Protein Kinase C and GSTP1 interactions in glioma drug resistance

描述(申请人提供)：目前中枢神经系统恶性肿瘤的化疗很少产生显著的长期反应。造成这种不良治疗结果的两个主要因素是脑肿瘤对化疗的内在抵抗力，以及目前治疗方法的低选择性和高毒性。然而，开发更具肿瘤特异性的治疗方法和治疗策略，将需要了解驱动肿瘤生长和治疗反应的分子机制和异常。这个项目建立在我们实验室最近关于第二阶段药物代谢和细胞信号蛋白谷胱甘肽S转移酶P1(GSTP1)和丝氨酸/苏氨酸蛋白激酶(PKC)之间相互作用的最新发现的基础上。这两种蛋白在包括脑肿瘤在内的许多人类肿瘤中都高度表达，并且在其中几种恶性肿瘤中的高表达与化疗的快速进展和失败有关。在胶质瘤中，GSTP1的高表达及其核定位与患者的生存不良有关。同样，在恶性胶质瘤中经常观察到高PKC活性，并与胶质瘤的耐药性有关。最近，我们报道了GSTP1蛋白是迄今为止未被识别的PKC下游靶标，并经历了PKC的磷酸化，导致其代谢活性显著增强。我们的初步数据表明，这两条通路可以相互作用，增加胶质瘤细胞对抗癌药的耐药性。我们在这项应用中的目标是研究这些开创性发现的预后意义，并作为开发更有效的恶性胶质瘤治疗方法的基础。有待检验的假设是，丝氨酸/苏氨酸激酶的PKC家族对GSTP1蛋白的磷酸化将增强GSTP1蛋白代谢和灭活化疗药物的能力，并抑制下游的Jun N末端激酶信号，从而导致胶质瘤更具侵袭性和增加耐药性。我们推测，PKC抑制/下调，单独和/或与GSTP1下调联合使用，将具有显著的抗胶质瘤疗效，并增加胶质瘤对化疗的敏感性。这项拟议的研究将为研究胶质瘤中GSTP1和PKC之间的这种新发现的串扰所介导的细胞通路以及这种相互作用在胶质瘤中的肿瘤生长和治疗反应中所起的作用提供重要的见解。这一结果可能导致恶性胶质瘤的新的治疗策略，特别是那些以GSTP1高表达和PKC升高或高度激活为特征的肿瘤。恶性胶质瘤是最难治疗的肿瘤之一。在这一应用中，我们建议进行研究，以更好地表征两种新发现的蛋白质之间的相互作用，谷胱甘肽S转移酶P1(GSTP1)是一种主要的II相药物代谢和细胞信号蛋白，以及丝氨酸/苏氨酸蛋白激酶(PKC)，后者在其中磷酸化并增加前者的催化活性。这两种蛋白在恶性胶质瘤中高度表达，并与化疗的快速进展和失败有关。公共卫生相关性我们表征了PKC对GSTP1的磷酸化，并研究了该磷酸化的调节如何在体外和体内改变胶质瘤的药物敏感性。这一结果可能导致恶性胶质瘤的新的治疗策略，特别是那些以GSTP1高表达和PKC升高或高度激活为特征的肿瘤。

DESCRIPTION (provided by applicant): Current chemotherapy of malignant tumors of the central nervous system rarely results in significant long-term responses. Two major factors underlying this poor therapeutic outcome are the intrinsic resistance of brain tumors to chemotherapy and the poor selectivity and high toxicity of current treatments. The development of more tumor-specific therapies and therapeutic strategies for brain tumors, however, will require knowledge of the molecular mechanisms and abnormalities that drive the growth and therapeutic response of the tumors. This project is built on recent findings in our laboratory on the crosstalk between a major Phase II drug metabolizing and cell signaling protein, the glutathione S-transferase P1 (GSTP1) and the serine/threonine protein kinase, PKC. These two proteins are highly expressed in many human tumors, including, those of the brain and the high expression has been associated with rapid progression and failure of chemotherapy in several of these malignancies. In gliomas, high GSTP1 expression and its nuclear localization have been associated with poor patient survival. Similarly, high PKC activity is frequently observed in malignant gliomas and has been associated with glioma drug resistance. Recently, we reported that the GSTP1 protein is a, heretofore, unrecognized downstream target of PKC and undergoes phosphorylation by PKC, resulting in a significant enhancement of its metabolic activity. Our preliminary data suggest that these two pathways can function interactively to increase the resistance of glioma cells to anticancer agents. Our goal in this application is to investigate these seminal findings for their prognostic significance and as a basis for developing more effective therapy for malignant gliomas. The hypothesis to be tested is that phosphorylation of the GSTP1 protein by the PKC family of serine/threonine kinases, will enhance the ability of the GSTP1 protein to metabolize and inactivate chemotherapeutic agents and to inhibit downstream jun N-terminal kinase signaling, thus, leading to more aggressive growth and increased drug resistance of gliomas. We postulate that PKC inhibition/downregulation, alone and/or in combination with GSTP1 downregulation, will have significant antiglioma efficacy and increase glioma sensitivity to chemotherapy. The proposed research will provide important insights into the cellular pathways mediated by this newly identified crosstalk between GSTP1 and PKC in gliomas and the role that this interaction plays in tumor growth and therapeutic response in gliomas. The results are likely to lead to novel therapeutic strategies for malignant gliomas, particularly those characterized by high GSTP1 expression and elevated or highly activated PKCs. Malignant gliomas are among the most therapeutically intractable tumors. In this application, we propose research to better characterize a newly identified crosstalk between two proteins, glutathione S-transferase P1 (GSTP1) a major Phase II drug metabolizing and cell signaling protein, and the serine/threonine protein kinase, PKC, in which the latter phosphorylates and increases the catalytic activity of the former. Both proteins are highly expressed in malignant gliomas and are associated with rapid progression and failure of chemotherapy. PUBLIC HEALTH RELEVANCE We characterize the phosphorylation of GSTP1 by PKC and examine how the modulation of the phosphorylation alters the drug sensitivity of gliomas in vitro and in vivo. The results are likely to lead to novel therapeutic strategies for malignant gliomas, particularly; those characterized by high GSTP1 expression and elevated or highly activated PKCs.