Bar Eli E, Chaudhry Aneeka, Lin Alex, Fan Xing, Schreck Karisa, Matsui William, Piccirillo Sara, Vescovi Angelo L, DiMeco Francesco, Olivi Alessandro, Eberhart Charles G
Johns Hopkins University School of Medicine, Department of Pathology, 720 Rutland Avenue, Ross Building 558, Baltimore, Maryland 21205, USA.
Stem Cells. 2007 Oct;25(10):2524-33. doi: 10.1634/stemcells.2007-0166. Epub 2007 Jul 12.
Brain tumors can arise following deregulation of signaling pathways normally activated during brain development and may derive from neural stem cells. Given the requirement for Hedgehog in non-neoplastic stem cells, we investigated whether Hedgehog blockade could target the stem-like population in glioblastoma multiforme (GBM). We found that Gli1, a key Hedgehog pathway target, was highly expressed in 5 of 19 primary GBM and in 4 of 7 GBM cell lines. Shh ligand was expressed in some primary tumors, and in GBM-derived neurospheres, suggesting a potential mechanism for pathway activation. Hedgehog pathway blockade by cyclopamine caused a 40%-60% reduction in growth of adherent glioma lines highly expressing Gli1 but not in those lacking evidence of pathway activity. When GBM-derived neurospheres were treated with cyclopamine and then dissociated and seeded in media lacking the inhibitor, no new neurospheres formed, suggesting that the clonogenic cancer stem cells had been depleted. Consistent with this hypothesis, the stem-like fraction in gliomas marked by both aldehyde dehydrogenase activity and Hoechst dye excretion (side population) was significantly reduced or eliminated by cyclopamine. In contrast, we found that radiation treatment of our GBM neurospheres increased the percentage of these stem-like cells, suggesting that this standard therapy preferentially targets better-differentiated neoplastic cells. Most importantly, viable GBM cells injected intracranially following Hedgehog blockade were no longer able to form tumors in athymic mice, indicating that a cancer stem cell population critical for ongoing growth had been removed. Disclosure of potential conflicts of interest is found at the end of this article.
脑肿瘤可在脑发育过程中正常激活的信号通路失调后发生，并且可能源自神经干细胞。鉴于刺猬信号通路（Hedgehog）在非肿瘤性干细胞中的作用，我们研究了阻断刺猬信号通路是否能够靶向多形性胶质母细胞瘤（GBM）中的干细胞样群体。我们发现，Gli1作为刺猬信号通路的关键靶点，在19例原发性GBM中的5例以及7种GBM细胞系中的4种中高表达。音猬因子（Shh）配体在一些原发性肿瘤以及GBM来源的神经球中表达，提示了通路激活的一种潜在机制。环杷明对刺猬信号通路的阻断导致高表达Gli1的贴壁胶质瘤细胞系的生长减少40%-60%，但对那些缺乏通路活性证据的细胞系则无此作用。当用环杷明处理GBM来源的神经球，然后解离并接种于不含抑制剂的培养基中时，没有形成新的神经球，这表明具有克隆能力的癌症干细胞已被耗尽。与该假设一致，环杷明显著减少或消除了以醛脱氢酶活性和Hoechst染料排泄（侧群细胞）标记的胶质瘤中的干细胞样部分。相比之下，我们发现对GBM神经球进行放射治疗会增加这些干细胞样细胞的百分比，这表明这种标准疗法优先靶向分化较好的肿瘤细胞。最重要的是，在阻断刺猬信号通路后颅内注射的活GBM细胞在无胸腺小鼠中不再能够形成肿瘤，这表明对持续生长至关重要的癌症干细胞群体已被清除。潜在利益冲突的披露见本文末尾。
