，将非小细胞肺癌细胞系Calu1（TP53基因缺失）和A549（野生型TP53）对2 Gy电离辐射的细胞周期反应与照射加UCN-01后的克隆形成存活率相关联。照射后的细胞在照射同时及照射后以3小时的间隔暴露于UCN-01。在Calu1细胞而非A549细胞中，观察到UCN-01对辐射的序列依赖性增强作用，当照射后6小时给予UCN-01时出现最大相互作用。这与G1期细胞耗竭最多的照射后时间一致。无论TP53状态如何，均观察到G2期阻滞的消除。使用小干扰RNA实现基因沉默来研究TP53的作用。这些研究表明，辐射加UCN-01在TP53活性降低的细胞中更有效，这与G1期检查点阻滞减少有关。这些研究表明，同时消除G1期、S期和G2期多个DNA损伤诱导的检查点可能会增强辐射效果，并且药物给药时间可能会影响临床疗效。
