BAP1 Status Determines the Sensitivity of Malignant Mesothelioma Cells to Gemcitabine Treatment

Our plain-English summary of BAP1 Status Determines the Sensitivity of Malignant Mesothelioma Cells to Gemcitabine Treatment, by A. Guazzelli, P. Meysami, E. Bakker, et al (International Journal of Molecular Sciences, 2019).

The study

• Authors: A. Guazzelli, P. Meysami, E. Bakker, C. Demonacos, A. Giordano, M. Krstic-Demonacos, L. Mutti
• Journal: International Journal of Molecular Sciences
• Published: 2019;20(2)
• Cited by: 46 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Malignant mesothelioma (MMe) is a cancer with poor prognosis and resistance to standard treatments. Recent reports have highlighted the role of the BRCA1 associated protein 1 gene (BAP1) in the development of MMe. In this study, the chemosensitivity of human mesothelioma cell lines carrying BAP1 wild-type (WT), mutant and silenced was analysed. The BAP1 mutant cells were significantly less sensitive than BAP1 WT cell lines to the clinically relevant drug gemcitabine. Silencing of BAP1 significantly increased resistance of MMe cells to gemcitabine. Cell cycle analysis suggested that gemcitabine induced Sub-G1 phase accumulation of the BAP1 WT cells and increased in the S-phase in both BAP1 WT and mutant cells. Analysis of the role of BAP1 in apoptosis suggested that gemcitabine induced early apoptosis in both BAP1 WT and BAP1 mutant cells but with a much higher degree in the WT cells. Effects on the population of cells in late apoptosis, which can mark necrosis and necroptosis, could not be seen in the mutant cells, highlighting the possibility that BAP1 plays a role in several types of cell death. Significantly decreased DNA damage in the form of double-strand breaks was observed in gemcitabine-treated BAP1 mutant cells, compared to BAP1 WT cells under the same conditions. After BAP1 silencing, a significant decrease in DNA damage in the form of double-strand breaks was observed compared to cells transfected with scramble siRNA. Taken together, the results presented in this manuscript shed light on the role of BAP1 in the response of MMe cells to gemcitabine treatment and in particular in the control of the DNA damage response, therefore providing a potential route for more efficient MMe therapy.

In plain English

This was a laboratory study of human malignant mesothelioma cells grown in culture. It did not involve patients and did not study asbestos exposure. The authors used four cell lines. Two had a normal (wild-type) BAP1 gene: PPM-Mill and REN. Two had an altered BAP1 gene: Phi, a pleural mesothelioma line with mutated BAP1, and Rob, which is BAP1 null. They treated the cells with the chemotherapy drug gemcitabine. They also switched off BAP1 in the two normal-BAP1 lines using small interfering RNA. At 0.1 µM gemcitabine, viability of PPM-Mill and REN cells fell by approximately 60%. Phi and Rob cells were only slightly affected at all tested concentrations. Switching off BAP1 significantly reduced sensitivity to the drug. Compared with Phi and Rob, the normal-BAP1 cells showed more cell death and greater apoptosis, a form of programmed cell death. They also showed more DNA double-strand breaks than mutant cells. Silencing BAP1 significantly reduced these breaks compared with a non-targeting control. The authors concluded that BAP1 inactivation confers resistance to gemcitabine and suggested BAP1 status could help stratify patients. They noted that this appears to conflict with clinical evidence that patients with BAP1 mutations survive longer.

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) experiment on human mesothelioma cell lines
• Who was studied: Four human malignant mesothelioma cell lines established by Pass et al.: PPM-Mill and REN (BAP1 wild-type), Phi (pleural, mutated BAP1) and Rob (BAP1 null). No human subjects.
• Exposure: The chemotherapy drug gemcitabine at concentrations from 0.1 µM to 50 µM, plus silencing of BAP1 with small interfering RNA. Asbestos exposure was not studied.
• Main results:
  • In the BAP1 wild-type lines PPM-Mill and REN, cell viability fell by approximately 60% at 0.1 µM gemcitabine compared with control (p < 0.05 in PPM-Mill and p < 0.01 in REN).
  • In the BAP1-mutant lines Phi and Rob, viability was only slightly reduced at all tested concentrations.
  • Silencing BAP1 in PPM-Mill and REN cells significantly reduced their sensitivity to gemcitabine.
  • In the four unaltered cell lines, gemcitabine induced more cell death, measured as Sub-G1 cells, in the BAP1 wild-type cells than in the BAP1-mutant cells. The proportion of cells in S-phase increased in all four lines.
  • Early apoptosis increased approximately 7-fold in PPM-Mill, 9-fold in REN and 3-fold in Phi cells after gemcitabine.
  • Late apoptosis increased approximately 6-fold in PPM-Mill and 2-fold in REN cells. There was no significant increase in Phi and Rob cells.
  • Gemcitabine increased DNA double-strand breaks in BAP1 wild-type cells but did not have the same effect in BAP1-mutant cells.
  • Wild-type cells with BAP1 silenced showed significantly fewer DNA double-strand breaks after gemcitabine than cells given non-targeting (scramble) siRNA.
• The authors' conclusion: The authors concluded that their evidence supports the view that BAP1 inactivation in mesothelioma cells confers resistance to gemcitabine. They suggested that BAP1 status could offer a way to stratify patients.
• Limitations the authors state:
  • The authors noted that the greater resistance of BAP1-mutant cells seems to go against clinical evidence that mesothelioma patients with BAP1 mutations survive longer.
  • The authors stated that further studies are needed to confirm the role of BAP1 status for other mesothelioma drugs, such as pemetrexed and platinum-based treatments.

Topics

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

Medical terms in this study, explained in our Lexicon: BAP1, Mesothelioma, Gemcitabine, Prognosis, Apoptosis, Necrosis.

Related studies

• Gemcitabine reactivates epigenetically silenced genes and functions as a DNA methyltransferase inhibitor — S.G. Gray, A.M. Baird, et al. (2012)
• A specific inhibitor of lactate dehydrogenase overcame the resistance toward gemcitabine in hypoxic mesothelioma cells, and modulated the expression of the human equilibrative transporter-1 — E. Giovannetti, L.G. Leon, et al. (2016)
• In vitro anti-mesothelioma activity of cisplatin-gemcitabine combinations: evidence for sequence-dependent effects — I. Zanellato, C.D. Boidi, et al. (2011)
• Thymidylate synthase expression determines pemetrexed targets and resistance development in tumour cells — A. Buqué, U. Aresti, et al. (2013)
• The role of gemcitabine in the treatment of malignant mesothelioma — H.L. Kindler, J.P. van Meerbeeck (2002)
• Gemcitabine as maintenance treatment of diffuse pleural mesothelioma: randomized phase II study — M.E. Sobeih, M. Helal, et al. (2026)

Browse more research in International Journal of Molecular Sciences, or return to medical research.