Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, 560012, India.
BMC Cancer. 2022 Jun 11;22(1):642. doi: 10.1186/s12885-022-09682-2.
Glioblastoma (GBM) is the most common primary malignant brain tumor in adults exhibiting infiltration into surrounding tissues, recurrence, and resistance to therapy. GBM infiltration is accomplished by many deregulated factors such as cell adhesion molecules (CAMs), which are membrane proteins that participate in cell-cell and cell-ECM interactions to regulate survival, proliferation, migration, and stemness.
A comprehensive bioinformatics analysis of CAMs (n = 518) in multiple available datasets revealed genetic and epigenetic alterations among CAMs in GBM. Univariate Cox regression analysis using TCGA dataset identified 127 CAMs to be significantly correlated with survival. The poor prognostic indicator PTGFRN was chosen to study its role in glioma. Silencing of PTGFRN in glioma cell lines was achieved by the stable expression of short hairpin RNA (shRNA) against the PTGFRN gene. PTGFRN was silenced and performed cell growth, migration, invasion, cell cycle, and apoptosis assays. Neurosphere and limiting dilution assays were also performed after silencing of PTGFRN in GSCs.
Among the differentially regulated CAMs (n = 181, 34.9%), major proportion of them were found to be regulated by miRNAs (n = 95, 49.7%) followed by DNA methylation (n = 32, 16.7%), and gene copy number variation (n = 12, 6.2%). We found that PTGFRN to be upregulated in GBM tumor samples and cell lines with a significant poor prognostic correlation with patient survival. Silencing PTGFRN diminished cell growth, colony formation, anchorage-independent growth, migration, and invasion and led to cell cycle arrest and induction of apoptosis. At the mechanistic level, silencing of PTGFRN reduced pro-proliferative and promigratory signaling pathways such as ERK, AKT, and mTOR. PTGFRN upregulation was found to be due to the loss of its promoter methylation and downregulation of miR-137 in GBM. PTGFRN was also found to be higher in glioma stem-like cells (GSCs) than the matched differentiated glioma cells (DGCs) and is required for GSC growth and survival. Silencing of PTGFRN in GSCs reduced transcript levels of reprogramming factors (Olig2, Pou3f2, Sall2, and Sox2).
In this study, we provide a comprehensive overview of the differential regulation of CAMs and the probable causes for their deregulation in GBM. We also establish an oncogenic role of PTGFRN and its regulation by miR-137 in GBM, thus signifying it as a potential therapeutic target.
胶质母细胞瘤（GBM）是成人中最常见的原发性恶性脑肿瘤，具有向周围组织浸润、复发和对治疗产生耐药性的特点。GBM 的浸润是由许多失调的因子完成的，如细胞粘附分子（CAMs），它们是参与细胞-细胞和细胞-细胞外基质相互作用的膜蛋白，以调节存活、增殖、迁移和干性。
对多个可用数据集的 518 个 CAMs 进行全面的生物信息学分析，揭示了 GBM 中 CAMs 的遗传和表观遗传改变。使用 TCGA 数据集的单变量 Cox 回归分析确定了 127 个与生存显著相关的 CAMs。选择预后不良的指标 PTGFRN 来研究其在神经胶质瘤中的作用。通过针对 PTGFRN 基因的短发夹 RNA（shRNA）的稳定表达来实现胶质瘤细胞系中 PTGFRN 的沉默。沉默 PTGFRN 后进行细胞生长、迁移、侵袭、细胞周期和凋亡检测。沉默 PTGFRN 后还在 GSCs 中进行神经球和有限稀释测定。
在差异调节的 CAMs（n=181，34.9%）中，大多数发现是由 miRNA 调节的（n=95，49.7%），其次是 DNA 甲基化（n=32，16.7%）和基因拷贝数变异（n=12，6.2%）。我们发现 PTGFRN 在 GBM 肿瘤样本和细胞系中上调，与患者生存的预后显著相关。沉默 PTGFRN 可减弱细胞生长、集落形成、无锚定生长、迁移和侵袭，并导致细胞周期停滞和诱导凋亡。在机制水平上，沉默 PTGFRN 可降低 ERK、AKT 和 mTOR 等促增殖和促迁移信号通路。PTGFRN 的上调是由于其启动子甲基化的丧失和 GBM 中 miR-137 的下调。PTGFRN 在神经胶质瘤干细胞（GSCs）中也高于匹配的分化神经胶质瘤细胞（DGCs），是 GSC 生长和存活所必需的。沉默 GSCs 中的 PTGFRN 可降低重编程因子（Olig2、Pou3f2、Sall2 和 Sox2）的转录水平。
在这项研究中，我们提供了 CAMs 差异调节的全面概述，并确定了它们在 GBM 中失调的可能原因。我们还建立了 PTGFRN 在 GBM 中的致癌作用及其受 miR-137 的调节，从而将其作为潜在的治疗靶点。
