Division of Oncology (J.L.A., R.M., N.O., A.L., S.S., R.D., M.F., L.M.C., L.H., M.D., B.D.), Experimental Hematology and Cancer Biology (R.R.W., J.W.), Pathology (L.M.), Developmental Biology, Center for Autoimmune Genomics and Etiology and Biomedical Informatics, Cincinnati Childrens Hospital Medical Center (CCHMC), Cincinnati, Ohio (M.L.W.); Division of Pediatric Oncology, Johns Hopkins University, Baltimore, Maryland (E.H.R.), Nemours Children’s Hospital, Orlando, Florida (L.M.)
Neuro Oncol. 2017 Aug 1;19(8):1068-1078. doi: 10.1093/neuonc/now299.
Diffuse intrinsic pontine glioma (DIPG) is a high-grade brainstem glioma of children with dismal prognosis. There is no single unifying model about the cell of origin of DIPGs. Proliferating cells in the developing human and mouse pons, the site of DIPGs, express neural stem/progenitor cell (NPC) markers, including Sox2, nestin, vimentin, Olig2, and glial fibrillary acidic protein, in an overlapping and non-overlapping manner, suggesting progenitor cell heterogeneity in the pons. It is thought that during a restricted window of postnatal pons development, a differentiation block caused by genetic/epigenetic changes leads to unrestrained progenitor proliferation and DIPG development. Nearly 80% of DIPGs harbor a mutation in the H3F3A or the related HIST1H3B gene. Supporting the impaired differentiation model, NPCs derived from human induced pluripotent stem cells expressing the H3F3A mutation showed complete differentiation block. However, the mechanisms regulating an altered differentiation program in DIPG are unknown.
We established syngeneic serum-dependent and independent primary DIPG lines, performed molecular characterization of DIPG lines in vitro and in an orthotopic xenograft model, and used small hairpin RNA to examine Olig2 function in DIPG.
The transcription factor Olig2 is highly expressed in 70%-80% of DIPGs. Here we report that Olig2 expression and DIPG differentiation are mutually exclusive events in vitro, and only DIPG cells that retained Olig2 in vitro formed robust Olig2-positive brainstem glioma with 100% penetrance in a xenograft model.
Our results indicate Olig2 as an onco-requisite factor in DIPG and propose investigation of Olig2 target genes as novel candidates in DIPG therapy.
弥漫性内在脑桥神经胶质瘤（DIPG）是一种儿童高级别脑干神经胶质瘤，预后较差。关于 DIPG 的起源细胞尚无单一的统一模型。在人类和小鼠脑桥的发育过程中，DIPG 的发生部位，增殖细胞以重叠和不重叠的方式表达神经干细胞/祖细胞（NPC）标志物，包括 Sox2、巢蛋白、波形蛋白、Olig2 和胶质纤维酸性蛋白，提示脑桥中祖细胞的异质性。据认为，在脑桥发育的一个有限的出生后窗口期间，遗传/表观遗传变化引起的分化阻滞导致祖细胞不受控制的增殖和 DIPG 发展。近 80%的 DIPG 携带 H3F3A 或相关 HIST1H3B 基因突变。支持受损分化模型，表达 H3F3A 突变的人诱导多能干细胞衍生的 NPC 显示出完全分化阻滞。然而，DIPG 中改变的分化程序的调节机制尚不清楚。
我们建立了同源血清依赖性和非依赖性原发性 DIPG 系，对 DIPG 系进行了体外和原位异种移植模型的分子特征分析，并使用短发夹 RNA 研究了 Olig2 在 DIPG 中的功能。
转录因子 Olig2 在 70%-80%的 DIPG 中高度表达。在这里，我们报告说，Olig2 表达和 DIPG 分化是体外相互排斥的事件，只有在体外保留 Olig2 的 DIPG 细胞才能在异种移植模型中形成具有 100%穿透性的强大 Olig2 阳性脑干神经胶质瘤。
我们的结果表明 Olig2 是 DIPG 的一个必需因素，并提出了对 Olig2 靶基因的研究作为 DIPG 治疗的新候选物。
