Inhibition of MDM2 via Nutlin-3A: A Potential Therapeutic Approach for Pleural Mesotheliomas with MDM2-Induced Inactivation of Wild-Type P53

Our plain-English summary of Inhibition of MDM2 via Nutlin-3A: A Potential Therapeutic Approach for Pleural Mesotheliomas with MDM2-Induced Inactivation of Wild-Type P53, by R.F.H. Walter, R. Werner, M. Wessolly, et al (Journal of Oncology, 2018).

The study

• Authors: R.F.H. Walter, R. Werner, M. Wessolly, E. Mairinger, S. Borchert, J. Schmeller, J. Kollmeier, T. Mairinger, T. Hager, A. Bankfalvi, D.C. Christoph, W.E.E. Eberhardt, T. Plönes, C. Aigner, K.W. Schmid, J. Wohlschlaeger, F.D. Mairinger
• Journal: Journal of Oncology
• Published: 2018;2018:1986982
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Previously, our group demonstrated that nuclear expression of E3 ubiquitin ligase (MDM2) in malignant pleural mesothelioma (MPM) is significantly associated with decreased overall survival. A possible explanation may be that overexpression of MDM2 leads to a proteasomal degradation of TP53 that eventually results in a loss of TP53-induced apoptosis and senescence. It is well known from other tumor entities that restoration of TP53 activity, e.g., by MDM2 inhibition, results in an instant TP53-induced stress and/or DNA damage response of cancer cells. Nutlin-3A (a cis-imidazoline analogue) has been described as a potent and selective MDM2 inhibitor preventing MDM2-TP53-interaction by specific binding to the hydrophobic TP53-binding pocket of MDM2. In the present study, the effects of MDM2 inhibition in MPM via Nutlin-3A and standard platinum based chemotherapeutic agents were comparatively tested in three MPM cell lines (NCI-H2052, MSTO-211H, and NCI-H2452) showing different expression profiles of TP53, MDM2, and its physiological inhibitor of MDM2-P14/ARF. Our in vitro experiments on MPM cell lines revealed that Nutlin-3A in combination with cisplatin resulted in up to 9.75 times higher induction of senescence (p=0.0050) and up to 5 times higher apoptosis rate (p=0.0067) compared to the commonly applied cisplatin and pemetrexed regimens. Thus Nutlin-3A, a potent inhibitor of MDM2, is associated with a significant induction of senescence and apoptosis in MPM cell lines, making Nutlin-3A a promising substance for a targeted therapy in the subgroup of MPM showing MDM2 overexpression.

In plain English

This was a laboratory (in vitro) study, not a study of patients or asbestos exposure. The authors grew three human malignant pleural mesothelioma (MPM) cell lines: NCI-H2052, MSTO-211H and NCI-H2452. These lines differed in how strongly they expressed MDM2, P53 and P14/ARF. Cells were treated for three days with cisplatin and pemetrexed, alone or together, or with Nutlin-3A, an experimental MDM2 blocker, alone or with cisplatin. The authors measured cell viability (low readings were read as senescence, a halt in growth), apoptosis (programmed cell death) and necrosis. The highest Nutlin-3A dose, 20 micromolar, reduced cell viability most in all three lines. With cisplatin, 10 and 20 micromolar Nutlin-3A reduced viability significantly more than the standard drugs in all three lines; 5 micromolar with cisplatin was not clearly better, matching cisplatin plus pemetrexed in MSTO-211H. Apoptosis results were mixed. In MSTO-211H pemetrexed alone caused the most apoptosis, and some differences elsewhere were not statistically significant. No drug changed necrosis. The authors concluded that their hypothesis, that MDM2-overexpressing MPM can be targeted by Nutlin-3A-based therapy, was proven in vitro.

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 (in vitro) cell line experiment
• Who was studied: Three human malignant pleural mesothelioma cell lines (NCI-H2052, NCI-H2452 and MSTO-211H) from the American Type Culture Collection. The lines had different MDM2, TP53 and P14/ARF expression profiles: MDM2 and TP53 were assessed by immunohistochemistry, and MDM2 and P14/ARF by RNA testing (qPCR).
• Exposure: Drug treatments, not asbestos: cisplatin (10 micromolar), pemetrexed (200 micromolar) and Nutlin-3A (5, 10 or 20 micromolar), alone or in combination, for three days
• Main results:
  • The cell lines differed in marker profile. For example, NCI-H2052 showed pronounced MDM2 immunoexpression but little P14/ARF and TP53 expression.
  • P14/ARF and MDM2 were measured as RNA expression by qPCR, not as protein.
  • Senescence was inferred from low luminescence readings in the cell viability assay.
  • Among single agents, 20 micromolar Nutlin-3A gave the strongest inhibition of cell viability in all three cell lines.
  • Single agents in NCI-H2052: the highest apoptosis rate was with 20 micromolar Nutlin-3A; other treatments were similar (p=0.14).
  • Single agents in NCI-H2452: the highest apoptosis rate was with 20 micromolar Nutlin-3A, followed by cisplatin (p=0.0359).
  • Single agents in MSTO-211H: the highest apoptosis rates were with pemetrexed (p=0.0219).
  • In all three cell lines, the higher Nutlin-3A doses (10 and 20 micromolar) combined with cisplatin gave the strongest inhibition of cell viability compared with the approved drugs.
  • In NCI-H2052, Nutlin-3A alone and Nutlin-3A with cisplatin significantly increased senescence compared with the other regimens (p=0.0051).
  • In MSTO-211H, any Nutlin-3A plus cisplatin combination significantly increased senescence compared with cisplatin, pemetrexed, or both (p=0.0059). However, cisplatin plus pemetrexed showed similar efficacy to the lowest Nutlin-3A/cisplatin regimen.
  • In NCI-H2452, Nutlin-3A with cisplatin, or Nutlin-3A alone, was superior to the other drugs except at 5 micromolar (p=0.0089).
  • In NCI-H2052, higher Nutlin-3A doses with cisplatin significantly increased apoptosis compared with pemetrexed alone or pemetrexed with cisplatin (p=0.0069).
  • In MSTO-211H, in the combination experiments, apoptosis was highest with pemetrexed alone (p=0.0035).
  • In NCI-H2452, apoptosis was highest with 20 micromolar Nutlin-3A alone and with 10 and 20 micromolar Nutlin-3A plus cisplatin, followed by cisplatin (p=0.1).
  • Necrosis was not influenced by any treatment compared with control; the data were not shown.
• The authors' conclusion: The authors concluded that, in this in vitro study, their hypothesis that MDM2-overexpressing MPM can be targeted by Nutlin-3A-based chemotherapy was proven.

Topics

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Overall Survival, Apoptosis, Cisplatin, Pemetrexed (Alimta), Targeted Therapy.

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