Antonietti Patrick, Linder Benedikt, Hehlgans Stephanie, Mildenberger Iris C, Burger Michael C, Fulda Simone, Steinbach Joachim P, Gessler Florian, Rödel Franz, Mittelbronn Michel, Kögel Donat
Experimental Neurosurgery, Goethe University Hospital, Frankfurt am Main, Germany.
Radiotherapy and Oncology, Goethe University Hospital, Frankfurt am Main, Germany.
Mol Cancer Ther. 2017 Jan;16(1):156-168. doi: 10.1158/1535-7163.MCT-16-0262. Epub 2016 Oct 24.
Malignant gliomas exhibit a high intrinsic resistance against stimuli triggering apoptotic cell death. HSF1 acts as transcription factor upstream of HSP70 and the HSP70 co-chaperone BAG3 that is overexpressed in glioblastoma. To specifically target this resistance mechanism, we applied the selective HSF1 inhibitor KRIBB11 and the HSP70/BAG3 interaction inhibitor YM-1 in combination with the pan-Bcl-2 inhibitor AT-101. Here, we demonstrate that lentiviral BAG3 silencing significantly enhances AT-101-induced cell death and reactivates effector caspase-mediated apoptosis in U251 glioma cells with high BAG3 expression, whereas these sensitizing effects were less pronounced in U343 cells expressing lower BAG3 levels. KRIBB11 decreased protein levels of HSP70, BAG3, and the antiapoptotic Bcl-2 protein Mcl-1, and both KRIBB11 and YM-1 elicited significantly increased mitochondrial dysfunction, effector caspase activity, and apoptotic cell death after combined treatment with AT-101 and ABT-737. Depletion of BAG3 also led to a pronounced loss of cell-matrix adhesion, FAK phosphorylation, and in vivo tumor growth in an orthotopic mouse glioma model. Furthermore, it reduced the plating efficiency of U251 cells in three-dimensional clonogenic assays and limited clonogenic survival after short-term treatment with AT-101. Collectively, our data suggest that the HSF1/HSP70/BAG3 pathway plays a pivotal role for overexpression of prosurvival Bcl-2 proteins and cell death resistance of glioma. They also support the hypothesis that interference with BAG3 function is an effective novel approach to prime glioma cells to anoikis. Mol Cancer Ther; 16(1); 156-68. ©2016 AACR.
恶性胶质瘤对触发凋亡性细胞死亡的刺激表现出高度的内在抗性。热休克因子1（HSF1）作为热休克蛋白70（HSP70）上游的转录因子，而HSP70共伴侣BAG3在胶质母细胞瘤中过表达。为了特异性靶向这种抗性机制，我们将选择性HSF1抑制剂KRIBB11和HSP70/BAG3相互作用抑制剂YM-1与泛Bcl-2抑制剂AT-101联合应用。在此，我们证明慢病毒介导的BAG3沉默显著增强了AT-101诱导的细胞死亡，并在高表达BAG3的U251胶质瘤细胞中重新激活了效应半胱天冬酶介导的凋亡，而在表达较低BAG3水平的U343细胞中，这些致敏作用不太明显。KRIBB11降低了HSP70、BAG3和抗凋亡Bcl-2蛋白Mcl-1的蛋白水平，并且在与AT-101和ABT-737联合治疗后，KRIBB11和YM-1均引发了显著增加的线粒体功能障碍、效应半胱天冬酶活性和凋亡性细胞死亡。在原位小鼠胶质瘤模型中，BAG3缺失还导致细胞-基质粘附、粘着斑激酶（FAK）磷酸化和体内肿瘤生长的显著丧失。此外，它降低了U251细胞在三维克隆形成试验中的接种效率，并限制了用AT-101短期处理后的克隆存活。总体而言，我们的数据表明HSF1/HSP70/BAG3通路在促生存Bcl-2蛋白的过表达和胶质瘤的细胞死亡抗性中起关键作用。它们还支持这样的假设，即干扰BAG3功能是使胶质瘤细胞对失巢凋亡敏感的一种有效的新方法。《分子癌症治疗》；16(1)；156 - 168。©2016美国癌症研究协会。
