Prmt5 Promotes Stat-1 Mediated T Cell Inflammatory Response And Is A Therapeutic Target For Acute Graft-Versus-Host Disease

Abstract Introduction T cell mediated acute graft-versus-host disease (aGVHD) is the main cause of non-relapse mortality in allogeneic hematopoietic cell transplant recipients. Protein arginine methyltransferase 5 (PRMT5) is a post-translational modifier and promotes activation of memory TH cells. We investigate mechanisms by which PRMT5 regulates T cell function and propose PRMT5 inhibition as a therapeutic strategy for aGVHD. Materials and Methods PRMT5 expression and function was evaluated in T cells of healthy and aGVHD mice and humans. We assessed T cell proliferation and effector function, using C220, a novel PRMT5 inhibitor. We tested effects of PRMT5 inhibition using in vivo mouse models of aGVHD, where mice received T cell depleted bone marrow + allogeneic splenocytes. In graft-versus-leukemia (GVL) experiments, P815 tumor cells were administered. Mice were treated with C220 or vehicle and monitored for survival and clinical aGVHD scores. Results PRMT5 expression and function is upregulated in T cells of mice and humans with aGVHD. Inhibition of PRMT5 reduces T cell proliferation, perturbs cell cycle and downregulates STAT-1 mediated interferon response. Administration of C220 improved survival in aGVHD mouse models and maintained tumor specific CTL response contributing to retention of Graft versus leukemia (GVL) effect. Conclusions Inhibition of PRMT5 using C220, down-regulates T cell proliferative and effector response, induces cell-cycle arrest, reduces interferon response and perturbs signaling pathways. C220 shows potent biological activity in vivo by reducing aGVHD clinical severity and prolonging survival in mouse models without compromising GVL. Therefore, PRMT5 is a novel and druggable target for aGVHD.