A protein-complex as a novel therapeutic target for K-Ras dependent colon cancer

描述（由申请人提供）： 恶性表型由一组协调的蛋白质驱动，靶向一组功能相互依赖的分子对于治疗干预应该更有效。这对于Ras依赖性癌症尤其如此，因为Ras癌蛋白是不可药物化的，并且靶向其与关键伴侣蛋白的相互作用对于治疗开发可能是必不可少的。K-Ras在高达50%的结肠癌中发生突变，并与恶性发展和进展有关。因此，迫切需要开发针对K-Ras突变（MT-K-Ras）结肠癌的靶向疗法。该提议将验证以下假设：p38 g活化的MT-K-Ras和热休克蛋白90（Hsp 90）三元复合物是K-Ras依赖性结肠癌的新治疗靶点。我们的初步研究表明，p38 g丝裂原活化蛋白激酶（MAPK），一个既定的Ras效应，结合Hsp 90，伴侣，和MT-K-Ras，但不野生型（WT）K-Ras，在结肠癌细胞中的支持这一假设。此外，p38 g磷酸化Hsp 90，p38 g或Hsp 90的药理学抑制剂破坏三元复合物，降低MT-K-Ras蛋白表达水平，并在体外和/或体内选择性抑制K-Ras依赖性生长。总之，这些结果表明p38 g活化的具有Hsp 90和MT-K-Ras的三元复合物是K-Ras依赖性结肠癌的潜在治疗靶标。以下具体目的将检验这一假设：1）证明p38 g和Hsp 90形成三元蛋白复合物，保护MT-K-Ras免受蛋白酶体依赖性降解; 2）证明p38 g是否通过诱导Hsp 90在S595处的磷酸化激活Hsp 90，以及该事件是否是MT-K-Ras/p38 g/Hsp 90复合物形成的中心; 3）探讨p38 g/Hsp 90/K-Ras复合物对结肠癌的治疗作用及临床意义。这些研究将证明p38 g激活的三元复合物是MT-K-Ras结肠癌的新的治疗靶点。用p38 g和Hsp 90的药理学抑制剂破坏这种复合物是治疗K-Ras依赖性结肠癌的非常有前途的治疗策略。由于结肠癌是美国癌症相关死亡的第二大原因，因此发现K-Ras依赖性结肠癌的新型靶向治疗方法将直接有助于退伍军人的健康护理。

DESCRIPTION (provided by applicant): Malignant phenotypes are driven by a group of coordinated proteins and targeting a cluster of functionally interdependent molecules should be more effective for therapeutic intervention. This is especially true for Ras- dependent cancers, as the Ras oncoprotein is non-druggable and targeting its interaction with key partner proteins may be essential for therapeutic development. K-Ras is mutated in up to 50% of colon cancers, and has been implicated in malignant development and progression. There is thus an urgent need to develop targeted therapies for K-Ras mutated (MT-K-Ras) colon cancer. This proposal will test the hypothesis that a p38g-activated ternary complex with MT-K-Ras and heat shock protein 90 (Hsp90) is a novel therapeutic target for K-Ras dependent colon cancer. This hypothesis is supported by our preliminary studies showing that p38g mitogen-activated protein kinase (MAPK), an established Ras effector, binds Hsp90, a chaperone, and MT-K-Ras, but not wild-type (WT) K-Ras, in colon cancer cells. Moreover, p38g phosphorylates Hsp90, and pharmacological inhibitors of p38g or Hsp90 disrupt the ternary complex, decrease MT-K-Ras levels of protein expression, and selectively inhibit K-Ras dependent growth in vitro and/or in vivo. Together, these results indicate that the p38g activated ternary complex with Hsp90 and MT-K-Ras is a potential therapeutic target for K-Ras dependent colon cancer. The following specific aims will test this hypothesis: 1) To demonstrate that p38g and Hsp90 form a ternary protein complex that protects MT-K-Ras from proteasome- dependent degradation; 2) To demonstrate if p38g activates Hsp90 by inducing its phosphorylation at S595 and whether this event is central to the formation of the MT-K-Ras/p38g/Hsp90 complex; and 3) To demonstrate the therapeutic potential and clinical significance of the p38g/Hsp90/K-Ras complex in colon cancer. These studies will demonstrate that the p38g-activated ternary-complex is a novel therapeutic target for MT-K-Ras colon cancer. Disruption of this complex with pharmacological inhibitors of p38g and Hsp90 is a highly promising therapeutic strategy for the treatment of K-Ras dependent colon cancer. Since colon cancer is the second leading cause of cancer-related death in the United States, discovery of novel targeted therapeutics for K-Ras dependent colon cancer will directly contribute to veteran's health care.