Department of Chemistry, Research Institute for Natural Sciences, Hanyang University, Seoul, Korea.
Oncogene. 2012 Nov 1;31(44):4655-66. doi: 10.1038/onc.2011.634. Epub 2012 Jan 16.
Uncovering the mechanisms that govern the maintenance of stem-like cancer cells is critical for developing therapeutic strategies for targeting these cells. Constitutive activation of c-Jun N-terminal kinase (JNK) has been reported in gliomas and correlates with histological grade. Here, we found that JNK signaling is crucial for the maintenance of 'stemness' in glioma cells. Sphere-cultured glioma cells showed more phosphorylation of JNK compared with serum-containing monolayer cultures. Importantly, blockade of JNK signaling with SP600125 or small interfering RNAs targeting JNK1 or JNK2 significantly reduced the CD133(+)/Nestin(+) population and suppressed sphere formation, colony formation in soft agar, and expression of stem cell markers in sphere-cultured glioma cells. Intriguingly, sphere-cultured glioma cells exhibited enhanced expression of Notch-2, but not Notch-1, -3 or -4, and JNK inhibition almost completely abrogated this increase. Blocking the phosphoinoside 3-kinase (PI3K)/Akt pathway with LY294002 or si-Akt also suppressed the self-renewal of sphere-cultured glioma cells. PI3K, but not Akt, had a role as an upstream kinase in JNK1/2 activation. In addition, treatment with si-JNK greatly increased etoposide- and ionizing radiation (IR)-induced cell death in glioma spheres. Consistent with glioma cell lines, glioma stem-like cells isolated from primary patient glioma cells also had a higher activity of JNK and Notch-2 expression. Importantly, inhibition of JNK2 led to a decrease of Notch-2 expression and suppressed the CD133(+)/Nestin(+) cell population in patient-derived primary glioma cells. Finally, downregulation of JNK2 almost completely suppressed intracranial tumor formation by glioma cells in nude mice. Taken together, these data demonstrate that JNK signaling is crucial for the maintenance of self-renewal and tumorigenicity of glioma stem-like cells and drug/IR resistance, and can be considered a promising target for eliminating stem-like cancer cells in gliomas.
揭示调控肿瘤干细胞自我更新的机制对于开发针对这些细胞的治疗策略至关重要。有研究报道，在神经胶质瘤中持续激活 c-Jun N 端激酶（JNK）与组织学分级相关。在这里，我们发现 JNK 信号通路对于维持神经胶质瘤细胞的“干性”至关重要。与含血清单层培养相比，球体培养的神经胶质瘤细胞 JNK 磷酸化程度更高。重要的是，用 SP600125 或靶向 JNK1 或 JNK2 的小干扰 RNA 阻断 JNK 信号通路，可显著减少 CD133(+)/Nestin(+) 群体，并抑制球体形成、软琼脂集落形成和球体培养的神经胶质瘤细胞中干细胞标志物的表达。有趣的是，球体培养的神经胶质瘤细胞表现出 Notch-2 表达增强，但 Notch-1、-3 或-4 没有，JNK 抑制几乎完全消除了这种增加。用 LY294002 或 si-Akt 阻断磷酯酰肌醇 3-激酶（PI3K）/Akt 通路也抑制了球体培养的神经胶质瘤细胞的自我更新。PI3K 而不是 Akt，作为 JNK1/2 激活的上游激酶发挥作用。此外，用 si-JNK 处理大大增加了神经胶质瘤球体中外源阿霉素和顺铂诱导的细胞死亡。与神经胶质瘤细胞系一致，从原发性患者神经胶质瘤细胞中分离出的神经胶质瘤干细胞也具有更高的 JNK 活性和 Notch-2 表达。重要的是，抑制 JNK2 导致 Notch-2 表达下降，并抑制患者来源的原发性神经胶质瘤细胞中 CD133(+)/Nestin(+)细胞群体。最后，下调 JNK2 几乎完全抑制了神经胶质瘤细胞在裸鼠颅内肿瘤的形成。综上所述，这些数据表明 JNK 信号通路对于维持神经胶质瘤干细胞的自我更新和致瘤性以及对药物/IR 耐药性至关重要，可被视为消除神经胶质瘤中干细胞样癌症细胞的有前途的靶点。
