MDM4 inhibition: a novel therapeutic strategy to reactivate p53 in hepatoblastoma

Sarah E Woodfield,Dolores López-Terrada,Ketan B Ghaghada,Yan Shi,Aryana M Ibarra,Rohit K Srivastava,Pavel Sumazin,Andrew Badachhape,Zbigniew Starosolski,Zhenghu Chen,Stephen F Sarabia,Roma H Patel,Sanjeev A Vasudevan,Samuel R Larson,Richard S Whitlock,D Allen Annis,Aayushi P Shah

doi:10.1038/s41598-021-82542-4

Abstract

Hepatoblastoma (HB) is the most common pediatric liver malignancy. High-risk patients have poor survival, and current chemotherapies are associated with significant toxicities. Targeted therapies are needed to improve outcomes and patient quality of life. Most HB cases are TP53 wild-type; therefore, we hypothesized that targeting the p53 regulator Murine double minute 4 (MDM4) to reactivate p53 signaling may show efficacy. MDM4 expression was elevated in HB patient samples, and increased expression was strongly correlated with decreased expression of p53 target genes. Treatment with NSC207895 (XI-006), which inhibits MDM4 expression, or ATSP-7041, a stapled peptide dual inhibitor of MDM2 and MDM4, showed significant cytotoxic and antiproliferative effects in HB cells. Similar phenotypes were seen with short hairpin RNA (shRNA)-mediated inhibition of MDM4. Both NSC207895 and ATSP-7041 caused significant upregulation of p53 targets in HB cells. Knocking-down TP53 with shRNA or overexpressing MDM4 led to resistance to NSC207895-mediated cytotoxicity, suggesting that this phenotype is dependent on the MDM4-p53 axis. MDM4 inhibition also showed efficacy in a murine model of HB with significantly decreased tumor weight and increased apoptosis observed in the treatment group. This study demonstrates that inhibition of MDM4 is efficacious in HB by upregulating p53 tumor suppressor signaling.

Highlights

Liver cancer remains one of the leading causes of cancer-related deaths worldwide[1]
We assess the effects of the established Murine double minute 4 (MDM4) inhibitor NSC207895 (XI-006), which is known to inhibit gene expression of MDM4 by physically binding its promoter and preventing transcription, induce apoptosis, and activate the p53 signaling p athway[23], and the peptide dual Murine double minute 2 (MDM2) and MDM4 inhibitor ATSP-7041 in a range of in vitro and in vivo assays to show that targeting MDM4 in HB may be an effective treatment strategy for this disease
We first examined gene expression levels of MDM4 and MDM2 along with a panel of p53 target genes in an Affymetrix microarray dataset of 50 HB patients and six normal pediatric liver tissues described in a previous key publication[20]. These analyses showed that gene expression of 22 established p53 target genes used as a readout for p53 activity significantly correlated with both MDM4 (p = 0.000456) and MDM2 (p = 0.000567) expression in the tumor samples (Fig. 1a)

Summary

Introduction

Liver cancer remains one of the leading causes of cancer-related deaths worldwide[1]. A study of 363 HCC cases showed that MDM4 expression and copy number were significantly increased in cases with wild-type TP53 but low expression of p53 targets, relative to other c ases[14]. We assess the effects of the established MDM4 inhibitor NSC207895 (XI-006), which is known to inhibit gene expression of MDM4 by physically binding its promoter and preventing transcription, induce apoptosis, and activate the p53 signaling p athway[23], and the peptide dual MDM2 and MDM4 inhibitor ATSP-7041 in a range of in vitro and in vivo assays to show that targeting MDM4 in HB may be an effective treatment strategy for this disease

Methods

Results

Conclusion