Leukemia inhibitory factor (LIF) modulates the development of dendritic cells in a dual manner

Leukemia inhibitory factor, a double-edged sword with therapeutic implications in human diseases

Leukemia inhibitory factor (LIF) is a pleiotropic cytokine of the interleukin-6 (IL-6) superfamily. LIF was initially discovered as a factor to induce the differentiation of myeloid leukemia cells and thus inhibit their proliferation. Subsequent studies have highlighted the multi-functions of LIF under a wide variety of physiological and pathological conditions in a highly cell-, tissue-, and context-dependent manner. Emerging evidence has demonstrated that LIF plays an essential role in the stem cell niche, where it maintains the homeostasis and regeneration of multiple somatic tissues, including intestine, neuron, and muscle. Further, LIF exerts a crucial regulatory role in immunity and functions as a protective factor against many immunopathological diseases, such as infection, inflammatory bowel disease (IBD), and graft-verse-host disease (GVHD). It is worth noting that while LIF displays a tumor-suppressive function in leukemia, recent studies have highlighted the oncogenic role of LIF in many types of solid tumors, further demonstrating the complexities and context-dependent effects of LIF. In this review, we summarize the recent insights into the roles and mechanisms of LIF in stem cell homeostasis and regeneration, immunity, and cancer, and discuss the potential therapeutic options for human diseases by modulating LIF levels and functions.

Flt3L, LIF, and IL-10 combination promotes the selective in vitro development of ESAMlow cDC2B from murine bone marrow

The development of two conventional dendritic cells (DC) subsets (cDC1 and cDC2) and the plasmacytoid DC (pDC) in vivo and in cultures of bone marrow (BM) cells is mediated by the growth factor Flt3L. However, little is known about the factors that direct the development of the individual DC subsets. Here, we describe the selective in vitro generation of murine ESAM^low CD103^- XCR1^- CD172a⁺ CD11b⁺ cDC2 from BM by treatment with a combination of Flt3L, LIF, and IL-10 (collectively named as FL10). FL10 promotes common dendritic cell progenitors (CDP) proliferation in the cultures, similar to Flt3L and CDP sorted and cultured in FL10 generate exclusively cDC2. These cDC2 express the transcription factors Irf4, Klf4, and Notch2, and their growth is reduced using BM from Irf4^-/- mice, but the expression of Batf3 and Tcf4 is low. Functionally they respond to TLR3, TLR4, and TLR9 signals by upregulation of the surface maturation markers MHC II, CD80, CD86, and CD40, while they poorly secrete proinflammatory cytokines. Peptide presentation to TCR transgenic OT-II cells induced proliferation and IFN-γ production that was similar to GM-CSF-generated BM-DC and higher than Flt3L-generated DC. Together, our data support that FL10 culture of BM cells selectively promotes CDP-derived ESAM^low cDC2 (cDC2B) development and survival in vitro.

Leukemia inhibitory factor protects against graft-versus-host disease while preserving graft-versus-leukemia activity

Graft-versus-host disease (GVHD) remains a major complication after allogeneic hematopoietic stem cell transplantation, a widely used therapy for hematologic malignancies and blood disorders. Here, we report an unexpected role of cytokine leukemia inhibitory factor (LIF) in protecting against GVHD development. Administrating recombinant LIF protein (rLIF) protects mice from GVHD-induced tissue damage and lethality without compromising the graft-versus-leukemia activity, which is crucial to prevent tumor relapse. We found that rLIF decreases the infiltration and activation of donor immune cells and protects intestinal stem cells to ameliorate GVHD. Mechanistically, rLIF downregulates IL-12-p40 expression in recipient dendritic cells after irradiation through activating STAT1 signaling, which results in decreased major histocompatibility complex II levels on intestinal epithelial cells and decreased donor T-cell activation and infiltration. This study reveals a previously unidentified protective role of LIF for GVHD-induced tissue pathology and provides a potential effective therapeutic strategy to limit tissue pathology without compromising antileukemic efficacy.

