Protein Kinase C and GSTP1 interactions in glioma drug resistance

描述（由申请人提供）：目前中枢神经系统恶性肿瘤的化疗很少导致显著的长期反应。导致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抗性以及当前治疗的低选择性和高毒性。然而，开发更多的肿瘤特异性疗法和脑肿瘤的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。该项目是建立在我们实验室最近发现的一个主要的II期药物代谢和细胞信号蛋白，谷胱甘肽S-转移酶P1（GSTP 1）和丝氨酸/苏氨酸蛋白激酶，PKC之间的串扰。这两种蛋白质在许多人类肿瘤中高度表达，包括脑肿瘤，并且高表达与这些恶性肿瘤中的几种中的快速进展和化疗失败相关。在神经胶质瘤中，GST 1高表达及其核定位与患者生存率低相关。类似地，在恶性胶质瘤中经常观察到高PKC活性，并且与胶质瘤耐药性相关。最近，我们报道了GST P1蛋白是迄今为止未被认识到的PKC下游靶点，并通过PKC进行磷酸化，导致其代谢活性显著增强。我们的初步数据表明，这两个途径可以相互作用，以增加胶质瘤细胞的抗癌药物的耐药性。我们的目标是在这个应用程序中，调查这些开创性的结果，其预后意义，并作为基础，开发更有效的治疗恶性胶质瘤。待测试的假设是，通过丝氨酸/苏氨酸激酶的PKC家族对GST 1蛋白的磷酸化将增强GST 1蛋白代谢和抑制化疗剂的能力，并抑制下游jun N-末端激酶信号传导，从而导致神经胶质瘤的更具侵袭性的生长和增加的耐药性。我们推测，PKC抑制/下调，单独和/或与GSTP 1下调，将有显着的抗胶质瘤疗效，并增加胶质瘤化疗的敏感性。拟议的研究将提供重要的见解，这种新发现的GSTP 1和PKC之间的串扰介导的神经胶质瘤的细胞途径，这种相互作用在肿瘤生长和治疗反应中发挥的作用。这些结果可能会导致恶性胶质瘤的新的治疗策略，特别是那些以高GSTP 1表达和升高或高度活化的PKC为特征的恶性胶质瘤。恶性胶质瘤是治疗上最难治的肿瘤之一。在这个应用程序中，我们提出的研究，以更好地表征一个新发现的串扰之间的两种蛋白质，谷胱甘肽S-转移酶P1（GSTP 1）的一个主要的第二阶段药物代谢和细胞信号蛋白，和丝氨酸/苏氨酸蛋白激酶，PKC，其中后者磷酸化，并增加了前者的催化活性。这两种蛋白质在恶性胶质瘤中高度表达，并且与快速进展和化疗失败相关。公共卫生相关性我们通过PKC表征GST 1的磷酸化，并研究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。这些结果可能会导致恶性胶质瘤的新的治疗策略，特别是那些以高GSTP 1表达和升高或高度活化的PKC为特征的恶性胶质瘤。

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.