P4 -TARGETING MULTIPLE MYELOMA BY COMBINING CDK INHIBITORS AND BCL-2 ANTAGONISTS

细胞周期调控异常与Bcl2家族蛋白在卵巢癌分子发病机制中的联系 多发性骨髓瘤(MM)引起了人们对细胞周期蛋白依赖性激酶(CDK)抑制剂和Bcl2的浓厚兴趣 治疗这种疾病的拮抗剂。此外，最近的发现表明，某些CDK抑制剂(例如， Fp)通过抑制CDK9/细胞周期蛋白T pTEFB复合体作为转录抑制因子，并通过 RNA Polll的羧基末端结构域的延伸、磷酸化。这类药物下调了 包括MM的关键生存因子Mcl-1在内的短寿命蛋白的表达 最近发现可以增强人类白血病中Bcl2拮抗剂(例如ABT-737)的杀伤力 通过从Bclxl和Mcl-1释放Bak，导致细胞凋亡的戏剧性增强。值得注意的是，一个 最近开发了一种新的FP程序，它在另一个B细胞中显示了显著的活动 恶性肿瘤(CLL)。因此，我们假设临床上相关的CDK抑制剂，如FP，Seliclib(罗斯科维汀)， 而SCH727965是一种对CDK9的1050为1 nM的试剂，代表逻辑候选 增强临床相关的Bcl2拮抗剂(如GX15-070，ABT-737)对MM的活性的药物。 事实上，初步证据表明，FP和GX15070之间以及 其他CDKI/Bcl2拮抗剂方案，用于MM细胞。有证据还表明，这样的治疗方案会导致基因上调。 促凋亡蛋白(例如，Bim、noxa和BIK)可能与Mcl-1下调协同作用 来触发细胞凋亡。在特定的目标#1中，我们将使用遗传工具来检验假设 CDK抑制剂和Bcl2拮抗剂之间的协同作用源于Mcl-1/XIAP下调， Bim、Noxa和BIK上调，Bak和Bim从Bclxl和Mcl-1释放，Bax/Bak 激活，并诱导线粒体损伤。这些信息将指导相关产品的选择 在随后计划的临床试验中进行实验室研究。在具体目标2中，我们将确定是否和到 这种策略克服传统耐药、基质/细胞黏附或生长的机制是什么(S) 因子介导的耐药性，以及MM细胞对硼替佐米或来那度胺的耐药性。在具体目标3中， 我们将通过将该策略的活性与患者衍生的原始策略进行比较来评估其选择性 CDI38*MM与其正常对应细胞(如CDI38“、CD34*细胞)的比较，并测试其体内疗效 采用侧翼和全身异种移植MM模型。在具体目标4中，我们将使用这些信息作为 启动CDKI(如FP)和Bcl2拮抗剂(如GX15-070)的一个或多个I期试验的基础 在难治性MM患者中，这些研究将为一种新的 临床相关的Bcl2拮抗剂(如GX15-070或ABT-2)治疗MM的探讨 737)通过与转录抑制的CDK抑制剂的合理结合来增强 难治性MM患者的pTEFb复合体(如FP、Seliclib或SCH727965)。

Evidence linking dysregulation of cell cycle and Bcl-2 family proteins in the molecular pathogenesis of multiple myeloma (MM) has prompted intense interest in cyclin-dependent kinase (CDK) inhibitors and Bcl-2 antagonists in this disease. Furthermore, recent findings suggest that certain CDK inhibitors (e.g., flavopiridol; FP) act as transcriptional repressors by inhibiting the CDK9/cyclinT pTEFB complex, and by extension, phosphorylation ofthe carboxy-terminal domain of RNA Polll. Such agents down-regulate expression of short-lived proteins including Mcl-1, a critical survival factor in MM. Significantly, CDK inhibitors have recently been found to enhance the lethality of Bcl-2 antagonists (e.g. ABT-737) in human leukemia cells by unleashing Bak from Bcl-xL and Mcl-1, leading to a dramatic potentiation of apoptosis. Notably, a novel FP schedule has recently been developed which displays significant activity in another B-cell malignancy (CLL). We therefore hypothesize that clinically relevant CDK inhibitors such as FP, seliciclib (Rroscovitine), and SCH727965, an agent with an 1050 of 1 nM toward CDK9, represent logical candidate agents to enhance the activity of clinically relevant Bcl-2 antagonists (e.g., GX15-070, ABT-737) in MM. Indeed, preliminary evidence suggests a high degree of synergism between FP and GX15070, as well as other CDKI/Bcl-2 antagonist regimens, in MM cells. Evidence also suggests that such regimens induce upregulation of pro-apoptotic proteins (e.g., Bim, NOXA, and BIK) which may cooperate with Mcl-1 downregulation to trigger apoptosis. In specific aim #1, we will employ genetic tools to test the hypothesis that synergistic interactions between CDK inhibitors and Bcl-2 antagonists stem from Mcl-1/XIAP downregulation, upregulation of Bim, NOXA, and BIK, release of Bak and BIM from both Bcl-xL and Mcl-1, Bax/Bak activation, and induction of mitochondrial injury. This information will guide the selection of correlative laboratory studies in subsequent planned clinical trials. In Specific Aim #2, we will determine whether and by what mechanism(s) this strategy overcomes conventional drug resistance, stromal/cell adhesion- or growth factor-mediated drug resistance, and bortezomib or lenalidomide resistance in MM cells. In specific aim #3, we will evaluate the selectivity of this strategy by comparing its activity against primary, patient-derived CDI38* MM versus their normal counterparts (e.g., CDI38", CD34* cells), and testing its in vivo efficacy using flank and systemic xenograft MM models. In Specific Aim #4, we will use this information as a foundation for initiating one or more Phase I trials of CDKIs (e.g., FP) and Bcl-2 antagonists (e.g., GX15-070) in patients with refractory MM. Collectively, these studies will provide a rational foundation for a novel approach to MM therapy in which the activity of clinically relevant Bcl-2 antagonists (e.g., GX15-070 or ABT- 737) is enhanced through rational combination with transcriptionally repressive CDK inhibitors that disrupt the pTEFb complex (e.g., FP, seliciclib, or SCH727965) in patients with refractory MM.