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

Our plain-English summary of An MDM2 inhibitor achieves synergistic cytotoxic effects with adenoviruses lacking E1B55kDa gene on mesothelioma with the wild-type p53 through augmenting NFI expression, by T.T.T. Nguyen, M. Shingyoji, M. Hanazono, et al (Cell Death & Disease, 2021).

The study

• Authors: T.T.T. Nguyen, M. Shingyoji, M. Hanazono, B. Zhong, T. Morinaga, Y. Tada, H. Shimada, K. Hiroshima, M. Tagawa
• Journal: Cell Death & Disease
• Published: 2021;12(7):663
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

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.

In plain English

This was a laboratory study in human mesothelioma cell lines with a mouse xenograft experiment. The authors tested replication-competent adenoviruses lacking the E1B55kDa gene (Ad-delE1B) with the MDM2 inhibitors nutlin-3a and RG7112 in mesothelioma cell lines with wild-type p53 (MSTO-211H, NCI-H226, NCI-H28) or mutated p53 (EHMES-1, JMN-1B); combination treatment was tested in MSTO-211H, NCI-H226, EHMES-1 and JMN-1B. Ad-delE1B inhibited growth regardless of p53 genotype, and p53 knockdown did not change susceptibility. Both MDM2 inhibitors were more cytotoxic to wild-type p53 cells than to mutated p53 cells (nutlin-3a average IC50 4.07 plus or minus 0.59 micromolar versus 30.85 plus or minus 2.76; RG7112 2.55 plus or minus 0.43 versus 10.51 plus or minus 0.49; p less than 0.01). Combining Ad-delE1B with an inhibitor gave combination index values below 1 (synergy) in MSTO-211H and NCI-H226 but above 1 (antagonism) in EHMES-1 and JMN-1B. In wild-type p53 cells the combination increased apoptosis, ATM-Chk2 phosphorylation, viral progeny production and NFI expression; progeny production did not increase in mutated p53 cells. In mice with intrapleural MSTO-211H tumours, the combination reduced tumour weights further than single agents.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: laboratory study in human mesothelioma cell lines with a mouse orthotopic xenograft experiment
• Who was studied: Human mesothelioma cell lines with wild-type p53 (MSTO-211H, NCI-H226, NCI-H28) and mutated p53 (EHMES-1, JMN-1B), A549 lung carcinoma cells, and BALB/c nu/nu mice (eight groups, 6 mice per group) injected intrapleurally with MSTO-211H cells; combination experiments used MSTO-211H, NCI-H226, EHMES-1 and JMN-1B
• Exposure: Replication-competent adenovirus lacking the E1B55kDa gene (Ad-delE1B), alone or combined with the MDM2 inhibitors nutlin-3a or RG7112; Ad-LacZ and Ad-p53 used as controls/comparators
• Main results:
  • Ad-delE1B inhibited growth of both wild-type and mutated p53 mesothelioma cells with similar IC50 values, and p53 knockdown did not change susceptibility
  • Average nutlin-3a IC50 in wild-type p53 cells was 4.07 plus or minus 0.59 micromolar
  • That nutlin-3a value was lower than in mutated p53 cells (30.85 plus or minus 2.76), and RG7112 values were 2.55 plus or minus 0.43 in wild-type versus 10.51 plus or minus 0.49 in mutated p53 cells
  • Synergy (combination index below 1) in the wild-type p53 lines MSTO-211H and NCI-H226 between fraction-affected points 0.2-0.8 for nutlin-3a and 0.2-0.7 for RG7112
  • In the mutated p53 lines EHMES-1 and JMN-1B the combination was rather antagonistic (combination index above 1)
  • In MSTO-211H and NCI-H226 (wild-type p53) the combination increased annexin V-positive fractions and caspase cleavages, without evidence of autophagy induction
  • DNA damage signalling was increased mainly through the ATM-Chk2 pathway rather than ATR-Chk1
  • MDM2 inhibitors raised viral progeny production and NFI expression in wild-type p53 cells, but not in mutated p53 cells; p53 siRNA abolished the enhanced replication, and Ad-p53 induced NFI dose-dependently
  • In mice bearing intrapleural MSTO-211H tumours, Ad-delE1B, nutlin-3a or RG7112 alone inhibited tumour growth and the combination further reduced tumour weights, without significant weight loss
• The authors' conclusion: The authors concluded that raising p53 with an MDM2 inhibitor activated the ATM-Chk2 pathway and augmented Ad-delE1B cytotoxicity through upregulated NFI, and suggested the combination as a therapeutic strategy for mesothelioma with the wild-type p53 genotype
• Limitations the authors state:
  • The authors stated they could not exclude that NFI induction was caused by viral replication rather than p53 alone
  • The authors stated that NFI expression level may not be directly related to viral progeny production, since other cellular factors are involved
  • The authors stated that the mechanism of the reciprocal regulation between NFI and p53 remains unknown
  • The authors stated that effects on normal tissues and therapeutic efficacy would need a clinical trial

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Mesothelioma.

Related studies

• Combination of a p53-activating CP-31398 and an MDM2 or a FAK inhibitor produces growth suppressive effects in mesothelioma with wild-type p53 genotype — B. Zhong, M. Shingyoji, et al. (2020)
• Combination of a third generation bisphosphonate and replication-competent adenoviruses augments the cytotoxicity on mesothelioma — Y. Jiang, B. Zhong, et al. (2016)
• Metformin produces growth inhibitory effects in combination with nutlin-3a on malignant mesothelioma through a cross-talk between mTOR and p53 pathways — K. Shimazu, Y. Tada, et al. (2017)
• Strategic selection of MDM2 inhibitors enhances the efficacy of FAK inhibition in mesothelioma based on TP53 genotype — X. Ning, T.T.T. Nguyễn, et al. (2026)
• Cytotoxicity of replication-competent adenoviruses powered by an exogenous regulatory region is not linearly correlated with the viral infectivity/gene expression or with the E1A-activating ability but is associated with the p53 genotypes — S. Yamauchi, B. Zhong, et al. (2017)
• Upregulated p53 expression activates apoptotic pathways in wild-type p53-bearing mesothelioma and enhances cytotoxicity of cisplatin and pemetrexed — Q. Li, K. Kawamura, et al. (2012)

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