Pareja Fresia, Macleod David, Shu Chang, Crary John F, Canoll Peter D, Ross Alonzo H, Siegelin Markus D
Authors' Affiliations: Department of Pathology & Cell Biology, Columbia University Medical Center, New York, New York; and.
Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts.
Mol Cancer Res. 2014 Jul;12(7):987-1001. doi: 10.1158/1541-7786.MCR-13-0650. Epub 2014 Apr 22.
Glioblastoma multiforme (GBM) is a highly malignant human brain neoplasm with limited therapeutic options. GBMs display a deregulated apoptotic pathway with high levels of the antiapoptotic Bcl-2 family of proteins and overt activity of the phosphatidylinositol 3-kinase (PI3K) signaling pathway. Therefore, combined interference of the PI3K pathway and the Bcl-2 family of proteins is a reasonable therapeutic strategy. ABT-263 (Navitoclax), an orally available small-molecule Bcl-2 inhibitor, and GDC-0941, a PI3K inhibitor, were used to treat established glioblastoma and glioblastoma neurosphere cells, alone or in combination. Although GDC-0941 alone had a modest effect on cell viability, treatment with ABT-263 displayed a marked reduction of cell viability and induction of apoptotic cell death. Moreover, combinatorial therapy using ABT-263 and GDC-0941 showed an enhanced effect, with a further decrease in cellular viability. Furthermore, combination treatment abrogated the ability of stem cell-like glioma cells to form neurospheres. ABT-263 and GDC-0941, in combination, resulted in a consistent and significant increase of Annexin V positive cells and loss of mitochondrial membrane potential compared with either monotherapy. The combination treatment led to enhanced cleavage of both initiator and effector caspases. Mechanistically, GDC-0941 depleted pAKT (Serine 473) levels and suppressed Mcl-1 protein levels, lowering the threshold for the cytotoxic actions of ABT-263. GDC-0941 decreased Mcl-1 in a posttranslational manner and significantly decreased the half-life of Mcl-1 protein. Ectopic expression of human Mcl-1 mitigated apoptotic cell death induced by the drug combination. Furthermore, GDC-0941 modulated the phosphorylation status of BAD, thereby further enhancing ABT-263-mediated cell death.
Combination therapy with ABT-263 and GDC-0941 has novel therapeutic potential by specifically targeting aberrantly active, deregulated pathways in GBM, overcoming endogenous resistance to apoptosis.
多形性胶质母细胞瘤（GBM）是一种高度恶性的人脑肿瘤，治疗选择有限。GBM表现出凋亡途径失调，抗凋亡Bcl-2家族蛋白水平高，磷脂酰肌醇3-激酶（PI3K）信号通路活性明显。因此，联合干扰PI3K途径和Bcl-2家族蛋白是一种合理的治疗策略。ABT-263（纳维托克）是一种口服可用的小分子Bcl-2抑制剂，GDC-0941是一种PI3K抑制剂，单独或联合用于治疗已建立的胶质母细胞瘤和胶质母细胞瘤神经球细胞。虽然单独使用GDC-0941对细胞活力有适度影响，但用ABT-263治疗显示细胞活力显著降低并诱导凋亡性细胞死亡。此外，使用ABT-263和GDC-0941的联合疗法显示出增强的效果，细胞活力进一步降低。此外，联合治疗消除了干细胞样胶质瘤细胞形成神经球的能力。与单一疗法相比，ABT-263和GDC-0941联合使用导致膜联蛋白V阳性细胞持续显著增加，线粒体膜电位丧失。联合治疗导致起始和效应半胱天冬酶的切割增强。从机制上讲，GDC-0941降低了pAKT（丝氨酸473）水平并抑制了Mcl-1蛋白水平，降低了ABT-263细胞毒性作用的阈值。GDC-0941以翻译后方式降低Mcl-1，并显著降低Mcl-1蛋白的半衰期。人Mcl-1的异位表达减轻了药物联合诱导的凋亡性细胞死亡。此外，GDC-0941调节了BAD的磷酸化状态，从而进一步增强了ABT-263介导的细胞死亡。
ABT-263和GDC-0941联合治疗通过特异性靶向GBM中异常活跃、失调的途径，克服内源性凋亡抗性，具有新的治疗潜力。