Mesenchymal stem cells and their microenvironment

Mesenchymal stem cells (MSCs), coming from a wide range of sources, have multi-directional differentiation ability. MSCs play vital roles in immunomodulation, hematopoiesis and tissue repair. The microenvironment of cells often refers to the intercellular matrix, other cells, cytokines and humoral components. It is also the place for cells’ interaction. The stability of the microenvironment is pivotal for maintaining cell proliferation, differentiation, metabolism and functional activities. Abnormal changes in microenvironment components can interfere cell functions. In some diseases, MSCs can interact with the microenvironment and accelerate disease progression. This review will discuss the characteristics of MSCs and their microenvironment, as well as the interaction between MSCs and microenvironment in disease.

Plasma proteomics identifies leukemia inhibitory factor (LIF) as a novel predictive biomarker of immune-checkpoint blockade resistance

BACKGROUND

Immune checkpoint blockers (ICBs) are now widely used in oncology. Most patients, however, do not derive benefit from these agents. Therefore, there is a crucial need to identify novel and reliable biomarkers of resistance to such treatments in order to prescribe potentially toxic and costly treatments only to patients with expected therapeutic benefits. In the wake of genomics, the study of proteins is now emerging as the new frontier for understanding real-time human biology.

PATIENTS AND METHODS

We analyzed the proteome of plasma samples, collected before treatment onset, from two independent prospective cohorts of cancer patients treated with ICB (discovery cohort n = 95, validation cohort n = 292). We then investigated the correlation between protein plasma levels, clinical benefit rate, progression-free survival and overall survival by Cox proportional hazards models.

RESULTS

By using an unbiased proteomics approach, we show that, in both discovery and validation cohorts, elevated baseline serum level of leukemia inhibitory factor (LIF) is associated with a poor clinical outcome in cancer patients treated with ICB, independently of other prognostic factors. We also demonstrated that the circulating level of LIF is inversely correlated with the presence of tertiary lymphoid structures in the tumor microenvironment.

CONCLUSION

This novel clinical dataset brings strong evidence for the role of LIF as a potential suppressor of antitumor immunity and suggests that targeting LIF or its pathway may represent a promising approach to improve efficacy of cancer immunotherapy in combination with ICB.

The emerging role of leukemia inhibitory factor in cancer and therapy

Leukemia inhibitory factor (LIF) is a multi-functional cytokine of the interleukin-6 (IL-6) superfamily. Initially identified as a factor that inhibits the proliferation of murine myeloid leukemia cells, LIF displays a wide variety of important functions in a cell-, tissue- and context-dependent manner in many physiological and pathological processes, including regulating cell proliferation, pluripotent stem cell self-renewal, tissue/organ development and regeneration, neurogenesis and neural regeneration, maternal reproduction, inflammation, infection, immune response, and metabolism. Emerging evidence has shown that LIF plays an important but complex role in human cancers; while LIF displays a tumor suppressive function in some types of cancers, including leukemia, LIF is overexpressed and exerts an oncogenic function in many more types of cancers. Further, targeting LIF has been actively investigated as a novel strategy for cancer therapy. This review summarizes the recent advances in the studies on LIF in human cancers and its potential application in cancer therapy. A better understanding of the role of LIF in different types of cancers and its underlying mechanisms will help to develop more effective strategies for cancer therapy.

Adipose Tissue-Derived Stromal Cells Induce a Highly Trophic Environment While Reducing Maturation of Monocyte-Derived Dendritic Cells

