590 to determine speciﬁcity for E2F1 and to rule out off-target effects or non-speciﬁc results because of the process of virus infection. The lentiviruses were aspirated and replaced with serum-free CGNP medium (above) contain- ing Shh. The cells were lysed 48-h post-infection. Immunostaining Tissues were ﬁxed in 4 % para-formaldehyde and parafﬁn- embedded as previously described [3]. After dehydration steps and sectioning, tissue slides were washed with 19 phosphate buffered saline (PBS) and permeabilized in 1 % TritonX-100 for 5 min. Slides were then blocked in 5 % goat serum in PBS-Tween (19 PBS and 0.1 % TritonX-100) for 1 h in room temperature, washed once with 19 PBS, and incubated with primary antibody in 2.5 % goat serum (in PBS- Tween) overnight at 4 C. They were washed three times with 19 PBS and incubated with secondary antibody for 2 h at room temperature, then washed and mounted in 40-6-diami- dino-2-phenylindole-containing mounting medium (Vector Labs, Burlingame, CA, USA). Primary antibodies used were: E2F1 (H-137; Santa Cruz), PPARc (E-8; Santa Cruz), FASN (Cell Signaling, Danvers MA), Hexokinase I (Cell Signaling), Hexokinase II (Cell Signaling), Glut4 (Cell Signaling), PKM2 (Cell Signaling), P-Histone H3 (Cell Signaling), and Ki67 (Vector Labs, Burlingame CA). Secondary ﬂuorescent-tagged antibodies were: Alexa Fluor goat anti-rabbit 488/594 (Invitrogen, Carlsbad, CA) and Alexa Fluor goat anti-mouse 488/594 (Invitrogen). Image capturing Immunostaining performed on tissue sections was visual- ized using a Leica DM5000B microscope and images were captured with Leica FW400 software (Leica Microsystems, Bannockburn, IL, USA). Oil Red O staining Oil Red O staining of neutral lipids in NeuroD2-SmoA1 medulloblastoma frozen sections was performed by the histology core in the Department of Pathology and Labo- ratory Medicine in the Hospital for Special Surgery and by the microcytometry core facility at Memorial Sloan–Ket- tering Cancer Center according to established protocols. PET scanning Acta Neuropathol (2012) 123:587–600 tail vein with 300 mCi of the PET radiotracer FDG in *200 ml of normal saline. At *45-min post-injection, the mouse was ﬁrst anesthetized by inhalation of a 2 % iso- ﬂuorane/oxygen gas mixture (ﬂow rate of 2 L/min.) and placed on the scanner bed in the prone position. The acquisition is set up for *5 min using a photopeak energy window of 350–750 keV, and a coincidence timing win- dow of 6 nsec—and launched using the microPET’s microPET ManagerTM computer software. Data are acquired in list mode. The resulting data are sorted into 2D histograms by Fourier re-binning and transverse images are reconstructed by ﬁltered back-projection (FBP) into a 3D imaging matrix using the system Nyquist frequency as the cut-off. The image data are normalized to correct for non- uniformity of response of the microPET, dead-time count losses, positron branching ratio, and physical decay to the time of injection, attenuation, scatter, or partial-volume averaging corrections are generally not applied. An empirically determined system calibration factor (in units of mCi/mL/cps/voxel) for mice is used to convert voxel count rates to activity concentrations, and the resulting image data are then normalized to the administered activity to parameterize images in terms of percent of the injected doses per gram (%ID/gm). Manually drawn 2D regions-of- interest (ROIs) or 3D volumes-of-interest (VOIs) are used to determined the mean and maximum %ID/g (decay cor- rected to the time of injection) in tumors and various organs using ASIPro VMTM computer software (Concorde Microsystems). Cell viability Cell viability was determined with the cell Titer Glo assay (Promega, Madison, WI) which utilizes luminescent reagents reacting with ATP yielding a quantitative expression of living cells in the sample expressed as a relative luminescence between samples. This luminescence was measured with the Glo Max Multi ? (Promega) plate reader. Statistical analysis was accomplished with SAS software package (SAS Inst. Inc., N.C., USA). Signiﬁcant differences between mean were determined by ANOVA procedure test and a P value of \0.05 was considered to be statistically signiﬁcant. The results are expressed as the mean ± SD from quadruplicate test data. Results For ﬂuorine-18 ﬂuoro-deoxyglucose (FDG) studies using the Focus 120 microPET small-animal PET scanner (Concorde Microsystems, Knoxville, TN), animals were fasted for 6 h prior to injection of the radiotracer; access to water was permitted. Mice were bolus injected via lateral Marked deregulation of PPARc in Shh-driven mouse medulloblastomas We have previously reported that the subclass of medul- loblastomas resulting from aberrant activation of Shh 123