The ITIM-containing receptor LAIR1 is essential for acute myeloid leukaemia development

LILRB1 enhances the progression of diffuse large B-cell lymphoma through the CREB-SORBS3 pathway

PURPOSE

Although 60-70% of diffuse large B-cell lymphoma (DLBCL) patients can be cured with the current standard of chemotherapy and immunotherapy, the remaining patients experience treatment resistance and have poor clinical outcomes. More effective strategies are needed for the DLBCL treatment.

METHODS

Databases of clinical patients were analyzed to investigate potential functions of leukocyte immunoglobulin-like receptor B1 (LILRB1) in DLBCL. Short hairpin RNAs were used for validation of in vitro and in vivo function of LILRB1 in DLBCL. RNA-seq was applied to explore potential mechanism, western blot and chromatin immunoprecipitation techniques were used to characterize the underlying signaling of CREB-SORBS3 pathway.

RESULTS

We found that LILRB1 was highly expressed in DLBCL cells and was adversely correlated with the overall survival of DLBCL patients. Knockdown of LILRB1 effectively inhibited the proliferation of DLBCL cells both in vitro and in vivo. Mechanistically, LILRB1 upregulated CREB/CREB phosphorylation and transactivated SORBS3 expression to maintain DLBCL cell proliferation and tumorigenicity.

CONCLUSION

In this work, we revealed that LILRB1 was highly expressed in DLBCL cells and was negatively correlated with patient survival. Furthermore, we found that the LILRB1-CREB-SORBS3 pathway played a role in maintaining the proliferation of DLBCL cells. These data suggest that LILRB1 might be a potential target for the treatment of DLBCL.

Immune checkpoints regulate acute myeloid leukemia stem cells

Acute myeloid leukemia stem cells (LSCs) express major histocompatibility complex (MHC) class I and II and many different immune checkpoint ligands and receptors, in which respect they resemble professional antigen-presenting cells. In addition, LSCs reside in the bone marrow (BM), a primary and secondary lymphoid organ, surrounded by immune cells. The function of these immune checkpoints (ICs) in the regulation of an anti-tumor immune response is well studied and IC inhibitors (ICIs) became a standard of care in many solid tumors. However, ICIs have very limited efficacy in AML. Nevertheless, the expression especially of immune activating ligands and receptors on LSCs is somewhat unexpected, since these cells have to evade protective immunity. Many ICs have been shown to mediate direct signaling in AML blasts and LSCs and thereby regulate self-renewal, differentiation and expansion of leukemic cells. Thus, the expression of ICs on the cell surface or their soluble forms often correlate with worse survival. In this review we summarize recent data on selected ICs of the immunoglobulin superfamily (IgSF) and the tumor necrosis factor receptor superfamily (TNFRSF) that have a documented role in the regulation of LSCs, independent of their immune regulatory role, and might become novel therapeutic targets.

Development of an anti-LAIR1 antibody-drug conjugate for acute myeloid leukemia therapy

Acute myeloid leukemia (AML) is a severe blood cancer with an urgent need for novel therapies for refractory or relapsed patients. Leukocyte-associated immunoglobulin-like receptor 1 (LAIR1), an immune suppressive receptor expressed on immune cells and AML blasts but minimally on hematopoietic stem cells (HSCs), represents a potential therapeutic target. But there has been limited research on therapies targeting LAIR1 for AML and no published reports on LAIR1 antibody-drug conjugate (ADC). We developed LA-057-MMAE, a first-in-class ADC, and evaluated its antitumor potential. LA-057-MMAE demonstrated strong binding to human LAIR1 with an affinity of 3.9 nM, efficient internalization of approximately 70 % within 4 h, and remarkable cytotoxicity against AML cells, with IC50 values of 0.22 nM for MV-4-11, 0.02 nM for U937, and 0.09 nM for HL-60 cells, respectively. In vivo, it achieved complete tumor regression in 100 % of MV-4-11 xenograft mice at 6 mg/kg, extending survival beyond 60 days. Our findings suggest that LA-057-MMAE, as a first-in-class treatment distinct from existing LAIR1 monoclonal therapies, could provide a groundbreaking therapeutic strategy for AML.

Collagen remodeling-mediated signaling pathways and their impact on tumor therapy

In addition to their traditional roles in maintaining tissue morphology and organ development, emerging evidence suggests that collagen (COL) remodeling-referring to dynamic changes in the quantity, stiffness, arrangements, cleavage states, and homo-/hetero-trimerization of COLs-serves as a key signaling mechanism that governs tumor growth and metastasis. COL receptors act as switches, linking various forms of COL remodeling to different cell types during cancer progression, including cancer cells, immune cells, and cancer-associated fibroblasts. In this review, we summarize recent findings on the signaling pathways mediated by COL arrangement, cleavage, and trimerization states (both homo- and hetero-), as well as the roles of the primary COL receptors-integrin, DDR1/2, LAIR-1/2, MRC2, and GPVI-in cancer progression. We also discuss the latest therapeutic strategies targeting COL fragments, cancer-associated fibroblasts, and COL receptors, including integrins, DDR1/2, and LAIR1/2. Understanding the pathways modulated by COL remodeling and COL receptors in various pathological contexts will pave the way for developing new precision therapies.

Polymorphisms in immunosuppression-related genes are associated with AML

Background

Acute myeloid leukemia (AML) is a hematologic malignancy with poor overall survival (OS). The immunosuppressive microenvironment significantly impacts AML development and chemoresistance. Despite new immunotherapeutic strategies entering standard clinical care for various tumors, progress in AML remains poor. Multi-omics analyses, such as single-cell transcriptomics, have revealed many potential new targets to improve AML prognosis from an immunological perspective.

Methods

DNA from 307 AML patients and 316 healthy individuals were extracted. We detected nine single nucleotide polymorphisms (SNPs) in five immunosuppression-related genes (CIITA, CD200, CD163, MRC1 and LILRB4) in these samples. SNP genotyping was performed on the MassARRAY platform. We then analyzed the relationship between these SNPs and AML susceptibility, treatment response, and prognosis.

Results

Our findings indicated that rs4883263 in the CD163 gene is a protective factor for AML susceptibility and chromosomal karyotype abnormalities. Additionally, rs4883263 in CD163 was related to low PLT count at diagnosis, while rs2272022 in CD200 was protective against low PLT count. rs4780335 in CIITA was associated with high WBC count at diagnosis and worse OS. Furthermore, rs1048801 in LILRB4 was linked to worse AML treatment response, lower OS, and may be an independent prognostic risk factor for AML. Lastly, expressions of CD163, CIITA, LILRB4, and CD200 were higher in AML patients than that in normal controls.

Conclusions

Our findings on SNP associations in AML immunosuppression-related genes provide important reference points for predicting treatment outcomes in AML patients.

