Bortezomib inhibits nuclear factor-kappaB dependent survival and has potent in vivo activity in mesothelioma

Our plain-English summary of Bortezomib inhibits nuclear factor-kappaB dependent survival and has potent in vivo activity in mesothelioma, by A. Sartore-Bianchi, F. Gasparri, A. Galvani, et al (Clinical Cancer Research, 2007).

The study

• Authors: A. Sartore-Bianchi, F. Gasparri, A. Galvani, L. Nici, J.W. Darnowski, D. Barbone, D.A. Fennell, G. Gaudino, C. Porta, L. Mutti
• Journal: Clinical Cancer Research
• Published: 2007;13(19):5942-51
• Cited by: 85 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Purpose: Purpose of this study has been the assessment of nuclear factor-kappaB (NF-kappaB) as a survival factor in human mesothelial cells (HMC), transformed HMC and malignant mesothelioma (MMe) cells. We aimed at verifying whether the proteasome inhibitor Bortezomib could abrogate NF-kappaB activity in MMe cells, leading to tumor cell death and may be established as a novel treatment for this aggressive neoplasm.

Experimental Design: In HMC and MMe cells, NF-kappaB nuclear translocation and DNA binding were studied by electrophoretic mobility shift assay, following treatment with tumor necrosis factor-alpha (TNF-alpha). The IKK inhibitor Bay11-7082 was also tested to evaluate its effects on HMC, transformed HMC, and MMe cell viability upon exposure to asbestos fibers. Following Bortezomib treatment, cytotoxicity of MMe cells was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, whereas apoptosis and cell-cycle blockade were investigated by high-content analysis. Bortezomib was also given to mice bearing i.p. xenografts of MMe cells, and its effects on tumor growth were evaluated.

Results: Here, we show that NF-kappaB activity is a constitutive survival factor in transformed HMC, MMe cells, and acts as a survival factor in HMC exposed to asbestos fibers. Bortezomib inhibits NF-kappaB activity in MMe cells and induces cell cycle blockade and apoptosis in vitro as well as tumor growth inhibition in vivo.

Conclusions: Inhibition of NF-kappaB constitutive activation in MMe cells by Bortezomib resulted in in vitro cytotoxicity along with apoptosis and in vivo tumor regression. Our results support the use of Bortezomib in the treatment of MMe and has led to a phase II clinical trial currently enrolling in Europe.

