TP53 and glioblastoma: To investigate whether NMD inhibition stabilizes the mRNA expression of p53β/γ isoforms and generates p53β/γ proteins lacking the negative regulatory region (Fig. 1, A and B), we used NSCLC cell lines (A549, H1944, and H460) and GBM cell lines (GSC289 and GSC231) bearing WT TP53 and MDM2 overexpression (Fig. S1, A and B).