Chronic Inflammation, apoptosis, and cancer

慢性炎症、细胞凋亡和癌症

• 批准号: 6840066
• 负责人: EMILY B SHACTER
• 金额: --
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6840066
• 关键词: antioxidants; apoptosis; blood proteins; free radical oxygen; guanosinetriphosphatases; hydrogen peroxide; inflammation; laboratory mouse; macrophage; neoplasm /cancer; neoplasm /cancer chemotherapy; neoplastic cell; oxidizing agents; phagocytes

The overall goal of the research in Dr. Shacter's laboratory is to find ways to understand and improve cancer treatment by applying our knowledge of basic biochemical and immunological pathways to the development of novel therapeutic approaches for eliminating tumor cells. Solid tumors such as lymphoma and breast cancer are often infiltrated by inflammatory phagocytes (neutrophils and macrophages) which can generate reactive oxygen species within the tumor tissue. The macrophages play a key role in removing dying tumor cells. Dr. Shacter's laboratory investigates how the oxidants (such as hydrogen peroxide and hypochlorous acid) may influence the efficacy of cancer chemotherapy drugs. Most antineoplastic drugs kill tumor cells by inducing a form of cell death called apoptosis. This mechanism of cell death is thought to be physiologically advantageous because the dying cells are removed from the tissue by phagocytosis prior to lysis and induction of a potentially adverse immune response. Dr. Shacter has found from in vitro studies that hydrogen peroxide, the main oxidant secreted by macrophages, interferes with the ability of chemotherapy drugs to induce apoptosis in human lymphoma cells. Moreover, exposure of apoptotic cells to hydrogen peroxide inhibits the phagocytosis of the dying cells by macrophages. Hence, this oxidant interferes with the ability of the immune system to quietly remove dying cancer cells. Her research shows further that addition of antioxidants to the treatment regimen restores chemotherapy-induced cell killing. These findings raise the possibility that administration of antioxidants together with cancer chemotherapy may reduce the negative, oxidant-related side effects of the chemotherapy drugs (e.g., adriamycin-induced cardiotoxicity) while maintaining full tumor cell killing. This theory is supported by studies in Dr. Shacter's laboratory using a pre-clinical mouse model for breast cancer treatment. Molecular studies being carried out in the laboratory examine mechanisms of chemotherapy-induced apoptosis and the involvement of signal transduction pathways in controlling cell survival. Finally, significant effort is directed towards identifying factors that control uptake and clearance of the dying cells by macrophages. Dr. Shacter's group recently discovered that immune system elimination of apoptotic cells requires the presence of serum protein S, which is a co-factor for activated protein C, a therapeutic protein recently approved for marketing under the tradename Xigris. The research suggests that protein S could serve as a potential therapeutic protein in the treatment of autoimmunity and sepsis. Oxidants and Cell Death. We are investigating how inflammatory oxidants such as hydrogen peroxide (H2O2) kill tumor