Downregulation of cyclin D1 sensitizes cancer cells to MDM2 antagonist Nutlin-3

Our plain-English summary of Downregulation of cyclin D1 sensitizes cancer cells to MDM2 antagonist Nutlin-3, by P. Yang, W. Chen, X. Li, et al (Oncotarget, 2016).

The study

• Authors: P. Yang, W. Chen, X. Li, G. Eilers, Q. He, L. Liu, Y. Wu, Y. Wu, W. Yu, J.A. Fletcher, W.B. Ou
• Journal: Oncotarget
• Published: 2016;7(22):32652-63
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The MDM2-p53 pathway has a prominent oncogenic function in the pathogenesis of various cancers. Nutlin-3, a small-molecule antagonist of MDM2-p53 interaction, inhibits proliferation in cancer cells with wild-type p53. Herein, we evaluate the expression of MDM2, both the full length and a splicing variant MDM2-A, and the sensitivity of Nutlin-3 in different cancer cell lines. Included are seven cell lines with wild-type p53 (four mesothelioma, one breast cancer, one chondrosarcoma, and one leiomyosarcoma), two liposarcoma cell lines harboring MDM2 amplification and wild-type p53, and one mesothelioma cell line harboring a p53 point mutation. Nutlin-3 treatment increased expression of cyclin D1, MDM2, and p53 in cell lines with wild-type p53. Additive effects were observed in cells containing wild-type p53 through coordinated attack on MDM2-p53 binding and cyclin D1 by lentivirual shRNA knockdown or small molecule inhibition, as demonstrated by immunoblots and cell viability analyses. Further results demonstrate that MDM2 binds to cyclin D1, and that an increase in cyclin D1 expression after Nutlin-3 treatment is correlated with expression and ubiquitin E3-ligase activity of MDM2. MDM2 and p53 knockdown experiments demonstrated inhibition of cyclin D1 by MDM2 but not p53. These results indicate that combination inhibition of cyclin D1 and MDM2-p53 binding warrants clinical evaluation as a novel therapeutic strategy in cancer cells harboring wild-type p53.

In plain English

This was a laboratory study of human cancer cell lines grown in dishes. It did not study people or asbestos exposure. The cell lines included five mesothelioma lines (four with normal, or 'wild-type', p53 and one, JMN1B, with a p53 mutation), plus breast cancer, chondrosarcoma, liposarcoma and leiomyosarcoma lines. The authors treated cells with Nutlin-3, an experimental drug that stops the MDM2 protein from binding p53. They also lowered the protein cyclin D1, either by gene silencing or with chemical inhibitors. In mesothelioma and liposarcoma lines, Nutlin-3 raised cyclin D1 levels 2-3-fold compared with control treatment. In wild-type p53 lines except LMS05, Nutlin-3 alone reduced cell viability by 30 to 50%. Combining it with cyclin D1 silencing or with cyclin D1 inhibitors reduced viability by 60 to 70% or 40 to 60%, respectively. In 293T cells, MDM2 bound cyclin D1 and cut cyclin D1 gene promoter activity by 35%. The authors read this as a likely p53-independent mechanism. They concluded that combined inhibition of MDM2-p53 binding and cyclin D1 warrants clinical evaluation in cancers with wild-type p53.

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) experiments on human cancer cell lines: drug treatment, gene silencing, immunoblotting, cell viability assays, immunoprecipitation, qRT-PCR and luciferase reporter assays
• Who was studied: Human cancer cell lines, not patients. Mesothelioma lines MESO924, MESO257, MESO296 and MESO428 (wild-type p53) and JMN1B (p53 point mutation G245S). Also breast cancer (MCF-7), chondrosarcoma (MCS170), liposarcoma (LPS lines), leiomyosarcoma (LMS05), and for MDM2 expression only, GIST, ovarian and non-small cell lung cancer lines. 293T cells were used for binding and reporter assays.
• Exposure: No asbestos or fiber exposure was studied. Cells were treated with the MDM2 inhibitor Nutlin-3 (2.5, 5 and 10 micromolar in immunoblots). Cyclin D1 was reduced by lentiviral CCND1 shRNA or by the small molecules CyP (50 micromolar) and 4-CPA (100 micromolar).
• Main results:
  • In mesothelioma and liposarcoma cell lines, 48 hours of Nutlin-3 treatment raised cyclin D1 2-3-fold compared with DMSO control.
  • Cyclin D1 silencing alone inhibited viability by about 45 to 55% in wild-type p53 lines and by about 20% in mutant-p53 JMN1B mesothelioma cells at 3 days, compared with empty vector control.
  • Nutlin-3 alone reduced viability by 30 to 50% in wild-type p53 cells (except LMS05). The effect was minimal in mutant-p53 JMN1B and wild-type p53 LMS05 cells.
  • In wild-type p53 cell lines, Nutlin-3 combined with CCND1 shRNA reduced viability by 60 to 70%. Nutlin-3 combined with CyP or 4-CPA reduced it by 40 to 60%.
  • In JMN1B cells, CCND1 shRNA knockdown or drug inhibition reduced viability by about 80% or 30 to 50%, respectively.
  • In 293T cells with MDM2 and cyclin D1 overexpressed, MDM2 bound cyclin D1. In reporter assays, MDM2 inhibited CCND1 promoter activity by 35%.
  • The authors interpreted the knockdown results as indicating that cyclin D1 might be inhibited by MDM2 but not p53. They noted that response to p53 knockdown was not consistent across the cell lines tested.
• The authors' conclusion: The authors concluded that combined inhibition of the MDM2-p53 interaction and of cyclin D1 warrants clinical evaluation as a therapeutic strategy in wild-type p53 cancers.

Topics

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

Related studies

• An MDM2 inhibitor achieves synergistic cytotoxic effects with adenoviruses lacking E1B55kDa gene on mesothelioma with the wild-type p53 through augmenting NFI expression — T.T.T. Nguyen, M. Shingyoji, et al. (2021)
• 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)
• HDACi inhibits liposarcoma via targeting of the MDM2-p53 signaling axis and PTEN, irrespective of p53 mutational status — W.B. Ou, J. Zhu, et al. (2015)
• 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)
• Pharmacological targeting of p53 through RITA is an effective antitumoral strategy for malignant pleural mesothelioma — D. Di Marzo, I.M. Forte, et al. (2014)

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