A Switch Protein Adapter for Anti-LILRB4 CAR-T Cells

Chimeric antigen receptor-T cell (CAR-T) immunotherapy has shown remarkable results for the treatment of certain hematologic malignancies. A redirection strategy that utilizes clinically relevant CAR-T cells in combination with adapter proteins may be an effective strategy to target other hematologic and solid cancers. We established a fusion antibody-based strategy with flexibility to target multiple tumor types in combination with a novel anti-leukocyte immunoglobulin-like receptor-B 4 (LILRB4) CAR-T cell. Specifically, we engineered switch protein (SwP) adapters containing the LILRB4 extracellular domain fused to either an anti-CD19 or anti-CD20 single-chain variable fragment (scFv). These SwPs were sufficient to stimulate anti-LILRB4 CAR-T cells against SwP-tagged LILRB4-CD19+ and LILRB4-CD20+ cancers in vitro and in vivo. This strategy may allow CAR-T cells to be redirected against a variety of tumor antigens and cancer types and become a valuable approach to expand the impact of cellular immunotherapy.

Is modulation of immune checkpoints on glioblastoma-infiltrating myeloid cells a viable therapeutic strategy?

The field of immunology has traditionally focused on immune checkpoint modulation of adaptive immune cells. However, many malignancies such as glioblastoma are mostly devoid of T cells and rather are enriched with immunosuppressive myeloid cells of the innate immune system. While some immune checkpoint targets are shared between adaptive and innate immunity, myeloid-specific checkpoints could also serve as potential therapeutics. To better understand the impact of immune checkpoint blockade on myeloid cells, we systematically summarize the current literature focusing on the direct immunological effects of PD-L1/PD-1, CD24/Siglec-10, collagen/LAIR-1, CX3CL1/CX3CR1, and CXCL10/CXCR3. By synthesizing the molecular mechanisms and the translational implications, we aim to prioritize agents in this category of therapeutics for glioblastoma.

The LILRB family in hematologic malignancies: prognostic associations, mechanistic considerations, and therapeutic implications

The leukocyte immunoglobulin-like receptor B (LILRB) proteins, characterized by their transmembrane nature and canonical immunoreceptor tyrosine-based inhibitory motifs (ITIM) signaling, play a pivotal role in maintaining immune homeostasis and are implicated in the pathogenesis of various disease states. This comprehensive review will focus on the intricate involvement of the LILRB family in hematologic malignancies. These receptors have emerged as valuable diagnostic and prognostic biomarkers in leukemia, lymphoma, and myeloma. Beyond their prognostic implications, LILRBs actively shape the immune microenvironment and directly influence the disease pathogenesis of hematologic malignancies. Furthermore, their identification as potential therapeutic targets offer a promising avenue for precision medicine strategies in the treatment of these disorders. Currently, multiple LILRB directed therapies are in the preclinical and clinical trial pipelines. This review underscores the multifaceted role of the LILRB family in hematologic malignancies, highlighting their significance from diagnostic and prognostic perspectives to their broader impact on disease pathophysiology and as valuable therapeutic targets.

Targeting SHP1 and SHP2 to suppress tumors and enhance immunosurveillance

The nonreceptor tyrosine phosphatases (PTPS) SHP1 and SHP2 have crucial roles in dephosphorylating an array of substrates involved in pathways comprising receptor tyrosine kinases (RTKs) and immune receptors. This regulation maintains a delicate balance between the activation and inhibition of signal transduction, ensuring appropriate biological outcomes. In this review, we summarize research focused on elucidating the functions of SHP1 and SHP2 in hematopoiesis, immune regulation, and tumor biology, emphasizing recent findings related to cancer-driven immune evasion. Furthermore, we highlight the significant effects of SHP1 and SHP2 inhibitors in enhancing cancer treatment, specifically through the facilitation of chemotherapy and augmentation of immune activation.

Leukocyte immunoglobulin-like receptor B4 (LILRB4) in acute myeloid leukemia: From prognostic biomarker to immunotherapeutic target

ABSTRACT

Leukocyte immunoglobulin-like receptor (LILR) B4 (also known as ILT3/CD85k) is an immune checkpoint protein that is highly expressed in solid tumors and hematological malignancies and plays a significant role in the pathophysiology of cancer. LILRB4 is highly expressed in acute myeloid leukemia (AML), and this phenotype is associated with adverse patient outcomes. Its differential expression in tumors compared to normal tissues, its presence in tumor stem cells, and its multifaceted roles in tumorigenesis position it as a promising therapeutic target in AML. Currently, several immunotherapies targeting LILRB4 are undergoing clinical trials. This review summarizes advancements made in the study of LILRB4 in AML, focusing on its structure, ligands, expression, and significance in normal tissues and AML; its protumorigenic effects and mechanisms in AML; and the application of LILRB4-targeted therapies in AML. These insights highlight the potential advantages of LILRB4 as an immunotherapeutic target in the context of AML.

Leukemic B cells expression of CD200 and Leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1, CD305) in Chronic Lymphocytic Leukemia patients in relation to Treg frequency

BACKGROUND

Chronic lymphocytic leukemia (CLL) is characterized by a wide range of tumor-induced immune alterations. Regulatory T cells (Treg) play a central role in these immune responses. CD200 and Leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1, CD305) are inhibitory markers said to be involved in Treg immune response. We aimed to analyze the expression of CD200 and LAIR-1 on leukemic cells and assess their interactions with the Treg frequency to elucidate their role in the CLL course.

SUBJECTS AND METHODS

This study was conducted on 70 participants: 50 newly diagnosed CLL cases classified according to Rai staging system into group 1 (n = 25) patients with stages 0, I, and II, and group 2 (n = 25) of advanced patients with stages III and IV. In addition to control group (n = 20) of healthy adults. Flow cytometry was used to investigate Treg frequency in bone marrow (BM) proportional to CD4+ T cell and to assess leukemic cell expression of CD200 and LAIR-1. Also, in-silico database analysis was performed to identify study markers interactions for future personalized target therapy.

RESULTS

Comparison between CLL groups 1 and 2 revealed increased leukemic cell percentage expressing LAIR-1 (p = 0.021) in group 1. Group 2 showed significant increase in frequency of Treg in BM and leukemic cells expressing CD200. There was a strong positive correlation between frequency of Treg and leukemic cells expressing CD200 (r = 0.669, p = 0.000). On the other hand, there was a negative correlation between frequency of Treg and leukemic cell expressing LAIR-1 (r = -0.342, p = 0.015). ROC curve analysis revealed that increased frequency of leukemic cells expressing CD200 yielded sensitivity (SN) and specificity (SP) of 96 % and 84 %, respectively in detecting CLL progression, with an AUC of 0.965. Leukemic cell percentages expressing LAIR-1 yielded a lower SN (75 %), SP (72 %), with an AUC of 0.688.

