We have previously described that the NFκB pathway is upregulated during differentiation of glioblastoma stem-like cells (GSCs) which keeps differentiating GSCs in a proliferative astrocytic precursor state. However, extracellular signals and cellular mediators of this pathway are not clear yet. Here, we show that TLR4 is a key factor to promote NFκB activation in differentiating GSCs. TLR4 is upregulated during differentiation of GSCs and promotes transcriptional activation of NFκB as determined by luciferase-reporter assays and expression of NFκB target genes. Downregulation of TLR4 by shRNAs or blockade with anti-TLR4 specific antibodies drastically inhibited NFκB activity which promoted further differentiation and reduced proliferation of GSCs. We found that hyaluronic acid (HA), a main component of brain extracellular matrix, triggers the TLR4-NFκB pathway in differentiating GSCs. Moreover, HA is synthesized and released by GSCs undergoing differentiation and leads to transcriptional activation of NFκB, which is inhibited following downregulation of TLR4 or blockade of HA synthesis. Thus, we have demonstrated that during the process of differentiation, GSCs upregulate TLR4 and release the TLR4 ligand HA, which activates the TLR4-NFκB signaling pathway. This strategy may efficiently be used by differentiating GSCs to maintain their proliferative potential and consequently their tumorigenic capacity.

中文翻译：

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通过TLR4的透明质酸信号传导促进分化成胶质母细胞瘤干样细胞中的NFκB活化。

先前我们已经描述了在胶质母细胞瘤干样细胞（GSC）分化过程中NFκB通路被上调，这使分化的GSC保持增殖性星形胶质细胞前体状态。但是，该途径的细胞外信号和细胞介质尚不清楚。在这里，我们显示TLR4是在分化GSC中促进NFκB活化的关键因素。TLR4在GSC分化过程中被上调，并通过荧光素酶报告基因测定法和NFκB靶基因的表达来促进NFκB的转录激活。shRNA下调TLR4的表达或用抗TLR4特异性抗体阻断可显着抑制NFκB活性，从而促进进一步分化并减少GSC的增殖。我们发现透明质酸（HA）是大脑细胞外基质的主要成分，在分化的GSC中触发TLR4-NFκB途径。此外，HA由经历分化的GSC合成和释放，并导致NFκB的转录激活，这在TLR4下调或HA合成受阻后被抑制。因此，我们已经证明，在分化过程中，GSCs上调TLR4并释放TLR4配体HA，从而激活TLR4-NFκB信号通路。该策略可通过区分GSC来有效地使用，以维持其增殖潜能，从而维持其致瘤能力。我们已经证明，在分化过程中，GSCs上调TLR4并释放TLR4配体HA，从而激活TLR4-NFκB信号通路。该策略可通过区分GSC来有效地使用，以维持其增殖潜能，从而维持其致瘤能力。我们已经证明，在分化过程中，GSCs上调TLR4并释放TLR4配体HA，从而激活TLR4-NFκB信号通路。该策略可通过区分GSC来有效地使用，以维持其增殖潜能，从而维持其致瘤能力。