Weller M, Malipiero U, Rensing-Ehl A, Barr P J, Fontana A
Department of Internal Medicine, University Hospital, Zürich, Switzerland.
Cancer Res. 1995 Jul 1;55(13):2936-44.
Human malignant glioma cells are susceptible to apoptosis induced by antibodies to Fas/APO-1, a cytokine receptor protein of the nerve growth factor/tumor necrosis factor receptor superfamily. Here we show that a critical level of cell surface expression of Fas/APO-1 is a prerequisite for induction of glioma cell apoptosis via Fas/APO-1. Although Fas/APO-1 mRNA was expressed in three Fas/APO-1 antibody-resistant glioma cell lines, these cells expressed either little Fas/APO-1 protein (LN-319 and LN-405) or an abnormal Fas/APO-1 protein that was not translocated to the cell membrane and therefore functionally inactive (LN-308). Although all glioma cell lines expressed mRNA for Fas/APO-1-delta TM, a soluble form of Fas/APO-1 lacking the transmembrane domain, none of the cell lines released detectable amounts of soluble Fas/APO-1, a potential endogenous antagonist of Fas/APO-1-mediated glioma cell apoptosis. Stable transfection of three resistant glioma cell lines with a human Fas/APO-1 cDNA expression vector dramatically enhanced cell surface expression of Fas/APO-1 and induced susceptibility to Fas/APO-1 antibody-mediated apoptosis. These data indicate that malignant glioma cells, unlike other tumor cells, uniformly harbor the intracellular cascade required for Fas/APO-1-mediated apoptosis. Low level of Fas/APO-1 expression results from inefficient transcription and translation of the Fas/APO-1 gene or the synthesis of mutant Fas/APO-1 proteins. gamma-Interferon, tumor necrosis factor-alpha, and interleukin 1 beta augmented Fas/APO-1-mediated apoptosis of Fas/APO-1-transfected glioma cells by acting on the subcellular suicidal cascade triggered by Fas/APO-1 activation. Dexamethasone attenuated Fas/APO-1 antibody-induced apoptosis, not only of constitutively Fas/APO-1-positive glioma cells, but also of Fas/APO-1-transfected glioma cells. The antiapoptotic effect of dexamethasone could be overcome by preexposure of the glioma cells to gamma-interferon or by coexposure to Fas/APO-1 antibodies and cycloheximide. Thus, Fas/APO-1 gene transfer and combined immunotherapy using Fas/APO-1 antibodies and cytokines may overcome Fas/APO-1 antibody resistance of Fas/APO-1-negative human malignant glioma cells, which may represent subpopulations within single gliomas or form a separate subgroup of human malignant gliomas.
人类恶性胶质瘤细胞对由抗Fas/APO-1抗体诱导的凋亡敏感，Fas/APO-1是神经生长因子/肿瘤坏死因子受体超家族的一种细胞因子受体蛋白。在此我们表明，Fas/APO-1细胞表面表达的临界水平是通过Fas/APO-1诱导胶质瘤细胞凋亡的前提条件。尽管Fas/APO-1 mRNA在三种抗Fas/APO-1抗体的胶质瘤细胞系中表达，但这些细胞要么几乎不表达Fas/APO-1蛋白（LN-319和LN-405），要么表达一种异常的Fas/APO-1蛋白，该蛋白未转运至细胞膜，因此功能失活（LN-308）。尽管所有胶质瘤细胞系均表达Fas/APO-1-δTM的mRNA，Fas/APO-1-δTM是一种缺乏跨膜结构域的可溶性Fas/APO-1形式，但没有一个细胞系释放出可检测量的可溶性Fas/APO-1，可溶性Fas/APO-1是Fas/APO-1介导的胶质瘤细胞凋亡的一种潜在内源性拮抗剂。用人类Fas/APO-1 cDNA表达载体稳定转染三种抗性胶质瘤细胞系，显著增强了Fas/APO-1的细胞表面表达，并诱导了对Fas/APO-1抗体介导的凋亡的敏感性。这些数据表明，与其他肿瘤细胞不同，恶性胶质瘤细胞一致地具有Fas/APO-1介导的凋亡所需的细胞内级联反应。Fas/APO-1低水平表达是由于Fas/APO-1基因转录和翻译效率低下或突变Fas/APO-1蛋白的合成所致。γ-干扰素、肿瘤坏死因子-α和白细胞介素1β通过作用于由Fas/APO-1激活触发的亚细胞自杀级联反应，增强了Fas/APO-1转染的胶质瘤细胞的Fas/APO-1介导的凋亡。地塞米松减弱了Fas/APO-1抗体诱导的凋亡，不仅对组成型Fas/APO-1阳性的胶质瘤细胞如此，对Fas/APO-1转染的胶质瘤细胞也是如此。地塞米松的抗凋亡作用可通过使胶质瘤细胞预先暴露于γ-干扰素或通过同时暴露于Fas/APO-1抗体和环己酰亚胺来克服。因此，Fas/APO-1基因转移以及使用Fas/APO-1抗体和细胞因子的联合免疫疗法可能克服Fas/APO-1阴性人类恶性胶质瘤细胞的Fas/APO-1抗体抗性，这些细胞可能代表单个胶质瘤内的亚群或形成人类恶性胶质瘤的一个单独亚组。
