Proliferating regions in transgenic mice (E/p53^−/−) were identified by administering BrdU 2 h before sacrifice. (A–B) Identification of BrdU+ cells next to the SVZ in transgenic mice developing tumors. Higher magnification of BrdU labeling (arrows) in stria terminalis of striatum, a WM region. (C) Proliferation (Ki67+) in WM structures (arrows): cc--corpus callosum, ec--external capsule. To investigate if v-erbB expanded NSCs and their progeny at P30, transgenic mice and non-transgenic mice were administered BrdU 2 h before sacrifice (insert). (D) T1 weighted MRI shows a supratentorial tumor (arrow) in a E/p53^−/− mouse. (E) Pathology obtained after MRI shows tumor in WM (arrowheads). (F) Tumor cells with round nuclei and perinuclear cytoplasmic retraction (arrows). (G–I) NG2+/Olig2+ cells (*) in CC in control p53^−/− mice (G) and in E/p53^−/− mice (H), quantification results are shown in (I). ***P < 0.001, Student’s t-test. Values are expressed as mean ± SEM. (J–O) H&E staining of (J–L) and NG2 expression in (M–O) a transgenic mouse brain. Arrows indicate WM tracts, cb--cerebellum, ot--optic tract, sp--septum, ctx--cortex, ob--olfactory bulb, hipp--hippocampus. (J, M) A parasagittal section shows multifocal tumors (*). (K, N) Tumors along CC. Arrows in the insert indicate perinuclear halos. (L, O) Tumors arising in cerebellum. The innermost WM structure is indicated by arrow. * indicates molecular cell layers (*). See also Figure S1.

(A) Illustration of two coronal sections of a mouse brain. Red dots represent brain regions that incorporated BrdU in P30 E/p53^−/− mice at 2 hr. Lateral ventricles (lv) are shown in blue. ec--external capsule, cc--corpus callosum, ac--anterior commisure, sp--septum pellucidum, st--stria terminalis, ot--optic tract. (B–D) Incorporation of BrdU (arrows). (E–G) Expresssion of the early glial marker Olig2 and the astrocytic marker GFAP in BrdU+ cells. (H–J) Co-expression of Olig2+ and NG2 in BrdU+ cells. See also Figure S2.

(A) Cells from three low-passage murine oligodendrogliomas or from p53^−/− SVZ were grown in the absence (w/o GF) or presence of indicated growth factors (7d) on coated plates and quantified by CyQuant proliferation assay. (B) Immunoblot of pAkt and pErk1/2 in adherent cells on coated plates from p53^−/− and E/p53^−/− mice. SVZ-subventricular zone, CC-corpus callosum, T-tumor. (C–D) Immunofluoresent analyses of NG2+ and O4+ cells from a representative murine oligodendroglioma without or with treatment with 1 μM PD for 7days (C), quantification data shown in (D). Scale bar: 40 μm. (E–F) Immunofluoresent analyses for the neuronal marker map2ab+ and the glial marker GFAP of SVZ NSCs without or with treatment with 1 μM PD for 7days. Values are expressed as mean ± SEM. See also Figure S3.

(A–C) Low-passage SVZ NSCs, GFAP-Ras murine astrocytoma cells, and murine oligodendroglioma cells were incubated with CNTF or BMP4 for 7d and their proliferation was measured using CyQuant proliferation assay. (D–F) Potential of acutely isolated SVZ NSCs and murine oligodendroglioma cells to differentiate into three neural cell lineages. (D) Murine oligodendroglioma cells or p53^−/− spheres from SVZ were stained for NG2, O4, Map2ab, and GFAP under differentiating conditions for 7d in response to forskolin, CNTF, and T3/IGF1. Scale bars: 40 μm. (E–F) Quantification of response for acutely isolated murine oligodendroglioma cells and SVZ NSC cultures, to agents shown in D, and to BMP4. Values are expressed as mean ± SEM. See also Figure S4.

(A) Expression of the NSC marker CD15 (arrows) and the progenitor marker NG2, in FACS sorted murine oligodendroglioma tumor cells. (B) Allografting of 1,000 low-passage tumor cells (10118T) analyzing tumor-forming ability of CD15− and CD15+ NSC -like cells (n = 5 per group) and survival of mice. (C) Animal survival following injection of 50 cells acutely isolated from tumor 30698, comparing NG2+, NG2−CD15−, and NG2−CD15+ cells. (D) Fraction of NG2+ cells shown as a function of passage (green--acutely isolated tumor cells, blue low passage; red high passage). (E–G) Tumorigencity of NG2+ cells and survival of grafted mice. Tumors isolated from E/p53^−/− mice were FACS sorted cells based on expression of NG2. (E) Tumor formation in mice grafted with 1,000 cells (n=5 mice per group) showing high expression of NG2 (NG2 high), low expression of NG2 (NG2 low), and NG2− cells (NG2 neg). (F) In a separate experiment, 50 acutely isolated (31193T), low-passage (10118T), or high-passage (24314T) NG2+ or NG2− tumor cells were grafted orthotopically. Tumor burden is indicated by surviving fraction. See also Figure S5.

