Department of Medicine (Neurology), HMRC 6-11, University of Alberta, Edmonton, AB, Canada.
Department of Medical Microbiology & Immunology, University of Alberta, Edmonton, AB, Canada.
J Neurooncol. 2019 Sep;144(2):265-273. doi: 10.1007/s11060-019-03230-y. Epub 2019 Jul 6.
Inflammation is a key aspect of glioblastoma multiforme (GBM) although it remains unclear how it contributes to GBM pathogenesis. Inflammasomes are intracellular multi-protein complexes that are involved in innate immunity and are activated by cellular stress, principally in macrophages. This study examined the expression of inflammasome-associated genes in GBM, particularly absent in melanoma 2 (AIM2).
Tissue samples from surgically-resected GBM tumors (n = 10) were compared to resected brain specimens from patients with epilepsy (age- and sex-matched Other Disease Controls (ODC, n=5)) by qRT-PCR, western blotting and immunofluorescence. Gene expression studies in human astrocytoma U251 cells were performed and the effects of deleting the absent in melanoma 2 (AIM2) gene using the CRISPR-Cas9 system were analyzed.
GBM tissues showed significantly elevated expression of multiple immune (CD3E, CD163, CD68, MX1, ARG1) and inflammasome (AIM2, NLRP1, IL18, CASP1, and IL-33) genes compared to ODC tissues, without induction of IL1B, IFNG or TNFA. An insert-containing AIM2 variant transcript was highly expressed in GBM tissues and in U251 cells. AIM2 immunoreactivity was concentrated in the tumor core in the absence of PCNA immunodetection and showed a predominant 52 kDa immunoreactive band on western blot. Deletion of AIM2 resulted in significantly enhanced proliferation of U251 cells, which also displayed increased resistance to temozolomide treatment.
GBM tumors express a distinct profile of inflammasome-associated genes in a tumor-specific manner. AIM2 expression in tumor cells suppressed cell proliferation while also conferring increased susceptibility to contemporary GBM therapy.
炎症是胶质母细胞瘤（GBM）的一个关键方面，但目前尚不清楚它如何促进 GBM 的发病机制。炎症小体是参与固有免疫的细胞内多蛋白复合物，主要在巨噬细胞中被细胞应激激活。本研究检测了 GBM 中炎症小体相关基因的表达，特别是黑色素瘤缺失 2 型（AIM2）。
通过 qRT-PCR、western blot 和免疫荧光，比较了手术切除的 GBM 肿瘤组织（n=10）与癫痫患者（年龄和性别匹配的其他疾病对照（ODC，n=5））的组织样本。在人星形细胞瘤 U251 细胞中进行了基因表达研究，并使用 CRISPR-Cas9 系统分析了缺失黑色素瘤缺失 2 型（AIM2）基因的影响。
与 ODC 组织相比，GBM 组织中多种免疫（CD3E、CD163、CD68、MX1、ARG1）和炎症小体（AIM2、NLRP1、IL18、CASP1 和 IL-33）基因的表达显著升高，但未诱导 IL1B、IFNG 或 TNFA。GBM 组织和 U251 细胞中高度表达含插入的 AIM2 变体转录本。AIM2 免疫反应性在肿瘤核心中集中，而 PCNA 免疫检测呈阴性，并在 western blot 上显示出主要的 52 kDa 免疫反应性条带。AIM2 的缺失导致 U251 细胞的增殖显著增强，同时对替莫唑胺治疗的耐药性也增加。
GBM 肿瘤以肿瘤特异性方式表达独特的炎症小体相关基因谱。肿瘤细胞中的 AIM2 表达抑制细胞增殖，同时也增加了对当代 GBM 治疗的敏感性。