CONCLUSION

Treg frequency in BM was significantly increased in CLL advanced stages according to Rai classification. Leukemic cells CD200 and LAIR-1 expression were differently associated with Treg frequency. Increased CD200 expressions on leukemic cells can be considered a sensitive and specific biomarker in detecting CLL progression. As demonstrated by the in-silico research, CD200 blockade targeting may offer therapeutic benefits for CLL treatment through Treg suppression.

Bone-marrow-homing lipid nanoparticles for genome editing in diseased and malignant haematopoietic stem cells

Therapeutic genome editing of haematopoietic stem cells (HSCs) would provide long-lasting treatments for multiple diseases. However, the in vivo delivery of genetic medicines to HSCs remains challenging, especially in diseased and malignant settings. Here we report on a series of bone-marrow-homing lipid nanoparticles that deliver mRNA to a broad group of at least 14 unique cell types in the bone marrow, including healthy and diseased HSCs, leukaemic stem cells, B cells, T cells, macrophages and leukaemia cells. CRISPR/Cas and base editing is achieved in a mouse model expressing human sickle cell disease phenotypes for potential foetal haemoglobin reactivation and conversion from sickle to non-sickle alleles. Bone-marrow-homing lipid nanoparticles were also able to achieve Cre-recombinase-mediated genetic deletion in bone-marrow-engrafted leukaemic stem cells and leukaemia cells. We show evidence that diverse cell types in the bone marrow niche can be edited using bone-marrow-homing lipid nanoparticles.

Inhibiting AGTR1 reduces AML burden and protects the heart from cardiotoxicity in mouse models

Clinical treatment of acute myeloid leukemia (AML) largely relies on intensive chemotherapy. However, the application of chemotherapy is often hindered by cardiotoxicity. Patient sequence data revealed that angiotensin II receptor type 1 (AGTR1) is a shared target between AML and cardiovascular disease (CVD). We found that inhibiting AGTR1 sensitized AML to chemotherapy and protected the heart against chemotherapy-induced cardiotoxicity in a human AML cell-transplanted mouse model. These effects were regulated by the AGTR1-Notch1 axis in AML cells and cardiomyocytes from mice. In mouse cardiomyocytes, AGTR1 was hyperactivated by AML and chemotherapy. AML leukemogenesis increased the expression of the angiotensin-converting enzyme and led to increased production of angiotensin II, the ligand of AGTR1, in an MLL-AF9-driven AML mouse model. In this model, the AGTR1-Notch1 axis regulated a variety of genes involved with cell stemness and chemotherapy resistance. AML cell stemness was reduced after Agtr1a deletion in the mouse AML cell transplant model. Mechanistically, Agtr1a deletion decreased γ-secretase formation, which is required for transmembrane Notch1 cleavage and release of the Notch1 intracellular domain into the nucleus. Using multiomics, we identified AGTR1-Notch1 signaling downstream genes and found decreased binding between these gene sequences with Notch1 and chromatin enhancers, as well as increased binding with silencers. These findings describe an AML/CVD association that may be used to improve AML treatment.

LAIR1 prevents excess inflammatory tissue damage in S. aureus skin infection and Cutaneous T-cell Lymphoma

Patients with cutaneous T cell lymphoma (CTCL) experience high morbidity and mortality due to S. aureus skin infections and sepsis, but the causative immune defect is unclear. We previously identified high levels of LAIR2, a decoy protein for the inhibitory receptor LAIR1, in advanced CTCL. Mice do not have a LAIR2 homolog, so we used Lair1 knock-out (KO) mice to model LAIR2 overexpression. In a model of subcutaneous S. aureus skin infection, Lair1 KO mice had significantly larger abscesses and areas of dermonecrosis compared to WT. Lair1 KO exhibited a pattern of increased inflammatory responses in infection and sterile immune stimulation, including increased production of proinflammatory cytokines and myeloid chemokines, neutrophil ROS, and collagen/ECM remodeling pathways. Notably, Lair1 KO infected skin had a similar bacterial burden and neutrophils and monocytes had equivalent S. aureus phagocytosis compared to WT. These findings support a model in which lack of LAIR1 signaling causes an excessive inflammatory response that does not improve infection control. CTCL skin lesions harbored similar patterns of increased expression in cytokine and collagen/ECM remodeling pathways, suggesting that high levels of LAIR2 in CTCL recapitulates Lair1 KO, causing inflammatory tissue damage and compromising host defense against S. aureus infection.

Kinome expression profiling improves risk stratification and therapeutic targeting in myelodysplastic syndromes

ABSTRACT

The human kinome, which comprises >500 kinases, plays a critical role in regulating numerous essential cellular functions. Although the dysregulation of kinases has been observed in various human cancers, the characterization and clinical implications of kinase expressions in myelodysplastic syndromes (MDS) have not been systematically investigated. In this study, we evaluated the kinome expression profiles of 341 adult patients with primary MDS and identified 7 kinases (PTK7, KIT, MAST4, NTRK1, PAK6, CAMK1D, and PRKCZ) whose expression levels were highly predictive of compromised patient survival. We then constructed the kinase stratification score (KISS) by combining the weighted expressions of the 7 kinases and validated its prognostic significance in 2 external MDS cohorts. A higher KISS was associated with older age, higher peripheral blood and marrow blast percentages, higher Revised International Prognostic Scoring System (IPSS-R) risks, complex karyotype, and mutations in several adverse-risk genes in MDS, such as ASXL1, EZH2, NPM1, RUNX1, STAG2, and TP53. Multivariate analysis confirmed that a higher KISS was an independent unfavorable risk factor in MDS. Mechanistically, the KISS-high patients were enriched for gene sets associated with hematopoietic and leukemic stem cell signatures. By investigating the Genomics of Drug Sensitivity in Cancer database, we identified axitinib and taselisib as candidate compounds that could potentially target the KISS-high myeloblasts. Altogether, our findings suggest that KISS holds the potential to improve the current prognostic scheme of MDS and inform novel therapeutic opportunities.

A new mechanism of antibody diversity: formation of the natural antibodies containing LAIR1 and LILRB1 extracellular domains

The recent discovery of public antibodies targeting Plasmodium falciparum-encoded repetitive interspersed families of polypeptides (RIFINs), which contain extracellular immunoglobulin-like domains from LAIR1 or LILRB1, constitutes a significant step forward in comprehending the reactivity of the Plasmodium parasite. These antibodies arise from unique B cell clones and demonstrate extensive cross-reactivity through their interaction with P. falciparum RIFINs. LAIR1 and LILRBs are specialized type I transmembrane glycoproteins, classified as immune inhibitory receptors, restricted to primates and mainly found on hematopoietic cells. They are instrumental in modulating interactions within the tumor microenvironment and across the immune system, and are increasingly recognized as important in anti-cancer immunotherapy and pathogen defense. The presence of LAIR1/LILRB1-containing antibodies offers new insights into malaria parasite evasion strategies and the immune system's response. Additionally, the innovative method of integrating extra exons into the antibody switch region is a noteworthy advancement, enriching the strategies for the generation of a varied array of bispecific and multispecific antibodies.

