CDK4 and neoplasm: We found that in the absence of Rack1 in either GNPs (cKO mice) or SHH‐MB tumor cells (Rescue mice), the transcription of ccnd3 (p = 0.0087, n = 5; and p = 0.0022, n = 5, respectively), ccne2 (p = 0.0021, n = 5; and p = 0.0381, n = 5, respectively), and cdk4 (p = 0.0065, n = 6; and p = 0.0033, n = 6, respectively) were all significantly decreased (Figure 3F).