The PD-L1/PD-1 pathway promotes dysfunction, but not "exhaustion", in tumor-responding T cells from pleural effusions in lung cancer patients

Our plain-English summary of The PD-L1/PD-1 pathway promotes dysfunction, but not "exhaustion", in tumor-responding T cells from pleural effusions in lung cancer patients, by H. Prado-Garcia, S. Romero-Garcia, A. Puerto-Aquino, et al (Cancer Immunology, Immunotherapy, 2017).

The study

• Authors: H. Prado-Garcia, S. Romero-Garcia, A. Puerto-Aquino, U. Rumbo-Nava
• Journal: Cancer Immunology, Immunotherapy
• Published: 2017;66(6):765-776
• Cited by: 42 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Malignant pleural effusions are frequent in patients with advanced stages of lung cancer and are commonly infiltrated by lymphocytes and tumor cells. CD8+ T cells from these effusions have reduced effector functions. The programmed death receptor 1(PD-1)/programmed death ligand 1 (PD-L1) pathway is involved in T-cell exhaustion, and it might be responsible for T-cell dysfunction in lung cancer patients. Here, we show that PD-L1 is expressed on tumor cell samples from malignant effusions, on lung cancer cell lines, and, interestingly, on MRC-5 lung fibroblasts. PD-L1 was up-regulated in lung cancer cell lines upon treatment with IFN-gamma, but not under hypoxic conditions, as detected by RT-qPCR and flow cytometry. Blockade of PD-L1 on tumor cells restored granzyme-B expression in allogenic CD8+ T cells in vitro. Remarkably, pleural effusion CD8+ T cells that responded to the tumor antigens MAGE-3A and WT-1 (identified as CD137+ cells) were lower in frequency than CMV pp65-responding CD8+ T cells and did not have an exhausted phenotype (PD-1+ TIM-3+). Nonetheless, tumor-responding CD8+ T cells had a memory phenotype and expressed higher levels of PD-1. A PD-L1 blocking antibody increased the expression of granzyme-B and perforin on polyclonal- and tumor-stimulated CD8+ T cells. Taken together, our data show that rather than being exhausted, tumor-responding CD8+ T cells are not completely differentiated into effector cells and are prone to negative regulation by PD-L1. Hence, our study provides evidence that lung cancer patients respond to immunotherapy due to blockade of the PD-L1/PD-1 pathway.

In plain English

This laboratory study in Mexico City examined how a signaling pathway called PD-L1/PD-1 affects immune cells (T cells) in fluid around the lungs (pleural effusions). Asbestos was not studied. The cancer group had 49 patients. Of their effusions, 43 came from non-small cell lung carcinoma and 6 from mesotheliomas, and mesothelioma results were not reported separately. PD-L1 was found on all tumor samples tested and on lung cancer cell lines. The immune signal IFN-gamma raised PD-L1 on the cell lines and on tumor cells in four of six patient samples. Low oxygen generally did not. Cancer cells carrying PD-L1 reduced a killing protein (granzyme-B) in donor T cells, and blocking PD-L1 prevented this. T cells in cancer effusions carried high PD-1 levels, as did those from tuberculosis effusions. Most did not carry the marker combination the authors link to 'exhaustion'. Blocking PD-L1 raised killing proteins in some patients' T cells, for example in 6 of 7 patients after stimulation with WT-1 peptides. The authors concluded that tumor-responding CD8+ T cells that express PD-1 are not exhausted but incompletely differentiated.

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 using lung cancer cell lines and cells from patients' pleural effusions and blood
• Who was studied: 49 patients with lung cancer-associated pleural effusion at a national respiratory diseases institute in Mexico City: 43 effusions from non-small cell lung carcinoma (36 adenocarcinomas, 7 squamous carcinomas) and 6 from mesotheliomas. Comparison groups were 16 patients with non-malignant exudative effusions, 10 patients with tuberculosis effusions and 12 healthy non-smoking volunteers. Study dates are not given.
• Exposure: Asbestos exposure was not studied or reported. The laboratory treatments were IFN-gamma, low-oxygen culture, tumor peptides (MAGE-3A, WT-1), a CMV control peptide and an anti-PD-L1 blocking antibody.
• Main results:
  • PD-L1 was detected on all tumor cell samples from pleural effusions and on the non-small cell lung carcinoma cell lines.
  • IFN-gamma increased PD-L1 on tumor cells from pleural effusions in four of six cases analyzed.
  • Under low oxygen, PD-L1 protein rose only in the A-549 cell line.
  • The percentage of granzyme-B-positive CD8+ T cells from healthy donors fell after coculture with PD-L1-expressing SKMES-1 cancer cells, and an anti-PD-L1 antibody blocked this reduction.
  • Pleural effusion T cells from both lung cancer and tuberculosis patients expressed high levels of PD-1.
  • In lung cancer pleural effusions, most PD-1-positive CD8+ T cells did not also carry TIM-3 or LAG-3, the markers the authors associate with exhaustion.
  • Among 20 lung cancer patients, responding (CD137+) T cells were detected after stimulation with CMV pp65 in 18 of 20, with MAGE-3A in 18 of 20 and with WT-1 in 16 of 20.
  • Frequencies of CD137+ CD8+ and CD137+ CD4+ T cells responding to CMV pp65 were significantly higher than those responding to MAGE-3A or WT-1.
  • Only a reduced proportion of antigen-responding CD8+ and CD4+ T cells carried both PD-1 and TIM-3.
  • Blocking PD-L1 increased the percentage of granzyme-B-positive and perforin-positive CD8+ T cells in 4 of 5 patients after anti-CD3/anti-CD28 stimulation, in 3 of 7 after MAGE-3A and in 6 of 7 after WT-1 stimulation.
• The authors' conclusion: The authors concluded that tumor-responding CD8+ T cells in lung cancer pleural effusions that express PD-1 are not exhausted but incompletely differentiated, and so lack effector functions.
• Limitations the authors state:
  • PD-L1 protein levels measured by flow cytometry did not match mRNA levels. The authors suggest the primers used may have missed one splice variant.
  • In the unstimulated condition, responding cells were too few for analysis in most samples, so only eight samples were shown.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma, Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: PD-L1, Pleural Effusion, Lung Cancer, Fibroblast, Wilms Tumor 1 (WT-1), Immunotherapy.

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