Tchoghandjian A, Jennewein C, Eckhardt I, Momma S, Figarella-Branger D, Fulda S
Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Komturstrasse 3a, Frankfurt, Germany.
Institute of Neuropathology, Goethe-University, Frankfurt, Germany.
Cell Death Differ. 2014 May;21(5):735-47. doi: 10.1038/cdd.2013.200. Epub 2014 Jan 31.
Recently, a broader role of inhibitor of apoptosis (IAP) proteins besides their antiapoptotic functions has been described. Therefore, we investigated the effect of non-toxic concentrations of the small-molecule Smac mimetic BV6, which antagonizes IAP proteins, on differentiation of cancer stem-like cells (CSLCs) derived from primary glioblastoma (GBM) specimens. Here, we identify a novel function of BV6 in regulating differentiation of GBM CSLCs by activating NF-κB. BV6 at non-lethal doses stimulates morphological changes associated with the differentiation of GBM CSLCs. BV6 increases transcriptional activity, mRNA and protein levels of the astrocytic marker GFAP without altering expression of the neuronal marker β-III-tubulin, indicating that BV6 induces astrocytic differentiation of GBM CSLCs. Molecular studies reveal that BV6 triggers processing of the NF-κB subunit p100 to p52, nuclear translocation of p52 and p50 and increased NF-κB DNA-binding. Intriguingly, inhibition of NF-κB by overexpression of dominant-negative IκBα super-repressor (IκBα-SR) blocks the BV6-stimulated increase in GFAP and differentiation. Interestingly, this BV6-stimulated differentiation is associated with reduced expression of stemness markers such as CD133, Nanog and Sox2 in GBM CSLCs. In contrast, BV6 does not alter cell morphology, differentiation and expression of stemness markers in non-malignant neural stem cells. Importantly, BV6 treatment reduces clonogenicity of GBM CSLCs in vitro and in vivo, suppresses their tumorigenicity in orthotopic and subcutaneous mouse models and significantly increases the survival of mice. By identifying a novel role of BV6 in promoting differentiation of GBM CSLCs, these findings provide new insights into Smac mimetic-regulated non-apoptotic functions with important implications for targeting GBM CSLCs.
最近，凋亡抑制蛋白（IAP）除了具有抗凋亡功能外，还被发现具有更广泛的作用。因此，我们研究了无毒浓度的小分子Smac模拟物BV6（一种IAP拮抗剂）对原发性胶质母细胞瘤（GBM）标本来源的癌症干细胞样细胞（CSLC）分化的影响。在此，我们通过激活核因子κB（NF-κB）确定了BV6在调节GBM CSLC分化中的新功能。非致死剂量的BV6刺激了与GBM CSLC分化相关的形态变化。BV6增加了星形胶质细胞标志物胶质纤维酸性蛋白（GFAP）的转录活性、mRNA和蛋白水平，而不改变神经元标志物β-III微管蛋白的表达，这表明BV6诱导了GBM CSLC的星形胶质细胞分化。分子研究表明，BV6触发了NF-κB亚基p100向p52的加工、p52和p50的核转位以及NF-κB与DNA结合能力的增强。有趣的是，通过过表达显性负性IκBα超级抑制剂（IκBα-SR）抑制NF-κB可阻断BV6刺激的GFAP增加和分化。有趣的是，这种BV6刺激的分化与GBM CSLC中干性标志物如CD133、Nanog和Sox2的表达降低有关。相比之下，BV6不会改变非恶性神经干细胞的细胞形态、分化和干性标志物的表达。重要的是，BV6处理降低了GBM CSLC在体外和体内的克隆形成能力，在原位和皮下小鼠模型中抑制了它们的致瘤性，并显著提高了小鼠的存活率。通过确定BV6在促进GBM CSLC分化中的新作用，这些发现为Smac模拟物调节的非凋亡功能提供了新的见解，对靶向GBM CSLC具有重要意义。