Allogeneic cell-based therapies using adipose tissue-derived stromal cells (ASCs) offer an off-the-shelf alternative to autologous therapy. An underlying assumption is that ASC can modulate the immune response of the recipient. However, in vitro models are required to explore and identify cell interactions and mechanisms of action, to ensure sufficient and sustained effects, and to document these. In this study, we shed light on the effect of ASC manufactured for clinical use on monocyte-derived dendritic cells and an inflammatory microenvironment. ASCs were isolated from healthy voluntary donors, expanded using a human platelet lysate in bioreactors, and cryopreserved as per clinical use. Monocyte-derived dendritic cells were generated by isolation of monocytes and differentiation with GM-CSF and IL-4. Dendritic cells were cocultured with different ratios of ASC and matured with LPS and IFN-γ. Dexamethasone was included as an immunosuppressive control. Dendritic cells were analyzed by flow cytometry for CD11c, CD40, CD80, CD83, CD86, PD-L1, and HLA-DR, and supernatants were analyzed for FGF2, HGF, IL-10, IL-12p70, LIF, MIF, PDGF, PlGF, and IDO. Reduced expression of maturation markers was observed on ASC-treated dendritic cells, while high levels of PD-L1 were maintained. Interestingly, the expression of CD83 was elevated. Escalating ratios of ASC did not affect the concentration of IL-10 considerably, whereas the presence of IL-12 was reduced in a dose-dependent manner. Besides offsetting the IL-12/IL-10 balance, the concentrations of IDO and MIF were elevated in cocultures. Concentrations of FGF2, HGF, LIF, and PIGF were high in ASC cocultures, whereas PDGF was depleted. In a robust coculture model, the addition of ASC to dendritic cells inhibited the dendritic maturation substantially, while inducing a less inflammatory and more tolerogenic milieu. Despite the exposure to dendritic cells and inflammatory stimuli, ASC resulted in supernatants with trophic factors relevant for regeneration. Thus, ASC can perform immunomodulation while providing a regenerative environment.

Macrophage subtype and cytokine expression characterization during the acute inflammatory phase of mouse bone fracture repair

Fracture repair is a complex process requiring heterotypic interactions between osteogenic cells and immune cells. Recent evidence indicates that macrophages are critically involved in fracture repair. Polarized macrophage populations differentially promote and regulate inflammation in other tissues, but little is known about the various macrophage subtypes and their signaling activities following a bone fracture. The authors hypothesized that classically activated (M1 subtype) and alternatively activated (M2 subtype) macrophages are active during the early repair process to initiate and regulate the inflammatory response. To test our hypothesis, bone marrow was collected from intact femurs (naïve group), contralateral and fractured femurs of mice on days 0, 1, 2, 4, and 7 postfracture. Macrophages were isolated from the bone marrow and macrophage subtypes were identified using flow cytometry with antibodies to F4/80, MHC II, CD86, CD11c, and CD40. Bone marrow cytokine levels were measured using xMAP. Flow cytometry revealed dynamic changes in M1 subtype (F4/80+/MHC II+/CD86+), M2 subtype (F4/80+/MHC II-/CD86-), and dendritic cell (DCs; MHCII+/CD11c+/CD40+) populations following fracture as compared to naïve controls. M1 subtype levels were correlated with IL-1α, IL-1ß, IL-2, IL-17, Eotaxin, and MCP-1, while DCs were correlated with IL-6, G-CSF, LIF, KC, and VEGF-A. The results indicate that M1 and M2 subtypes and DCs are recruited to the fracture site early during the repair process and consequently may work in tandem to regulate the inflammatory response required to recruit osteogenic cells needed for later stages of repair.

Myokines: a descriptive review

In the last years, scientists have shown that skeletal muscle is not a pure locomotor unit or responsible for propulsion and posture. Skeletal muscle encompasses one of the major organs of the body (constituting about 40% of the body mass in non-obese men). It regulates energy and metabolic processes and is now recognized as an organ capable of producing molecules with vital functions. These molecules are termed myokines, a new field of research in the health sciences, and represent an open field of discoveries and applications in several areas. The aim of this review was to show the role of some well-known myokines in the maintenance of homeostasis. Our search was performed in databases such as Medline/Pubmed, Embase and Scielo. Some relevant myokines are interleukin-6 (IL-6), IL-8, IL-15, irisin, myostatin, fibroblast growth factor 21 (FGF21), leukemia inhibitory factor (LIF), brain-derived neurotrophic factor (BDNF), and insulin-like growth factor-1 (IGF-1). They are related to play a positive or negative role in muscle function and metabolism homeostasis. They are associated with the regulation of glucose and lipid metabolism, the deposition of fat in the adipose tissue, and the "browning" of the white adipose tissue. For these reasons, they can interfere with the prevention of obesity, diabetes, metabolic syndrome, and cardiovascular diseases. The discovery of the myokines has opened a new direction in understanding the effects of exercises on humans.