RB1 and medulloblastoma: CDKN2A suppressed RB phosphorylation less effectively in tumor cells than in CGNPs, as the pRB+ fractions of CDKN2A+ cells were significantly higher in M-Smo/EedcKO and M-Smo/Ezh2cKO medulloblastomas compared to P7 EedcKO cerebella (Fig. 6B).