Bertrand Julian, Begaud-Grimaud Gaëlle, Bessette Barbara, Verdier Mireille, Battu Serge, Jauberteau Marie-Odile
Faculty of Medicine, University of Limoges, 87025 Limoges cedex, France.
Int J Oncol. 2009 Mar;34(3):717-27. doi: 10.3892/ijo_00000198.
Glioblastoma is the most common primary brain tumor, characterized by its resistance to treatments. To define efficient therapy, the origin of tumor-forming cells needs to be elucidated in order to search for new therapeutic pathways. The objective of this study was to determine the different cell populations constituting a human glioblastoma cell line, U-87 MG and their sensitivity to apoptosis induced through the activation of Fas, a membranous death receptor. By a cell sorting method, the sedimentation field flow fractionation, two major cell subpopulations were identified, a most differentiated cell fraction, containing large and adherent cells, sensitive to Fas-induced apoptosis and another one, characterized by small cells forming aggregates, expressing CD133, a marker of stem cells and more resistant to Fas-activated apoptosis. By using a selective method of culture, adapted for neural stem cell cultures, we have verified that the U-87 MG cell line contained cancer stem cells similar to the immature ones obtained by the cell sorting method. Interestingly, while these tumor stem cells, expressing CD133, were resistant to Fas-induced apoptosis, monomeric form of Fas protein was detected predominantly in these cells. In contrast, the most mature cells, responsive to Fas-activated apoptosis, collected in another cell fraction, contained oligomeric aggregates of Fas protein, a pre-signalling form of the Fas receptor, essential for the initiation of apoptosis through its activation. These results suggest that these immature stem cells in glioma could be an important factor of resistance to chemotherapy requiring apoptosis through Fas signalling system. Indeed, future strategies of treatment, inducing differentiation of these stem cells need to be considered to enhance therapeutic efficiency.
胶质母细胞瘤是最常见的原发性脑肿瘤，其特点是对治疗具有抗性。为了确定有效的治疗方法，需要阐明肿瘤形成细胞的起源，以便寻找新的治疗途径。本研究的目的是确定构成人胶质母细胞瘤细胞系U-87 MG的不同细胞群体及其对通过激活Fas（一种膜死亡受体）诱导的凋亡的敏感性。通过细胞分选方法，即沉降场流分级分离，鉴定出两个主要的细胞亚群，一个是高度分化的细胞部分，包含大的贴壁细胞，对Fas诱导的凋亡敏感；另一个以形成聚集体的小细胞为特征，表达干细胞标志物CD133，对Fas激活的凋亡更具抗性。通过使用适用于神经干细胞培养的选择性培养方法，我们证实U-87 MG细胞系含有与通过细胞分选方法获得的未成熟细胞相似的癌症干细胞。有趣的是，虽然这些表达CD133的肿瘤干细胞对Fas诱导的凋亡具有抗性，但在这些细胞中主要检测到Fas蛋白的单体形式。相反，在另一个细胞部分中收集的对Fas激活的凋亡有反应的最成熟细胞含有Fas蛋白的寡聚体聚集体，这是Fas受体的一种预信号形式，通过其激活对于启动凋亡至关重要。这些结果表明，胶质瘤中的这些未成熟干细胞可能是通过Fas信号系统诱导凋亡的化疗抗性的重要因素。事实上，需要考虑未来诱导这些干细胞分化的治疗策略以提高治疗效率。
