Inhibition of Mitochondrial Antioxidant Defense and CDK4/6 in Mesothelioma

Our plain-English summary of Inhibition of Mitochondrial Antioxidant Defense and CDK4/6 in Mesothelioma, by M. Kratzke, G. Scaria, S. Porter, et al (Molecules, 2023).

The study

• Authors: M. Kratzke, G. Scaria, S. Porter, B. Kren, M.A. Klein
• Journal: Molecules
• Published: 2023;28(11)
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Advanced mesothelioma is considered an incurable disease and new treatment strategies are needed. Previous studies have demonstrated that mitochondrial antioxidant defense proteins and the cell cycle may contribute to mesothelioma growth, and that the inhibition of these pathways may be effective against this cancer. We demonstrated that the antioxidant defense inhibitor auranofin and the cyclin-dependent kinase 4/6 inhibitor palbociclib could decrease mesothelioma cell proliferation alone or in combination. In addition, we determined the effects of these compounds on colony growth, cell cycle progression, and the expression of key antioxidant defense and cell cycle proteins. Auranofin and palbociclib were effective in decreasing cell growth and inhibiting the above-described activity across all assays. Further study of this drug combination will elucidate the contribution of these pathways to mesothelioma activity and may reveal a new treatment strategy.

In plain English

This was a laboratory study of mesothelioma cells grown in dishes, not of patients, and it did not examine asbestos exposure. The authors tested two drugs on four mesothelioma cell lines (H2052, H2373, H2452 and H2461). Auranofin blocks a mitochondrial defense against oxidative stress. Palbociclib blocks the cell-division proteins CDK4 and CDK6. Each drug reduced the growth of all the cell lines over 72 hours. In two cell lines, palbociclib nearly completely stopped colony formation at 50 µM, and auranofin did so at 5 and 10 µM. Palbociclib held cells at an early stage of the division cycle. Auranofin increased a cell fraction that the authors said may indicate cell death. Numerous dose combinations of the two drugs gave combination indices below 1, which the authors said suggested synergism. In 3T3 control cells, the concentrations that cut growth by half were 2.71 µM for auranofin and 22.6 µM for palbociclib. The authors concluded that the combination approach holds promise as a potential treatment strategy for mesothelioma, and that future studies are needed.

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: cell growth, colony formation, cell cycle and protein (Western blot) assays. It is not a study of patients.
• Who was studied: Four mesothelioma cell lines (H2052, H2373, H2452, H2461), with Met5A (non-transformed) and 3T3 cells as controls. The work was done at the Minneapolis VA Health Care System and the University of Minnesota. No patients were studied.
• Exposure: Drug treatments, not asbestos. Auranofin (an antioxidant defense or Trx2 inhibitor) and palbociclib (a CDK4/6 inhibitor) were given alone and in combination at 0.5, 1, 2.5, 5 and 10 µM. Pemetrexed was used for comparison in H2373 and H2452 cells.
• Main results:
  • Both palbociclib and auranofin decreased cell proliferation at 72 hours in all cell lines tested.
  • For comparison, the pemetrexed IC50 (concentration halving growth) was 14.58 nM in H2373 cells and 34.71 nM in H2452 cells.
  • In 3T3 control cells, the IC50 was 2.71 µM for auranofin and 22.6 µM for palbociclib.
  • In the combination experiments, numerous combination indices were below 1, which the authors said suggested synergism.
  • In H2373 and H2452 cells, palbociclib nearly completely inhibited colony formation at 50 µM.
  • Auranofin nearly completely inhibited colony formation at 5 µM and 10 µM.
  • After 48 hours, palbociclib significantly increased the percentage of mesothelioma cells in the G1 phase of the cell cycle.
  • Auranofin increased the proportion of cells in the sub-G1 fraction, which the authors said may indicate cell death (apoptosis).
  • Auranofin at 2.5 µM for 72 hours killed more than 90% of H2052 and H2373 cells.
  • FOXM1 protein expression was lost with either drug, with a greater loss under palbociclib.
• The authors' conclusion: The authors concluded that combination therapy inhibiting mitochondrial antioxidant defense and CDK4/6 holds promise as a potential therapeutic strategy in mesothelioma.
• Limitations the authors state:
  • The authors stated that future studies are needed to fill gaps in their proposed model.

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.

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• Potential toxicity of nonregulated asbestiform minerals: balangeroite from the western Alps. Part 3: Depletion of antioxidant defenses — E. Gazzano, C. Riganti, et al. (2005)
• Impact of acute and subchronic asbestos exposure on some parameters of antioxidant defense system and lung tissue injury — A. Kaiglová, Z. Kováciková, et al. (1999)
• Preclinical evaluation of CDK4 phosphorylation predicts high sensitivity of pleural mesotheliomas to CDK4/6 inhibition — S. Paternot, E. Raspé, et al. (2024)
• Antioxidants prevent the RhoA inhibition evoked by crocidolite asbestos in human mesothelial and mesothelioma cells — E. Aldieri, C. Riganti, et al. (2011)

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