LILRB3 Supports Immunosuppressive Activity of Myeloid Cells and Tumor Development

The existing T cell-centered immune checkpoint blockade therapies have been successful in treating some but not all patients with cancer. Immunosuppressive myeloid cells, including myeloid-derived suppressor cells (MDSC), that inhibit antitumor immunity and support multiple steps of tumor development are recognized as one of the major obstacles in cancer treatment. Leukocyte Ig-like receptor subfamily B3 (LILRB3), an immune inhibitory receptor containing tyrosine-based inhibitory motifs (ITIM), is expressed solely on myeloid cells. However, it is unknown whether LILRB3 is a critical checkpoint receptor in regulating the activity of immunosuppressive myeloid cells, and whether LILRB3 signaling can be blocked to activate the immune system to treat solid tumors. Here, we report that galectin-4 and galectin-7 induce activation of LILRB3 and that LILRB3 is functionally expressed on immunosuppressive myeloid cells. In some samples from patients with solid cancers, blockade of LILRB3 signaling by an antagonistic antibody inhibited the activity of immunosuppressive myeloid cells. Anti-LILRB3 also impeded tumor development in myeloid-specific LILRB3 transgenic mice through a T cell-dependent manner. LILRB3 blockade may prove to be a novel approach for immunotherapy of solid cancers.

DNAJC10 maintains survival and self-renewal of leukemia stem cells through PERK branch of the unfolded protein response

Leukemia stem cells (LSC) require frequent adaptation to maintain their self-renewal ability in the face of longer exposure to cell-intrinsic and cell-extrinsic stresses. However, the mechanisms by which LSC maintain their leukemogenic activities, and how individual LSC respond to stress, remain poorly understood. Here, we found that DNAJC10, a member of HSP40 family, was frequently up-regulated in various types of acute myeloid leukemia (AML) and in LSC-enriched cells. Deficiency of DNAJC10 leads to a dramatic increase in the apoptosis of both human leukemia cell lines and LSC-enriched populations. Although DNAJC10 is not required for normal hematopoiesis, deficiency of Dnajc10 significantly abrogated AML development and suppressed self-renewal of LSC in the MLL-AF9-induced murine leukemia model. Mechanistically, inhibition of DNAJC10 specifically induces endoplasmic reticulum stress and promotes activation of PERK-EIF2α-ATF4 branch of unfolded protein response (UPR). Blocking PERK by GSK2606414 (PERKi) or shRNA rescued the loss of function of DNAJC10 both in vitro and in vivo. Importantly, deficiency of DNAJC10 increased sensitivity of AML cells to daunorubicin (DNR) and cytarabine (Ara-C). These data revealed that DNAJC10 functions as an oncogene in MLL-AF9-induced AML via regulation of the PERK branch of the UPR. DNAJC10 may be an ideal therapeutic target for eliminating LSC, and improving the effectiveness of DNR and Ara-C.

SHP-1 inhibition targets leukaemia stem cells to restore immunosurveillance and enhance chemosensitivity by metabolic reprogramming

Leukaemia stem cells (LSCs) in acute myeloid leukaemia present a considerable treatment challenge due to their resistance to chemotherapy and immunosurveillance. The connection between these properties in LSCs remains poorly understood. Here we demonstrate that inhibition of tyrosine phosphatase SHP-1 in LSCs increases their glycolysis and oxidative phosphorylation, enhancing their sensitivity to chemotherapy and vulnerability to immunosurveillance. Mechanistically, SHP-1 inhibition leads to the upregulation of phosphofructokinase platelet (PFKP) through the AKT-β-catenin pathway. The increase in PFKP elevates energy metabolic activities and, as a consequence, enhances the sensitivity of LSCs to chemotherapeutic agents. Moreover, the upregulation of PFKP promotes MYC degradation and, consequently, reduces the immune evasion abilities of LSCs. Overall, our study demonstrates that targeting SHP-1 disrupts the metabolic balance in LSCs, thereby increasing their vulnerability to chemotherapy and immunosurveillance. This approach offers a promising strategy to overcome LSC resistance in acute myeloid leukaemia.

LPS and type I and II interferons have opposing effects on epigenetic regulation of LAIR1 expression in mouse and human macrophages

Inhibitory immune receptors are important for maintaining immune homeostasis. We identified epigenetic alterations in 2 members of this group, LAIR1 and LAIR2, in lymphoma patients with inflammatory tissue damage and susceptibility to infection. We predicted that the expression of LAIR genes is controlled by immune mediators acting on transcriptional regulatory elements. Using flow cytometry, quantitative reverse-transcription polymerase chain reaction, and RNA sequencing, we measured LAIR1 and LAIR2 in human and murine immune cell subsets at baseline and posttreatment with immune mediators, including type I and II interferons, tumor necrosis factor α, and lipopolysaccharide (LPS). We identified candidate regulatory elements using epigenome profiling and measured their regulatory activity using luciferase reporters. LAIR1 expression substantially increases during monocyte differentiation to macrophages in both species. In contrast, murine and human macrophages exhibited opposite changes in LAIR1 in response to immune stimuli: human LAIR1 increased with LPS while mouse LAIR1 increased with interferon γ. LAIR genes had distinct patterns of enhancer activity with variable responses to immune stimuli. To identify relevant transcription factors (TFs), we developed integrative bioinformatic techniques applied to TF chromatin immunoprecipitation sequencing, RNA sequencing, and luciferase activity, revealing distinct sets of TFs for each LAIR gene. Most strikingly, LAIR1 TFs include nuclear factor kappa B factors RELA and RELB, while Lair1 and LAIR2 instead include STAT3 and/or STAT5. Regulation by nuclear factor kappa B factors may therefore explain the LPS-induced increase in LAIR1 expression, in contrast to Lair1 decrease. Our findings reveal new insights into transcriptional mechanisms that control distinct expression patterns of LAIR genes in response to inflammatory stimuli in human and murine myeloid and lymphoid cells.

TMIGD2 is an orchestrator and therapeutic target on human acute myeloid leukemia stem cells

Acute myeloid leukemia (AML) is initiated and sustained by a hierarchy of leukemia stem cells (LSCs), and elimination of this cell population is required for curative therapies. Here we show that transmembrane and immunoglobulin domain containing 2 (TMIGD2), a recently discovered co-stimulatory immune receptor, is aberrantly expressed by human AML cells, and can be used to identify and enrich functional LSCs. We demonstrate that TMIGD2 is required for the development and maintenance of AML and self-renewal of LSCs but is not essential for normal hematopoiesis. Mechanistically, TMIGD2 promotes proliferation, blocks myeloid differentiation and increases cell-cycle of AML cells via an ERK1/2-p90RSK-CREB signaling axis. Targeting TMIGD2 signaling with anti-TMIGD2 monoclonal antibodies attenuates LSC self-renewal and reduces leukemia burden in AML patient-derived xenograft models but has negligible effect on normal hematopoietic stem/progenitor cells. Thus, our studies reveal the function of TMIGD2 in LSCs and provide a promising therapeutic strategy for AML.

