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Curated Journal Articles on Mesothelioma

Malignant mesothelioma effusions are infiltrated by CD3+ T cells highly expressing PD-L1 and the PD-L1+ tumor cells within these effusions are susceptible to ADCC by the anti-PD-L1 antibody avelumab

Journal of Thoracic Oncology: Official Publication of the International Association for the Study of Lung Cancer 2016 August 17 [Epub ahead of print] [Link]

Khanna S, Thomas A, Abate-Daga D, Zhang J, Morrow B, Steinberg SM, Orlandi A, Ferroni P, Schlom J, Guadagni F, Hassan R

Abstract

INTRODUCTION:
The functional aspects of programmed death 1 (PD-1) and PD ligand 1 (PD-L1) immune checkpoints in malignant mesothelioma have not been studied.
METHODS:
Tumor samples from 65 patients with mesothelioma were evaluated for PD-L1 expression by immunohistochemistry and its prognostic significance. Malignant effusions from patients with pleural and peritoneal mesothelioma were evaluated for PD-1+ and PD-L1+ infiltrating lymphocytes and their role in inducing tumor cell PD-L1 expression. Antibody dependent cellular cytotoxicity (ADCC) of avelumab, a fully humanized IgG1 anti PD-L1 antibody towards primary mesothelioma cell lines was evaluated in presence of autologous and allogeneic NK cells.
RESULTS:
Of 65 pleural and peritoneal mesothelioma tumors examined, 41 (63%) were PD-L1 positive, which was associated with slightly inferior overall survival compared to patients with PD-L1 negative tumors (median 23.0 vs. 33.3 months; p=0.35). The frequency of PD-L1 expression was similar in pleural and peritoneal mesothelioma patients with 62% and 64% of samples positive, respectively. Of nine mesothelioma effusion samples evaluated, the fraction of cells expressing PD-L1 ranged from 12 to 83%. Of 7 patients with paired malignant effusion and peripheral blood mononuclear cells (PBMC) samples, PD-L1 expression was significantly higher on CD3+ T cells present in malignant effusions as compared with PBMC (p=0.016). In addition, CD14+PD-1+ cells were elevated in malignant effusions compared with PBMC (p=0.031). The lymphocytes present in malignant effusions recognized autologous tumor cells and induced IFN-γ-mediated PD-L1 expression on the tumor cell surface. Of the three primary mesothelioma cell lines tested, two were susceptible to avelumab mediated ADCC in presence of autologous NK cells.
CONCLUSION:
The majority of pleural as well as peritoneal mesothelioma express PD-L1. Malignant effusions in this disease are characterized by presence of tumor cells and CD3+ T cells that highly express PD-L1. In addition, mesothelioma tumor cells are susceptible to ADCC by anti-PD-L1 antibody avelumab.

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