Flavopiridol as a Potential Therapy in Multiple Myeloma

描述（由申请人提供）：多发性骨髓瘤是浆细胞的克隆性恶性肿瘤，在美国每年导致超过11，000例死亡。包括自体干细胞移植在内的治疗可以提高生存率，然而，骨髓瘤患者的平均预期寿命仅为3至5年。虽然没有单一的分子缺陷已被确定为疾病的特异性，相当多的证据表明白细胞介素-6/JAK/STAT途径的激活作为骨髓瘤的一个重要的潜在治疗靶点。我们最近发现，flavopiridol，一种小分子CDK抑制剂，在体外临床试验中，1）与DNA结合的解离常数与其他DNA导向的CDK抑制剂相似，2）在三种模型系统中破坏STAT-3/DNA的体外相互作用，和3）在体外转录水平和体内蛋白水平下调STAT-3下游的抗凋亡蛋白（例如Mcl-1）。初步证据还表明，flavopiridol可能是特别的细胞毒性在体外骨髓瘤细胞已经失去了对外源性IL-6刺激的依赖。因此，我们假设flavopiridol诱导的STAT-3/DNA相互作用的破坏可能是重要的flavopiridol诱导的细胞毒性和flavopiridol可能代表多发性骨髓瘤的靶向治疗。我们现在建议在初步研究的基础上：1.检查flavopiridol对体内骨髓瘤细胞中所选细胞多肽水平的影响，并评估离体flavopiridol敏感性和/或基线骨髓瘤细胞多肽水平的能力，以结合我们的CTEP批准的flavopiridol在骨髓瘤中的2期临床试验预测患者反应，2.检查flavopiridol对转录和对转录因子/DNA相互作用的影响，并使用mye/oma细胞系评估IL-6独立性和/或内源性上调STAT-3信号传导可能与flavopiridol敏感性增加相关的假设，和3.使用以STAT-3信号级联的选定组分的强制改变为特征的骨髓瘤细胞，评价STAT-3信号对flavopiridol诱导的细胞毒性的重要性。拟议研究的结果将提高对flavopiridol在骨髓瘤细胞中的作用和作用机制的理解，从而可能有助于该药物的进一步临床开发。

DESCRIPTION (provided by applicant): Multiple myeloma is a clonal malignancy of plasma cells that results in over 11,000 deaths in the United States annually. Therapies, including autologous stem cell transplantation, can improve survival, however, average life expectancy among patients with myeloma is only about 3 to 5 years. Although no single molecular defect has been identified as pathognomonic of the disease, considerable evidence implicates activation of the interleukin-6/JAK/STAT pathway as an important potential therapeutic target in myeloma. We have recently found that flavopiridol, a small molecule CDK inhibitor in antineoplastic clinical trials, 1) binds to DNA with a dissociation constant similar to that of other DNA-directed antineoplastic agents, 2) disrupts STAT-3/DNA interactions in vitro in three model systems, and 3) down regulates antiapoptotic proteins (e.g. Mcl-1) downstream of STAT-3 at the transcriptional level in vitro and at the protein level in vivo. Preliminary evidence also suggests that flavopiridol may be especially cytotoxic in vitro to myeloma cells that have lost dependence upon exogenous IL-6 stimulation. We therefore hypothesize that flavopiridol-induced disruption of STAT-3/DNA interactions may be important in flavopiridol-induced cytotoxicity and that flavopiridol may represent a target-directed therapy in multiple myeloma. We now propose to build on our preliminary studies and: 1. Examine the effects of flavopiridol on levels of selected cellular polypeptides in myeloma cells in vivo, and evaluate the ability of ex vivo flavopiridol sensitivity, and/or baseline myeloma cell polypeptide levels, to predict patient response in conjunction with our CTEP-approved Phase 2 clinical trial of flavopiridol in myeloma, 2. Examine the effects of flavopiridol on transcription and on transcription factor/DNA interactions, and evaluate the hypothesis that IL-6 independence and/or endogenously up regulated STAT-3 signaling may be associated with increased flavopiridol sensitivity using mye/oma cell lines, and 3. Evaluate the importance of STAT-3 signaling on flavopiridol-induced cytotoxicity using myeloma cells characterized by forced alterations of selected components of the STAT-3 signaling cascade. Results of proposed studies will improve understanding of the effects and mechanism(s) of action of flavopiridol in myeloma cells, thereby potentially contributing to the further clinical development of the drug.