PPM1D and medulloblastoma: Furthermore, the relative expression level of PPM1D mRNA was higher in medulloblastoma cell lines with 17q-gained aberrations (D283-MED, D458-MED and MEB-MED8A) compared to cell lines with normal 17q (DAOY, UW228-3 and PFSK-1), further demonstrating a gene-dosage effect on PPM1D mRNA expression (Figure 1A,C).