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的降解，并在基本的细胞过程中发挥重要作用，如有丝分裂和凋亡。我们过去的工作通过显示抑制剂诱导c-myc转化细胞的优先凋亡，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，帮助建立了蛋白酶体作为治疗靶点。这些研究导致了第二阶段多中心试验，证实了一种这样的抑制剂Bortezomib的活性，该药现在已被FDA批准用于临床。虽然这些抑制物可能通过几条途径触发细胞凋亡，但我们最近的工作表明，通过诱导MKP磷酸酶来抑制p44/42 MAPK具有重要作用。初步证据表明，MKP-1的诱导部分是通过p38MAPK发生的，而且MKP-1也可能通过降低JNK活性来抗凋亡，因为p38抑制剂减少了MKP的表达，并增强了细胞凋亡和磷酸化JNK的水平。为了扩大这些发现，我们建议：1.研究p38MAPK和MKP-1在蛋白酶体抑制物介导的细胞凋亡中的作用。药理学p38抑制剂将与突变型p38和MKP-1构建体、p38和MKP敲除细胞以及异种移植一起使用，以验证p38激活和MKP表达是重要的抗凋亡元件的假设；2.评估下游p44/42靶标p90RSK和Bad的参与。药理学的MEK抑制剂，以及突变的p90RSK和Bad结构，将被用来检验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；以及3.确定双重MAPK阻断与蛋白酶体抑制的可能性。由于p38和MKP抑制增强了p44/42的活性，我们已经证明p44/42是抗凋亡的，我们推测共同阻断这两个途径应该会进一步增强蛋白酶体抑制的抗肿瘤效果。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，识别可能提高其疗效的药物，并用体内模型评估这些方案。由于p38和mek抑制剂目前正在进行临床开发，这项工作将建立新的、合理的基于蛋白酶体抑制剂的联合方案的框架，具有增强抗肿瘤疗效的潜力。 临床领域。

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.