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

细胞周期失调和Bcl-2家族蛋白在恶性肿瘤分子发病机制中的证据 多发性骨髓瘤（MM）引起了对细胞周期蛋白依赖性激酶（CDK）抑制剂和Bcl-2的强烈兴趣 这种疾病的拮抗剂。此外，最近的研究结果表明，某些CDK抑制剂（例如， flavopiridol; FP）通过抑制CDK9/细胞周期蛋白T pTEFB复合物， RNA Polll的羧基端结构域的磷酸化。这些代理下调 包括Mcl-1在内的短寿命蛋白的表达，Mcl-1是MM中的关键存活因子。 最近发现在人类白血病中， 通过从Bcl-xL和Mcl-1释放巴克，导致细胞凋亡的显著增强。值得注意的是， 最近开发了一种新的FP时间表，其在另一种B细胞中显示出显著的活性 恶性肿瘤（CLL）。因此，我们假设临床相关的CDK抑制剂，如FP，seliciclib（Rroscovitine）， 和SCH 727965，对CDK9具有1 nM的1050的试剂，代表逻辑候选物 增强临床相关Bcl-2拮抗剂活性的试剂（例如，GX 15 - 070，ABT-737）。 事实上，初步证据表明FP和GX 15070之间的高度协同作用，以及 其他CDKI/Bcl-2拮抗剂方案。证据还表明，这些方案诱导上调 促凋亡蛋白（例如，Bim、NOXA和BIK），其可能与Mcl-1下调协同作用 引发细胞凋亡在具体目标#1中，我们将使用遗传工具来测试假设， CDK抑制剂和Bcl-2拮抗剂之间的协同相互作用源于Mcl-1/XIAP下调， Bim、NOXA和BIK的上调，巴克和BIM从Bcl-xL和Mcl-1的释放，Bax/巴克 激活和诱导线粒体损伤。这些信息将指导选择相关的 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 这种策略克服传统耐药性、基质/细胞粘附或生长的机制是什么？ 因子介导的耐药性，以及硼替佐米或来那度胺耐药性。在具体目标#3中， 我们将通过比较其活性与原发性、患者源性 CDI38 * MM与其正常对应物（例如，CD138-，CD34 * 细胞），并测试其体内功效 使用侧腹和全身性异种移植MM模型。在具体目标#4中，我们将使用此信息作为 启动一项或多项CDKI I期试验的基础（例如，FP）和Bcl-2拮抗剂（例如，GX 15 - 070） 总的来说，这些研究将为一种新的治疗方法提供合理的基础。 MM治疗的方法，其中临床相关的Bcl-2拮抗剂（例如，GX 15 - 070或ABT- 737)通过与转录抑制性CDK抑制剂的合理组合， pTEFb复合物（例如，FP、seliciclib或SCH 727965）。

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.