LAIR-1 limits macrophage activation in acute inflammatory lung injury

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are serious health problems that manifest as acute respiratory failure in response to different conditions, including viral respiratory infections. Recently, the inhibitory properties of leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1) were demonstrated in allergic and viral airway inflammation. In this study, we investigate the implication of LAIR-1 in ALI/ARDS and explore the underlying mechanisms. Polyinosinic:polycytidylic acid, a synthetic analog of double-stranded RNA, was used to mimic acute inflammation in viral infections. We demonstrate that LAIR-1 is predominantly expressed on macrophages and regulates their recruitment to the lungs as well as their activation in response to polyinosinic:polycytidylic acid. Interestingly, LAIR-1 deficiency increases neutrophil recruitment as well as lung resistance and permeability. In particular, we highlight the capacity of LAIR-1 to regulate the secretion of CXCL10, considered a key marker of macrophage overactivation in acute lung inflammation. We also reveal in COVID-19-induced lung inflammation that LAIR1 is upregulated on lung macrophages in correlation with relevant immune regulatory genes. Altogether, our findings demonstrate the implication of LAIR-1 in the pathogenesis of ALI/ARDS by means of the regulation of macrophages, thereby providing the basis of a novel therapeutic target.

LAIR-1 agonism as a therapy for acute myeloid leukemia

Effective eradication of leukemic stem cells (LSCs) remains the greatest challenge in treating acute myeloid leukemia (AML). The immune receptor LAIR-1 has been shown to regulate LSC survival; however, the therapeutic potential of this pathway remains unexplored. We developed a therapeutic LAIR-1 agonist antibody, NC525, that induced cell death of LSCs, but not healthy hematopoietic stem cells in vitro, and killed LSCs and AML blasts in both cell- and patient-derived xenograft models. We showed that LAIR-1 agonism drives a unique apoptotic signaling program in leukemic cells that was enhanced in the presence of collagen. NC525 also significantly improved the activity of azacitidine and venetoclax to establish LAIR-1 targeting as a therapeutic strategy for AML that may synergize with standard-of-care therapies.

LAIR1 drives glioma progression by nuclear focal adhesion kinase dependent expressions of cyclin D1 and immunosuppressive chemokines/cytokines

Leukocyte-associated immunoglobulin-like receptor-1 (LAIR1), an immune receptor containing immunoreceptor tyrosine-based inhibiory motifs (ITIMs), has emerged as an attractive target for cancer therapy. However, the intrinsic function of LAIR1 in gliomas remains unclear. In this study, the poor prognosis of glioma patients and the malignant proliferation of glioma cells in vitro and in vivo were found to be closely correlated with LAIR1. LAIR1 facilitates focal adhesion kinase (FAK) nuclear localization, resulting in increased transcription of cyclin D1 and chemokines/cytokines (CCL5, TGFβ2, and IL33). LAIR1 specifically supports in the immunosuppressive glioma microenvironment via CCL5-mediated microglia/macrophage polarization. SHP2Q510E (PTP domain mutant) or FAKNLM (non-nuclear localizing mutant) significantly reversed the LAIR1-induced growth enhancement in glioma cells. In addition, LAIR1Y251/281F (ITIMs mutant) and SHP2Q510E mutants significantly reduced FAK nuclear localization, as well as CCL5 and cyclin D1 expression. Further experiments revealed that the ITIMs of LAIR1 recruited SH2-containing phosphatase 2 (SHP2), which then interacted with FAK and induced FAK nuclear localization. This study uncovered a critical role for intrinsic LAIR1 in facilitating glioma malignant progression and demonstrated a requirement for LAIR1 and SHP2 to enhance FAK nuclear localization.

Perspectives of targeting LILRB1 in innate and adaptive immune checkpoint therapy of cancer

Immune checkpoint blockade is a compelling approach in tumor immunotherapy. Blocking inhibitory pathways in T cells has demonstrated clinical efficacy in different types of cancer and may hold potential to also stimulate innate immune responses. A novel emerging potential target for immune checkpoint therapy is leukocyte immunoglobulin-like receptor subfamily B member 1 (LILRB1). LILRB1 belongs to the superfamily of leukocyte immunoglobulin-like receptors and exerts inhibitory functions. The receptor is expressed by a variety of immune cells including macrophages as well as certain cytotoxic lymphocytes and contributes to the regulation of different immune responses by interaction with classical as well as non-classical human leukocyte antigen (HLA) class I molecules. LILRB1 has gained increasing attention as it has been demonstrated to function as a phagocytosis checkpoint on macrophages by recognizing HLA class I, which represents a 'Don't Eat Me!' signal that impairs phagocytic uptake of cancer cells, similar to CD47. The specific blockade of the HLA class I:LILRB1 axis may provide an option to promote phagocytosis by macrophages and also to enhance cytotoxic functions of T cells and natural killer (NK) cells. Currently, LILRB1 specific antibodies are in different stages of pre-clinical and clinical development. In this review, we introduce LILRB1 and highlight the features that make this immune checkpoint a promising target for cancer immunotherapy.

SHP-1 phosphatase acts as a coactivator of PCK1 transcription to control gluconeogenesis

We previously reported that the protein-tyrosine phosphatase SHP-1 (PTPN6) negatively regulates insulin signaling, but its impact on hepatic glucose metabolism and systemic glucose control remains poorly understood. Here, we use co-immunoprecipitation assays, chromatin immunoprecipitation sequencing, in silico methods, and gluconeogenesis assay, and found a new mechanism whereby SHP-1 acts as a coactivator for transcription of the phosphoenolpyruvate carboxykinase 1 (PCK1) gene to increase liver gluconeogenesis. SHP-1 is recruited to the regulatory regions of the PCK1 gene and interacts with RNA polymerase II. The recruitment of SHP-1 to chromatin is dependent on its association with the transcription factor signal transducer and activator of transcription 5 (STAT5). Loss of SHP-1 as well as STAT5 decrease RNA polymerase II recruitment to the PCK1 promoter and consequently PCK1 mRNA levels leading to blunted gluconeogenesis. This work highlights a novel nuclear role of SHP-1 as a key transcriptional regulator of hepatic gluconeogenesis adding a new mechanism to the repertoire of SHP-1 functions in metabolic control.

Inhibitory innate receptors and their potential role in transplantation

The regulatory arm of the immune system plays a crucial role in maintaining immune tolerance and preventing excessive immune responses. Immune regulation comprises various regulatory cells and molecules that work together to suppress or regulate immune responses. The programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte-associated protein 4 (CTLA-4) are examples of inhibitory receptors that counteract activating signals and fine-tune immune responses. While most of the discoveries of immune regulation have been related to T cells and the adaptive immune system, the innate arm of the immune system also has a range of inhibitory receptors that can counteract activating signals and suppress the effector immune responses. Targeting these innate inhibitory receptors may provide a complementary therapeutic approach in several immune-related conditions, including transplantation. In this review, we will explore the potential role of innate inhibitory receptors in controlling alloimmunity during solid organ transplantation.

