An MDM2 inhibitor achieves synergistic cytotoxic effects with adenoviruses lacking E1B55kDa gene on mesothelioma with the wild-type p53 through augmenting NFI expression

Thao Thi Thanh Nguyen,Kenzo Hiroshima,Takao Morinaga,Boya Zhong,Masato Shingyoji,Michiko Hanazono,Masatoshi Tagawa,Hideaki Shimada,Yuji Tada

doi:10.1038/s41419-021-03934-y

Abstract

A majority of mesothelioma specimens were defective of p14 and p16 expression due to deletion of the INK4A/ARF region, and the p53 pathway was consequently inactivated by elevated MDM2 functions which facilitated p53 degradaton. We investigated a role of p53 elevation by MDM2 inhibitors, nutlin-3a and RG7112, in cytotoxicity of replication-competent adenoviruses (Ad) lacking the p53-binding E1B55kDa gene (Ad-delE1B). We found that a growth inhibition by p53-activating Ad-delE1B was irrelevant to p53 expression in the infected cells, but combination of Ad-delE1B and the MDM2 inhibitor produced synergistic inhibitory effects on mesothelioma with the wild-type but not mutated p53 genotype. The combination augmented p53 phosphorylation, activated apoptotic but not autophagic pathway, and enhanced DNA damage signals through ATM-Chk2 phosphorylation. The MDM2 inhibitors facilitated production of the Ad progenies through augmented expression of nuclear factor I (NFI), one of the transcriptional factors involved in Ad replications. Knocking down of p53 with siRNA did not increase the progeny production or the NFI expression. We also demonstrated anti-tumor effects by the combination of Ad-delE1B and the MDM2 inhibitors in an orthotopic animal model. These data collectively indicated that upregulation of wild-type p53 expression contributed to cytotoxicity by E1B55kDa-defective replicative Ad through NFI induction and suggested that replication-competent Ad together with augmented p53 levels was a therapeutic strategy for p53 wild-type mesothelioma.

Highlights

Mutations of p53 gene were infrequent in mesothelioma but a majority of the clinical specimens did not express p14 or p16 due to either deletion of the encoding CDKN2A locus or methylation of the transcriptional regulatory regions [1]
We investigated a role of p53 in nuclear factor I (NFI) expression with siRNA (Fig. 6C) and replication-deficient Ad expressing wild-type p53 (Ad-p53) (Fig. 6D)
Ad-delE1B upregulated p53 levels in the wild-type p53 mesothelioma but the p53 upregulation did not contribute to the Ad-mediated cytotoxicity

Summary

INTRODUCTION

Mutations of p53 gene were infrequent in mesothelioma but a majority of the clinical specimens did not express p14 or p16 due to either deletion of the encoding CDKN2A locus or methylation of the transcriptional regulatory regions [1]. Forced expression of p53 in mesothelioma activated p53-mediated cell death pathways but dephosphorylated pRb since p21, one of the p53 targets, blocked cyclin-dependent kinase 2 [5]. We examined effects of Ad defective of the gene encoding E1B55kDa molecules (Ad-delE1B) on mesothelioma with the wild-type p53 genotype, and demonstrated that Ad-delE1B upregulated p53 expression. An agent to inhibit the MDM2 function can increase endogenous p53 levels An imidazole compound such as nutlin-3a and RG7112 functions as an MDM2 inhibitor, upregulated p53 levels and activated p53-mediated apoptosis in tumors with the wild-type p53 genotype [12, 13].

MATERIALS AND METHODS

RESULTS

DISCUSSION

10 COMPETING INTERESTS

Ethics statement