Effects of selected deubiquitinating enzyme inhibitors on the proliferation and motility of lung cancer and mesothelioma cell lines

Our plain-English summary of Effects of selected deubiquitinating enzyme inhibitors on the proliferation and motility of lung cancer and mesothelioma cell lines, by T. Mirzapoiazova, A. Pozhitkov, A. Nam, et al (International Journal of Oncology, 2020).

The study

• Authors: T. Mirzapoiazova, A. Pozhitkov, A. Nam, I. Mambetsariev, M.S. Nelson, Y.C. Tan, K. Zhang, D. Raz, S. Singhal, M.W. Nasser, P. Kulkarni, S.K. Batra, M. Sattler, R. Salgia
• Journal: International Journal of Oncology
• Published: 2020;57(1):80-86
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The post‑translational modification of proteins by ubiquitinating enzymes plays a central role in a number of cellular functions, such as cell proteolysis, DNA repair, and cell signaling and communication. Deubiquitinating enzymes (DUBs) disassemble ubiquitin chains and remove ubiquitin moieties from proteins. Targeting DUBs in cancer models has revealed an important role for these enzymes in tumorigenesis, and they therefore have emerged as attractive therapeutic targets. In the present study, the effects of three DUB inhibitors, PR‑619, RA‑9 and LDN‑91946, on a non‑small cell lung cancer cell line (A549) and a mesothelioma cell line (H2373) were investigated. PR‑619 significantly inhibited cell adhesion and the proliferation of both cell lines. RA‑9 exerted an inhibitory effect on the adhesion and proliferation of H2373 cells, whereas it had no effect on A549 cells. Notably, however, while PR‑619 attenuated the proliferation of both cell lines, it exerted an opposite effect on cell motility; in the case of A549 cells, there was a significant increase in cell motility, while for the H2373 cells, there was a significant decrease. Furthermore, protein phosphorylation kinetic analyses revealed that the effects were cell line‑specific. In H2373 cells, the phosphorylation of only one peptide corresponding to the P85A protein was significantly affected, and while LDN‑91946 treatment increased phosphorylation, treatment with RA‑9 or PR‑619 decreased its phosphorylation compared to the DMSO control. By contrast, in the case of A549 cells, the phosphorylation of 21 peptides was significantly affected by the same compounds. In light of the potential for the negative side‑effects of DUB inhibition, such as increased cancer cell motility, the data presented herein underscore the dire need for the development of specific DUB inhibitors and to elucidate the individual role of DUB family members in cancer biology before they can be specifically pharmacologically targeted.

In plain English

This was a laboratory study on two cancer cell lines grown in dishes: A549, a non-small cell lung cancer line, and H2373, a malignant pleural mesothelioma line. No people or animals were studied, and the article does not discuss asbestos. The authors tested three drugs that block deubiquitinating enzymes (DUBs), which remove ubiquitin tags from proteins. The drugs were PR-619, RA-9 and LDN-91946. In A549 lung cancer cells, LDN-91946 and PR-619 reduced cell growth and attachment, while RA-9 did not. In H2373 mesothelioma cells, PR-619 and RA-9 reduced growth, while LDN-91946 did not. PR-619 increased the movement (migration) of the lung cancer cells but decreased it in the mesothelioma cells. In the mesothelioma cells, the drugs significantly changed the phosphorylation of only one protein fragment, P85A. In the lung cancer cells, more than 20 fragments changed. The authors concluded that the drugs acted unpredictably across cell types and that more specific DUB inhibitors are needed. Their reported results came from only these two cell lines. They mentioned preliminary tests on two other cell lines, BEAS-2B and Met 5A, but did not show those data.

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) experiments on cultured cancer cell lines testing three enzyme-inhibiting drugs
• Who was studied: Two human cancer cell lines supplied the reported results: A549 (non-small cell lung cancer) and H2373 (malignant pleural mesothelioma). The authors also mention preliminary work with BEAS-2B and Met 5A cell lines, with data not shown. No patients were studied.
• Exposure: Three deubiquitinating enzyme (DUB) inhibitor drugs, compared with a DMSO control: PR-619 at 10 µM, RA-9 at 5 µM and LDN-91946 at 10 µM, generally for 24 hours. The migration and phosphorylation assays used 10 µM. Asbestos was not studied.
• Main results:
  • A549 lung cancer cells, adhesion and proliferation measured by electrical resistance at 20-21 h (mean relative resistance): DMSO control 1.284, LDN-91946 0.939 and PR-619 0.944 (both significant, P<0.05), RA-9 1.314 (not significant).
  • H2373 mesothelioma cells, adhesion and proliferation at 47-48 h (mean relative resistance): DMSO control 3.166, PR-619 0.909 and RA-9 1.705 (both significant, P<0.05), LDN-91946 2.993 (not significant).
  • Cell migration in a wound healing assay (average migration rate): with PR-619, A549 lung cancer cells rose from 0.037 (DMSO) to 0.052, and H2373 mesothelioma cells fell from 0.039 (DMSO) to 0.022 (both P<0.05).
  • LDN-91946 and RA-9 had no detectable effect on migration in either cell line.
  • In H2373 mesothelioma cells, only one peptide (from the protein P85A) had significantly changed phosphorylation. In the Results section, it increased with LDN-91946 and RA-9 and decreased with PR-619 compared with DMSO.
  • In A549 lung cancer cells, more than 20 peptides had significantly changed phosphorylation. The abstract gives the number as 21.
  • In western blot checks of ubiquitin levels, PR-619 was the only inhibitor with a robust effect in both cell lines. RA-9 had very little effect on ubiquitin levels in A549 cells.
• The authors' conclusion: The authors concluded that the drugs' effects differed unpredictably between cell types. Because DUB inhibition could have negative side-effects such as increased cancer cell motility, they called for more specific DUB inhibitors and for study of individual DUB family members before they are targeted with drugs.
• Limitations the authors state:
  • Reported results came from only two cell lines, and additional cell lines might behave differently. Preliminary work with BEAS-2B and Met 5A cells, whose data were not shown, also gave unexpected outcomes.
  • Current knowledge of the cell lines was not detailed enough to explain the mechanisms behind the differing effects.
  • For LDN-91946, the western blot method could not show whether its effect on A549 proliferation was an on-target effect.

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: Lung Cancer, Mesothelioma, Carcinogenesis, Small Cell Lung Cancer, A549 Cells.

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