Chicoine Michael R, Zahner Michael, Won Eun Kyung, Kalra Ricky R, Kitamura Tetsuya, Perry Arie, Higashikubo Ryuji
Department of Neurosurgery, Washington University School of Medicine, Saint Louis, Missouri 63110, USA.
Neurosurgery. 2007 Feb;60(2):372-80; discussion 381. doi: 10.1227/01.NEU.0000249280.61761.2E.
Toll-like receptor 4 (Tlr-4) mediates many biological effects of lipopolysaccharide (LPS), which has antitumoral effects on glioblastoma both in vivo and in vitro. However, the precise role of Tlr-4 in these antitumoral effects remains unknown.
The role of Tlr-4 in the antitumoral effect of LPS on glioblastomas was assessed in wild-type BALB/c mice and in Tlr-4 knockout (KO) BALB/c mice. Mice were implanted with DBT glioblastoma cells intracranially or subcutaneously, were treated with intratumoral LPS, and were assessed by histopathological examination for degrees of tumor progression and inflammation. Flow cytometry and Western blotting with antibodies to the Tlr-4 receptor and flow cytometry to the related CD14 moiety were performed to quantitate the expression levels of these two receptors by glioblastoma cells.
For subcutaneous tumors, LPS caused near complete tumor elimination in wild-type mice, but only a 50% reduction in Tlr-4 KO mice. For mice implanted with intracranial glioblastomas, LPS increased survival times modestly in wild-type mice, but showed no benefit in the Tlr-4 KO mice. There were no histological differences among wild-type and Tlr-4 KO mice, except for tumor size. In both models, an early neutrophilic and later macrophage-rich inflammatory infiltrate were seen after LPS administration. Quantitative flow cytometry and Western blotting showed no Tlr-4 receptor or CD14 expression in murine and human glioblastoma cells in vitro, and Western blotting suggested that Tlr-4 effects are mediated by nontumoral elements such as microglia and inflammatory cells.
LPS-induced antitumoral effects on glioblastoma multiforme are mediated, in part, by the Tlr-4 receptor. Further understanding of this process may lead to novel treatment strategies for this uniformly fatal disease.
Toll样受体4（Tlr-4）介导脂多糖（LPS）的多种生物学效应，LPS在体内和体外对胶质母细胞瘤均具有抗肿瘤作用。然而，Tlr-4在这些抗肿瘤效应中的确切作用仍不清楚。
在野生型BALB/c小鼠和Tlr-4基因敲除（KO）的BALB/c小鼠中评估Tlr-4在LPS对胶质母细胞瘤的抗肿瘤作用中的作用。小鼠颅内或皮下植入DBT胶质母细胞瘤细胞，给予瘤内LPS治疗，并通过组织病理学检查评估肿瘤进展和炎症程度。采用流式细胞术和针对Tlr-4受体的抗体进行蛋白质印迹分析以及针对相关CD14部分的流式细胞术，以定量胶质母细胞瘤细胞中这两种受体的表达水平。
对于皮下肿瘤，LPS可使野生型小鼠的肿瘤几乎完全消除，但在Tlr-4基因敲除小鼠中仅减少50%。对于颅内植入胶质母细胞瘤的小鼠，LPS使野生型小鼠的存活时间适度延长，但在Tlr-4基因敲除小鼠中未显示出益处。除肿瘤大小外，野生型和Tlr-4基因敲除小鼠之间无组织学差异。在两种模型中，给予LPS后均可见早期中性粒细胞浸润和后期富含巨噬细胞的炎症浸润。定量流式细胞术和蛋白质印迹分析显示，在体外培养的鼠和人胶质母细胞瘤细胞中无Tlr-4受体或CD14表达，蛋白质印迹分析表明Tlr-4的作用由非肿瘤成分如小胶质细胞和炎症细胞介导。
LPS对多形性胶质母细胞瘤的抗肿瘤作用部分由Tlr-4受体介导。对这一过程的进一步了解可能会为这种一致致命的疾病带来新的治疗策略。
