Importance of Cullin4 Ubiquitin Ligase in Malignant Pleural Mesothelioma

Our plain-English summary of Importance of Cullin4 Ubiquitin Ligase in Malignant Pleural Mesothelioma, by M. Meerang, J. Kreienbühl, V. Orlowski, et al (Cancers, 2020).

The study

• Authors: M. Meerang, J. Kreienbühl, V. Orlowski, S.L.C. Müller, M.B. Kirschner, I. Opitz
• Journal: Cancers
• Published: 2020;12(11)
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Neurofibromatosis type 2 (NF2), the tumor suppressor frequently lost in malignant pleural mesothelioma (MPM), suppresses tumorigenesis in part by inhibiting the Cullin4 ubiquitin ligase (CUL4) complex in the nucleus. Here, we evaluated the importance of CUL4 in MPM progression and tested the efficacy of cullin inhibition by pevonedistat, a small molecule inhibiting cullin neddylation. CUL4 paralogs (CUL4A and CUL4B) were upregulated in MPM tumor specimens compared to nonmalignant pleural tissues. High gene and protein expressions of CUL4B was associated with a worse progression-free survival of MPM patients. Among 13 MPM cell lines tested, five (38%) were highly sensitive to pevonedistat (half maximal inhibitory concentration of cell survival IC50 < 0.5 µM). This remained true in a 3D spheroid culture. Pevonedistat treatment caused the accumulation of CDT1 and p21 in both sensitive and resistant cell lines. However, the treatment induced S/G2 cell cycle arrest and DNA rereplication predominantly in the sensitive cell lines. In an in vivo mouse model, the pevonedistat treatment significantly prolonged the survival of mice bearing both sensitive and resistant MPM tumors. Pevonedistat treatment reduced growth in sensitive tumors but increased apoptosis in resistant tumors. The mechanism in the resistant tumor model may be mediated by reduced macrophage infiltration, resulting from the suppression of macrophage chemotactic cytokines, C-C motif chemokine ligand 2 (CCL2), expression in tumor cells.

In plain English

This laboratory study looked at two related proteins, CUL4A and CUL4B, in malignant pleural mesothelioma. It also tested pevonedistat, a drug that blocks neddylation, a process regulating all cullin proteins, including these two, and some other proteins. It did not study asbestos exposure. Gene activity of CUL4A and, more markedly, CUL4B was raised in a subset of 94 mesothelioma tissue samples, compared with 18 samples from patients with chronic pleural inflammation. This gene data showed no link with survival, most probably because the sample was small. In a public dataset of 82 patients, high CUL4B gene activity was associated with shorter disease-free survival. In protein staining of tumors from 143 patients, high CUL4B was associated with shorter progression-free survival. Five of 13 mesothelioma cell lines (38%) were highly sensitive to the drug. In immune-deficient mice with human mesothelioma tumors in the peritoneal cavity, the drug prolonged survival by 13 days for one tumor type and 32.5 days for another. The authors concluded that CUL4B may serve as a treatment target and that this drug class may be efficacious.

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 combining analysis of patient tumor tissue (gene and protein expression), a public gene-expression dataset (TCGA), experiments on cell lines grown in 2D and 3D culture, and a mouse experiment
• Who was studied: Malignant pleural mesothelioma (MPM) tissues from patients in Zürich: 94 tumor samples taken at diagnosis (34), surgery (50) or relapse (10), compared with 18 non-MPM samples from patients with chronic pleural inflammation. Also a tissue microarray of 143 patients (tumor samples collected 1999 to 2009), 82 patients in the TCGA dataset, 13 MPM cell lines plus 2 nonmalignant mesothelial cell lines, and male immune-deficient (SCID) mice
• Exposure: No asbestos exposure was studied. The experimental exposure was the drug pevonedistat (MLN-4924). It inhibits protein neddylation, which regulates all cullins (not only CUL4A and CUL4B) and some other proteins such as p53. It was given to cells in culture and to mice at 50 mg/kg twice daily in cycles of five days on and five days off.
• Main results:
  • Gene expression of CUL4A and, more significantly, CUL4B was elevated in a subset of MPM tumors at all time points, compared with non-MPM tissues
  • In the authors' own gene-expression cohort, CUL4A and CUL4B expression did not correlate with progression-free or overall survival
  • In the public TCGA dataset (n = 82), high CUL4B gene expression was associated with shorter disease-free survival
  • In the tissue microarray cohort (n = 143), high CUL4B protein expression was associated with shorter progression-free survival. High cytoplasmic CUL4A protein expression was associated with longer progression-free survival (p = 0.01).
  • 5 of 13 MPM cell lines (38%) were very sensitive to pevonedistat (IC50 less than 0.5 µM). The two nonmalignant mesothelial cell lines were relatively resistant (IC50 2.4 µM for Met5A and 2.7 µM for SDM104).
  • In cell lines, pevonedistat caused CDT1 and p21 to accumulate in all lines tested. The extent of DNA rereplication was more pronounced in the sensitive lines.
  • In 3D (spheroid) culture, the MPM cell lines needed at least five times higher drug concentrations than in 2D culture, but the differences in sensitivity between lines remained
  • In mice, pevonedistat prolonged survival by 13 days in mice bearing MSTO211H (sensitive) tumors and by 32.5 days in mice bearing ACC-Meso-1 (resistant) tumors
  • In ACC-Meso-1 tumors in mice, treatment significantly reduced tumor-associated macrophages and suppressed human CCL2 expression. Macrophages in MSTO211H tumors were not affected.
• The authors' conclusion: The authors concluded that CUL4B may serve as an additional treatment target. They also concluded that inhibiting cullin activity with a neddylation inhibitor may be efficacious for treating MPM.
• Limitations the authors state:
  • The lack of a survival correlation in the authors' own gene-expression cohort was most probably due to the small sample size
  • The mouse model lacked functional T cells and B cells, so effects with a working immune system remain to be investigated
  • Pevonedistat acts on many targets besides CUL4: all cullins and some other proteins such as p53 are also regulated by neddylation
  • In the fast-growing MSTO211H mouse tumors, the drug may have diffused poorly into tumor nodules

Topics

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Carcinogenesis, Progression-Free Survival, Apoptosis, Macrophage, Cytokine.

Related studies

• Cullin 4B Ubiquitin Ligase Is Important for Cell Survival and Regulates TGF-β1 Expression in Pleural Mesothelioma — J. Kreienbühl, S. Changkhong, et al. (2023)
• The CUL4A ubiquitin ligase is a potential therapeutic target in skin cancer and other malignancies — J. Hannah, P.B. Zhou (2013)
• Importance of excision repair cross-complementation group 1 and ribonucleotide reductase M1 as prognostic biomarkers in malignant pleural mesothelioma treated with platinum-based induction chemotherapy followed by surgery — L. Frischknecht, M. Meerang, et al. (2015)
• Immunohistochemical analysis of the ubiquitin-conjugating enzyme UbcH10 in lung cancer: a useful tool for diagnosis and therapy — I. Perrotta, L. Bruno, et al. (2012)
• Structure and interaction of ubiquitin-associated domain of human Fas-associated factor 1 — J. Song, J.K. Park, et al. (2009)
• The importance of surgical staging in the treatment of malignant pleural mesothelioma — V.W. Rusch, E. Venkatraman (1996)

Browse more research in Cancers, or return to medical research.