Potential Diagnostic and Prognostic Role of Microenvironment in Malignant Pleural Mesothelioma

Our plain-English summary of Potential Diagnostic and Prognostic Role of Microenvironment in Malignant Pleural Mesothelioma, by I.C. Salaroglio, J. Kopecka, F. Napoli, et al (Journal of Thoracic Oncology, 2019).

The study

• Authors: I.C. Salaroglio, J. Kopecka, F. Napoli, M. Pradotto, F. Maletta, L. Costardi, M. Gagliasso, V. Milosevic, P. Ananthanarayanan, P. Bironzo, F. Tabbò, C.F. Cartia, E. Passone, V. Comunanza, F. Ardissone, E. Ruffini, F. Bussolino, L. Righi, S. Novello, M. Di Maio, M. Papotti, G.V. Scagliotti, C. Riganti
• Journal: Journal of Thoracic Oncology
• Published: 2019;14(8):1458-1471
• Cited by: 61 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Introduction: A comprehensive analysis of the immune cell infiltrate collected from pleural fluid and from biopsy specimens of malignant pleural mesothelioma (MPM) may contribute to understanding the immune-evasion mechanisms related to tumor progression, aiding in differential diagnosis and potential prognostic stratification. Until now such approach has not routinely been verified.

Methods: We enrolled 275 patients with an initial clinical diagnosis of pleural effusion. Specimens of pleural fluids and pleural biopsy samples used for the pathologic diagnosis and the immune phenotype analyses were blindly investigated by multiparametric flow cytometry. The results were analyzed using the Kruskal-Wallis test. The Kaplan-Meier and log-rank tests were used to correlate immune phenotype data with patients' outcome.

Results: The cutoffs of intratumor T-regulatory (>1.1%) cells, M2-macrophages (>36%), granulocytic and monocytic myeloid-derived suppressor cells (MDSC; >5.1% and 4.2%, respectively), CD4 molecule-positive (CD4+) programmed death 1-positive (PD-1+) (>5.2%) and CD8+PD-1+ (6.4%) cells, CD4+ lymphocyte activating 3-positive (LAG-3+) (>2.8% ) and CD8+LAG-3+ (>2.8%) cells, CD4+ T cell immunoglobulin and mucin domain 3-positive (TIM-3+) (>2.5%), and CD8+TIM-3+ (>2.6%) cells discriminated MPM from pleuritis with 100% sensitivity and 89% specificity. The presence of intratumor MDSC contributed to the anergy of tumor-infiltrating lymphocytes. The immune phenotype of pleural fluid cells had no prognostic significance. By contrast, the intratumor T-regulatory and MDSC levels significantly correlated with progression-free and overall survival, the PD-1+/LAG-3+/TIM-3+ CD4+ tumor-infiltrating lymphocytes correlated with overall survival.

Conclusions: A clear immune signature of pleural fluids and tissues of MPM patients may contribute to better predict patients' outcome.

Copyright © 2019 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.

In plain English

Researchers at two hospitals in the Torino area of Italy enrolled 275 patients with fluid around the lungs (pleural effusion) of unknown cause between June 2016 and June 2018. Without knowing the diagnoses, they used flow cytometry to measure immune cell types in pleural fluid and pleural tissue from patients later diagnosed with malignant pleural mesothelioma (49 fluid and 33 tissue samples), non-cancerous pleuritis, or other cancers spread to the pleura. Several immune cell types, including T-regulatory cells, M2-macrophages and myeloid-derived suppressor cells (MDSCs), were higher in mesothelioma, and chosen cutoffs separated mesothelioma from pleuritis. In laboratory tests, MDSCs from mesothelioma tissue reduced T-cell activity. The levels of these immune cells in pleural fluid showed no statistically significant link with progression-free or overall survival. In tumor tissue, higher T-regulatory cells and MDSCs were linked with shorter progression-free and overall survival. The authors concluded that tumor tissue was more reliable than fluid for predicting outcome. They noted that their cutoffs came from a small cohort and called the work a pilot needing validation. The article reported no analysis of asbestos exposure.

