Antitumoral effects of Bortezomib in malignant mesothelioma: evidence of mild endoplasmic reticulum stress in vitro and activation of T cell response in vivo

Our plain-English summary of Antitumoral effects of Bortezomib in malignant mesothelioma: evidence of mild endoplasmic reticulum stress in vitro and activation of T cell response in vivo, by M. Benvenuto, V. Angiolini, C. Focaccetti, et al (Biology Direct, 2023).

The study

• Authors: M. Benvenuto, V. Angiolini, C. Focaccetti, D. Nardozi, C. Palumbo, R. Carrano, A. Rufini, R. Bei, M.T. Miele, P. Mancini, G. Barillari, M. Cirone, E. Ferretti, G.R. Tundo, L. Mutti, L. Masuelli, R. Bei
• Journal: Biology Direct
• Published: 2023;18(1):17
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Malignant mesothelioma (MM) is a rare tumor with a dismal prognosis. The low efficacy of current treatment options highlights the urge to identify more effective therapies aimed at improving MM patients' survival. Bortezomib (Bor) is a specific and reversible inhibitor of the chymotrypsin-like activity of the 20S core of the proteasome, currently approved for the treatment of multiple myeloma and mantle cell lymphoma. On the other hand, Bor appears to have limited clinical effects on solid tumors, because of its low penetration and accumulation into tumor tissues following intravenous administration. These limitations could be overcome in MM through intracavitary delivery, with the advantage of increasing local drug concentration and decreasing systemic toxicity.

Methods: In this study, we investigated the effects of Bor on cell survival, cell cycle distribution and modulation of apoptotic and pro-survival pathways in human MM cell lines of different histotypes cultured in vitro. Further, using a mouse MM cell line that reproducibly forms ascites when intraperitoneally injected in syngeneic C57BL/6 mice, we investigated the effects of intraperitoneal Bor administration in vivo on both tumor growth and the modulation of the tumor immune microenvironment.

Results: We demonstrate that Bor inhibited MM cell growth and induced apoptosis. Further, Bor activated the Unfolded Protein Response, which however appeared to participate in lowering cells' sensitivity to the drug's cytotoxic effects. Bor also affected the expression of EGFR and ErbB2 and the activation of downstream pro-survival signaling effectors, including ERK1/2 and AKT. In vivo, Bor was able to suppress MM growth and extend mice survival. The Bor-mediated delay of tumor progression was sustained by increased activation of T lymphocytes recruited to the tumor microenvironment.

Conclusions: The results presented herein support the use of Bor in MM and advocate future studies aimed at defining the therapeutic potential of Bor and Bor-based combination regimens for this treatment-resistant, aggressive tumor.

© 2023. The Author(s).

In plain English

This was a laboratory and animal study of the drug bortezomib in malignant mesothelioma. It did not study asbestos exposure or patients. The authors treated three human mesothelioma cell lines and one mouse cell line with bortezomib at 6.25 to 100 nM. The drug reduced cell growth in all four lines, more with higher doses and longer treatment, and caused cell death by apoptosis. It also triggered a cell stress response that the authors interpreted as possibly lowering the cells' sensitivity to the drug. In mice injected in the abdomen with mouse mesothelioma cells (10 per group), bortezomib given into the abdomen twice a week reduced abdominal swelling. Median survival was 7.2 weeks with the drug versus 5.7 weeks without it; the hazard ratio for untreated versus treated mice was 4.1 (95% confidence interval 1.28 to 13.11). In groups of 5 mice examined at 30 days, T cells in the abdominal fluid showed more signs of activation with the drug. The authors concluded that the results support the use of bortezomib in mesothelioma and warrant further studies.

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 vitro experiments on human and mouse mesothelioma cell lines, plus an animal experiment in mice transplanted intraperitoneally with a mouse mesothelioma cell line
• Who was studied: Three human malignant mesothelioma cell lines (H-Meso-1, epithelial; MM-F1, sarcomatous; MM-B1, biphasic) and the mouse cell line #40a (epithelial). In vivo: C57BL/6 mice, 10 per group for tumor growth and survival, 5 per group for immune-cell analysis at 30 days. No human subjects.
• Exposure: The exposure studied was the proteasome inhibitor bortezomib, not asbestos. In vitro it was given at 6.25 to 100 nM for 24, 48 and 72 hours, compared with DMSO vehicle. In mice it was given intraperitoneally at 0.5 mg/kg, starting at tumor cell inoculation and repeated twice a week, compared with PBS-DMSO vehicle.
• Main results:
  • In all four cell lines, bortezomib inhibited cell growth in a dose- and time-dependent manner.
  • The concentration inhibiting growth by 50% (IC50) for MM-B1 was 15.0 plus or minus 1.0 nM at 48 hours and 13.3 plus or minus 0.8 nM at 72 hours. For H-Meso-1 it was 62.3 plus or minus 13.9 nM at 48 hours.
  • When a caspase inhibitor was added, the rise in sub-G1 cells caused by bortezomib was reduced in all cell lines, which the authors took as confirming apoptotic cell death.
  • GRP78/BiP, a marker of ER stress, was increased in all bortezomib-treated cell lines. The authors interpreted the activation of the unfolded protein response as possibly lowering the cells' sensitivity to the drug.
  • Bortezomib lowered EGFR and/or ErbB2 levels in all cell lines except MM-F1.
  • Bortezomib reduced ERK1 and/or ERK2 activation in all cell lines.
  • After four weeks, mean abdominal circumference was 7.1 plus or minus 0.6 cm in bortezomib-treated mice versus 7.9 plus or minus 0.7 cm in control mice (p = 0.015).
  • After five weeks, mean abdominal circumference was 7.4 plus or minus 0.8 cm in bortezomib-treated mice versus 9.1 plus or minus 0.8 cm in control mice (p = 0.0003).
  • Median survival was 7.2 weeks in bortezomib-treated mice versus 5.7 weeks in vehicle-treated mice (p = 0.02). The table gives 7.25 vs 5.75 weeks.
  • The hazard ratio for control mice versus bortezomib-treated mice was 4.1 (95% confidence limits 1.28 to 13.11, p = 0.0172).
  • In ascitic fluid at day 30 (5 mice per group), the frequency of CD4+ T lymphocytes was lower with bortezomib than in controls: 5.1 plus or minus 2.4 versus 13.8 plus or minus 2.7.
  • In ascitic fluid, the frequency of CD4+/CD25+ T cells was 32.1 plus or minus 7.8 with bortezomib versus 14.5 plus or minus 7.2 in controls.
  • In ascitic fluid, the frequency of CD8+ T cells producing IFN-gamma was 54.2 plus or minus 5.3 with bortezomib versus 34.4 plus or minus 13.3 in controls.
  • In ascitic fluid, the frequency of CD8+ T cells expressing PD-1 was 14.8 plus or minus 3.4 with bortezomib versus 20.6 plus or minus 3.6 in controls.
• The authors' conclusion: The authors concluded that the results support the use of bortezomib in malignant mesothelioma and warrant further studies of different delivery strategies and combination regimens.
• Limitations the authors state:
  • The authors state that further studies are needed to define how bortezomib activates AKT in mesothelioma cells.
  • The authors note that, to their knowledge, bortezomib delivered into the body cavity has not been tested in mesothelioma patients.

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, Prognosis, Myeloma, Ascites, Apoptosis, EGFR, Tumor Microenvironment.

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• Combined treatment with inhibitors of ErbB Receptors and Hh signaling pathways is more effective than single treatment in reducing the growth of malignant mesothelioma both in vitro and in vivo — R. Bei, M. Benvenuto, et al. (2022)
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