LncRNA Snhg6 regulates the differentiation of MDSCs by regulating the ubiquitination of EZH2

Myeloid-derived suppressor cells (MDSCs) are derived from bone marrow progenitor cells commonly, which is a heterogeneous cell group composed of immature granulocytes, dendritic cells, macrophages and early undifferentiated bone marrow precursor cells. Its differentiation and immunosuppressive function are regulated by complex network signals, but the specific regulation mechanisms are not yet fully understood. In this study, we found that in mouse of Lewis lung cancer xenograft, long non-coding RNA Snhg6 (lncRNA Snhg6) was highly expressed in tumor-derived MDSCs compared with spleen-derived MDSCs. LncRNA Snhg6 facilitated the differentiation of CD11b+ Ly6G− Ly6Chigh monocytic MDSCs (Mo-MDSCs) rather than CD11b+ Ly6G+ Ly6Clow polymorphonuclear MDSCs (PMN-MDSCs), but did not affect the immunosuppressive function of MDSCs. Notably, lncRNA Snhg6 could inhibit the expression of EZH2 by ubiquitination pathway at protein level rather than mRNA level during the differentiation of mouse bone marrow cells into MDSCs in vitro. EZH2 may be an important factor in the regulation of lncRNA Snhg6 to promote the differentiation of Mo-MDSCs. So what we found may provide new ideas and targets for anti-tumor immunotherapy targeting MDSCs.

Tumor-Released Products Promote Bone Marrow-Derived Macrophage Survival and Proliferation

Macrophages play a central role within the tumor microenvironment, with relevant implications for tumor progression. The modulation of their phenotype is one of the mechanisms used by tumors to escape from effective immune responses. This study was designed to analyze the influence of soluble products released by tumors, here represented by the tumor-conditioned media of two tumor cell lines (3LL from Lewis lung carcinoma and MN/MCA from fibrosarcoma), on murine macrophage differentiation and polarization in vitro. Data revealed that tumor-conditioned media stimulated macrophage differentiation but influenced the expression levels of macrophage polarization markers, cytokine production, and microRNAs of relevance for macrophage biology. Interestingly, tumor-derived soluble products supported the survival and proliferation rate of bone marrow precursor cells, an effect observed even with mature macrophages in the presence of M2 but not M1 inducers. Despite presenting low concentrations of macrophage colony-stimulating factor (M-CSF), tumor-conditioned media alone also supported the proliferation of cells to a similar extent as exogenous M-CSF. This effect was only evident in cells positive for the expression of the M-CSF receptor (CD115) and occurred preferentially within the CD16+ subset. Blocking CD115 partially reversed the effect on proliferation. These results suggest that tumors release soluble products that not only promote macrophage development from bone marrow precursors but also stimulate the proliferation of cells with specific phenotypes that could support protumoral functions.

Akt+ IKKα/β+ Rab5+ Signalosome Mediate the Endosomal Recruitment of Sec61 and Contribute to Cross-Presentation in Bone Marrow Precursor Cells

Cross-presentation in dendritic cells (DC) requires the endosomal relocations of internalized antigens and the endoplasmic reticulum protein Sec61. Despite the fact that endotoxin-containing pathogen and endotoxin-free antigen have different effects on protein kinase B (Akt) and I-kappa B Kinase α/β (IKKα/β) activation, the exact roles of Akt phosphorylation, IKKα or IKKβ activation in endotoxin-containing pathogen-derived cross-presentation are poorly understood. In this study, endotoxin-free ovalbumin supplemented with endotoxin was used as a model pathogen. We investigated the effects of endotoxin-containing pathogen and endotoxin-free antigen on Akt phosphorylation, IKKα/β activation, and explored the mechanisms that the endotoxin-containing pathogen orchestrating the endosomal recruitment of Sec61 of the cross-presentation in bone marrow precursor cells (BMPC). We demonstrated that endotoxin-containing pathogen and endotoxin-free antigen efficiently induced the phosphorylation of Akt-IKKα/β and Akt-IKKα, respectively. Endotoxin-containing pathogen derived Akt+ IKKα/β+ Rab5+ signalosome, together with augmented the recruitment of Sec61 toward endosome, lead to the increased cross-presentation in BMPC. Importantly, the endosomal recruitment of Sec61 was partly mediated by the formation of Akt+ IKKα/β+ signalosome. Thus, these data suggest that Akt+ IKKα/β+ Rab5+ signalosome contribute to endotoxin-containing pathogen-induced the endosomal recruitment of Sec61 and the superior efficacy of cross-presentation in BMPC.

Monocyte as an Emerging Tool for Targeted Drug Delivery: A Review

Monocytes are leading component of the mononuclear phagocytic system that play a key role in phagocytosis and removal of several kinds of microbes from the body. Monocytes are bone marrow precursor cells that stay in the blood for a few days and migrate towards tissues where they differentiate into macrophages. Monocytes can be used as a carrier for delivery of active agents into tissues, where other carriers have no significant access. Targeting monocytes is possible both through passive and active targeting, the former one is simply achieved by enhanced permeation and retention effect while the later one by attachment of ligands on the surface of the lipid-based particulate system. Monocytes have many receptors e.g., mannose, scavenger, integrins, cluster of differentiation 14 (CD14) and cluster of differentiation 36 (CD36). The ligands used against these receptors are peptides, lectins, antibodies, glycolipids, and glycoproteins. This review encloses extensive introduction of monocytes as a suitable carrier system for drug delivery, the design of lipid-based carrier system, possible ways for delivery of therapeutics to monocytes, and the role of monocytes in the treatment of life compromising diseases such as cancer, inflammation, stroke, etc.

