Combination of a third generation bisphosphonate and replication-competent adenoviruses augments the cytotoxicity on mesothelioma

Our plain-English summary of Combination of a third generation bisphosphonate and replication-competent adenoviruses augments the cytotoxicity on mesothelioma, by Y. Jiang, B. Zhong, K. Kawamura, et al (BMC Cancer, 2016).

The study

• Authors: Y. Jiang, B. Zhong, K. Kawamura, T. Morinaga, M. Shingyoji, I. Sekine, Y. Tada, K. Tatsumi, H. Shimada, K. Hiroshima, M. Tagawa
• Journal: BMC Cancer
• Published: 2016;16:455
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Approximately 80 % of mesothelioma specimens have the wild-type p53 gene, whereas they contain homozygous deletions in the INK4A/ARF locus that encodes p14 (ARF) and the 16 (INK4A) genes. Consequently, the majority of mesothelioma is defective of the p53 pathways. We examined whether zoledronic acid (ZOL), a third generation bisphosphonate, and adenoviruses with a deletion of the E1B-55kD gene (Ad-delE1B55), which augments p53 levels in the infected tumors, could produce combinatory anti-tumor effects on human mesothelioma cells bearing the wild-type p53 gene.

Methods: Cytotoxicity of ZOL and Ad-delE1B55 was assessed with a WST assay. Cell cycle changes were tested with flow cytometry. Expression levels of relevant molecules were examined with western blot analysis to investigate a possible mechanism of cytotoxicity. Furthermore, the expressions of Ad receptors on target cells and infectivity were estimated with flow cytometry. Viral replication was assayed with the tissue culture infection dose method.

Results: A combinatory use of ZOL and Ad-delE1B55 suppressed cell growth and increased sub-G1 or S-phase populations compared with a single agent, depending on cells tested. The combinatory treatment up-regulated p53 levels and subsequently enhanced the cleavage of caspase-3, 8, 9 and poly (ADP-ribose) polymerase, but expression of molecules involved in autophagy pathways were inconsistent. ZOL-treated cells also increased Ad infectivity with a dose-dependent manner and augmented Ad replication although the expression levels of integrin molecules, one of the Ad receptors, were down-regulated.

Conclusions: These findings indicated that ZOL and Ad-delE1B55 achieved combinatory anti-tumor effects through augmented apoptotic pathways or increased viral replication.

In plain English

This was a laboratory study in human mesothelioma cell lines, not in patients. The authors screened zoledronic acid (ZOL), a third generation bisphosphonate, and a replication-competent adenovirus lacking the E1B-55kD gene (Ad-delE1B55) separately in five mesothelioma cell lines with the wild-type p53 gene, then combined the two agents in MSTO-211H, NCI-H226 and NCI-H28 cells, which were sensitive to both. In WST viability assays, combination index values were below 1 at most of the fraction-affected points tested (0.3 to 0.8 in MSTO-211H and NCI-H226 cells, 0.4 to 0.9 in NCI-H28 cells), which the authors read as additive or synergistic. The combination raised sub-G1 cells in MSTO-211H (40.75 ± 0.08 % at 96 h) and S-phase cells in NCI-H28 (47.98 ± 1.01 % at 48 h). In MSTO-211H cells, western blotting showed increased p53, phosphorylated p53 and cleaved caspase-3, 8, 9 and PARP at 24 and 48 h. ZOL increased adenoviral infectivity and progeny production in NCI-H28 but not MSTO-211H cells, although integrin levels fell. Asbestos appears only in the background, where the authors state mesothelioma is often associated with asbestos exposure in the patient history.

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: In vitro laboratory experiments on human mesothelioma cell lines (cytotoxicity, flow cytometry, western blot, viral titration); no animals or patients
• Who was studied: Five human mesothelioma cell lines (MSTO-211H, NCI-H226, NCI-H28, EHMES-10, NCI-H2452) screened with the single agents, with combination work in MSTO-211H, NCI-H226 and NCI-H28; HEK293 and A549 cells used for virus preparation and titration; work performed in Japan
• Exposure: Zoledronic acid at cell-specific concentrations (10 to 100 micromolar) and replication-competent adenovirus Ad-delE1B55 (with replication-incompetent Ad-LacZ and Ad-GFP as controls), alone and combined
• Main results:
  • Combination index values were below 1 at most of the fraction-affected points tested in the three cell lines, which the authors interpreted as additive or synergistic cytotoxicity
  • In MSTO-211H cells at 96 h, sub-G1 cells were 40.75 ± 0.08 % with ZOL plus Ad-delE1B55, compared with 9.32 ± 0.11 % with ZOL alone, 12.14 ± 0.27 % with Ad-delE1B55 alone and 1.03 ± 0.07 % untreated
  • In NCI-H28 cells at 48 h, S-phase cells were 47.98 ± 1.01 % with the combination versus 25.64 ± 0.15 % with ZOL alone
  • In MSTO-211H cells only, the combination increased p53, phosphorylated p53 and cleaved caspase-3, 8, 9 and PARP at 24 and 48 h more than either agent alone
  • Autophagy-related molecules were not consistently changed by the treatments
  • ZOL (80 micromolar) lowered integrin αvβ3 and αvβ5 on NCI-H28 cells (αvβ5 mean fluorescent intensity 44.01 ± 0.09 untreated versus 22.01 ± 0.03 treated, 50.01 ± 0.13 percent ratio), while CAR changed little
  • Adenoviral infectivity measured with Ad-GFP rose in NCI-H28 cells after ZOL but not in MSTO-211H cells
  • Viral progeny production increased with ZOL in NCI-H28 cells but was unchanged (or decreased at 72 h) in MSTO-211H cells
  • EHMES-10 cells were resistant to Ad-delE1B55 and NCI-H2452 cells were reported to have truncated p53, so both were excluded from further analyses
• The authors' conclusion: The authors concluded that ZOL and Ad-delE1B55 produced combinatory cytotoxic effects on p53 wild-type mesothelioma cells, acting through enhanced apoptotic pathways or increased viral replication
• Limitations the authors state:
  • The authors state the mechanism behind the hyperploidy and S-phase arrest they observed is not known
  • High ZOL concentrations could not be tested in MSTO-211H cells because the cells died at those doses
  • Effects differed between cell lines, and the authors attribute this to divergent small G protein effects rather than a single established mechanism
  • No animal experiments were performed; the work is presented as preclinical for a possible future 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, Homozygous Deletion.

Related studies

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• Zoledronic acid produces antitumor effects on mesothelioma through apoptosis and S-phase arrest in p53-independent and Ras prenylation-independent manners — S. Okamoto, K. Kawamura, et al. (2012)
• Zoledronic acid produces combinatory anti-tumor effects with cisplatin on mesothelioma by increasing p53 expression levels — S. Okamoto, Y. Jiang, et al. (2013)
• An MDM2 inhibitor achieves synergistic cytotoxic effects with adenoviruses lacking E1B55kDa gene on mesothelioma with the wild-type p53 through augmenting NFI expression — T.T.T. Nguyen, M. Shingyoji, et al. (2021)
• Metformin produces growth inhibitory effects in combination with nutlin-3a on malignant mesothelioma through a cross-talk between mTOR and p53 pathways — K. Shimazu, Y. Tada, et al. (2017)
• Zoledronic acid induces apoptosis and S-phase arrest in mesothelioma through inhibiting Rab family proteins and topoisomerase II actions — S. Okamoto, Y. Jiang, et al. (2014)

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