XI-011 inhibits MDM4 transcription by transcription factor downregulation. (A) MDM4 mRNA level at 16 h following XI-011 treatment of HepG2 and HLE cells. (B) MDM4 protein expression as detected by Western immunoblots and corresponding densitometric analysis (lower panel) 16 h following XI-011 treatment of HepG2 and HLE cell lines. (C) Luciferase activity of a MDM4 promoter reporter following XI-011 treatment in HepG2 and HLE cells, respectively. (D) Induction of p53 and PARP protein cleavage following XI-011 treatment of HCC cell lines as indicated. (E) XI-011 treatment led to p21 mRNA induction in both HCC cell lines. (F) p53 protein expression over time following XI-011 treatment (1 µM) with or without additional cycloheximide (CHX) treatment in p53-wildtype HepG2 and p53-mutant HLE cells as detected by Western immunoblotting. (G) Relative cell viability of HepG2 and HLE cells over time after XI-011 treatment using the indicated doses compared to control cells. (H) Western immunoblots following XI-011 treatment of HepG2 and HLE cells. Original western blots are shown in Figures S9–S12. Data are presented as mean ± SEM. One-way and two-way ANOVA with Tukey’s test were used in panel C and G, respectively; all the other data were analyzed by Kruskal–Wallis followed by Dunn’s test: * p < 0.05, ** p < 0.01, *** p < 0.001. Abbreviations: fl, full-length PARP protein; cl, cleaved PARP protein; GLuc, Gaussia luciferase; SEAP, secreted alkaline phosphatase; norm., normalized against control; CHX, cycloheximide.