Department of Pediatrics, University of Alabama at Birmingham, 35294, USA.
BMC Cancer. 2011 Apr 14;11:136. doi: 10.1186/1471-2407-11-136.
Medulloblastoma is a highly malignant pediatric brain tumor that requires surgery, whole brain and spine irradiation, and intense chemotherapy for treatment. A more sophisticated understanding of the pathophysiology of medulloblastoma is needed to successfully reduce the intensity of treatment and improve outcomes. Nuclear factor kappa-B (NFκB) is a signaling pathway that controls transcriptional activation of genes important for tight regulation of many cellular processes and is aberrantly expressed in many types of cancer.
To test the importance of NFκB to medulloblastoma cell growth, the effects of multiple drugs that inhibit NFκB, pyrrolidine dithiocarbamate, diethyldithiocarbamate, sulfasalazine, curcumin and bortezomib, were studied in medulloblastoma cell lines compared to a malignant glioma cell line and normal neurons. Expression of endogenous NFκB was investigated in cultured cells, xenograft flank tumors, and primary human tumor samples. A dominant negative construct for the endogenous inhibitor of NFκB, IκB, was prepared from medulloblastoma cell lines and flank tumors were established to allow specific pathway inhibition.
We report high constitutive activity of the canonical NFκB pathway, as seen by Western analysis of the NFκB subunit p65, in medulloblastoma tumors compared to normal brain. The p65 subunit of NFκB is extremely highly expressed in xenograft tumors from human medulloblastoma cell lines; though, conversely, the same cells in culture have minimal expression without specific stimulation. We demonstrate that pharmacological inhibition of NFκB in cell lines halts proliferation and leads to apoptosis. We show by immunohistochemical stain that phosphorylated p65 is found in the majority of primary tumor cells examined. Finally, expression of a dominant negative form of the endogenous inhibitor of NFκB, dnIκB, resulted in poor xenograft tumor growth, with average tumor volumes 40% smaller than controls.
These data collectively demonstrate that NFκB signaling is important for medulloblastoma tumor growth, and that inhibition can reduce tumor size and viability in vivo. We discuss the implications of NFκB signaling on the approach to managing patients with medulloblastoma in order to improve clinical outcomes.
成神经管细胞瘤是一种高度恶性的小儿脑肿瘤，需要手术、全脑和脊柱照射以及强化化疗治疗。为了成功降低治疗强度并改善预后，需要更深入地了解成神经管细胞瘤的病理生理学。核因子-κB（NFκB）是一种信号通路，可控制对许多细胞过程的紧密调节至关重要的基因的转录激活，并且在许多类型的癌症中异常表达。
为了测试 NFκB 对成神经管细胞瘤细胞生长的重要性，研究了多种抑制 NFκB 的药物，包括吡咯烷二硫代氨基甲酸盐、二乙基二硫代氨基甲酸盐、柳氮磺胺吡啶、姜黄素和硼替佐米，在成神经管细胞瘤细胞系与恶性神经胶质瘤细胞系和正常神经元进行了比较。研究了培养细胞、异种移植 flank 肿瘤和原发性人肿瘤样本中内源性 NFκB 的表达。从成神经管细胞瘤细胞系制备了内源性 NFκB 抑制剂 IκB 的显性负突变体，并建立了 flank 肿瘤，以允许特定途径抑制。
我们报告了与正常脑相比，成神经管细胞瘤肿瘤中经典 NFκB 通路的高组成活性，这可以通过 NFκB 亚基 p65 的 Western 分析看出。NFκB 的 p65 亚基在来自人成神经管细胞瘤细胞系的异种移植肿瘤中高度表达；然而，相反，在没有特定刺激的情况下，相同的细胞在培养中几乎没有表达。我们证明细胞系中 NFκB 的药理学抑制可阻止增殖并导致细胞凋亡。我们通过免疫组织化学染色表明，在大多数检查的原发性肿瘤细胞中发现磷酸化的 p65。最后，表达内源性 NFκB 抑制剂的显性负形式 dnIκB，导致异种移植肿瘤生长不良，平均肿瘤体积比对照组小 40%。
这些数据共同表明 NFκB 信号对成神经管细胞瘤肿瘤生长很重要，并且抑制可以减少体内肿瘤的大小和活力。我们讨论了 NFκB 信号对管理成神经管细胞瘤患者的方法的影响，以改善临床结果。
