Extended Data Fig. 2. Knockdown of p53 decreases MHC-I expression in murine and human medulloblastoma cells.

(a) FACS histogram of MHC-I expression in normal neural stem cells (NSCs). Isotype control is shown in gray and MHC-I staining in black. Quantification of the mean fluorescence intensity (MFI) values for three independent NSC samples (isolated from three separate litters of mice) is shown below the histogram; data points represent MFIs for individual NSC samples. p-value, determined by two-sided unpaired t-test, is indicated on bar graph. (b and d) FACS histograms of MHC-I or HLA-I expression in murine MG tumor cells (b) and human HD-MB03 tumor cells (d) transduced with control shRNA (black histograms) or shRNAs that target sequences conserved in mouse and human p53 (shp53 #109, blue histograms; shp53 #110, pink histograms). Quantification of the MFI values for three independent tumors are shown below each histogram; data points represent MFIs for individual tumor samples. p-values were determined by two-sided unpaired t-test. p-values are indicated on each bar graph. (c and e) Protein levels of p53 and β-Actin were determined by western blotting in MG tumor cells (c) and HD-MB03 cells (e). Western blots are cropped at the molecular weights for p53 (53 kDa) and β-actin (42 kDa); original blots are available in Source Data. (f) Murine Ptch-KO MB tumor cells overexpressing dominant negative p53 (Ptch-KO MB-DNP53) were transplanted into NSG or aB6 mice. Survival curves (n=8) are shown. p-values for the difference in survival between Ptch-KO MB and Ptch-KO MB-DNP53 were determined by two-sided log-rank (Mantel-Cox) test. NS (not significant), p=0.6939 (NSG) and ** p=0.0021 (aB6). (g) FACS histograms of MHC-I expression in Ptch-KO MB (black) and Ptch-KO MB-DNP53 (blue) tumor cells. Quantification of MFI values for three independent tumor samples is shown below the histogram; data points represent MFIs for each tumor sample. p-value, determined by two-sided unpaired t-test, is indicated on bar graph.