Yao, Ke

Abstract Front-line pharmaceutical interventions for treating acute graft-versus-host disease (GVHD) are not uniformly effective and have toxic side effects. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells with potent in vitro and in vivo immunosuppressive functions. Clinical translation of in vitro–generated MDSCs has been limited because of requirements for multiple, high infusion doses, the relatively low yield from peripheral blood–sourced MDSCs (PB-MDSCs), and inconsistent product quality. To circumvent these obstacles, we developed a methodology to generate MDSCs using human induced pluripotent stem cell (iPSC)–derived CD34+ cells. Compared with PB-MDSCs, iPSC-derived MDSCs (iMDSCs) shared similar morphology, phenotype, and suppressive function. We found that the CD14+ iMDSC subset possessed the highest suppressor function. In previous studies, we reported that MDSCs transferred into mice with GVHD lost suppressor function because of inflammasome activation and immature myeloid cell maturation. In striking contrast to human PB-MDSCs, we show herein that iMDSCs retained 95% of suppressor function in vitro despite exposure to lipopolysaccharide (LPS) plus adenosine triphosphate (ATP), which are stimuli that activate the inflammasome via danger-associated molecular patterns released during early posttransplant conditioning and GVHD-induced injury. In an in vivo xenogenic GVHD model with PB mononuclear cells, iMDSCs significantly increased recipient survival without loss of antileukemia effects. iMDSC RNA sequencing and gene knockdown studies revealed that the maintenance of the purine metabolizing enzyme, phosphoglycerate dehydrogenase, during LPS plus ATP treatment, was linked to iMDSC inflammasome resistance. Taken together, these findings provide a platform for translating in vitro–generated, off-the-shelf iMDSCs into the clinic for suppressing a spectrum of adverse immune responses, including GVHD.

Abstract The key functional molecules involved in inflammatory bowel disease (IBD) and IBD-induced colorectal tumorigenesis remain unclear. In this study, we found that the apoptosis repressor with caspase recruitment domain (ARC) protein plays critical roles in IBD. ARC-deficient mice exhibited substantially higher susceptibility to dextran sulfate sodium (DSS)-induced IBD compared with wild-type mice. The inflammatory burden induced in ARC-deficient conditions was inversely correlated with CCL5 and CXCL5 levels in immune cells, especially CD4-positive T cells. Pathologically, ARC expression in immune cells was significantly decreased in clinical biopsy specimens from patients with IBD compared with normal subjects. In addition, ARC levels inversely correlated with CCL5 and CXCL5 levels in human biopsy specimens. ARC interacted with TNF receptor associated factor (TRAF) 6, regulating ubiquitination of TRAF6, which was associated with NF-κB signaling. Importantly, we identified a novel ubiquitination site at lysine 461, which was critical in the function of ARC in IBD. ARC played a critical role in IBD and IBD-associated colon cancer in a bone marrow transplantation model and azoxymethane/DSS-induced colitis cancer mouse models. Overall, these findings reveal that ARC is critically involved in the maintenance of intestinal homeostasis and protection against IBD through its ubiquitination of TRAF6 and subsequent modulation of NF-κB activation in T cells. Significance: This study uncovers a crucial role of ARC in the immune system and IBD, giving rise to a novel strategy for IBD and IBD-associated colon cancer therapy.

Abstract The c-jun-NH2-kinases (JNK) play a critical role in tumor promoter–induced cell transformation and apoptosis. Here, we showed that the nuclear factor of activated T3 (NFAT3) is phosphorylated by JNK1 or JNK2 at Ser213 and Ser217, which are located in the conserved SP motif. The transactivation domain of NFAT3 is found between amino acids (aa) 113 and 260 and includes the phosphorylation targets of JNK1 and JNK2. NFAT3 transactivation activity was suppressed in JNK1−/− or JNK2−/− mouse embryonic fibroblast (MEF) cells compared with wild-type MEF cells. Moreover, a 3xNFAT-luc reporter gene assay indicated that NFAT3 transcriptional activity was increased in a dose-dependent manner by JNK1 or JNK2. Double mutations at Ser213 and Ser217 suppressed NFAT3 transactivation activity; and SP600125, a JNK inhibitor, suppressed NFAT3-induced 3xNFAT-luciferase activity. Knockdown of JNK1 or JNK2 suppressed foci formation in NIH3T3 cells. Importantly, ectopic expression of NFAT3 inhibited AP-1 activity and suppressed foci formation. Furthermore, knockdown of NFAT3 enhanced Ras-JNK1 or JNK2-induced foci formation in NIH3T3 cells. Taken together, these results provided direct evidence for the anti-oncogenic potential of the NFAT3 transcription factor. [Cancer Res 2007;67(18):8725–35]