RESUMEN
Immune checkpoint inhibitors, such as monoclonal antibodies targeting programmed death 1 (PD-1) and programmed death ligand-1 (PD-L1), have achieved enormous success in the treatment of several cancers. However, monoclonal antibodies are expensive to produce, have poor tumor penetration, and may induce autoimmune side effects, all of which limit their application. Here, we demonstrate that PDI-1 (also name PD1/PD-L1 inhibitor 1), a small molecule antagonist of PD-1/PD-L1 interactions, shows potent anti-tumor activity in vitro and in vivo and acts by relieving PD-1/PD-L1-induced T cell exhaustion. We show that PDI-1 binds with high affinity to purified human and mouse PD-1 and PD-L1 proteins and is a competitive inhibitor of human PD-1/PD-L1 binding in vitro. Incubation of ex vivo activated human T cells with PDI-1 enhanced their cytotoxicity towards human lung cancer and melanoma cells, and concomitantly increased the production of granzyme B, perforin, and inflammatory cytokines. Luciferase reporter assays showed that PDI-1 directly increases TCR-mediated activation of NFAT in a PD-1/PD-L1-dependent manner. In two syngeneic mouse tumor models, the intraperitoneal administration of PDI-1 reduced the growth of tumors derived from human PD-L1-transfected mouse lung cancer and melanoma cells; increased and decreased the abundance of tumor-infiltrating CD8+ and FoxP3+ CD4+ T cells, respectively; decreased the abundance of PD-L1-expressing tumor cells, and increased the production of inflammatory cytokines. The anti-tumor effect of PDI-1 in vivo was comparable to that of the anti-PD-L1 antibody atezolizumab. These results suggest that the small molecule inhibitors of PD-1/PD-L1 may be effective as an alternative or complementary immune checkpoint inhibitor to monoclonal antibodies.
Asunto(s)
Antígeno B7-H1/metabolismo , Carcinoma de Pulmón de Células no Pequeñas/inmunología , Carcinoma de Pulmón de Células no Pequeñas/metabolismo , Inhibidores de Puntos de Control Inmunológico/farmacología , Melanoma/inmunología , Melanoma/metabolismo , Receptor de Muerte Celular Programada 1/metabolismo , Animales , Antígeno B7-H1/química , Línea Celular , Citocinas/metabolismo , Citotoxicidad Inmunológica , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Humanos , Inhibidores de Puntos de Control Inmunológico/química , Inhibidores de Puntos de Control Inmunológico/uso terapéutico , Neoplasias Pulmonares/tratamiento farmacológico , Neoplasias Pulmonares/inmunología , Neoplasias Pulmonares/metabolismo , Activación de Linfocitos/efectos de los fármacos , Activación de Linfocitos/inmunología , Melanoma/tratamiento farmacológico , Melanoma Experimental , Ratones , Modelos Biológicos , Estructura Molecular , Receptor de Muerte Celular Programada 1/química , Unión Proteica/efectos de los fármacos , Transducción de Señal , Relación Estructura-Actividad , Linfocitos T/efectos de los fármacos , Linfocitos T/inmunología , Linfocitos T/metabolismo , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
The mitochondrial intermembrane space evolved from the bacterial periplasm. Presumably as a consequence of their common origin, most proteins of these compartments are stabilized by structural disulfide bonds. The molecular machineries that mediate oxidative protein folding in bacteria and mitochondria, however, appear to share no common ancestry. Here we tested whether the enzymes Erv1 and Mia40 of the yeast mitochondrial disulfide relay could be functionally replaced by corresponding components of other compartments. We found that the sulfhydryl oxidase Erv1 could be replaced by the Ero1 oxidase or the protein disulfide isomerase from the endoplasmic reticulum, however at the cost of respiration deficiency. In contrast to Erv1, the mitochondrial oxidoreductase Mia40 proved to be indispensable and could not be replaced by thioredoxin-like enzymes, including the cytoplasmic reductase thioredoxin, the periplasmic dithiol oxidase DsbA, and Pdi1. From our studies we conclude that the profound inertness against glutathione, its slow oxidation kinetics and its high affinity to substrates renders Mia40 a unique and essential component of mitochondrial biogenesis. Evidently, the development of a specific mitochondrial disulfide relay system represented a crucial step in the evolution of the eukaryotic cell.