California Pacific Medical Center Research Institute, San Francisco, California, USA.
PLoS One. 2013 Jul 5;8(7):e68176. doi: 10.1371/journal.pone.0068176. Print 2013.
Glioblastoma multiforme (GBM) is a highly malignant primary central nervous system neoplasm characterized by tumor cell invasion, robust angiogenesis, and a mean survival of 15 months. Human cytomegalovirus (HCMV) infection is present in >90% of GBMs, although the role the virus plays in GBM pathogenesis is unclear. We report here that HCMV pp71, a viral protein previously shown to promote cell cycle progression, is present in a majority of human GBMs and is preferentially expressed in the CD133+, cancer stem-like cell population. Overexpression of pp71 in adult neural precursor cells resulted in potent induction of stem cell factor (SCF), an important pro-angiogenic factor in GBM. Using double immunofluorescence, we demonstrate in situ co-localization of pp71 and SCF in clinical GBM specimens. pp71 overexpression in both normal and transformed glial cells increased SCF secretion and this effect was specific, since siRNA mediated knockdown of pp71 or treatment with the antiviral drug cidofovir resulted in decreased expression and secretion of SCF by HCMV-infected cells. pp71- induced upregulation of SCF resulted in downstream activation of its putative endothelial cell receptor, c-kit, and angiogenesis as measured by increased capillary tube formation in vitro. We demonstrate that pp71 induces a pro-inflammatory response via activation of NFΚB signaling which drives SCF expression. Furthermore, we show that pp71 levels and NFKB activation are selectively augmented in the mesenchymal subtype of human GBMs, characterized by worst patient outcome, suggesting that HCMV pp71-induced paracrine signaling may contribute to the aggressive phenotype of this human malignancy.
多形性胶质母细胞瘤（GBM）是一种高度恶性的中枢神经系统原发性肿瘤，其特征为肿瘤细胞侵袭、丰富的血管生成以及平均 15 个月的生存时间。人类巨细胞病毒（HCMV）感染存在于>90%的 GBM 中，尽管该病毒在 GBM 发病机制中的作用尚不清楚。我们在此报告，HCMV pp71，一种先前被证明可促进细胞周期进程的病毒蛋白，存在于大多数人类 GBM 中，并优先在 CD133+、癌症干细胞样细胞群体中表达。在成人神经前体细胞中过表达 pp71 会导致强烈诱导干细胞因子（SCF）的表达，SCF 是 GBM 中一种重要的促血管生成因子。通过双重免疫荧光，我们在临床 GBM 标本中证明了 pp71 和 SCF 的原位共定位。pp71 在正常和转化的神经胶质细胞中的过表达均增加了 SCF 的分泌，并且这种作用是特异性的，因为 pp71 的 siRNA 介导的敲低或抗病毒药物更昔洛韦的治疗导致 HCMV 感染细胞中 SCF 的表达和分泌减少。pp71 诱导的 SCF 上调导致其潜在的内皮细胞受体 c-kit 的下游激活，并通过体外毛细血管管形成的增加来测量血管生成。我们证明 pp71 通过激活 NFΚB 信号转导诱导促炎反应，从而驱动 SCF 的表达。此外，我们表明 pp71 水平和 NFKB 激活在人类 GBM 的间充质亚型中选择性增强，其特征是患者预后最差，这表明 HCMV pp71 诱导的旁分泌信号可能有助于这种人类恶性肿瘤的侵袭表型。