Pivotal Roles of GM-CSF in Autoimmunity and Inflammation

Granulocyte macrophage-colony stimulating factor (GM-CSF) is a hematopoietic growth factor, which stimulates the proliferation of granulocytes and macrophages from bone marrow precursor cells. In autoimmune and inflammatory diseases, Th17 cells have been considered as strong inducers of tissue inflammation. However, recent evidence indicates that GM-CSF has prominent proinflammatory functions and that this growth factor (not IL-17) is critical for the pathogenicity of CD4+T cells. Therefore, the mechanism of GM-CSF-producing CD4+T cell differentiation and the role of GM-CSF in the development of autoimmune and inflammatory diseases are gaining increasing attention. This review summarizes the latest knowledge of GM-CSF and its relationship with autoimmune and inflammatory diseases. The potential therapies targeting GM-CSF as well as their possible side effects have also been addressed in this review.

Administration of rhIL-7 Is Associated with Increase in Precursor T-Cells in Bone Marrows of Patients with Idiopathic CD4 Lymphocytopenia

Introduction Idiopathic CD4+ Lymphocytopenia (ICL) is a rare, likely heterogeneous syndrome characterized by persistent CD4+ lymphopenia (<300/μl) in the absence of HIV infection or other known immunodeficiency. The diverse clinical presentation may include opportunistic infections, malignancies, and autoimmune diseases. Though the etiology of ICL remains unknown, previous studies have suggested decreased production, proliferation, or survival of CD4+ T-cells. There is currently no FDA-approved therapy for ICL. Methods We analyzed bone marrow core biopsies of 12 ICL patients in a phase I/IIA NIH clinical trial designed to evaluate recombinant human Interleukin-7 (rhIL-7) as a potential therapy for ICL . Subjects received 3 injections of rhIL-7 over two 24-week periods. Bone marrow biopsies were performed at week 1 and week 24 to analyze numbers of T-cells and T-cell precursors at baseline and post rhIL-7 therapy. Peripheral blood T-cell counts were assessed in parallel. Double chromogenic immunohistochemical staining using anti-terminal deoxynucleotidyl transferase (TdT) and anti-CD3 antibodies was performed on fixed, paraffin-embedded samples using an automated stainer (Ventana). Single CD3-positive T-cells and double-positive TdT/CD3 precursor T-cells were counted in at least ten consecutive fields under a light microscope and results expressed as mean positive cell number per field before and after treatment with rhIL-7. Similar staining procedure using TdT and CD79a was performed to evaluate precursor B-cells in the same patient cohort. In addition, bone marrow biopsies from 10 healthy control subjects were analyzed in parallel. Results Compared to healthy controls, ICL patients showed no significant differences in the number of bone marrow precursor T-cells (p=0.069) but had lower levels of mature T-cells (p<0.0001) in marrow core biopsies. These data correlated with presence of peripheral blood T-lymphopenias. ICL patients had higher levels of precursor B-cells that were double positive for TdT/CD79a (p=0.016) compared to control marrows, but showed no significant differences in the number of mature B-cells (p=0.059). After treatment with rhIL-7, bone marrow precursor T-cells increased significantly between weeks 1-24 (p=0.016). Mature T-cells also increased significantly (p=0.031). Precursor B-cells and mature B-cells did not change significantly (p=0.313 and 0.375, respectively). During the same time, peripheral blood CD3+ T-cell counts and CD4+ T-cell counts also increased. Conclusion Novel histological technique for double chromogenic staining allows for the visualization of T-cell precursors in bone marrow biopsies. Our study revealed no evidence that lymphopenia in ICL patients is associated with lack of T-cell precursors in bone marrow, suggesting downstream defects in T-cell differentiation, proliferation or survival. Administration of rhIL-7 was associated with an increase in peripheral blood T-cells and increase in bone marrow precursor T-cells, while B-cell lineage cells remained unchanged. Disclosures No relevant conflicts of interest to declare.

The basic leucine zipper transcription factor NFIL3 directs the development of a common innate lymphoid cell precursor

Innate lymphoid cells (ILCs) are recently identified lymphocytes that limit infection and promote tissue repair at mucosal surfaces. However, the pathways underlying ILC development remain unclear. Here we show that the transcription factor NFIL3 directs the development of a committed bone marrow precursor that differentiates into all known ILC lineages. NFIL3 was required in the common lymphoid progenitor (CLP), and was essential for the differentiation of αLP, a bone marrow cell population that gives rise to all known ILC lineages. Clonal differentiation studies revealed that CXCR6+ cells within the αLP population differentiate into all ILC lineages but not T- and B-cells. We further show that NFIL3 governs ILC development by directly regulating expression of the transcription factor TOX. These findings establish that NFIL3 directs the differentiation of a committed ILC precursor that gives rise to all ILC lineages and provide insight into the defining role of NFIL3 in ILC development.