cells and how they may influence tumor cell recognition and elimination by the immune system. Most chemotherapeutic agents kill tumor cells by inducing apoptosis. Solid tumors are often infiltrated by inflammatory phagocytes which can generate oxidative stress within the tumor tissue. Previously, we found that in the presence of H2O2, human Burkitt's lymphoma (BL) cells are unable to undergo apoptosis in response to cancer chemotherapy drugs and die instead by a form of necrosis. One of the most important consequences of the interaction between H2O2 and the chemotherapy drugs is that the cells do not become phagocytosed by co-cultured macrophages until after their membranes have lysed. This can lead to an undesirable inflammatory reaction to the dying cells, which can further complicate tumor cell depletion. Our recent research has been aimed at identifying the molecular mechanism whereby H2O2 inhibits uptake of dying tumor cells by macrophages and at identifying endogenous cofactors for the phagocytic process. H2O2 inhibits the protein S-stimulated phagocytosis of BL cells even when they express phosphatidylserine (PS) on the exofacial surface of the plasma membrane. These results indicate that PS is necessary, but is not sufficient for recognition and uptake of apoptotic cells by macrophages. Further, they suggest that H2O2 acts by modifying a separate, as yet unidentified phagocytic marker on the surface of apoptotic cells. The molecular target for H2O2 action is being sought so that we may identify additional mechanisms of controlling cell death. Recently, we discovered that phagocytosis of apoptotic lymphoma cells requires the presence of protein S, a serum protein that regulates the activity of activated protein C. This finding identifies a novel link between the coagulation and immune systems and suggests a possible role for protein S in both autoimmunity and in the disseminated intravascular coagulation associated with sepsis. The Role of Small GTPases in Control of Tumor Cell Apoptosis. The goal of this research project is to understand the molecular mechanisms through which Rac GTPase and its associated regulatory proteins control apoptosis in response to cancer chemotherapy drugs. Rac GTPases are members of the Rho family of the Ras superfamily of small GTP-binding proteins. These proteins are key regulators of many aspects of cell function, including cytoskeletal organization, transmission of growth signals from intracellular oxidants, gene transcription, and cell transformation. Rac proteins regulate cell signalling by binding to and activating downstream effector molecules, such as protein kinases, NADPH oxidases, and other regulatory proteins. Rac and other Rho GTPases are overexpressed in many cancers. We study how the Rac GTPases are regulated in response to apoptotic stimuli, and how the perturbation of Rac-related signaling pathways contributes to cell death. Greater understanding of how Rac controls of cancer cell growth and death can lead to the identification of drugs that aid in the selective killing of tumor cells by targeting aberrant Rac signaling pathways. In initial studies, we evaluated the possibility that cellular Rac