Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, Michigan 48109-2200, USA.
Stem Cells. 2010 Jan;28(1):5-16. doi: 10.1002/stem.254.
Cancer stem cells (CSCs) are thought to be critical for the engraftment and long-term growth of many tumors, including glioblastoma (GBM). The cells are at least partially spared by traditional chemotherapies and radiation therapies, and finding new treatments that can target CSCs may be critical for improving patient survival. It has been shown that the NOTCH signaling pathway regulates normal stem cells in the brain, and that GBMs contain stem-like cells with higher NOTCH activity. We therefore used low-passage and established GBM-derived neurosphere cultures to examine the overall requirement for NOTCH activity, and also examined the effects on tumor cells expressing stem cell markers. NOTCH blockade by gamma-secretase inhibitors (GSIs) reduced neurosphere growth and clonogenicity in vitro, whereas expression of an active form of NOTCH2 increased tumor growth. The putative CSC markers CD133, NESTIN, BMI1, and OLIG2 were reduced following NOTCH blockade. When equal numbers of viable cells pretreated with either vehicle (dimethyl sulfoxide) or GSI were injected subcutaneously into nude mice, the former always formed tumors, whereas the latter did not. In vivo delivery of GSI by implantation of drug-impregnated polymer beads also effectively blocked tumor growth, and significantly prolonged survival, albeit in a relatively small cohort of animals. We found that NOTCH pathway inhibition appears to deplete stem-like cancer cells through reduced proliferation and increased apoptosis associated with decreased AKT and STAT3 phosphorylation. In summary, we demonstrate that NOTCH pathway blockade depletes stem-like cells in GBMs, suggesting that GSIs may be useful as chemotherapeutic reagents to target CSCs in malignant gliomas.
癌症干细胞（CSCs）被认为是许多肿瘤，包括神经胶质瘤（GBM）的植入和长期生长的关键。这些细胞至少部分免受传统化疗和放疗的影响，因此寻找可以靶向 CSCs 的新治疗方法对于提高患者生存率可能至关重要。已经表明，NOTCH 信号通路调节大脑中的正常干细胞，并且 GBM 中存在具有更高 NOTCH 活性的干细胞样细胞。因此，我们使用低传代和已建立的 GBM 衍生的神经球培养物来检查 NOTCH 活性的总体需求，并且还检查了对表达干细胞标记物的肿瘤细胞的影响。γ-分泌酶抑制剂（GSIs）的 NOTCH 阻断减少了体外神经球的生长和集落形成能力，而 NOTCH2 的活性形式的表达增加了肿瘤的生长。NOTCH 阻断后，假定的 CSC 标记物 CD133、NESTIN、BMI1 和 OLIG2 减少。当用载体（二甲亚砜）或 GSI 预处理的相同数量的存活细胞被皮下注射到裸鼠中时，前者总是形成肿瘤，而后者则没有。通过植入载药聚合物珠的体内递送 GSI 也有效地阻断了肿瘤生长，并显著延长了存活时间，尽管在相对较小的动物队列中。我们发现 NOTCH 途径抑制似乎通过与 AKT 和 STAT3 磷酸化减少相关的减少增殖和增加凋亡来耗尽干细胞样癌细胞。总之，我们证明 NOTCH 途径阻断可耗尽 GBM 中的干细胞样细胞，表明 GSIs 可用作针对恶性神经胶质瘤中的 CSCs 的化疗试剂。
