CDKN1A and glioma: PITAR silencing in U87 glioma cells increased the luciferase activity from PG13-Luc, a p53-dependent reporter (el-Deiry et al., 1993; Figure 5—figure supplement 1A), decreased PITAR and TRIM28 mRNA levels, and increased CDKN1A mRNA levels with no change in TP53 mRNA levels (Figure 5A).