GTPases serve as caspase substrates. Caspases catalyze the cleavage of intracellular substrates and cause the biochemical and morphological changes that are characteristic of apoptotic death. We found that endogenous Rac1 is, in fact, cleaved in human lymphoma cells in response to chemotherapy drugs during the course of apoptosis. The proteolysis occurs at to non-canonical caspase-3 sites and results in inactivation of Rac1 GTPase and effector-binding activities. Expression of caspase-3-resistant Rac1 mutants in the cells suppresses drug-induced apoptosis. Overall, the results suggest that native Rac1 activity interferes with the apoptotic process and needs to be diminished in order to maximize cell killing by chemotherapy drugs. More recent studies have looked for the pathway through which Rac1 regulates cell survival, focusing specifically on the bcl-2-family member Bad. This protein is known to undergo a reversible phosphorylation cycle that regulates cell survival and apoptosis. Our recent research examines which cellular protein kinases control phosphorylation of Bad in response to Rac1 activity.

Shacter博士实验室研究的总体目标是通过将我们对基本的生化和免疫学途径的了解来理解和改善癌症治疗方法，以开发消除肿瘤细胞的新型治疗方法。 诸如淋巴瘤和乳腺癌等实体瘤通常会被炎性吞噬细胞（中性粒细胞和巨噬细胞）浸润，这些吞噬细胞可以在肿瘤组织中产生活性氧。 巨噬细胞在去除垂死的肿瘤细胞中起关键作用。 Shacter博士的实验室调查了氧化剂（例如过氧化氢和次甲酸氢）如何影响癌症化学疗法药物的疗效。 大多数抗塑性药物通过诱导一种称为凋亡的细胞死亡形式杀死肿瘤细胞。 这种细胞死亡的机制在生理上是有利的，因为在裂解和诱导潜在的不良免疫反应之前，通过吞噬作用将垂死的细胞从组织中取出。 Shacter博士从体外研究中发现，巨噬细胞分泌的主要氧化剂氢氢氢氢氢氢化药物会干扰化学疗法药物在人淋巴瘤细胞中诱导凋亡的能力。 此外，凋亡细胞暴露于过氧化氢会抑制巨噬细胞对垂死细胞的吞噬作用。 因此，这种氧化剂会干扰免疫系统悄悄去除垂死的癌细胞的能力。 她的研究进一步表明，在治疗方案中添加抗氧化剂可恢复化学疗法引起的细胞杀伤。 这些发现提出了一种可能性，即抗氧化剂与癌症化疗可以减少化学疗法药物的负面，氧化剂相关的副作用（例如，阿霉素诱导的心脏毒性），同时保持全肿瘤细胞杀伤。 该理论得到了Shacter博士实验室的研究，使用临床前小鼠模型进行乳腺癌治疗。 在实验室检查化学疗法诱导的细胞凋亡的机制以及信号转导途径控制细胞存活中的分子研究。 最后，大量的努力是针对识别控制巨噬细胞对垂死细胞的吸收和清除率的因素。 Shacter博士的小组最近发现，免疫系统消除凋亡细胞需要血清蛋白S的存在，血清蛋白S是活化蛋白C的共同因素，这是一种蛋白质，这是一种最近在Xigris下批准营销的治疗蛋白。 该研究表明，蛋白质可以作为自身免疫和败血症治疗的潜在治疗蛋白。 氧化剂和细胞死亡。我们正在研究炎性氧化剂，例如过氧化氢（H2O2）如何杀死肿瘤细胞，以及它们如何影响免疫系统的肿瘤细胞识别和消除。 大多数化学治疗剂通过诱导凋亡杀死肿瘤细胞。 实体瘤通常会被炎症性吞噬细胞浸润，这些吞噬细胞会在肿瘤组织中产生氧化应激。 以前，我们发现在存在H2O2的情况下，人伯基特的淋巴瘤（BL）细胞无法响应癌症化学疗法药物而无法凋亡，而是因坏死形式而死。 H2O2与化学疗法药物之间相互作用的最重要后果之一是，直到膜裂解后，细胞才会被共培养的巨噬细胞吞噬。 这可能导致对垂死细胞的不良炎症反应，这可能会使肿瘤细胞的耗竭复杂化。 我们最近的研究旨在确定H2O2通过巨噬细胞抑制垂死的肿瘤细胞的摄取，并鉴定内源性辅助因子以抑制吞噬过程的分子机制。 H2O2即使在质膜的外部表面上表达磷脂酰丝氨酸（PS），也可以抑制BL细胞的蛋白质S刺激的吞噬作用。 这些结果表明PS是必要的，但不足以通过巨噬细胞识别和吸收凋亡细胞。 此外，他们建议H2O2通过修改凋亡细胞表面上的单独的吞噬标记来作用。 正在寻求H2O2作用的分子靶标，以便我们可以确定控制细胞死亡的其他机制。 最近，我们发现凋亡淋巴瘤细胞的吞噬作用需要蛋白S的存在，蛋白S是一种调节活化蛋白的活性C的血清蛋白。这一发现确定了凝结和免疫系统之间的新联系，并提出了蛋白质S在自身免疫性和与散发性的静脉内静脉内相关的蛋白质中的可能作用。 小GTPases在控制肿瘤细胞凋亡中的作用。该研究项目的目的是了解RAC GTPase及其相关调节蛋白控制凋亡对癌症化学疗法药物的凋亡的分子机制。 RAC GTPases是小型GTP结合蛋白的RAS RAS家族的成员。 这些蛋白质是细胞功能许多方面的关键调节剂，包括细胞骨架组织，细胞内氧化剂的生长信号传播，基因转录和细胞转化。 RAC蛋白通过结合并激活下游效应分子（例如蛋白激酶，NADPH氧化酶和其他调节蛋白）来调节细胞信号传导。 RAC和其他Rho GTPases在许多癌症中都过表达。 我们研究如何根据凋亡刺激来调节RAC GTPases，以及与RAC相关信号通路的扰动如何有助于细胞死亡。 更了解RAC对癌细胞生长和死亡的控制如何通过靶向异常RAC信号通路来鉴定有助于杀死肿瘤细胞的药物。 在最初的研究中，我们评估了细胞RAC GTPases用作caspase底物的可能性。 胱天蛋白酶催化细胞内底物的裂解，并引起凋亡死亡的特征的生化和形态变化。 我们发现，在凋亡过程中，内源性RAC1实际上是对化学疗法药物的响应在人淋巴瘤细胞中裂解的。 蛋白水解发生在非典型的caspase-3位点，导致Rac1 GTPase和效应子结合活性失活。 细胞中caspase-3耐药RAC1突变体的表达抑制了药物诱导的凋亡。 总体而言，结果表明，天然RAC1活性会干扰凋亡过程，并且需要减少，以最大程度地通过化学疗法药物杀死细胞。 最近的研究已经寻找了Rac1调节细胞生存的途径，专门针对BCL-2家庭成员BAD。 已知该蛋白会经历可逆的磷酸化周期，从而调节细胞存活和凋亡。 我们最近的研究研究了哪种细胞蛋白激酶控制RAC1活性的不良磷酸化。