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J. De Waele
MINI 24 - Epidemiology, Early Detection, Biology (ID 140)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Thymoma, Mesothelioma and Other Thoracic Malignancies
- Presentations: 1
MINI24.11 - Expression of PD-1 and Its Ligands in Human Malignant Pleural Mesothelioma (ID 1676)
16:45 - 18:15 | Author(s): J. De Waele
The discovery of immune checkpoint receptors as cytotoxic T lymphocyte antigen-4 (CTLA-4) and more recently programmed death-1 (PD-1) introduced a new era in cancer immunotherapy. Immune checkpoints are responsible for controlling and inactivating the immune system in order to avoid autoimmunity and prevent tissue damage. PD-1 is expressed primarily on activated effector T lymphocytes. Its natural ligands are programmed death ligand-1 (PD-L1) and programmed death ligand-2 (PD-L2). Expression of PD-L1/PD-L2 on tumor cells or in stroma impairs effector T lymphocyte activity within the tumor microenvironment. Trials with antibodies that block the ligand-immune checkpoint interaction have shown promising results in several cancer types.Data on few mesothelioma patients suggest that blocking immune checkpoints could offer new opportunities for treatment of this very aggressive tumor.. We investigated PD-1, PD-L1 and PD-L2 expression in MPM. Furthermore the effect of interferon-gamma (IFNg), an important cytokine for immune-mediated tumor control, on their expression pattern was analyzed.
Flow cytometry and immunohistochemistry (IHC) were used for the expression of PD-1, PD-L1 and PD-L2 on human primary MPM and T cells and on MPM cell lines that cover the three major histological subtypes of of MPM, i.e. epitheloid (M28, H2795, H2818), sarcomatoid (VAMT-1, H2731, H-Meso-1) and mixed (NKI04, MSTO-211H) mesothelioma cells. The effect of stimulation with IFNg on expression of PD-1 and its ligands was measured.
PD-1 surface expression was found on T cells and not on MPM tumor cells, corresponding to literature showing that PD-1 is only expressed on T cells, B cells and macrophages. Different expression patterns were observed regarding PD-L1 and PD-L2. Flow cytometry showed significant PD-L1 expression on all the epitheloid and sarcomatoid mesothelioma cell lines. Two out of three cell lines tested positive for PD-L2, both for the epitheloid and the sarcomatoid subtype. The mixed cell lines were negative for PD-1 and its ligands. Following IFNg stimulation, PD-L1 and PD-L2 expression was induced or upregulated on all cell lines. Primary MPM cells showed variable expression of PD-L1. IHC data for PD-1 and PD-L1 expression correspond to the flow cytometry results.
Taken together, these data on PD-1, PD-L1 and PD-L2 expression on human MPM cells and T cells support further investigation of the expression profile of the immune checkpoint PD-1 and its ligands in MPM patients samples. We are currently performing this using multicolor flow cytometry and IHC.
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