Therapeutic targeting of HSP90-dependent signaling

描述（由申请人提供）：尽管最近发现了其他对卵巢癌具有活性的药物，包括吉西他滨、拓扑替康和脂质体阿霉素，但绝大多数III/IV期卵巢癌患者死于这种疾病。这一观察结果强调了需要改进方法来规避卵巢癌的耐药性。新出现的证据表明，许多导致卵巢癌发展的相同变化也可能导致耐药性。来自细胞表面受体HER 2/neu和胰岛素样生长因子受体（IGFR）的信号传导激活磷脂酰肌醇-3（PI 3）激酶/Akt通路（抑制细胞凋亡）和Ras/Raf/MEK/Erk通路（增强增殖）。此外，由复制应激和DNA损伤激活的检查点激酶信号传导在确定细胞是否将恢复稳态或经历凋亡中起关键作用。有趣的是，热休克蛋白90（HSP 90）伴侣复合物的持续活性对所有这些途径的稳定性和功能至关重要。该项目的核心假设是，HSP 90定向治疗将通过抑制增殖和存活信号来克服卵巢癌的化疗耐药性。我们的初步研究表明，17-烯丙基氨基-17-去甲氧基格尔德霉素（17-AAG）或格尔德霉素（GA）导致多种卵巢癌细胞中HER 2，IGFR和Akt的下调。另外的实验证明，17-AAG抑制检查点激酶1（Chk 1）的活化并增强吉西他滨在OVCAR-3细胞中的细胞毒性。最后，我们正在进行的I期研究已经证明，17-AAG在治疗上可达到的剂量下成功地靶向患者的HSP 90复合物，并且17-AAG可以在临床环境中与顺铂和吉西他滨组合。我们现在提出1）确定HSP 90如何参与卵巢癌细胞中吉西他滨触发的Chk 1信号传导; 2）评估17-AAG使各种卵巢癌细胞对吉西他滨、顺铂和拓扑替康敏感的程度，并确定敏感性的差异是否反映HSP 90伴侣蛋白复合物功能和/或HSP 90受体水平的变化; 3）评价17-AAG单用及联合吉西他滨或顺铂治疗卵巢癌患者的临床和生物学效果。总的来说，这些研究将提供关于改变卵巢癌细胞在体外和临床环境中对化疗药物的反应的能力的信息。

DESCRIPTION (provided by applicant): Despite the recent identification of additional drugs with activity in ovarian cancer, including gemcitabine, topotecan and liposomal doxorubicin, the vast majority of patients with stage Ill/IV ovarian cancer succumb to this disease. This observation highlights the need for improved methods to circumvent drug resistance in ovarian cancer. Emerging evidence suggests that many of the same changes that contribute to the development of ovarian cancer might also contribute to drug resistance. Signaling from the cell surface receptors HER2/neu and insulin-like growth factor receptor (IGFR) activates the phosphatidylinositol-3 (PI3) kinase/Akt pathway, which inhibits apoptosis, and the Ras/Raf/MEK/Erk pathway, which enhances proliferation. In addition, checkpoint kinase signaling that is activated by replication stress and DNA damage plays a critical role in determining whether cells will restore homeostasis or undergo apoptosis. Interestingly, the ongoing activity of the heat shock protein 90 (HSP90) chaperone complex is critical for the stability and function of components of all of these pathways. The central hypothesis underlying this project is that HSP90 directed therapy would overcome chemotherapy resistance in ovarian cancer through inhibition of proliferation and survival signaling. Our preliminary studies demonstrate that 17-allylamino-17- demethoxygeldanamycin (17-AAG) or geldanamycin (GA) causes downregulation of HER2, IGFR, and Akt in multiple ovarian cancer cells. Additional experiments demonstrate that 17-AAG inhibits the activation of checkpoint kinase 1 (Chk1) and enhances the cytotoxicity of gemcitabine in OVCAR-3 cells. Finally, our ongoing phase I study has demonstrated that 17-AAG successfully targets the HSP90 complex in patients at therapeutically achievable doses and that 17-AAG can be combined with cisplatin and gemcitabine in the clinical setting. We now propose to 1) to determine how HSP90 participates in gemcitabine-triggered Chk1 signaling in ovarian cancer cells; 2) assess the extent to which 17-AAG sensitizes various ovarian cancer cells to gemcitabine, cisplatin, and topotecan and determine whether differences in sensitization reflect variations in HSP90 chaperone complex function and/or levels of HSP90 clients; and 3) to evaluate the clinical and biologic effects of 17-AAG alone and when combined with gemcitabine or cisplatin in ovarian cancer patients. Collectively, these studies will provide information about the ability to alter the response of ovarian cancer cells to chemotherapeutic agents in vitro and in the clinical setting.