The endoplasmic reticulum mitochondrial calcium cross talk is downregulated in malignant pleural mesothelioma cells and plays a critical role in apoptosis inhibition

Our plain-English summary of The endoplasmic reticulum mitochondrial calcium cross talk is downregulated in malignant pleural mesothelioma cells and plays a critical role in apoptosis inhibition, by S. Patergnani, C. Giorgi, S. Maniero, et al (Oncotarget, 2015).

The study

• Authors: S. Patergnani, C. Giorgi, S. Maniero, S. Missiroli, P. Maniscalco, I. Bononi, F. Martini, G. Cavallesco, M. Tognon, P. Pinton
• Journal: Oncotarget
• Published: 2015;6(27):23427-44
• Cited by: 31 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The failure of apoptosis may contribute to the formation of cancer and to its resistance to therapy. Malignant pleural mesothelioma (MPM) is an aggressive tumor that responds poorly to standard chemo- and radio-therapies. Several studies have demonstrated that a plethora of oncogenes and tumor suppressors contribute to MPM onset/progression. Importantly, most of these genes are involved in the regulation of calcium (Ca2+)-handling. Cellular Ca2+ signaling is an important regulator of many physiological processes, and it has been widely reported to participate in the regulation of apoptotic cell death in cancer cells and tissues. However, in MPM the role of cellular Ca2+ has been poorly investigated. Therefore, we examined whether Ca2+ is involved in MPM. We found that mesothelioma cell lines and short-term cultures obtained from MPM-affected patients exhibited a critical dysregulation in Ca2+ signaling. We determined that this characteristic was associated with resistance to apoptotic stimuli and that correction of intracellular Ca2+ signaling resulted in the rescue of efficient apoptotic responses. In addition, we discovered that mitochondrial Ca2+-uptake plays a pivotal role as an inducer of apoptosis in MPM. Altogether, these findings suggest the identification of new MPM markers, which in turn could be potential targets for new therapeutic approaches.

In plain English

In this laboratory study of cells, not people, the authors compared normal mesothelial cells with malignant pleural mesothelioma (MPM) cells. The normal cells came from biopsies of patients aged 29 to 35 without cancer who had pneumothorax. The MPM cells were short-term cultures from tumor biopsies and a commercial cell line, MPP89. Asbestos exposure was not tested. The authors measured calcium inside cells and apoptosis, a form of programmed cell death. After stimulation, mesothelioma cells took up less calcium into mitochondria. They also had less resting calcium in the endoplasmic reticulum and less apoptosis. Menadione, a cell-death trigger, induced apoptosis in normal cells but did not induce an apoptotic response in mesothelioma cells. Mesothelioma cells had less MCU, a protein carrying calcium into mitochondria. Raising calcium in mesothelioma cells slowed their growth and restored apoptosis. Methods included high outside calcium, sodium orthovanadate, silencing the pump ATP2B4, or transfecting cells with an MCU plasmid to raise MCU levels. The authors concluded that calcium signaling plays an important role in MPM and MCU is a key mediator. They noted they could not be sure orthovanadate acted only on ATP2B4.

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 cells: primary short-term cultures and a commercial cell line
• Who was studied: Normal mesothelial cells from biopsies of young patients without cancer (age 29 to 35) who had pneumothorax, at the University/Hospital of Ferrara, Italy; primary MPM cells from tumor biopsies of MPM patients; the commercial MPM cell line MPP89. The number of patients is not stated.
• Exposure: No asbestos exposure was studied. Laboratory treatments were: menadione (30 μM) as a cell-death trigger; high external calcium (10 mM) or sodium orthovanadate (1 μM) to raise calcium inside cells; silencing of ATP2B4; transfection with an MCU plasmid to increase MCU expression; and silencing of MCU in normal cells.
• Main results:
  • After stimulation with bradykinin, peak mitochondrial calcium uptake was lower in primary MPM cultures than in healthy cultures: 37.89 versus 56.83 μM (n = 16, where n is the number of independent experiments).
  • Steady-state endoplasmic reticulum calcium was lower in primary MPM cultures than in healthy cultures: 217.86 versus 298.45 μM (n = 12).
  • Basal calcium inside cells was lower in primary MPM cultures than in healthy cultures: 193.98 versus 304.48 nM (n = 14).
  • Fewer primary MPM cells than healthy cells released cytochrome c, a sign of apoptosis: 22.91% versus 56.87% (n = 5).
  • Menadione strongly induced apoptosis in normal mesothelial cell-line cells. Its ability to induce apoptosis was abrogated in MPM cells.
  • Primary MPM cells had less of the mitochondrial calcium uniporter (MCU) protein than normal mesothelial cells.
  • After 5 days with high external calcium or sodium orthovanadate, primary MPM cultures grew less.
  • In primary MPM cells, Annexin-V staining (a marker of apoptosis, in arbitrary fluorescence units) was 9.85 in controls, 14.71 with menadione, 42.75 after transfection with the MCU plasmid, and 64.11 after MCU plasmid transfection plus menadione.
  • Silencing the calcium pump ATP2B4 in primary MPM cells reactivated apoptosis and made the cells sensitive to menadione.
• The authors' conclusion: The authors concluded that calcium signaling inside cells plays an important role in MPM, that reduced calcium handling impairs apoptosis, and that MCU is a key mediator whose modulation restores apoptosis in these cells.
• Limitations the authors state:
  • The authors could not be sure that the effects of sodium orthovanadate came only from blocking ATP2B4. They tested ATP2B4 silencing to address this.
  • Cell lines can differ genetically from primary tissue. The authors repeated experiments in primary cultures to address this.
  • The authors did not exclude a role for other molecular pathways in MPM.

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: Pleural Mesothelioma, Apoptosis, Mesothelioma.

Related studies

• BAP1 regulates IP3R3-mediated Ca2+ flux to mitochondria suppressing cell transformation — A. Bononi, C. Giorgi, et al. (2017)
• BAK and NOXA are critical determinants of mitochondrial apoptosis induced by bortezomib in mesothelioma — S. Busacca, A.D. Chacko, et al. (2013)
• Repression of GADD153/CHOP by NF-kappaB: a possible cellular defense against endoplasmic reticulum stress-induced cell death — S. Nozaki, G.W. Sledge, et al. (2001)
• Increased sensitivity to apoptosis upon endoplasmic reticulum stress-induced activation of the unfolded protein response in chemotherapy-resistant malignant pleural mesothelioma — D. Xu, S.Q. Liang, et al. (2018)
• Asbestos-induced alveolar epithelial cell apoptosis. The role of endoplasmic reticulum stress response — D.W. Kamp, G. Liu, et al. (2013)
• Pemetrexed induces apoptosis in malignant mesothelioma and lung cancer cells through activation of reactive oxygen species and inhibition of sirtuin 1 — K.E. Hwang, Y.S. Kim, et al. (2015)

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