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: Diagnostic and prognostic laboratory study. Patients were enrolled over two years and samples were taken during routine diagnostic thoracostomies. Immune cells were measured by flow cytometry by researchers unaware of the diagnosis, and survival was compared with the Kaplan-Meier method. The authors call it a pilot experience.
• Who was studied: 275 patients with pleural effusion of unknown origin, enrolled June 2016 to June 2018 at San Luigi Gonzaga Hospital, Orbassano, and AOU Città della Salute e della Scienza, Torino, Italy. Samples analyzed: pleural fluid from 63 pleuritis, 49 malignant pleural mesothelioma (MPM) and 32 pleural metastasis patients. Pleural tissue from 16 pleuritis, 33 MPM and 5 metastasis patients. 9 pleuritis and 20 MPM patients had both fluid and tissue analyzed. All MPM patients were in advanced clinical stage and received standard chemotherapy.
• Exposure: Asbestos exposure was not analyzed. The study measured immune cell types (T-regulatory cells, macrophages, myeloid-derived suppressor cells, and T cells carrying the immune checkpoints PD-1, LAG-3, TIM-3 and CTLA-4). Patients' asbestos exposure history, when available, was listed only in a supplementary table not included in the text.
• Main results:
  • Among patients with both fluid and tissue analyzed, T-regulatory cell cutoffs of greater than 1.4% in pleural fluid and greater than 1.1% in pleural tissue identified all 20 of 20 MPM cases and excluded 8 of 9 (88.8%) pleuritis cases.
  • M2-macrophages were below 29% in fluid and below 36% in tissue in all pleuritis patients. They were above 41% in fluid and above 44% in tissue in all MPM patients.
  • A threshold of 5.1% granulocytic myeloid-derived suppressor cells (Gr-MDSCs) in both pleural fluid and tissue separated all pleuritis from all MPM cases.
  • In laboratory tests, MDSCs taken from MPM tissue produced more ROS, nitric oxide and kynurenine than those from other groups. They reduced the proliferation and activity of T lymphocytes, both from the same patient and from pleuritis patients. The authors interpreted this as MDSCs causing T-lymphocyte anergy.
  • The checkpoints PD-1, LAG-3 and TIM-3 were higher on CD4 and CD8 T lymphocytes in MPM than in pleuritis and metastases. CTLA-4 expression did not differ between groups.
  • None of the immune cell measurements in pleural fluid (49 MPM patients) showed a significant correlation with progression-free or overall survival.
  • In pleural tissue (33 MPM patients, split at the median), low versus high T-regulatory cells had mean progression-free survival of 9.1 versus 4.7 months (p = 0.0172). Mean overall survival was 12.1 versus 7.6 months (p = 0.0046).
  • In pleural tissue, low versus high Gr-MDSCs had mean progression-free survival of 9.1 versus 5.6 months (p = 0.0427) and overall survival of 11.3 versus 7.5 months (p = 0.037). Low versus high monocytic MDSCs had progression-free survival of 11.2 versus 7.3 months (p = 0.0178) and overall survival of 11.1 versus 8.0 months (p = 0.026).
  • In pleural tissue, low versus high LAG-3-positive CD4 cells had mean overall survival of 11.5 versus 8.0 months (p = 0.0077). Mean progression-free survival was 8.3 versus 7.0 months, not significant (p = 0.364).
  • In pleural tissue, low versus high PD-1-positive CD4 cells had mean overall survival of 11.4 versus 8.3 months (p = 0.043). For TIM-3-positive CD4 cells it was 11.7 versus 7.8 months (p = 0.044). Checkpoints on CD8 cells in tissue showed no significant prognostic association.
  • In pleural tissue, the amount of CD8 T cells and M2-macrophages showed no significant prognostic association.
• The authors' conclusion: The authors concluded that the immune cells inside the tumor, more than those in the pleural fluid, were more reliable for predicting patients' outcome. They said the immune tests were meant to complement, not replace, pathologic diagnosis.
• Limitations the authors state:
  • The discriminating cutoff values were obtained in a small patient cohort.
  • Finding the optimal cutoff was outside the study's scope. For survival, patients were split at median values because no validated cutoffs existed.
  • The survival analysis was exploratory and used p less than 0.05 with no adjustment for multiple testing.
  • The CTLA-4 results need re-assessment once staining for intracellular CTLA-4 is optimized.
  • The findings are a pilot and need confirmation in a larger validation study before the markers could be used.

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: Pleural Mesothelioma, Biopsy, Differential Diagnosis, Pleural Effusion, Pleural Biopsy, Macrophage, Tumor-Infiltrating Lymphocytes, Overall Survival.

Related studies

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• Molecular and Histopathological Characterization of the Tumor Immune Microenvironment in Advanced Stage of Malignant Pleural Mesothelioma — N.S. Patil, L. Righi, et al. (2018)
• Clonal architecture in mesothelioma is prognostic and shapes the tumour microenvironment — M. Zhang, J.L. Luo, et al. (2021)
• Characterization of the immune microenvironment in malignant pleural mesothelioma reveals prognostic subgroups of patients — N. Fusco, V. Vaira, et al. (2020)
• Prognostic Role of PD-L1 in Malignant Pleural Mesothelioma: Unraveling the Complexity of the Tumor Microenvironment in Mesothelioma — M. de Perrot (2021)
• MicroRNA signature of malignant mesothelioma with potential diagnostic and prognostic implications — S. Busacca, S. Germano, et al. (2010)

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