CELL CYCLE CHECKPOINTS AND CHEMOSENSITIVITY OF HUMAN CANCER CELLS

该研究项目以细胞周期检查点为主要研究对象 化疗敏感性的决定因素。我们还致力于利用新兴市场 了解这些检查站控制系统以设计新的 癌症治疗的化疗策略。我们正在澄清 在DNA之后将人类细胞滞留在G1和G2期的检查点 损伤，并发现癌细胞中这些系统的缺陷。我们希望 从DNA损伤或未复制的DNA开始追踪这些系统 由细胞感应到阻止细胞周期的反应元件， 在某些情况下还会诱导细胞凋亡。我们正在搜索的组件 这些系统可以通过检测来预测检查点完整性和 对化学药物敏感。我们的结果表明，p53基因突变可以防止 阻止细胞在DNA损伤后滞留在G1期并增加 对这些药物产生抗药性的可能性。这种阻力至少是有原因的。 部分原因是逃避了P53介导的细胞凋亡，尽管还有其他变化 突变的p53细胞中也存在这种情况。我们正在探索 P53调控基因产物WAF1/CIP1依赖于G1/S细胞周期蛋白 为了更好地确定该蛋白在G1期停滞中的意义， DNA修复和细胞凋亡。我们正在研究G2的机制 癌细胞中G2检查点的阻止和完整性。此检查站 似乎通过延长可用时间来保护细胞免受DNA损伤 用于DNA修复。我们已经发现DNA损伤抑制了 Cyclin A/CDc2和Cyclin B/CDc2通过维持抑制作用 氯化镉上的磷酸化作用。与我们发现的这一观察结果一致 在处理的细胞中，CDC25C磷酸酶的激活被抑制 使用DNA破坏剂。我们正在研究CDC25C的作用机理。 激活以更好地定义未复制和损坏的途径 DNA使细胞停滞于G2期。我们已经将流式细胞仪分析应用于 检测NCI细胞系中G1和G2检查点的完整性- 抗癌药物筛选发现存在较大差异。我们是 目前正在探索这些完整性之间的关系- 检查站和化疗敏感性。

This research project focuses on cell cycle checkpoints as major determinants of chemosensitivity. We also aim to utilize emerging knowledge of these checkpoint control systems to design new chemotherapeutic stratagems for cancer treatment. We are elucidating the checkpoints that arrest human cells in G1 and G2 phases following DNA damage, and uncovering defects in these systems in cancer cells. We hope to trace these systems from the point where DNA damage or unreplicated DNA is sensed by the cell to the response elements that arrest the cell cycle, and in some cases induce apoptosis. We are searching for components of these systems that could be assayed to predict checkpoint integrity and chemosensitivity. Our results suggest that p53 gene mutations prevent cells from arresting in G1 following DNA damage and increase the likelihood of resistance to these agents. This resistance is due, at least in part, to an evasion of p53-mediated apoptosis, although other changes also occur in the mutant p53 cells. We are exploring the interaction of the p53 regulated gene product WAF1/CIP1 with the G1/S cyclin dependent kinases to better define the significance of this protein in G1 arrest, DNA repair and apoptosis. We are investigating both the mechanism of G2 arrest and integrity of the G2 checkpoint in cancer cells. This checkpoint appears to protect cells from DNA damage by extending the time available for DNA repair. We have found DNA damage suppresses activation of the cyclin A/Cdc2 and cyclin B/Cdc2 kinases by maintaining inhibitory phosphorylations on Cdc2. Consistent with this observation we have found that activation of the Cdc25C phosphatase is suppressed in cells treated with DNA damaging agents. We are investigating the mechanism of Cdc25C activation to better define the pathway by which unreplicated and damaged DNA arrest cells in G2 phase. We have applied flow cytometric assays to test the integrity of the G1 and G2 checkpoints in cell lines of the NCI- Anticancer Drug Screen and found that major differences exist. We are presently probing for relationships between the integrity of these- checkpoints and chemosensitivity.