Virginia Tech Carilion Research Institute, Virginia Tech, Roanoke, Virginia.
Graduate Program in Translational Biology, Medicine, and Health, Virginia Tech, Blacksburg, Virginia.
Neuro Oncol. 2018 Mar 27;20(4):494-505. doi: 10.1093/neuonc/nox181.
Glioblastoma (GBM) is difficult to treat. Phosphoinositide 3-kinase (PI3K) is an attractive therapeutic target for GBM; however, targeting this pathway to effectively treat GBM is not successful because the roles of PI3K isoforms remain to be defined. The aim of this study is to determine whether PIK3CB/p110β, but not other PI3K isoforms, is a biomarker for GBM recurrence and important for cell survival.
Gene expression and clinical relevance of PI3K genes in GBM patients were analyzed using online databases. Expression/activity of PI3K isoforms was determined using immunoblotting. PI3K genes were inhibited using short hairpin RNAs or isoform-selective inhibitors. Cell viability/growth was assessed by the MTS assay and trypan blue exclusion assay. Apoptosis was monitored using the caspase activity assay. Mouse GBM xenograft models were used to gauge drug efficacy.
PIK3CB/p110β was the only PI3K catalytic isoform that significantly correlated with high incidence rate, risk, and poor survival of recurrent GBM. PIK3CA/p110α, PIK3CB/p110β, and PIK3CD/p110δ were differentially expressed in GBM cell lines and primary tumor cells derived from patient specimens, whereas PIK3CG/p110γ was barely detected. PIK3CB/p110β protein levels presented a stronger association with the activities of PI3K signaling than other PI3K isoforms. Blocking p110β deactivated PI3K signaling, whereas inhibition of other PI3K isoforms had no effect. Specific inhibitors of PIK3CB/p110β, but not other PI3K isoforms, remarkably suppressed viability and growth of GBM cells and xenograft tumors in mice, with minimal cytotoxic effects on astrocytes.
PIK3CB/p110β is a biomarker for GBM recurrence and selectively important for GBM cell survival.
胶质母细胞瘤（GBM）难以治疗。磷酸肌醇 3-激酶（PI3K）是 GBM 的一个有吸引力的治疗靶点；然而，靶向该途径以有效治疗 GBM 并不成功，因为 PI3K 同工型的作用仍有待确定。本研究旨在确定 PIK3CB/p110β是否是 GBM 复发的生物标志物，以及是否对细胞存活很重要。
使用在线数据库分析 GBM 患者的 PI3K 基因的基因表达和临床相关性。使用免疫印迹法测定 PI3K 同工型的表达/活性。使用短发夹 RNA 或同工型选择性抑制剂抑制 PI3K 基因。通过 MTS 测定和台盼蓝排斥试验评估细胞活力/生长。通过 caspase 活性测定监测细胞凋亡。使用小鼠 GBM 异种移植模型来评估药物疗效。
PIK3CB/p110β 是唯一与复发性 GBM 发生率高、风险高和预后不良显著相关的 PI3K 催化同工型。PIK3CA/p110α、PIK3CB/p110β 和 PIK3CD/p110δ 在 GBM 细胞系和源自患者标本的原代肿瘤细胞中表达不同，而 PIK3CG/p110γ 几乎检测不到。PIK3CB/p110β 蛋白水平与 PI3K 信号转导的活性具有更强的相关性，而其他 PI3K 同工型则没有。阻断 p110β 可使 PI3K 信号失活，而抑制其他 PI3K 同工型则没有影响。PIK3CB/p110β 的特异性抑制剂，但不是其他 PI3K 同工型，可显著抑制 GBM 细胞和小鼠异种移植肿瘤的活力和生长，对星形胶质细胞的细胞毒性最小。
PIK3CB/p110β 是 GBM 复发的生物标志物，对 GBM 细胞存活具有选择性重要性。