Human oligodendrogliomas differ from astrocytomas in their increased sensitivity to alkylating agents. (A–B) Adherent low-passage murine oligodendroglioma cells (10118T) were treated with 100 μM TMZ for 7d (TMZ100). (C–D) Immunofluorescence staining of representative tumor cells demonstrating expression of NG2 before and after incubation with TMZ. (E–F) Proliferation assay demonstrating response of acutely isolated murine oligodendroglioma cells (30698T) to increasing concentrations of TMZ (0–100 μM), as a function of NG2 status. (G–H) Response of low-passage human oligodendroglioma cells (SF8245) to TMZ, as a function of NG2 status. (I) Flow cytometry of SF7987 demonstrating the fraction of NG2+ cells in an acutely isolated 1p/19q deleted grade II oligodendroglioma. (J) FACS analyses: expression of NG2 in high-passage (red) GBMs, acutely dissociated oligodendrogliomas (green), and a low-passage oligodendroglioma (blue). (K–L) Surviving fraction of mice grafted with 1,000 NG2+ or NG2− cells per mouse from acutely isolated oligodendroglioma SF7987 and from an acutely isolated grade II oligodendroglioma SF7891 (showing EGFR expression and p53 mutation). Values are expressed as mean ± SEM. See also Figure S6.

(A) Grade II–III gliomas lacking frank contrast-enhancement on T1-weighted MRI were subclassified based on association with the lateral ventricles and measurement of the apparent diffusion coefficient (ADC) according to the flow chart. (B) Example illustrating distance between edge of tumor and lateral ventricle for astrocytoma grade III (A-III), and 1p/19q co-deleted oligodendroglioma (O-II). (C) T1-weighted spoiled gradient echo and T2-weighted fast low angle inversion recovery (FLAIR) images were used to localize the tumor within the brain parenchyma. The next two images were acquired with a diffusion-weighted imaging technique that is sensitive to fluid mobility within the tumor. Image maps of the ADC and the fractional anisotropy (FA) highlight regions of isotropic and directional fluid movement, respectively. Representative images of tumors located within the white matter: one subset typically exhibited well-circumscribed borders (A-II) on the FA maps while a second subset typically showed diffuse borders (O-II) (compare magnifications in (C)). (D) The majority of grade II-III astrocytomas were touching the lateral ventricles (Type 1) and had a well-circumscribed border on both the anatomic MRI (T2-weighted and FLAIR) as well as on the diffusion weighted FA map of directional water mobility along WM structures. A second group of astrocytomas (Type 2) were not touching the lateral ventricles but showed a pattern on FA maps with well-circumscribed borders similar to Type 1 astrocytomas. A third group of astrocytomas (Type 3) were away from the ventricles and showed diffuse borders on FA maps similar to (E) 1p/19q oligodendrogliomas. (F) Gene expression patterns in human oligodendroglioma cells and WM glial progenitors (OPCs). Quantitative real-time PCR identified relative abundance of transcripts in A2B5+ human oligodendroglioma cells (n=3) and human astrocytomas (n=4) relative OPCs (n=3) normalized to their A2B5− remainders. Scale bars: 2 cm.

Cells were isolated from a human 1p/19q deleted oligodendroglioma (T2-weighted FLAIR image in A, SF#8245) and cultured as adherent (M41 media in insert, B) or clusters (C). (D) Sphere formation potential in NG2+ and NG2− cells from 2 acutely isolated 1p/19q deleted oligodendrogliomas. (E–F) Incubation of cells from (A) with BrdU 2h before fixation, followed by staining for OPC-related genes NG2 and Nkx2.2, and stem cell marker Nestin. (G–I) To investigate differentiation, we incubated tumor cells that had been passaged once, with forskolin, BMP4, or T3/IGF1 (7d). Quantification (G) with representative images (H–I) demonstrating staining with NG2 and O4 in response to forskolin. Values are expressed as mean ± SEM. See also Figure S7.