Mechanisms of cisplatin-induced cell death in malignant mesothelioma cells: role of inhibitor of apoptosis proteins (IAPs) and caspases

Our plain-English summary of Mechanisms of cisplatin-induced cell death in malignant mesothelioma cells: role of inhibitor of apoptosis proteins (IAPs) and caspases, by I.L. Cregan, A.M. Dharmarajan, S.A. Fox (International Journal of Oncology, 2013).

The study

• Authors: I.L. Cregan, A.M. Dharmarajan, S.A. Fox
• Journal: International Journal of Oncology
• Published: 2013;42(2):444-52
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Malignant mesothelioma (MM) is an aggressive and highly chemoresistant tumour. Although cisplatin is used in frontline therapy of this disease treatment remains palliative at best. The biochemical pathways activated by cisplatin and the mechanisms of resistance in mesothelioma cells are poorly understood. Overexpression of inhibitor of apoptosis proteins (IAPs) has been described in clinical mesothelioma tumours and proposed as therapeutic targets. In this study, we examined cisplatin-induced cell death pathways and IAPs in three mesothelioma-derived cell lines. Cisplatin induced cell death in mesothelioma cell lines was characterised by biochemical mechanisms classically associated with apoptosis including: mitochondrial depolarisation, phosphatidylserine translocation and caspase activation. Surprisingly mRNA expression of IAPs in mesothelioma was not upregulated relative to primary mesothelial cells except for survivin which was higher in the most resistant cell line. In contrast, protein expression of both XIAP and survivin was upregulated in all mesothelioma cells, consistent with post-translational regulation. Knockdown of either XIAP or survivin by RNAi did not affect the sensitivity to cisplatin in any of the cell lines. Survivin RNAi did, however, inhibit proliferation in the highest expressing cell line, ONE58. The pan-caspase inhibitor z-VAD and the more selective caspase 3/7 inhibitor z-DEVD had no effect upon the sensitivity of any of the cell lines to cisplatin indicating that caspase-independent pathways predominate. The findings of the present study provide insights into cisplatin-induced mechanisms in mesothelioma cells and show that alternative pathways are operating which may provide new options for targeting this extremely resistant tumour.

In plain English

This laboratory study used three human malignant mesothelioma cell lines (JU77, LO68, ONE58) grown from pleural fluid of different patients with malignant pleural mesothelioma. It did not study asbestos exposure or patients. The authors exposed the cells to the chemotherapy drug cisplatin for 24 hours. ONE58 was the least sensitive: a 50% drop in a viability reading (MTT absorbance) compared with untreated cells needed 3.08 µg/ml, against 1.14 µg/ml for JU77 and 1.2 µg/ml for LO68. In all three lines, cisplatin caused changes typical of programmed cell death, including mitochondrial depolarisation and caspase 3/7 activation. Compared with primary mesothelial cell cultures, the cancer cells had higher levels of two proteins that inhibit cell death, XIAP and survivin. Lowering either protein had little or no effect on how sensitive the cells were to cisplatin, although lowering survivin reduced ONE58 cell viability on its own. Drugs that blocked caspases did not significantly change cisplatin's killing effect. The authors concluded that caspase activation is not essential for cisplatin-induced death in these cells and that caspase-independent pathways most likely predominate.

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) study of human mesothelioma cell lines
• Who was studied: Three human malignant mesothelioma cell lines (JU77, LO68, ONE58) derived from pleural effusions of different patients with malignant pleural mesothelioma, compared with primary mesothelial cell cultures. No patients were studied directly.
• Exposure: The chemotherapy drug cisplatin at 0 to 100 µg/ml for 24 hours. Asbestos exposure was not studied.
• Main results:
  • Cisplatin sensitivity was measured as IC50, the concentration causing a 50% reduction in MTT absorbance relative to untreated controls. Values were JU77 1.14 plus or minus 0.21 µg/ml, LO68 1.2 plus or minus 0.45 µg/ml and ONE58 3.08 plus or minus 0.83 µg/ml. ONE58 was the least sensitive.
  • All three cell lines showed dose-dependent loss of mitochondrial membrane potential after cisplatin.
  • All three cell lines showed increased Annexin-V binding (a membrane change of cell death) after cisplatin.
  • All three cell lines showed increased caspase 3/7 activation in response to cisplatin.
  • At the mRNA level, IAP1 and survivin were higher in ONE58. Apart from that, there was no clear difference between the mesothelioma cell lines and mesothelial cultures.
  • At the protein level, XIAP and survivin were higher in the mesothelioma cell lines than in primary mesothelial cells.
  • Knocking down XIAP had little effect on cisplatin sensitivity in all three cell lines.
  • Knocking down survivin did not affect cisplatin sensitivity in JU77 and LO68 cells.
  • In ONE58 cells, lowering survivin significantly reduced baseline cell viability, independent of cisplatin.
  • The caspase inhibitors z-VAD-fmk and z-DEVD-cmk did not significantly change cisplatin-induced cell killing.
• The authors' conclusion: The authors concluded that in these cell lines caspase activation is not essential for cisplatin-induced cell death and that caspase-independent pathways most likely predominate.
• Limitations the authors state:
  • The authors reported that survivin was harder to knock down at the protein level than XIAP.

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: Cisplatin, Mesothelioma, Apoptosis, Palliative Care, Translocation, Mesothelial Cells.

Related studies

• Phosphatidylinositol Induces Caspase-Independent Apoptosis of Malignant Pleural Mesothelioma Cells by Accumulating AIF in the Nucleus — S. Kanemura, A. Tsuchiya, et al. (2015)
• Pro-oxidant activity of sulforaphane and cisplatin potentiates apoptosis and simultaneously promotes autophagy in malignant mesothelioma cells — Y.J. Lee, S.H. Lee (2017)
• Apoptosis induced by piroxicam plus cisplatin combined treatment is triggered by p21 in mesothelioma — A. Baldi, M.T. Piccolo, et al. (2011)
• Death receptor 5 and cellular FLICE-inhibitory protein regulate pemetrexed-induced apoptosis in human lung cancer cells — L. Su, G. Liu, et al. (2011)
• Deficiency of Fyn protein is prerequisite for apoptosis induced by Src family kinase inhibitors in human mesothelioma cells — R. Eguchi, S. Kubo, et al. (2012)
• Overexpression of Numb suppresses tumor cell growth and enhances sensitivity to cisplatin in epithelioid malignant pleural mesothelioma — Y. Kang, M. Ding, et al. (2013)

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