title: A novel regulation of PD-1 ligands on mesenchymal stromal cells through MMP-mediated proteolytic cleavage.
abstract: Whether fibroblasts regulate immune response is a crucial issue in the modulation of inflammatory responses. Herein, we demonstrate that foreskin fibroblasts (FFs) potently inhibit CD3+T cell proliferation through a mechanism involving early apoptosis of activated T cells. Using blocking antibodies, we demonstrate that the inhibition of T cell proliferation occurs through cell-to-cell interactions implicating PD-1 receptor expressed on T cells and its ligands, PD-L1 and PD-L2, on fibroblasts. Dual PD-1 ligand neutralization is required to abrogate (i) binding of the PD-1-Fc fusion protein, (ii) early apoptosis of T cells, and (iii) inhibition of T cell proliferation. Of utmost importance, we provide the first evidence that PD-1 ligand expression is regulated through proteolytic cleavage by endogenous matrix metalloproteinases (MMPs) without transcriptional alteration during culture-time. Using (i) different purified enzymatic activities, (ii) MMP-specific inhibitors, and (iii) recombinant human MMP-9 and MMP-13, we demonstrated that in contrast to CD80/CD86, PD-L1 was selectively cleaved by MMP-13, while PD-L2 was sensitive to broader MMP activities. Their cleavage by exogenous MMP-9 and MMP-13 with loss of PD-1 binding domain resulted in the reversion of apoptotic signals on mitogen-activated CD3+T cells. We suggest that MMP-dependent cleavage of PD-1 ligands on fibroblasts may limit their immunosuppressive capacity and thus contribute to the exacerbation of inflammation in tissues. In contrast, carcinoma-associated fibroblasts appear PD-1 ligand-depleted through MMP activity that may impair physical deletion of exhausted defective memory T cells through apoptosis and facilitate their regulatory functions. These observations should be considered when using the powerful PD-1/PD-L1 blocking immunotherapies.
authors.affiliation: Université de Lyon, Lyon, France; Université Lyon 1, ISPB, Lyon, France; INSERM U1052, Center de Recherche en Cancérologie de Lyon, Lyon, France; CNRS UMR5286, Center de Recherche en Cancérologie de Lyon, Lyon, France.
authors.forename: Colette
authors.initials: C
authors.lastname: Dezutter-Dambuyant
authors.affiliation: Université de Lyon, Lyon, France; Université Lyon 1, ISPB, Lyon, France; INSERM U1052, Center de Recherche en Cancérologie de Lyon, Lyon, France; CNRS UMR5286, Center de Recherche en Cancérologie de Lyon, Lyon, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Durand
authors.affiliation: Université de Lyon, Lyon, France; Université Lyon 1, ISPB, Lyon, France; INSERM U1052, Center de Recherche en Cancérologie de Lyon, Lyon, France; CNRS UMR5286, Center de Recherche en Cancérologie de Lyon, Lyon, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Alberti
authors.affiliation: Université de Lyon, Lyon, France; Université Lyon 1, ISPB, Lyon, France; INSERM U1052, Center de Recherche en Cancérologie de Lyon, Lyon, France; CNRS UMR5286, Center de Recherche en Cancérologie de Lyon, Lyon, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Bendriss-Vermare
authors.affiliation: Université de Lyon, Lyon, France; Université Lyon 1, ISPB, Lyon, France; INSERM U1052, Center de Recherche en Cancérologie de Lyon, Lyon, France; CNRS UMR5286, Center de Recherche en Cancérologie de Lyon, Lyon, France.
authors.forename: Jenny
authors.initials: J
authors.lastname: Valladeau-Guilemond
authors.affiliation: Université de Lyon, Lyon, France; Université Lyon 1, ISPB, Lyon, France; INSERM U1052, Center de Recherche en Cancérologie de Lyon, Lyon, France; CNRS UMR5286, Center de Recherche en Cancérologie de Lyon, Lyon, France.
authors.forename: Adeline
authors.initials: A
authors.lastname: Duc
authors.affiliation: Université de Lyon, Lyon, France; Université Lyon 1, ISPB, Lyon, France; INSERM U1052, Center de Recherche en Cancérologie de Lyon, Lyon, France; CNRS UMR5286, Center de Recherche en Cancérologie de Lyon, Lyon, France.
authors.forename: Audrey
authors.initials: A
authors.lastname: Magron
authors.affiliation: Université de Lyon, Lyon, France; Université Lyon 1, ISPB, Lyon, France; INSERM U1052, Center de Recherche en Cancérologie de Lyon, Lyon, France; CNRS UMR5286, Center de Recherche en Cancérologie de Lyon, Lyon, France.
authors.forename: Anne-Pierre
authors.initials: AP
authors.lastname: Morel
authors.affiliation: Université de Lyon, Lyon, France; Université Lyon 1, ISPB, Lyon, France; INSERM U1052, Center de Recherche en Cancérologie de Lyon, Lyon, France; CNRS UMR5286, Center de Recherche en Cancérologie de Lyon, Lyon, France.
authors.forename: Vanja
authors.initials: V
authors.lastname: Sisirak
authors.affiliation: Université de Lyon, Lyon, France; Université Lyon 1, ISPB, Lyon, France; INSERM U1052, Center de Recherche en Cancérologie de Lyon, Lyon, France; CNRS UMR5286, Center de Recherche en Cancérologie de Lyon, Lyon, France.
authors.forename: Céline
authors.initials: C
authors.lastname: Rodriguez
authors.affiliation: Université de Lyon, Lyon, France; Université Lyon 1, ISPB, Lyon, France; INSERM U1052, Center de Recherche en Cancérologie de Lyon, Lyon, France; CNRS UMR5286, Center de Recherche en Cancérologie de Lyon, Lyon, France.
authors.forename: David
authors.initials: D
authors.lastname: Cox
authors.affiliation: Aix-Marseille Université, Marseille, France, Inserm U1068, Center de Recherche en Cancérologie de Marseille (CRCM), Immunity & Cancer Institut Paoli-Calmettes; Aix-Marseille Université UM 105, CNRS UMR 7258, IBiSA Cancer Immunomonitoring Platform, Marseilles, France.
authors.forename: Daniel
authors.initials: D
authors.lastname: Olive
authors.affiliation: Université de Lyon, Lyon, France; Université Lyon 1, ISPB, Lyon, France; INSERM U1052, Center de Recherche en Cancérologie de Lyon, Lyon, France; CNRS UMR5286, Center de Recherche en Cancérologie de Lyon, Lyon, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Caux
keywords: Apoptosis; MMP-13; PD-L1; PD-L2; PD1; fibroblasts; immunosuppression