Jerome Lipper Multiple Myeloma Disease Center, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA.
Oncogene. 2010 Apr 22;29(16):2325-36. doi: 10.1038/onc.2009.510. Epub 2010 Jan 25.
Dysregulated cell cycling is a universal hallmark of cancer and is often mediated by abnormal activation of cyclin-dependent kinases (CDKs) and their cyclin partners. Overexpression of individual complexes are reported in multiple myeloma (MM), making them attractive therapeutic targets. In this study, we investigate the preclinical activity of a novel small-molecule multi-CDK inhibitor, AT7519, in MM. We show the anti-MM activity of AT7519 displaying potent cytotoxicity and apoptosis; associated with in vivo tumor growth inhibition and prolonged survival. At the molecular level, AT7519 inhibited RNA polymerase II (RNA pol II) phosphorylation, a CDK9, 7 substrate, associated with decreased RNA synthesis confirmed by [(3)H] Uridine incorporation. In addition, AT7519 inhibited glycogen synthase kinase 3beta (GSK-3beta) phosphorylation; conversely pretreatment with a selective GSK-3 inhibitor and shRNA GSK-3beta knockdown restored MM survival, suggesting the involvement of GSK-3beta in AT7519-induced apoptosis. GSK-3beta activation was independent of RNA pol II dephosphorylation confirmed by alpha-amanitin, a specific RNA pol II inihibitor, showing potent inhibition of RNA pol II phosphorylation without corresponding effects on GSK-3beta phosphorylation. These results offer new insights into the crucial, yet controversial role of GSK-3beta in MM and show significant anti-MM activity of AT7519, providing the rationale for its clinical evaluation in MM.
细胞周期调控失常是癌症的普遍特征，通常是由细胞周期蛋白依赖性激酶（CDKs）及其细胞周期蛋白伴侣的异常激活介导的。多发性骨髓瘤（MM）中报道了多个复合物的过表达，这使其成为有吸引力的治疗靶点。在这项研究中，我们研究了新型小分子多 CDK 抑制剂 AT7519 在 MM 中的临床前活性。我们显示了 AT7519 的抗 MM 活性，表现出强大的细胞毒性和细胞凋亡；与体内肿瘤生长抑制和延长存活相关。在分子水平上，AT7519 抑制 RNA 聚合酶 II（RNA pol II）磷酸化，这是 CDK9、7 的底物，与减少 RNA 合成有关，这通过 [(3)H]尿嘧啶掺入得到证实。此外，AT7519 抑制糖原合酶激酶 3β（GSK-3β）磷酸化；相反，用选择性 GSK-3 抑制剂和 shRNA GSK-3β 敲低预处理恢复了 MM 的存活，这表明 GSK-3β 参与了 AT7519 诱导的细胞凋亡。GSK-3β 的激活不依赖于 RNA pol II 的去磷酸化，这通过特定的 RNA pol II 抑制剂 alpha-amanitin 得到证实，alpha-amanitin 对 RNA pol II 磷酸化具有强大的抑制作用，而对 GSK-3β 磷酸化没有相应的影响。这些结果为 GSK-3β 在 MM 中的关键但有争议的作用提供了新的见解，并显示了 AT7519 对 MM 的显著抗 MM 活性，为其在 MM 中的临床评估提供了依据。
