Candidate genes for the recurrence of glioblastoma multiforme identified by microarray

Background: Glioblastoma multiforme (GBM) is the most aggressive and most lethal primary malignant brain tumor, correlated with survival rates of less than one year from the time of diagnosis. Current surgical procedure attempts to remove the bulk of the tumor mass, whereas GBM frequently recurs within 1-3cm from the primary tumor resection site. Molecular mechanisms involved in the recurrence of the tumor are still poorly understood. The aim of the study was to define the molecular signature of GBM surrounding white matter (WM) in order to better understand the molecular mechanisms involved with tumor relapse. Material & Methods: Human GBM tumor bulk and surrounding tissue (1-3cm from the border of the tumor) were obtained from five patients who underwent total tumour resection, while normal white matter was harvested from patients who underwent surgical procedure for nonmalignant pathologies. Samples were processed for hybridization on the Affymetrix Human U133A arrays and data were examined with the GeneSpring analysis software. Results: Gene expression analysis of the samples was done in 2 independent steps. First, molecular profiling comparison of GBM surrounding WM and normal WM resulted in 59 genes differentially expressed between both tissues. Among these, numerous genes expressed by mature neural cells were down-regulated in GBM surrounding WM, while gene products supporting invasion were overexpressed. Moreover, KLRC1, a specific natural killer receptor naturally involved in the activation of antitumoral cells was drastically repressed in GBM surrounding WM, suggesting that the antitumoral immune surveillance is compromised in this tissue. Second, we focused our study on genes specifically regulated in GBM periphery respectively to GBM core. The highest up-regulated gene in GBM surrounding tissue encodes for DTX4, a regulator of NOTCH signalling pathway described for its key role in maintaining neural progenitors in an uncommitted state. Conclusion: This study revealed unique molecular characteristics of GBM surrounding tissue, showing the dysregulation of genes involved in immune surveillance along with genes associated to stemness maintenance. All together, these data may help to understand the molecular mechanisms associated with GBM recurrence This study attempted to define the molecular characteristics of the GBM surrounding tissue. To this end, GBM tumor samples were obtained from 5 patients who underwent total tumor resection. Surrounding tumor mass tissue was retrieved in all cases from not infiltrated white matter sited at 2 cm from the macroscopic tumor border. Furthermore, control white matter biopsies were harvested from patients operated on for deep intracerebral cavernomas. Each sample was hybridized onto Affymetrix human U133 arrays. For each patient, tumor core sample and surrounding tissue were harvested and are identified with the same suffix number. In 2 cases, (patients 3 and 4), two tumor peripheral tissue samples were harvested and are identified with the same number followed by "R" (replicate).

背景：多形性胶质母细胞瘤（Glioblastoma multiforme, GBM）是恶性程度最高、致死性最强的原发性脑肿瘤，确诊后患者生存期通常不足1年。当前临床手术尝试切除大部分肿瘤组织，但GBM常在原发肿瘤切除部位1~3厘米范围内复发，目前对肿瘤复发相关的分子机制仍知之甚少。本研究旨在明确GBM周围白质（white matter, WM）的分子特征，以深入解析肿瘤复发相关的分子机制。
材料与方法：本研究纳入5例接受肿瘤全切术的患者，采集其GBM肿瘤主体组织及距肿瘤边界1~3厘米的周围组织；同时从因非恶性病变接受手术的患者体内获取正常白质样本。所有样本均通过Affymetrix人类U133A基因芯片进行杂交检测，数据采用GeneSpring分析软件进行处理。
结果：本研究分两个独立阶段开展样本基因表达分析。第一阶段，对比GBM周围白质与正常白质的分子谱，筛选得到59个差异表达基因。其中，成熟神经细胞表达的众多基因在GBM周围白质中呈下调趋势，而支持肿瘤侵袭的基因产物则呈现过表达。尤为关键的是，KLRC1（杀伤细胞凝集素样受体C1）——一种天然参与抗肿瘤细胞活化的特异性自然杀伤细胞受体——在GBM周围白质中被显著抑制，提示该组织内的抗肿瘤免疫监视功能受损。第二阶段，本研究聚焦于GBM外周相对于肿瘤核心的特异性调控基因。在GBM周围组织中，上调幅度最高的基因编码DTX4，该基因是NOTCH信号通路的调控因子，此前研究证实其在维持神经前体细胞未分化状态中发挥关键作用。
结论：本研究揭示了GBM周围组织独特的分子特征，显示免疫监视相关基因以及干细胞干性维持相关基因均存在表达失调。综上，本研究数据有助于阐明GBM复发相关的分子机制。本研究尝试明确GBM周围组织的分子特征：共纳入5例接受肿瘤全切术的患者，采集其肿瘤主体组织，所有病例的肿瘤周围组织均取自距肉眼可见肿瘤边界2厘米的未浸润白质区域；此外，本研究还从因颅内深部海绵状血管瘤接受手术的患者体内获取了对照白质活检样本。每例患者的肿瘤核心样本与周围组织样本采用相同的后缀编号进行标识。其中3号和4号患者各采集了两份肿瘤外周组织样本，分别以相同编号加“R”（重复样本）进行区分。