Janss A J, Levow C, Bernhard E J, Muschel R J, McKenna W G, Sutton L, Phillips P C
Division of Neuro-Oncology, Department of Neurosurgery, Chilren's Hospital of Philadelphia, 515 Abramson Building, 3400 Civic Center Boulevard, Philadelphia, Pennsylvania, 19104, USA.
Exp Cell Res. 1998 Aug 25;243(1):29-38. doi: 10.1006/excr.1998.4122.
Caffeine and staurosporine have been shown to attenuate G2 delay produced by DNA-damaging agents and to augment the cytotoxicity of these agents in a number of cell lines in vitro. Studies in rodent brain tumor cell lines suggest that modulation of the G2/M transition may not contribute to the enhanced cytotoxicity produced by caffeine in brain tumor cells. To evaluate the impact of agents that decrease G2 delay on the cytotoxicity of chemotherapy in human brain tumor cells, we examined the ability of caffeine and staurosporine to modulate the G2 delay and cytotoxicity produced by cisplatin (CDDP) and camptothecin (CPT) in U251 glioma and DAOY medulloblastoma cells. Synchronized U251 were incubated with 20 microM CDDP in the presence or absence of 2 mM caffeine. DAOY cells were incubated with 100 nM CPT in the presence or absence of 2 nM staurosporine. Caffeine and staurosporine attenuated G2 delay produced by CDDP and CPT, respectively. Clonogenic assays indicated that continuous exposure to 2 mM caffeine substantially lowered the ID50 and ID90 of CDDP in U251 cells without significantly altering plating efficiency. Twenty-four-hour exposure to 2 nM staurosporine lowered the ID50 and ID90 of CPT in DAOY cells without significantly altering plating efficiency. Evaluation of programmed cell death using terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling assay indicated that one mechanism for synergistic cytotoxicty of caffeine with CDDP and staurosporine with CPT in U251 and DAOY cells, respectively, is to promote apoptosis. These results underscore the importance of understanding regulation of G2/M transition in brain tumor cells. Such an understanding may lead to novel therapies that target G2 check points to augment the efficacy of currently available treatments for brain tumors.
咖啡因和星形孢菌素已被证明可减轻DNA损伤剂所产生的G2期延迟，并在多种体外细胞系中增强这些药物的细胞毒性。对啮齿动物脑肿瘤细胞系的研究表明，G2/M期转换的调节可能与咖啡因在脑肿瘤细胞中产生的增强细胞毒性无关。为了评估降低G2期延迟的药物对人脑肿瘤细胞化疗细胞毒性的影响，我们检测了咖啡因和星形孢菌素调节顺铂（CDDP）和喜树碱（CPT）在U251胶质瘤细胞和DAOY髓母细胞瘤细胞中所产生的G2期延迟和细胞毒性的能力。将同步化的U251细胞在存在或不存在2 mM咖啡因的情况下与20 μM CDDP一起孵育。将DAOY细胞在存在或不存在2 nM星形孢菌素的情况下与100 nM CPT一起孵育。咖啡因和星形孢菌素分别减轻了CDDP和CPT所产生的G2期延迟。克隆形成试验表明，持续暴露于2 mM咖啡因可显著降低U251细胞中CDDP的ID50和ID90，而不会显著改变接种效率。24小时暴露于2 nM星形孢菌素可降低DAOY细胞中CPT的ID50和ID90，而不会显著改变接种效率。使用末端脱氧核苷酸转移酶介导的dUTP-生物素缺口末端标记试验评估程序性细胞死亡表明，咖啡因与CDDP以及星形孢菌素与CPT在U251和DAOY细胞中协同细胞毒性的一种机制分别是促进细胞凋亡。这些结果强调了了解脑肿瘤细胞中G2/M期转换调节的重要性。这样的理解可能会带来针对G2检查点的新疗法，以增强目前可用的脑肿瘤治疗方法的疗效。
