CELL CYCLE CHECKPOINTS AND CHEMOSENSITIVITY OF HUMAN CANCER CELLS

这个研究小组的主要重点是研究细胞的作用 在人类癌细胞的化学敏感性的周期检查点。等 研究的目的是解决4个基本问题：（1）做细胞 人类癌细胞中存在周期检查点差异;（2） 当观察到检查点差异时， 目前可用的抗癌药物;（3）我们可以解剖出 这些检查点的分子组成，并确定这些 组分介导细胞周期停滞、DNA修复和凋亡，以及 (4)我们能否发现新的化疗药物和/或策略， 利用检查点差异作为优先 破坏癌细胞。我们把重点放在检查站， 响应DNA损伤以阻止G1和/或G2期细胞周期进展 相位G1 DNA损伤检查点通常在癌症中被破坏 这是由于p53通路的缺陷。我们发现 许多癌细胞系也表现出减弱的G2 检查点对DNA损伤的反应。尽管这种衰减不能 在p53状态的基础上得到充分解释，我们发现， 检查点调节剂如戊茶碱和UCN-01， 优先消除p53缺陷细胞中的G2检查点。 我们 已经利用了药物组合的这种脆弱性， 体外杀伤p53缺陷癌细胞系。我们的目标是披露 这种脆弱性的分子基础，并将重点放在UCN-01， 刚刚进入临床试验阶段我们发现p53的破坏 改变了对一些常用抗癌药物的敏感性 这些作用取决于细胞类型和 用于处理细胞的药剂类别。最近我们发现 p53调控基因CIP 1/WAF 1的破坏优先于 使细胞对DNA交联剂敏感。与博士合作。 Fornace的实验室，我们发现这种致敏作用与 CIP 1/WAF 1破坏细胞中DNA修复活性降低， Cip 1/Waf 1参与DNA修复我们和其他人现在 表征了NCI细胞筛选中p53通路的完整性。 这种分析允许发现潜在的代理人 在具有突变型p53的细胞中具有更高的活性。我们正在准备几个 等基因细胞系统，以进一步研究这些代理商。 我们 目前正在继续研究G1和G2阻滞的机制。为 G2期阻滞，我们关注Wee 1和PLK激酶，G1期阻滞， 我们正在调查的逮捕 一种新的p53调控的 磷酸酶（Wip 1），最近被克隆为一个 与国家癌症研究所的Appella博士团队合作。

The major focus of this research group is to study the role of cell cycle checkpoints in the chemosensitivity of human cancer cells. Such studies are aimed at addressing 4 fundamental questions: (1) Do cell cycle checkpoint differences exist in human cancer cells; (2) Do checkpoint differences, when observed, impart altered sensitivity to currently available anticancer agents; (3) Can we dissect out the molecular components of these checkpoints and determine how these components mediate cell cycle arrest, DNA repair and apoptosis, and (4) Can we discover new chemotherapeutic agents and/or stratagems that exploit checkpoint differences as a basis for the preferential destruction of cancer cells. We are focusing on the checkpoints that respond to DNA damage to arrest cell cycle progression in G1 and/or G2 phase. The G1 DNA damage checkpoint is commonly disrupted in cancer cells and this results from defects in the p53 pathway. We have found that a number of cancer cell lines also exhibit an attenuated G2 checkpoint response to DNA damage. Although this attenuation cannot be fully explained on the basis of p53 status, we have found that checkpoint modulators such as pentoxifylline and UCN-01, preferentially abrogate the G2 checkpoint in p53 defective cells. We have exploited this vulnerability in drug combinations to preferential kill p53 defective cancer cell lines in vitro. We aim to disclose the molecular basis of this vulnerability and will focus on UCN-01, which has just entered clinical trials. We have found that p53 disruption imparts altered sensitivity to a number of commonly used anticancer agents and these effects are dependent upon both the cell type and class of agents used to treat the cells. Most recently we have found that disruption of the p53-regulated gene CIP1/WAF1 preferentially sensitizes cells to DNA crosslinking agents. In collaboration with Dr. Fornace's laboratory, we have found this sensitization correlates with reduced DNA repair activity in the CIP1/WAF1 disrupted cells, implicating Cip1/Waf1 in DNA repair. We and others have now characterized the integrity of the p53 pathway in the NCI cell screen. This analysis has allowed the discovery of agents with potentially greater activity in cells with mutant p53. We are preparing several isogenic cell systems for further investigation of these agents. We are continuing to investigate the mechanisms of G1 and G2 arrest. For G2 arrest, we are focusing on the Wee1 and PLK kinases and for G1 arrest we are investigating the role of a novel p53-regulated phosphatase (Wip1), that was recently cloned as part of a collaboration with Dr. Appella's group at the NCI.