Dual Proteasome and MAPK Inhibition in Cancer Therapy

描述（由申请人提供）：泛素-蛋白酶体途径负责大部分细胞内蛋白质降解，并在有丝分裂和凋亡等基本细胞过程中发挥重要作用。我们过去的研究表明，蛋白酶体抑制剂在c-myc转化细胞中诱导优先凋亡，在体内模型中证明了它们的活性，并在I期试验中证明了它们的安全性和有效性，从而帮助建立了蛋白酶体作为治疗靶点。这些研究导致了II期多中心试验，证实了其中一种抑制剂硼替佐米（bortezomib）的活性，目前已被FDA批准用于临床。虽然这些抑制剂可能通过几种途径引发细胞凋亡，但我们最近的工作暗示了通过诱导MKP磷酸酶抑制p44/42 MAPK的重要作用。初步证据表明，MKP-1的诱导部分是通过p38 MAPK发生的，并且MKP-1也可能通过降低JNK活性来抗凋亡，因为p38抑制剂降低了MKP的表达，增强了凋亡和磷酸化JNK的水平。为了扩展这些发现，我们建议：1。研究p38 MAPK和MKP-1在蛋白酶体抑制剂介导的细胞凋亡中的作用。药理学p38抑制剂将与突变体p38和MKP-1构建体、p38和MKP敲除细胞以及异种移植物一起使用，以检验p38激活和MKP表达是重要抗凋亡因素的假设；2. 评估下游p44/42指标p90RSK和Bad的参与情况。药理学MEK抑制剂，以及突变体p90RSK和Bad构建体，将用于验证p90和Bad是蛋白酶体抑制剂的主要促凋亡靶点，以及p44/42通路抑制促进细胞凋亡的假设；和3。确定双重MAPK阻断与蛋白酶体抑制的可能性。由于p38和MKP抑制可增强p44/42活性，而我们已经证明p44/42具有抗凋亡作用，我们推测阻断这两种途径可能会进一步增强蛋白酶体抑制的抗肿瘤作用。综上所述，这些研究将进一步阐明蛋白酶体抑制剂诱导细胞凋亡的一些机制，确定可能增加其疗效的药物，并通过体内模型评估这些方案。由于p38和MEK抑制剂目前正处于临床开发阶段，这项工作将为新的、合理的基于蛋白酶体抑制剂的联合治疗方案建立框架，这些方案具有增强抗肿瘤疗效的潜力

DESCRIPTION (provided by applicant): The ubiquitin-proteasome pathway is responsible for the majority of intracellular protein degradation, and plays an essential role in fundamental cellular processes such as mitosis and apoptosis. Our past efforts helped establish the proteasome as a therapeutic target by showing that inhibitors induce preferential apoptosis in c-myc-transformed cells, demonstrating their activity in in vivo models, and documenting their safety and efficacy in Phase I trials. These studies led to Phase II multicenter trials that confirmed the activity of one such inhibitor, bortezomib, which has now been approved by the FDA for clinical use. While these inhibitors likely trigger apoptosis through several pathways, our recent work implicates an important role for inhibition of p44/42 MAPK by induction of MKP phosphatases. Preliminary evidence suggests MKP-1 induction occurs in part through p38 MAPK, and that MKP-1 may also be anti-apoptotic by decreasing JNK activity, since p38 inhibitors decrease MKP expression, and enhance apoptosis and phospho-JNK levels. To expand upon these findings, we propose to: 1. Study the role of p38 MAPK, and of MKP-1 in proteasome inhibitor-mediated apoptosis. Pharmacologic p38 inhibitors will be used in conjunction with mutant p38 and MKP-1 constructs, p38- and MKP-knockout cells, as well as xenografts, to test the hypotheses that p38 activation and MKP expression are important anti-apoptotic elements; 2. Evaluate the involvement of the downstream p44/42 targets p90RSK and Bad. Pharmacologic MEK inhibitors, as well as mutant p90RSK and Bad constructs, will be used to test the hypotheses that p90 and Bad are major pro-apoptotic targets of proteasome inhibitors, and that p44/42 pathway inhibition enhances apoptosis; and 3. Determine the potential of dual MAPK blockade with proteasome inhibition. Since p38 and MKP inhibition enhances p44/42 activity, which we have shown is anti-apoptotic, we suspect that blockade of both pathways together should further enhance the anti-tumor efficacy of proteasome inhibition. Taken together, these studies will further clarify some of the mechanisms by which proteasome inhibitors induce apoptosis, identify agents that may increase their efficacy, and evaluate these regimens with in vivo models. Since p38 and MEK inhibitors are currently undergoing clinical development, this work will establish the framework for translation of novel, rational proteasome inhibitor-based combination regimens with the potential for enhanced anti-tumor efficacy into the clinical arena.