Dipeptidylpeptidase 4 promotes survival and stemness of acute myeloid leukemia stem cells

Leukemic-stem-cell-specific targeting may improve the survival of patients with acute myeloid leukemia (AML) by avoiding the ablative effects of standard regimens on normal hematopoiesis. Herein, we perform an unbiased screening of compounds targeting cell surface proteins and identify clinically used DPP4 inhibitors as strong suppressors of AML development in both murine AML models and primary human AML cells xenograft model. We find in retrovirus-induced AML mouse models that DPP4-deficient AML cell-transplanted mice exhibit delay and reversal of AML development, whereas deletion of DPP4 has no significant effect on normal hematopoiesis. DPP4 activates and sustains survival of AML stem cells that are critical for AML development in both human and animal models via binding with Src kinase and activation of nuclear factor κB (NF-κB) signaling. Thus, inhibition of DPP4 is a potential therapeutic strategy against AML development through suppression of survival and stemness of AML cells.

Repair of Limb Ischemia Is Dependent on Hematopoietic Stem Cell Specific-SHP-1 Regulation of TGF-β1

BACKGROUND

Hematopoietic stem cell (HSC) therapy has shown promise for tissue regeneration after ischemia. Therefore, there is a need to understand mechanisms underlying endogenous HSCs activation in response to ischemic stress and coordination of angiogenesis and repair. SHP-1 plays important roles in HSC quiescence and differentiation by regulation of TGF-β1 signaling. TGF-β1 promotes angiogenesis by stimulating stem cells to secrete growth factors to initiate the formation of blood vessels and later aid in their maturation. We propose that SHP-1 responds to ischemia stress in HSC and progenitor cells (HSPC) via regulation of TGF-β1.

METHODS

A mouse hind limb ischemia model was used. Local blood perfusion in the limbs was determined using laser doppler perfusion imaging. The number of positive blood vessels per square millimeter, as well as blood vessel diameter (μm) and area (μm²), were calculated. Hematopoietic cells were analyzed using flow cytometry. The bone marrow transplantation assay was performed to measure HSC reconstitution.

RESULTS

After femoral artery ligation, TGF-β1 was initially decreased in the bone marrow by day 3 of ischemia, followed by an increase on day 7. This pattern was opposite to that in the peripheral blood, which is concordant with the response of HSC to ischemic stress. In contrast, SHP-1 deficiency in HSC is associated with irreversible activation of HSPCs in the bone marrow and increased circulating HSPCs in peripheral blood following limb ischemia. In addition, there was augmented auto-induction of TGF-β1 and sustained inactivation of SHP-1-Smad2 signaling, which impacted TGF-β1 expression in HSPCs in circulation. Importantly, restoration of normal T GF-β1 oscillations helped in the recovery of limb repair and function.

CONCLUSIONS

HSPC-SHP-1-mediated regulation of TGF-β1 in both bone marrow and peripheral blood is required for a normal response to ischemic stress.

LAIR1, an ITIM-Containing Receptor Involved in Immune Disorders and in Hematological Neoplasms

Leukocyte-associated immunoglobulin (Ig)-like receptor 1 (LAIR1, CD305) belongs to the family of immune-inhibitory receptors and is widely expressed on hematopoietic mature cells, particularly on immune cells. Four different types of ligands of LAIR1 have been described, including collagens, suggesting a potential immune-regulatory function on the extracellular matrix. By modulating cytokine secretion and cellular functions, LAIR1 displays distinct patterns of expression among NK cell and T/B lymphocyte subsets during their differentiation and cellular activation and plays a major negative immunoregulatory role. Beyond its implications in physiology, the activity of LAIR1 can be inappropriately involved in various autoimmune or inflammatory disorders and has been implicated in cancer physiopathology, including hematological neoplasms. Its action as an inhibitory receptor can result in the dysregulation of immune cellular responses and in immune escape within the tumor microenvironment. Furthermore, when expressed by tumor cells, LAIR1 can modulate their proliferation or invasion properties, with contradictory pro- or anti-tumoral effects depending on tumor type. In this review, we will focus on its role in normal physiological conditions, as well as during pathological situations, including hematological malignancies. We will also discuss potential therapeutic strategies targeting LAIR1 for the treatment of various autoimmune diseases and cancer settings.

Retinoblastoma protein as an intrinsic BRD4 inhibitor modulates small molecule BET inhibitor sensitivity in cancer

Bromodomain and extraterminal (BET) proteins including BRD4 play important roles in oncogenesis and immune inflammation. Here we demonstrate that cancer cells with loss of the retinoblastoma (RB) tumor suppressor became resistant to small molecule bromodomain inhibitors of BET proteins. We find that RB binds to bromodomain-1 (BD1) of BRD4, but binding is impeded by CDK4/6-mediated RB phosphorylation at serine-249/threonine-252 (S249/T252). ChIP-seq analysis shows RB knockdown increases BRD4 occupancy at genomic loci of genes enriched in cancer-related pathways including the GPCR-GNBIL-CREB axis. S249/T252-phosphorylated RB positively correlates with GNBIL protein level in prostate cancer patient samples. BET inhibitor resistance in RB-deficient cells is abolished by co-administration of CREB inhibitor. Our study identifies RB protein as a bona fide intrinsic inhibitor of BRD4 and demonstrates that RB inactivation confers resistance to small molecule BET inhibitors, thereby revealing a regulatory hub that converges RB upstream signaling onto BRD4 functions in diseases such as cancer.

Cytotoxic T Cell Expression of Leukocyte-Associated Immunoglobulin-Like Receptor-1 (LAIR-1) in Viral Hepatitis C-Mediated Hepatocellular Carcinoma

Virus-related hepatocellular carcinoma (HCC) pathogenesis involves liver inflammation, therefore, despite successful treatment, hepatitis C virus (HCV) may progress to HCC from initiated liver cirrhosis. Cytotoxic T cells (Tcs) are known to be involved in HCV-related cirrhotic complications and HCC pathogenesis. The inhibitory checkpoint leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1) is expressed on Tcs. Therefore, we aimed to determine whether the Tc expression level of LAIR-1 is associated with HCC progression and to evaluate LAIR-1 expression as a noninvasive biomarker for HCC progression in the context of liver cirrhosis related to HCV genotype 4 (G4) in Egyptian patients’ peripheral venous blood liquid biopsy. A total of 64 patients with HCC and 37 patients with liver cirrhosis were enrolled in this case-controlled study, and their LAIR-1 expression on Tc related to the progression of liver cirrhosis was examined and compared to that of the apparently healthy control group (n = 20). LAIR-1 expression was analyzed using flow cytometry. Results: The HCC group had significantly higher LAIR-1 expression on Tc and percentage of Tc positive for LAIR-1 (LAIR-1+Tc%) than the HCV G4-related liver cirrhosis group. LAIR-1+Tc% was correlated with the HCC surrogate tumor marker AFP (r = 0.367, p = 0.001) and insulin resistance and inflammation prognostic ratios/indices. A receiver operating characteristic (ROC) curve revealed that adding LAIR-1+Tc% to AFP can distinguish HCC transformation in the Egyptian patients’ cohort. Upregulated LAIR-1 expression on Tc could be a potential screening noninvasive molecular marker for chronic inflammatory HCV G4 related liver cirrhosis. Moreover, LAIR-1 expression on Tc may be one of the players involved in the progression of liver cirrhosis to HCC.

