Sensitivity Multiple Myeloma Cells to mTOR Inhibitors

描述(由申请人提供)：本提案的长期目标是改善多发性骨髓瘤患者的医疗管理。我们以前的研究表明，以雷帕霉素或CCI-779为靶点的哺乳动物雷帕霉素(MTOR)在这种恶性肿瘤中具有巨大的治疗潜力，AKT活性的水平决定了对mTOR抑制剂的敏感性：当AKT活性增强时，骨髓瘤细胞对G1期停滞高度敏感，而AKT活性降低会诱导相对耐药。抑制mTOR通常会抑制关键细胞周期蛋白的帽子依赖的翻译和表达。与这一观点一致的是，mTOR抑制剂在敏感的骨髓瘤细胞中诱导抑制细胞周期蛋白-D和c-myc的翻译，而在耐药细胞中的翻译不受影响。这些发现提出了以下假设：具有高AKT活性的骨髓瘤细胞对mTOR抑制剂抑制D-Cyclin和myc表达的能力高度敏感，从而解释了它们对G1期停滞的敏感性。此外，我们假设AKT通过瘫痪Cyclin/myc帽非依赖性翻译的挽救途径来调节这一反应，并且这种AKT依赖的功能是由Cyclin/myc RNA中的内部核糖体进入位点(IRESes)和p38Mark途径介导的。为了验证这些假设，我们的具体目标包括： 测试AKT依赖的对mTOR抑制剂敏感性的调节是否可以通过对D型细胞周期蛋白和/或c-myc表达的不同影响来解释。 II.检测AKT对细胞周期蛋白/myc表达的调节是否通过影响翻译效率来实现。 确定IRES相关反式作用因子(ITAFs)的变化，以解释AKT对大小写非依赖性翻译的调控。 这些研究将在骨髓瘤细胞系以及原发患者的骨髓标本中进行

DESCRIPTION (provided by applicant): The long term objective of this proposal is to improve medical management of patients with multiple myeloma. Our prior studies demonstrated that targeting the mammalian target of rapamycin (mTOR) with rapamycin or CCI-779 has great therapeutic potential in this malignancy and that the level of AKT activity determines sensitivity to mTOR inhibitors: When AKT activity is heightened, myeloma cells are hypersensitive to G1 arrest, while lowered AKT activity induces relative resistance. Inhibition of mTOR often inhibits cap-dependent translation and expression of critical cell cycle proteins. Consistent with this notion is the fact that mTOR inhibitors induced inhibition of cyclin-D and c-myc translation in sensitive myeloma cells while translation was unaffected in resistant cells. These findings have prompted the following hypothesis: Myeloma cells with high AKT activity are hypersensitive to the ability of mTOR inhibitors to depress D-cyclin and myc expression, thus explaining their sensitivity to G1 arrest. Furthermore, we hypothesize that AKT regulates this response by paralyzing the salvage pathway of cyclin/myc cap-independent translation and that this AKT-dependent function is mediated by function of internal ribosome entry sites (IRESes) in cyclin/myc RNA and the p38 MARK pathway. To test these hypotheses, our specific aims include: I. To test if the AKT-dependent regulation of sensitivity to mTOR inhibitors is explained by differential effects on expression of D-type cyclins and/or c-myc. II. To test if AKT's regulation of cyclin/myc expression is mediated by effects on translational efficiency. III. To identify alterations in IRES-associated trans-acting factors (ITAFs) that may explain AKTregulation of cap-independent translation. These studies will performed in myeloma cell lines as well as primary patient marrow specimens