Modulation of reactive oxygen species via ERK and STAT3 dependent signalling are involved in the response of mesothelioma cells to exemestane

Our plain-English summary of Modulation of reactive oxygen species via ERK and STAT3 dependent signalling are involved in the response of mesothelioma cells to exemestane, by B. Nuvoli, E. Camera, A. Mastrofrancesco, et al (Free Radical Biology & Medicine, 2018).

The study

• Authors: B. Nuvoli, E. Camera, A. Mastrofrancesco, S. Briganti, R. Galati
• Journal: Free Radical Biology & Medicine
• Published: 2018;115:266-277
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Pleural mesothelioma is a deadly form of cancer. The prognosis is extremely poor due to the limited treatment modalities. Uptake of asbestos fibres, the leading cause of mesothelioma, lead to the accumulation of reactive-oxygen-species (ROS). Interestingly, increasing ROS production by using ROS-generating drugs may offer a strategy to selectively trigger cell death. Exemestane, an aromatase inhibitor, has previously shown anti-tumor properties in mesothelioma preclinical models suggesting a role of G protein-coupled receptor 30 (GPR30) in the drug response. As exemestane, in addition to blocking estrogen biosynthesis, generates ROS that are able to arrest the growth of breast cancer, we explored the role of ROS, antioxidant defense system, and ROS-induced signalling pathways in mesothelioma cells during exemestane response. Here we report that exemestane treatment reduced cell proliferation with an increase in ROS production and reduction of cyclic adenosine monophosphate (cAMP) levels in MSTO-H211, Ist-Mes1, Ist-Mes2 and MPP89 exemestane-sensitive mesothelioma cell lines, but not in NCI-H2452 exemestane-insensitive mesothelioma cells. Exemestane induced a significant antioxidant response in NCI-H2452 cells, as highlighted by an increase in γ-glutamylcysteine levels, catalase (Cat), superoxide-dismutase and (SOD) and glutathione-peroxidase (GSH-Px) activity and nuclear factor E2-related factor 2 (Nrf2) activation, responsible for drug insensitivity. Conversely, exemestane elevated ROS levels along with increased ERK phosphorylation and a reduction of p-STA3 in exemestane-sensitive mesothelioma cells. ROS generation was the crucial event of exemestane action because ROS inhibitor N-acetyl-L-cysteine (NAC) abrogated p-ERK and p-STAT3 modulation and cellular death. Exemestane also modulates ERK and STAT3 signalling via GPR30. Results indicate an essential role of ROS in the antiproliferative action of exemestane in mesothelioma cells. It is likely that the additional oxidative insults induced by exemestane results in the lethal effects of mesothelioma cells by increasing ROS production. As such, manipulating ROS levels with exemestane seems to be a feasible strategy to selectively kill mesothelioma cells with less toxicity to normal cells by regulating ERK and STAT3 activity.

Copyright © 2017 Elsevier Inc. All rights reserved.

In plain English

This was a laboratory study of five human malignant mesothelioma cell lines grown in culture. It did not study asbestos exposure or patients. The authors treated the cells with exemestane, a drug that blocks estrogen production, at 35 µM (micromolar) for 24 and 48 hours. They examined reactive oxygen species (ROS, chemically reactive molecules that can damage cells), antioxidant defenses and cell-signalling proteins. Exemestane did not affect growth of the NCI-H2452 line but was effective on Ist-Mes1, Ist-Mes2, MSTO-H211 and MPP89. ROS rose in these four lines but not in NCI-H2452. In Ist-Mes1 cells, adding the antioxidant N-acetyl-L-cysteine (NAC) reversed exemestane's effect on proliferation. In NCI-H2452 cells, exemestane significantly increased antioxidant enzyme activity, increased nuclear Nrf2 (a regulator of antioxidant responses) and raised the glutathione precursor γ-glutamylcysteine 26-fold. When glutathione synthesis was blocked with BSO, both lines showed comparable sensitivity to exemestane. In Ist-Mes1, exemestane raised ERK and lowered STAT3 phosphorylation. The authors concluded that exemestane can be considered a potential new pharmacological tool for aggressive and resistant mesothelioma.

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 mesothelioma cell lines; no patients and no asbestos exposure were studied
• Who was studied: Five human malignant mesothelioma cell lines. MSTO-211H and NCI-H2452 came from the American Type Culture Collection, and Ist-Mes1, Ist-Mes2 and MPP89 came from the Genova Institute Culture Collection. Later experiments focused on Ist-Mes1 (most sensitive) and NCI-H2452 (not sensitive).
• Exposure: Exemestane, an aromatase inhibitor that blocks estrogen biosynthesis, at 35 µM for 24 and 48 h. Other treatments were hydrogen peroxide (100 µM), the glutathione-synthesis inhibitor BSO (100 µM), the antioxidant NAC (5 mM), estradiol (10 nM) and the GPR30 antagonist G15 (100 nM). No asbestos fibers were used.
• Main results:
  • Exemestane (35 µM) had no effect on growth of NCI-H2452 cells.
  • Exemestane was effective against growth of the Ist-Mes1, Ist-Mes2, MSTO-H211 and MPP89 lines.
  • After 30 minutes of exemestane, ROS production increased in the four sensitive lines but not in NCI-H2452.
  • In Ist-Mes1 cells, adding the antioxidant NAC reversed exemestane's effect on cell proliferation.
  • cAMP levels fell with exemestane in the four sensitive lines and rose in NCI-H2452.
  • Only in NCI-H2452 cells did exemestane significantly increase the activity of the antioxidant enzymes SOD, GSH-Px and especially catalase.
  • In Ist-Mes1 cells, exemestane significantly reduced SOD activity.
  • Exemestane increased nuclear accumulation of Nrf2 in NCI-H2452 cells, peaking at 120 minutes. No significant change was seen in Ist-Mes1.
  • Basal glutathione (GSH) was 50.9 ± 10.6 nmole per million cells in NCI-H2452 and 24.6 ± 8.75 nmole per million cells in Ist-Mes1.
  • After 24 h of exemestane, GSH increased 1.7-fold in NCI-H2452 (p=0.03) and 4.1-fold in Ist-Mes1 (p less than 0.001).
  • In NCI-H2452 cells, exemestane increased γ-glutamylcysteine 26-fold (p less than 0.001), to 249.4 ± 47.1 nmole per million cells.
  • When cells were first treated with BSO (which blocks glutathione synthesis), both NCI-H2452 and Ist-Mes1 showed significant and comparable sensitivity to exemestane.
  • In Ist-Mes1 cells, exemestane reduced STAT3 phosphorylation and increased ERK phosphorylation.
  • In Ist-Mes1 cells, the GPR30 antagonist G15, like exemestane, increased p-ERK and decreased p-STAT3.
• The authors' conclusion: The authors concluded that exemestane acts in mesothelioma cells through generating ROS, and that it can be considered a potential new pharmacological tool for treating aggressive and resistant malignant mesothelioma.

Topics

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

Medical terms in this study, explained in our Lexicon: Reactive Oxygen Species (ROS), Mesothelioma, Pleural Mesothelioma, Prognosis, Superoxide, Glutathione (GSH).

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