CD93 promotes acute myeloid leukemia development and is a potential therapeutic target

CD93 is a transmembrane receptor belonging to the Group XIV C-Type lectin family. It is expressed in a variety of cellular types such as monocytes, neutrophils, platelets, microglia, and endothelial cells. CD93 has been reported to play important roles in cell proliferation, cell migration, and tumor angiogenesis. Here, we show CD93 is highly expressed in M4 and M5 subtypes of acute myeloid leukemia (AML) patients, and highly expressed in leukemia stem cells, AML progenitor cells, as well as more differentiated AML cells. We found that CD93 promotes AML cell proliferation, while CD93 deficient AML cells commit to differentiation. We further show that CD93 exerts its proliferative function through downstream SHP-2/Syk/CREB cascade in AML cells. Moreover, human AML cells treated with CD93 mAb combined with αMFc-NC-DM1 (an IgG Fc specific antibody conjugated to maytansinoid DM1), showed a striking reduction of proliferation. Our study revealed that CD93 is a critical participator of AML development and provides a potential therapeutic cell surface target. (160 words).

Blocking LAIR1 signaling in immune cells inhibits tumor development

The current immune checkpoint blockade therapy has been successful in treating some cancers but not others. New molecular targets and therapeutic approaches of cancer immunology need to be identified. Leukocyte associated immunoglobulin like receptor 1 (LAIR1) is an immune inhibitory receptor expressing on most immune cell types. However, it remains a question whether we can specifically and actively block LAIR1 signaling to activate immune responses for cancer treatment. Here we report the development of specific antagonistic anti-LAIR1 monoclonal antibodies and studied the effects of LAIR1 blockade on the anti-tumor immune functions. The anti-LAIR1 antagonistic antibody stimulated the activities of T cells, natural killer cells, macrophages, and dendritic cells in vitro. The single-cell RNA sequencing analysis of intratumoral immune cells in syngeneic human LAIR1 transgenic mice treated with control or anti-LAIR1 antagonist antibodies indicates that LAIR1 signaling blockade increased the numbers of CD4 memory T cells and inflammatory macrophages, but decreased those of pro-tumor macrophages, regulatory T cells, and plasmacytoid dendritic cells. Importantly, the LAIR1 blockade by the antagonistic antibody inhibited the activity of immunosuppressive myeloid cells and reactivated T cells from cancer patients in vitro and impeded tumor metastasis in a humanized mouse model. Blocking LAIR1 signaling in immune cells represents a promising strategy for development of anti-cancer immunotherapy.

FcγRIIB controls antibody-mediated target cell depletion by ITIM-independent mechanisms

Many therapeutic antibodies deplete target cells and elicit immunotherapy by engaging activating Fc gamma receptors (FcγRs) on host effector cells. These antibodies are negatively regulated by the inhibitory FcγRIIB (CD32B). Dogma suggests inhibition is mediated through the FcγRIIB immunoreceptor tyrosine-based inhibition motif (ITIM), negatively regulating immunoreceptor tyrosine-based activation motif (ITAM)-mediated signaling from activating FcγR. To assess this, we generated experimental models expressing human (h)FcγRIIB on targets or effectors, lacking or retaining ITIM signaling capacity. We demonstrate that signaling through the hFcγRIIB ITIM is dispensable for impairing monoclonal antibody (mAb)-mediated depletion of normal and malignant murine target cells through three therapeutically relevant surface receptors (CD20, CD25, and OX40) affecting immunotherapy. We demonstrate that hFcγRIIB competition with activating FcγRs for antibody Fc, rather than ITIM signaling, is sufficient to impair activating FcγR engagement, inhibiting effector function and immunotherapy.

Development and validation of a leukocyte-associated immunoglobulin-like receptor-1 prognostic signature for lower-grade gliomas

OBJECTIVE

Leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1), is an immunosuppressive receptor, widely expressed by immune cells, but the part of LAIR-1 in glioma progression remains unclear. The purpose of this study was to explore the relationship between LAIR-1 expression and the development of lower-grade glioma (LGG) using publicly available data sets.

METHODS

We took advantage of The Cancer Genome Atlas (TCGA) to analyze the expression of LAIR-1 in patients with LGG. Second, Kaplan-Meier methods and univariate and multivariate Cox regression analyses were used to examine the clinical significance of LAIR-1 expression in combination with CGGA databases, and then receiver operating characteristic curve analysis was used to verify the prognostic utility of LAIR-1. Gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and gene set enrichment analysis (GSEA) were used to explore the function of LAIR-1. Analysis of the correlation with immune infiltration was conducted using the ESTIMATE algorithm and single sample gene set enrichment analysis.

RESULTS

Our results showed that LAIR-1 expression to be positively correlated with malignant clinicopathologic features of LGG. Univariate analysis and multivariate analysis revealed that overexpression of LAIR-1 was correlated with a worse prognosis in patients. A nomogram model combining LAIR-1 was more useful in guiding clinical diagnosis, and functional enrichment analysis showed that malignant development of glioma was closely affiliated with the tumor immune microenvironment.

CONCLUSION

These results indicate that LAIR 1 is a latent marker for determining the prognosis of LGG patients. LAIR 1 may also participate a critical part in TIME of LGG by regulating the infiltration of immune cells, suggesting that LAIR 1 might be used as a therapeutic target to regulate the antitumor immune response.

Design, Synthesis and Biological Evaluation of Prodrugs of 666-15 as Inhibitors of CREB-Mediated Gene Transcription

cAMP-response element binding protein (CREB) is a transcription factor involved in multiple cancers. Chemical inhibitors of CREB represent potential anticancer agents. We previously identified 666-15 as a potent CREB inhibitor. While 666-15 showed efficacious anticancer activity in vivo through intraperitoneal (IP) injection, its oral bioavailability is limited. To increase its oral bioavailability, we describe synthesis and evaluation of prodrugs based on 666-15. The amino acid esters were attempted, but they were not stable for detailed characterization. The corresponding sulfate and phosphates were prepared. The sulfate of 666-15 was too stable to release 666-15 while the phosphates were converted into 666-15 with half-lives of ∼2 h. Phosphate 3 was also a potent CREB inhibitor with anti-breast cancer activity. Furthermore, compound 3 showed much improved oral bioavailability at 38%. These studies support that 3 can be used as an oral CREB inhibitor while IP administration of 666-15 is preferred for in vivo applications.

