MDM4 is one of the major regulators of p53. The biological effect of MDM4 on tumor is controversial, its role and molecular mechanism in colon cancer progression and prognosis are still unclear. In this study, we identify that MDM4 is significantly overexpressed in human colon cancer and high MDM4 expression was associated with poor prognosis of colon cancer with mutant p53. MDM4 inhibits the ubiquitination of the ferroptosis marker protein GPX4 at K167 and K191 by upregulating the protein expression level of the E3 ubiquitin ligase TRIM21, which promotes the polyubiquitination of GPX4 transfer from K48- to K63- linked ubiquitination. Thereby, MDM4 enhances the stability of GPX4 protein, inhibiting ferroptosis, increasing the resistance of colon cancer patients to chemotherapy, and promoting colon cancer progression. These findings elucidate the ferroptosis inhibition effect of MDM4 via regulating TRIM21/GPX4 on p53-mutated colon cancer and provide a potential therapeutic strategy for colon cancer therapy.

MDM4 is one of the MDM protein family and is generally recognized as the key negative regulator of p53. As a cancer-promoting factor, it plays a non-negligible role in tumorigenesis and development. In this article, we analyzed the expression levels of MDM4 in pan-cancer through multiple databases. We also investigated the correlations between MDM4 expression and prognostic value, immune features, genetic mutation, and tumor-related pathways. We found that MDM4 overexpression is often accompanied by adverse clinical features, poor prognosis, oncogenic mutations, tumor-immune infiltration and aberrant activation of oncogenic signaling pathways. We also conducted transcriptomic sequencing to investigate the effect of MDM4 on transcript levels in colon cancer and performed qPCR to verify this. Finally, we carried out some in vitro experiments including colony formation assay, chemoresistance and senescence-associated β-galactosidase activity assay to study the anti-tumor treatment effect of small molecule MDM4 inhibitor, NSC146109. Our research confirmed that MDM4 is a prognostic biomarker and potential therapeutic target for a variety of malignancies.

MDMX serves as a significant regulator of p53, which is a crucial tumor suppressor protein. However, the biological functions and underlying mechanism of MDMX in hepatocellular carcinoma (HCC) remain inadequately understood. In this study, we demonstrate that MDMX is overexpressed in HCC, and elevated expression of MDMX is significantly correlated with poor prognosis in HCC harboring mutant p53. MDMX inhibits the degradation of 14-3-3γ and facilitates its localization within cytoplasm, thereby enhances the interaction between FOXO1 and 14-3-3γ, which promotes the degradation of FOXO1. Consequently, the overexpression of MDMX results in downregulation of FOXO1 followed by increase of RPIA and decrease of PCK1, leading to increased glucose uptake, lactate secretion, and ATP production. These findings elucidate the role of MDMX in promoting glycolysis through the regulation of the 14-3-3γ/FOXO1 axis in p53-mutated HCC, thereby offering a potential therapeutic target for the treatment of HCC.

Background Mouse double minute 4 (MDM4) is a well-established regulator of the tumor suppressor p53, but its independent role in the context of TP53 mutations in oral squamous cell carcinoma (OSCC) has not been elucidated. This study aims to investigate the metabolic regulatory function of MDM4 in TP53-mutant OSCC and explore its potential as a therapeutic target. Methods Bioinformatic analysis, qRT-PCR, western blotting, metabolomics, and Seahorse assays were used to assess MDM4-mediated metabolic regulation. Mechanistic studies included co-immunoprecipitation, site-directed mutagenesis, and ubiquitination assays to examine regulation of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 2 (PFKFB2). In vitro and in vivo experiments were performed to evaluate the antitumor effects of combined inhibition of MDM4 and PFKFB2. Results We demonstrate that MDM4 enhances tumor cell proliferation and glycolytic activity in TP53-mutant OSCC. Mechanistically, MDM4 stabilizes the glycolytic enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 2 (PFKFB2) by promoting its interaction with the adaptor protein YWHAG and inhibiting K48-linked ubiquitination. This interaction protects phosphorylated PFKFB2 (Ser466/Ser483) from ubiquitin-mediated degradation and promotes the binding of YWHAG to PFKFB2, thereby preventing its K490 ubiquitination. Silencing PFKFB2 significantly reduces the glycolysis-promoting effects of MDM4, and combined inhibition of both MDM4 and PFKFB2 leads to a synergistic suppression of tumor growth both in vitro and in vivo. Conclusions These findings uncover a novel p53-independent role of MDM4 in metabolic regulation in TP53-mutant OSCC and identify the MDM4-YWHAG-PFKFB2 axis as a potential therapeutic vulnerability. Targeting this pathway may provide a promising therapeutic strategy for TP53-mutant OSCC and support MDM4 as a candidate therapeutic target. Graphical abstract Schematic illustration of the mechanism by which MDM4 promotes glycolysis and proliferation in TP53-mutant OSCC. In TP53-mutant OSCC, MDM4 enhances glycolysis by stabilizing PFKFB2. Mechanistically, MDM4 reinforces the interaction between YWHAG and PFKFB2 phosphorylated at S466/S483, thereby protecting PFKFB2 from ubiquitination at K490 and subsequent degradation. As a consequence, stabilized PFKFB2 increases the level of F-2,6-BP, which activates PFK1 and promotes glycolytic flux. Enhanced glycolysis further increases ATP production, ultimately supporting tumor cell growth and proliferation in TP53-mutant OSCC. Abbreviations: ATP, adenosine triphosphate; F-1,6-BP, fructose-1,6-bisphosphate; F-2,6-BP, fructose-2,6-bisphosphate; F6P, fructose-6-phosphate; G6P, glucose-6-phosphate; K490, lysine 490; MDM4, mouse double minute 4; OSCC, oral squamous cell carcinoma; PFK1, phosphofructokinase-1; PFKFB2, 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 2; S466, serine 466; S483, serine 483; TP53, tumor protein p53; YWHAG, 14-3-3γ.