NF KAPPA B MEDIATED CHEMORESISTANCE IN HUMAN LUNG CANCER

肺癌是男性和女性癌症死亡的最常见原因。 所有新诊断的肺癌中有80%是非小细胞肺癌（NSCLC），超过75%的人患有晚期疾病。 由于这个原因以及完全切除后远处复发的倾向，大多数患者接受单独化疗或与其他方式联合治疗。 不幸的是，尽管使用第二代或第三代化疗剂的治疗方案，但大多数NSCLC仍具有化学抗性。 肿瘤化学抗性归因于细胞克服程序性细胞死亡（细胞凋亡）的能力。 最近，已经确定化疗上调NF-κ B转录因子，这与细胞对化疗诱导的细胞凋亡的抵抗有关。 基于这种理解，进行实验以确定在添加吉西他滨和顺铂（两种常用于治疗NSCLC的遗传毒性剂）后，NF-κ B是否在NSCLC细胞系中提供类似的细胞存活信号。 初步数据表明，这些化疗剂诱导NF-κ B转录活性。 更重要的是，NF-κ B的缺失使NSCLC细胞系对化疗诱导的细胞凋亡敏感。 尽管化疗诱导的细胞死亡涉及某些细胞类型中的死亡受体途径，但NSCLC细胞中化疗诱导的细胞凋亡不涉及Fas或半胱天冬酶-8依赖性死亡受体途径。 相比之下，需要NF-κ B来克服化疗后的肿瘤介导的凋亡。 此外，神经酰胺最近被证明可以抑制抗凋亡P13 K/Akt途径以及激活NF κ B。 由于NF-κ B活性的丧失使NSCLC细胞对化疗诱导的细胞凋亡敏感，因此本提案的主要目标是检查在添加化疗后控制细胞凋亡和化学抗性的细胞信号传导机制。 为了实现这一目标，我们将使用（由P.I.）缺乏NF-κ B活性的细胞系，并将它们与对照进行比较。 将这些细胞暴露于化疗剂，并在体外检查凋亡和抗凋亡信号通路。该提案的具体目的是：1）确定化疗是否通过肿瘤依赖性机制杀死NSCLC细胞，2）确定细胞的氧化还原状态是否负责调节化疗后NF-κ B依赖性细胞存活，3）确定神经酰胺作为化疗后促凋亡和抗凋亡介质的作用。 这些研究将提供重要的洞察化疗如何激活凋亡途径，以及肿瘤通过上调NF-κ B变得耐药的机制。 本研究的最终目的是为设计用于治疗晚期肺癌患者的新治疗策略的启动提供必要的背景。

Lung cancer is the most common cause of cancer death in both men and women. Eighty percent of all newly diagnosed lung cancers are non-small cell lung cancers (NSCLC), and over 75 percent present with advanced stage disease. For this reason as well as the predilection for distant recurrence after complete resection, most patients are treated with chemotherapy alone or in combination with other modalities. Unfortunately, the majority of NSCLC are chemoresistant despite treatment regimens with second or third generation of chemotherapeutic agents. Tumor chemoresistance has been attributed to the ability of cells to overcome programmed cell death (apoptosis). Recently, it has been established that chemotherapy upregulates the NF-kappaB transcription factor and this is associated with cellular resistance to chemotherapy-induced apoptosis. With this understanding, experiments were performed to determine whether NF-kappaB provided a similar cell survival signal in NSCLC cell lines following the addition of gemcitabine and cisplatin, two genotoxic agents commonly used to treat NSCLC. Preliminary data demonstrates that these chemotherapeutic agent induce NF-kappaB transcriptional activity. More importantly, the loss of NF- kappaB sensitizes NSCLC cell lines to chemotherapy-induced apoptosis. Although cell death induced by chemotherapy involves death receptor pathways in certain cell types, chemotherapy- induced apoptosis in NSCLC cells did not involve either Fas- or caspase-8-dependent death receptor pathways. In contrast, NF- kappaB was required to overcome mitochondrial-mediated apoptosis following chemotherapy addition. In addition, ceramide has recently been shown to inhibit the anti-apoptotic P13K/Akt pathway as well as activate NFkappaB. Since the loss of NF- kappaB activity sensitizes NSCLC cells to chemotherapy-induced apoptosis, the major goal of this proposal is to examine the cell signaling mechanisms governing apoptosis and chemoresistance following the addition of chemotherapy. To achieve this objective, we will use established (by the P.I.) cell lines which lack NF-kappaB activity and compare them to controls. These cells will be exposed to chemotherapeutic agents and apoptotic and anti-apoptotic signaling pathways will be examined in vitro. The specific aims of the proposal are to: 1) establish whether chemotherapy kills NSCLC cells through mitochondrial-dependent mechanisms, 2) determine whether the redox status of the cell is responsible for modulating NF-kappaB-dependent cell survival in response to chemotherapy, and 3) determine the role of ceramide as both a pro- and anti-apoptotic mediator following chemotherapy. These studies will provide important insight into how chemotherapy activates apoptotic pathways, as well as mechanisms by which tumors become chemoresistant through upregulation of NF-kappaB. The ultimate goal of this study is to provide the necessary background for the initiation of novel treatment strategies designed to treat patients with advanced lung cancer.