Duan Zhenfeng, Bradner James, Greenberg Edward, Mazitschek Ralph, Foster Rosemary, Mahoney Jennifer, Seiden Michael V
Department of Hematology/Oncology, Massachusetts General Hospital, 100 Blossom St. Jackson 1008, Boston, MA 02114, USA.
Mol Pharmacol. 2007 Nov;72(5):1137-45. doi: 10.1124/mol.107.038117. Epub 2007 Aug 3.
Interleukin 6 and the signal transducer and activator of transcription (STAT) 3 proteins have important roles in cancer cell survival and proliferation. Recent studies demonstrate that abnormal STAT3 activation promotes tumor growth and supports survival of many human cancers, and thus, this protein or the pathway responsible for its activation is a potential target for the new anticancer therapy. STAT3 is a DNA binding transcription factor, and therefore, its function depends on nuclear translocation. To discover inhibitors of the STAT3 pathway, we designed a cell-based screening assay capable of identifying small molecules that inhibit nuclear translocation. Among the 2000-compound National Cancer Institute Diversity set, we identified 8-benzyl-4-oxo-8-azabicyclo[3.2.1]oct-2-ene-6,7-dicarboxylic acid (SD-1008) as a micromolar inhibitor of interleukin-6 or oncostatin-induced STAT3 nuclear translocation. In addition, SD-1008 inhibits tyrosyl phosphorylation of STAT3, Janus kinase 2 (JAK2), and Src. SD-1008 also reduces STAT3-dependent luciferase activity. Biochemical studies with recombinant JAK2 proteins demonstrate that high concentrations of SD-1008 directly inhibit JAK2 kinase autophosphorylation. Exposure of various cell lines to SD-1008 decreases levels of the STAT3-dependent proteins, Bcl-X(L) and survivin, inducing apoptosis. SD-1008 also enhances apoptosis induced by paclitaxel in ovarian cancer cells. These results demonstrate that SD-1008 directly blocks the JAK-STAT3 signaling pathway in human cancer cells that express constitutively active Stat and add to the growing literature that identifies this pathway as a viable target for drug development. Finally, SD-1008 may be a suitable prototype for further chemical modification and exploration as a therapeutic agent.
白细胞介素6以及信号转导与转录激活因子（STAT）3蛋白在癌细胞的存活和增殖中发挥着重要作用。最近的研究表明，STAT3的异常激活促进肿瘤生长并维持多种人类癌症的存活，因此，这种蛋白或负责其激活的信号通路是新型抗癌疗法的潜在靶点。STAT3是一种DNA结合转录因子，因此，其功能依赖于核转位。为了发现STAT3信号通路的抑制剂，我们设计了一种基于细胞的筛选试验，能够识别抑制核转位的小分子。在2000种化合物的美国国立癌症研究所多样性化合物库中，我们鉴定出8-苄基-4-氧代-8-氮杂双环[3.2.1]辛-2-烯-6,7-二羧酸（SD-1008）是白细胞介素6或制瘤素诱导的STAT3核转位的微摩尔级抑制剂。此外，SD-1008抑制STAT3、Janus激酶2（JAK2）和Src的酪氨酸磷酸化。SD-1008还降低STAT3依赖性荧光素酶活性。对重组JAK2蛋白的生化研究表明，高浓度的SD-1008直接抑制JAK2激酶的自身磷酸化。将各种细胞系暴露于SD-1008会降低STAT3依赖性蛋白Bcl-X(L)和生存素的水平，从而诱导细胞凋亡。SD-1008还增强了紫杉醇诱导的卵巢癌细胞凋亡。这些结果表明，SD-1008直接阻断了在表达组成型活性Stat的人类癌细胞中的JAK-STAT3信号通路，并为越来越多将该信号通路确定为药物开发可行靶点的文献增添了内容。最后，SD-1008可能是作为治疗剂进行进一步化学修饰和探索的合适原型。