In plain English

This was a laboratory study using cultured cells and mice, not people. The authors studied a protein called NF-kappaB in normal human mesothelial cells and in three malignant mesothelioma cell lines (REN, MMB and MMP). NF-kappaB activity was barely detectable in the normal cells but was constantly present in the mesothelioma cells. Exposing normal cells to amosite asbestos fibers switched it on, and blocking NF-kappaB with a compound called Bay 11-7082 made amosite more toxic to them. The cancer drug Bortezomib reduced NF-kappaB activity in mesothelioma cells and killed them. Bortezomib did not reduce the viability of normal mesothelial cells. In mice injected in the abdomen with REN cells, Bortezomib at 1 mg/kg significantly reduced tumor weight in both of two trials. Fluid in the abdomen (ascites) was found in 88.5% of untreated mice, 46.0% at 0.5 mg/kg and 17.4% at 1 mg/kg. None of the 11 mice given 1.0 mg/kg showed visible diaphragm involvement at day 30, compared with 8 of 9 untreated mice. The authors concluded that their results support using Bortezomib to treat malignant 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 study in cultured human mesothelial and mesothelioma cell lines, plus two experiments (trials) in mice carrying implanted human mesothelioma tumors
• Who was studied: Malignant mesothelioma cell lines REN, MMB and MMP (MMB and MMP derived from pleural effusions of patients with mesothelioma), and normal human mesothelial cells from the pleural fluid of a patient with heart failure. Also 4- to 6-week-old male beige nude Xid mice, in groups of four to eight, injected in the abdomen with REN cells.
• Exposure: Cells were exposed to amosite asbestos fibers (from the UICC) at 10 micrograms per square centimeter for 24 hours. In a long-term exposure, cells received two 72-hour treatments at 2 or 5 micrograms per square centimeter and were then cultured for 60 days. Viability tests used 2.5 micrograms per square centimeter. The drug studied was Bortezomib: 3 to 800 nmol/L in cells, and 0.5 or 1.0 mg/kg twice weekly for 4 weeks in mice.
• Main results:
  • NF-kappaB DNA binding was barely detectable in normal mesothelial cells but was constitutive (always present) in the MMP, MMB and REN mesothelioma cells.
  • In normal mesothelial cells, amosite at 2.5 micrograms per square centimeter caused cell toxicity. Adding the NF-kappaB blocker Bay 11-7082 increased that toxicity (P = 0.0001).
  • In REN mesothelioma cells, 24-hour exposure to 25 or 100 nmol/L Bortezomib lowered NF-kappaB DNA binding, with a greater effect at the higher dose.
  • The estimated Bortezomib concentration giving half-maximal cell killing (EC50) was 18.6 nmol/L (SD 3.6) for REN cells and 51.4 nmol/L (SD 18.8) for MMP cells.
  • The viability of normal mesothelial cells was not affected by Bortezomib under the tested conditions.
  • After 24 hours of 10 to 100 nmol/L Bortezomib, cleavage of PARP (a marker of apoptotic cell death) occurred in REN and MMP cells but was undetectable in normal mesothelial cells.
  • In mice, Bortezomib at 1 mg/kg significantly reduced tumor weight in both trials (P less than 0.05 in trial 1; P less than 0.01 in trial 2). At 0.5 mg/kg, tumor growth was significantly reduced in trial 2 (P less than 0.01).
  • Across both trials, ascites was present in 88.5% of control mice, 46.0% of the 0.5 mg/kg group and 17.4% of the 1 mg/kg group (P less than 0.0001).
  • Diaphragm involvement, scored at day 30 by whether tumor was visible to the eye, was absent in all of the 1 mg/kg group (11/11 'none') and mild only in 15.4% of the 0.5 mg/kg group (2/13). Among controls, 55.5% had massive, 33.3% moderate or mild, and 11.1% no apparent involvement (P less than 0.0001).
  • No significant weight loss was noted in any drug-treated mouse.
• The authors' conclusion: The authors concluded that Bortezomib's ability to stop tumor spread to the diaphragm and the formation of malignant fluid in mice, along with its safety, supports its use in treating malignant mesothelioma. They reported that a phase II clinical trial was ongoing in Europe.
• Limitations the authors state:
  • The authors stated that their results do not clarify which signaling pathway drives NF-kappaB activity in the cells studied.
  • The authors stated that effects of Bortezomib through survival pathways other than NF-kappaB cannot be excluded.
  • Tumor weight differed significantly between the two mouse trials, so tumor weight was analyzed only within each trial.

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, Mesothelial Cells, Malignant Mesothelioma, Neoplasm, Translocation, Tumor Necrosis Factor-alpha (TNF-α), Apoptosis, Clinical Trial.

Related studies

• Phase II clinical trial of first or second-line treatment with bortezomib in patients with malignant pleural mesothelioma — D.A. Fennell, C. McDowell, et al. (2012)
• TNF-alpha inhibits asbestos-induced cytotoxicity via a NF-kappaB-dependent pathway, a possible mechanism for asbestos-induced oncogenesis — H. Yang, M. Bocchetta, et al. (2006)
• The plexin-A1 receptor activates vascular endothelial growth factor-receptor 2 and nuclear factor-kappaB to mediate survival and anchorage-independent growth of malignant mesothelioma cells — A. Catalano, R. Lazzarini, et al. (2009)
• Asbestos induces nuclear factor kappa B (NF-kappa B) DNA-binding activity and NF-kappa B-dependent gene expression in tracheal epithelial cells — Y.M. Janssen, A. Barchowsky, et al. (1995)
• Activated TNF-alpha/NF-kappaB signaling via down-regulation of Fas-associated factor 1 in asbestos-induced mesotheliomas from Arf knockout mice — D.A. Altomare, C.W. Menges, et al. (2009)
• Phase II study of first-line bortezomib and cisplatin in malignant pleural mesothelioma and prospective validation of progression free survival rate as a primary end-point for mesothelioma clinical trials (European Organisation for Research and Treatment of Cancer 08052) — M.E. O'Brien, R.M. Gaafar, et al. (2013)

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