Cytochrome C Oxidase in Malignant Gliomas

描述(申请人提供)：多形性胶质母细胞瘤(GBM)是最常见的原发颅内肿瘤，其致死率几乎一致。替莫唑胺(TMZ)是治疗GBM患者的标准护理，在4周的中位生存期有轻微但显着的增加。然而，TMZ耐药的获得是阻碍GBM患者有效治疗的主要障碍之一。尽管采取了积极的治疗方法，90%的GBM患者仍会复发。造成这种不良结果的一个原因是产生了抗药性。耐药的机制仍不清楚，因此需要开发更有效的策略和/或新的疗法来克服这种耐药。线粒体(Mt)处于能量产生和细胞凋亡途径的十字路口。它们在癌症病因学中的作用是重要的；然而，关于MT功能和化疗耐药的信息仍然不清楚。细胞色素c氧化酶(CcO)(EC 1.9.3.1)是一种大的线粒体跨膜蛋白复合体。它是呼吸电子传递链(ETC)中的最后一种酶，将电子从细胞色素c(Cytc)传递到分子氧(O2)。Cytc和O2是CcO的主要底物，它们都直接参与内源性线粒体凋亡途径和缺氧。虽然到目前为止，大多数研究都集中在CcO参与线粒体氧化磷酸化的过程中，但CcO活性、CcO核编码亚基与GBM抗凋亡发展之间的任何因果关系尚不清楚，这也是本研究的主题。最近，我们证明了TMZ耐药的获得与培养的胶质瘤细胞中CcO活性的显著增加以及成对的原发-复发的GBM患者的活检组织有关。在接受TMZ放射治疗的患者中，在初次和复发的人GBM标本中发现类似的CcO活性变化，强调了这些发现的临床意义和TMZ在调节这些影响中的主要作用。此外，药物或遗传抑制TMZ耐药细胞中的CcO可恢复TMZ诱导的细胞凋亡。这项建议的目的是检验这一假设，即CcO亚单位4亚型1(COX4-1)通过改变1)CcO组装/功能和2)细胞氧化还原动态平衡，从而驱动GBM的化疗耐药性，从而实现三个特定目标：(1)确定COX4-1和2亚型对CcO组装/功能和TMZ耐药性的影响；(2)确定COX4-1和2亚型对细胞氧化还原状态和对TMZ耐受性的影响；3)确定Cco的活性以及COX4-1和2亚型在脑肿瘤患者活检组织中的表达。在这项研究完成后，我们希望对CcO在TMZ的细胞凋亡反应中的作用有一个坚实的知识基础。我们的长期目标是将这些信息应用于基于CCO的治疗的开发以及化疗耐药和GBM复发的预后标志物的开发。

DESCRIPTION (provided by applicant): Glioblastoma multiforme (GBM) is the most common primary intracranial neoplasm and its almost uniform lethality. Temozolomide (TMZ) is the standard of care for the treatment of GBM patients showing small but significant increases in median survival of 4 weeks. However, acquisition of TMZ-chemoresistance is one of the major obstacles to efficient therapy for GBM patients. Despite aggressive treatment approaches, recurrence occurs in 90% of GBM patients. One cause of this poor outcome is development of a drug resistance. The mechanism underlying drug resistance is still not well understood thus challenging the development of more effective strategies and/or novel therapeutics to overcome this resistance. Mitochondria (mt) are at the cross road of energy production and apoptotic pathways. Their role in cancer etiology is significant; however, information regarding mt function and chemoresistance remains poorly defined. The enzyme cytochrome c oxidase (CcO) (EC 1.9.3.1) is a large mt transmembrane protein complex. It is the last enzyme in the respiratory electron transport chain (ETC) that transfers electrons from cytochrome c (Cyt c) to molecular oxygen (O2). Cyt c and O2 are the main substrates of CcO and both are directly involved in the intrinsic mt apoptotic pathway and hypoxia. While most of the studies to date have focus on CcO involvement in mt oxidative phosphorylation, any casual relation between CcO activity, CcO-nuclear-encoded subunits and the development of resistance to apoptosis in GBM is unclear and is the subject of this proposal. Recently, we demonstrated that acquisition of TMZ-resistance correlates with a significant increase of CcO activity in culture glioma cells as well a paired primary-recurrent GBM patient biopsies. The discovery of similar alterations in CcO activity between primary and recurrent human GBM specimens in patients subjected to TMZ-radiotherapy emphasizes the clinical significance of the findings and the primary role of TMZ in mediating these effects. Moreover, pharmacological or genetic inhibition of CcO in TMZ-resistant cells restores TMZ-induced apoptosis. The goal of this proposal is to test the hypothesis that CcO subunit 4 isoform 1 (COX4-1) drives chemoresistance in GBM through changes in 1) CcO assembly/ function and 2) cellular redox homeostasis by achieving three specific aims: We will determine whether: (1) Determine the effects of COX4-1 and 2 isoforms on the assembly/ function of CcO and on resistance to TMZ, (2) Determine the effects of COX4-1 and 2 isoforms on cellular redox status and on resistance to TMZ and 3) Determine the activity of CcO and expression of COX4-1 and 2 isoforms in brain tumor patient biopsies. Upon completion of this research, we expect to have developed a substantial base of knowledge on the role of CcO in the apoptotic response to TMZ. Our long term goal is to apply this information for the development of CcO-based therapies as well as for the development of prognostic markers for chemoresistance and GBM recurrence.