Tumor-infiltrating lymphocytes are functionally inactivated by CD90+ stromal cells and reactivated by combined Ibrutinib and Rapamycin in human pleural mesothelioma

Our plain-English summary of Tumor-infiltrating lymphocytes are functionally inactivated by CD90+ stromal cells and reactivated by combined Ibrutinib and Rapamycin in human pleural mesothelioma, by H. Yang, S. Berezowska, P. Dorn, et al (Theranostics, 2022).

The study

• Authors: H. Yang, S. Berezowska, P. Dorn, P. Zens, P. Chen, R.W. Peng, T.M. Marti, G.J. Kocher, R.A. Schmid, S.R.R. Hall
• Journal: Theranostics
• Published: 2022;12(1):167-185
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Rationale: Despite evidence suggesting that the tumor microenvironment (TME) in malignant pleural mesothelioma (MPM) is linked with poor prognosis, there is a lack of studies that functionally characterize stromal cells and tumor-infiltrating lymphocytes (TILs). Here, we aim to characterize the stromal subsets within MPM, investigate their relationship to TILs, and explore the potential therapeutic targets. Methods: We curated a core set of genes defining stromal/immune signatures expressed by mesenchymal cells within the TME using molecular analysis of The Cancer Genome Atlas (TCGA) MPM cohort. Stromal and immune profiles were molecularly characterized using flow cytometry, immunohistochemistry, microarray, and functionally evaluated using T cell-activation/expansion, coculture assays and drug compounds treatment, based on samples from an independent MPM cohort. Results: We found that a high extracellular matrix (ECM)/stromal gene signature, a high ECM score, or the ratio of ECM to an immune activation gene signature are significantly associated with poor survival in the MPM cohort in TCGA. Analysis of an independent MPM cohort (n = 12) revealed that CD8+ and CD4+ TILs were characterized by PD1 overexpression and concomitant downregulation in degranulation and CD127. This coincided with an increase in CD90+ cells that overexpressed PD-L1 and were enriched for ECM/stromal genes, activated PI3K-mTOR signaling and suppressed T cells. Protein array data demonstrated that MPM samples with high PD-L1 expression were most associated with activation of the mTOR pathway. Further, to reactivate functionally indolent TILs, we reprogrammed ex vivo TILs with Ibrutinib plus Rapamycin to block interleukin-2-inducible kinase (ITK) and mTOR pathways, respectively. The combination treatment shifted effector memory (TEM) CD8+ and CD4+ TILs towards T cells that re-expressed CD45RA (TEMRA) while concomitantly downregulating exhaustion markers. Gene expression analysis confirmed that Ibrutinib plus Rapamycin downregulated coinhibitory and T cell signature pathways while upregulating pathways involved in DNA damage and repair and immune cell adhesion and migration. Conclusions: Our results suggest that targeting the TME may represent a novel strategy to redirect the fate of endogenous TILs with the goal of restoring anti-tumor immunity and control of tumor growth in MPM.

© The author(s).

In plain English

This laboratory study examined non-cancer and immune cells inside malignant pleural mesothelioma (MPM) tumors. It did not study asbestos exposure. The authors analyzed gene data from The Cancer Genome Atlas (TCGA) MPM cohort. They also ran experiments on patient tumor samples from the University Hospital of Bern. In TCGA, a high ratio of a stromal (connective-tissue) gene signature to an immune activation signature went with poorer overall and recurrence-free survival. In Bern tumor samples, memory T cells showed more of the marker PD1 than matched non-adjacent lung tissue did. A population of CD90+ cells was more common in tumors. In the lab, these cells resisted pemetrexed/cisplatin, and only after priming with the immune signals TNFα and IFNγ did they suppress healthy donors' T cells. When patients' tumor T cells were grown with the drugs ibrutinib and rapamycin, they shifted toward a cell type called TEMRA and showed fewer markers of exhaustion. The authors concluded this approach may represent a novel treatment strategy. They noted the small sample size and did not determine whether the reprogrammed cells would attack the tumor.

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 public tumor gene and protein data (TCGA) with experiments on patient tumor samples and cells grown outside the body (ex vivo)
• Who was studied: The TCGA MPM cohort (the article text does not give its size), plus MPM samples collected at the University Hospital of Bern, Switzerland. The number of Bern samples was 12 in the flow cytometry analysis of CD90+ cells, 9 matched tumor/normal pairs in the T-cell comparison, 10 patients with samples before and after chemotherapy, and 8 in the T-cell expansion experiments.
• Exposure: Asbestos exposure was not studied. The laboratory treatments were ibrutinib (10 nM) plus low-dose rapamycin (1 nM) given to tumor-derived T cells during expansion, and cisplatin with pemetrexed given to CD90+ cells and MPM cell lines.
• Main results:
  • In the TCGA MPM cohort, a high ratio of the ECM/stromal gene signature to the immune activation gene signature was linked with poor overall and recurrence-free survival.
  • In Bern patients, PD1 was higher on memory T cells in tumor than in matched non-adjacent uninvolved lung tissue. For CD4 cells the values were 35 ± 17.2 (tumor) versus 23.6 ± 18 (normal). For CD8 cells they were 38.2 ± 13.5 (tumor) versus 24.6 ± 14.5 (normal).
  • Tumor cell PD-L1 expression rose after chemotherapy in 2 of 10 patients. The authors said this might reflect the small sample size.
  • Cells positive for CD90 alone were the main mesenchymal cluster in tumors. The values were 44.2 ± 32 in tumor versus 10.3 ± 8.8 in normal tissue, n = 12.
  • In laboratory co-culture, CD90+CD73- cells suppressed CD4 and CD8 T cells from healthy donors only after being immune-primed with TNFα and IFNγ.
  • In laboratory tests, CD90+CD73- cells resisted the cytotoxic effects of pemetrexed/cisplatin.
  • T cells expanded from tumors with ibrutinib plus rapamycin shifted away from effector memory toward TEMRA cells. A trend toward higher PD1 in these cells was not statistically significant.
  • T cells expanded with ibrutinib plus rapamycin showed lower levels of several co-inhibitory molecules, namely LAG3, TIGIT, CTLA4, CD96 and DUSP4.
• The authors' conclusion: The authors concluded that CD90+ MPM cells represent a major subpopulation building an immunosuppressive tumor environment. They suggested that targeting this environment together with tuning tumor-derived T cells through ITK and mTOR signaling may represent a novel approach for treating MPM.
• Limitations the authors state:
  • Gene expression was examined in bulk tumor T cells rather than in separate CD8+ and CD4+ cells.
  • The sample size was small, and the findings need confirmation in a larger cohort.
  • It is unclear whether the CD90+ cells are mesothelial precursor cells that have undergone epithelial-to-mesenchymal transition or a subset of cancer-associated fibroblasts.
  • It was not determined whether reprogramming the T cells could induce a tumor-specific immune response.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Tumor-Infiltrating Lymphocytes, Pleural Mesothelioma, Tumor Microenvironment, Prognosis, Immunohistochemistry, PD-L1.

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