PGE2 inhibits natural killer and γδ T cell cytotoxicity triggered by NKR and TCR through a cAMP-mediated PKA type I-dependent signaling

Abstract Natural killer (NK) and unconventional γδ T cells, by their ability to sense ligands induced by oncogenic stress on cell surface and to kill tumor cells without a need for clonal expansion, show a great therapeutic interest. They use numerous activating and inhibitory receptors which can function with some independence to trigger or inhibit destruction of target cells. Previous reports demonstrated that PGE 2 is able to suppress the destruction of some tumor cell lines by NK and γδ T cells but it remained uncertain if PGE 2 interferes with the different activating receptors governing the cytolytic responses of NK and γδ T cells. In this report, using the model of specific redirected lysis of the mouse FcγR + cell line P815, we clearly demonstrate that the major NK receptors (NKR): NKG2D, CD16 and natural cytotoxicity receptors (NCR: NKp30, NKp44, NKp46) and γδ T cell receptors TCR Vγ9Vδ2, NKG2D and CD16 are all inhibited by PGE 2 . As is the case with γδ T cells, we show that PGE 2 binds on E-prostanoid 2 (EP2) and EP4 receptors on NK cells. Finally, we delineate that the signaling of the blockade by PGE 2 is mediated through a cAMP-dependent activation of PKA type I which inhibits early signaling protein of cytotoxic cells. In the discussion, we focused on how these data should impact particular approaches in the treatment of cancer.