Glucagon signaling via supraphysiologic GCGR can reduce cell viability without stimulating gluconeogenic gene expression in liver cancer cells

Background

Deregulated glucose metabolism is a critical component of cancer growth and survival, clinically evident via FDG-PET imaging of enhanced glucose uptake in tumor nodules. Tumor cells utilize glucose in a variety of interconnected biochemical pathways to generate energy, anabolic precursors, and other metabolites necessary for growth. Glucagon-stimulated gluconeogenesis opposes glycolysis, potentially representing a pathway-specific strategy for targeting glucose metabolism in tumor cells. Here, we test the hypothesis of whether glucagon signaling can activate gluconeogenesis to reduce tumor proliferation in models of liver cancer.

Methods

The glucagon receptor, GCGR, was overexpressed in liver cancer cell lines consisting of a range of etiologies and genetic backgrounds. Glucagon signaling transduction was measured by cAMP ELISAs, western blots of phosphorylated PKA substrates, and qPCRs of relative mRNA expression of multiple gluconeogenic enzymes. Lastly, cell proliferation and apoptosis assays were performed to quantify the biological effect of glucagon/GCGR stimulation.

Results

Signaling analyses in SNU398 GCGR cells treated with glucagon revealed an increase in cAMP abundance and phosphorylation of downstream PKA substrates, including CREB. qPCR data indicated that none of the three major gluconeogenic genes, G6PC, FBP1, or PCK1, exhibit significantly higher mRNA levels in SNU398 GCGR cells when treated with glucagon; however, this could be partially increased with epigenetic inhibitors. In glucagon-treated SNU398 GCGR cells, flow cytometry analyses of apoptotic markers and growth assays reproducibly measured statistically significant reductions in cell viability. Finally, proliferation experiments employing siCREB inhibition showed no reversal of cell death in SNU398 GCGR cells treated with glucagon, indicating the effects of glucagon in this setting are independent of CREB.

Conclusions

For the first time, we report a potential tumor suppressive role for glucagon/GCGR in liver cancer. Specifically, we identified a novel cell line-specific phenotype, whereby glucagon signaling can induce apoptosis via an undetermined mechanism. Future studies should explore the potential effects of glucagon in diabetic liver cancer patients.

LILRB3 supports acute myeloid leukemia development and regulates T-cell antitumor immune responses through the TRAF2-cFLIP-NF-κB signaling axis

Leukocyte immunoglobulin-like receptor B (LILRB), a family of immune checkpoint receptors, contributes to acute myeloid leukemia (AML) development, but the specific mechanisms triggered by activation or inhibition of these immune checkpoints in cancer is largely unknown. Here we demonstrate that the intracellular domain of LILRB3 is constitutively associated with the adaptor protein TRAF2. Activated LILRB3 in AML cells leads to recruitment of cFLIP and subsequent NF-κB upregulation, resulting in enhanced leukemic cell survival and inhibition of T-cell-mediated anti-tumor activity. Hyperactivation of NF-κB induces a negative regulatory feedback loop mediated by A20, which disrupts the interaction of LILRB3 and TRAF2; consequently the SHP-1/2-mediated inhibitory activity of LILRB3 becomes dominant. Finally, we show that blockade of LILRB3 signaling with antagonizing antibodies hampers AML progression. LILRB3 thus exerts context-dependent activating and inhibitory functions, and targeting LILRB3 may become a potential therapeutic strategy for AML treatment.

Bone marrow niche ATP levels determine leukemia-initiating cell activity via P2X7 in leukemic models

How particular bone marrow niche factors contribute to the leukemogenic activities of leukemia-initiating cells (LICs) remains largely unknown. Here, we showed that ATP levels were markedly increased in the bone marrow niches of mice with acute myeloid leukemia (AML), and LICs preferentially localized to the endosteal niche with relatively high ATP levels, as indicated by a sensitive ATP indicator. ATP could efficiently induce the influx of ions into LICs in an MLL-AF9-induced murine AML model via the ligand-gated ion channel P2X7. P2x7 deletion led to notably impaired homing and self-renewal capacities of LICs and contributed to an approximately 5-fold decrease in the number of functional LICs but had no effect on normal hematopoiesis. ATP/P2X7 signaling enhanced the calcium flux-mediated phosphorylation of CREB, which further transactivated phosphoglycerate dehydrogenase (Phgdh) expression to maintain serine metabolism and LIC fates. P2X7 knockdown resulted in a markedly extended survival of recipients transplanted with either human AML cell lines or primary leukemia cells. Blockade of ATP/P2X7 signaling could efficiently inhibit leukemogenesis. Here, we provide a perspective for understanding how ATP/P2X7 signaling sustains LIC activities, which may benefit the development of specific strategies for targeting LICs or other types of cancer stem cells.

Strategy for Leukemia Treatment Targeting SHP-1,2 and SHIP

Protein tyrosine phosphatases (PTPs) are modulators of cellular functions such as differentiation, metabolism, migration, and survival. PTPs antagonize tyrosine kinases by removing phosphate moieties from molecular signaling residues, thus inhibiting signal transduction. Two PTPs, SHP-1 and SHP-2 (SH2 domain-containing phosphatases 1 and 2, respectively) and another inhibitory phosphatase, SH2 domain-containing inositol phosphatase (SHIP), are essential for cell function, which is reflected in the defective phenotype of mutant mice. Interestingly, SHP-1, SHP-2, and SHIP mutations are identified in many cases of human leukemia. However, the impact of these phosphatases and their mutations regarding the onset and progression of leukemia is controversial. The ambiguity of the role of these phosphatases imposes challenges on the development of targeting therapies for leukemia. This fundamental problem, confronted by the expanding investigational field of leukemia, will be addressed in this review, which will include a discussion of the molecular mechanisms of SHP-1, SHP-2, and SHIP in normal hematopoiesis and their role in leukemia. Clinical development of leukemic therapies achieved by targeting these phosphatases will be addressed as well.

Homeostatic functions of monocytes and interstitial lung macrophages are regulated via collagen domain-binding receptor LAIR1

Myeloid cells encounter stromal cells and their matrix determinants on a continual basis during their residence in any given organ. Here, we examined the impact of the collagen receptor LAIR1 on myeloid cell homeostasis and function. LAIR1 was highly expressed in the myeloid lineage and enriched in non-classical monocytes. Proteomic definition of the LAIR1 interactome identified stromal factor Colec12 as a high-affinity LAIR1 ligand. Proteomic profiling of LAIR1 signaling triggered by Collagen1 and Colec12 highlighted pathways associated with survival, proliferation, and differentiation. Lair1^-/- mice had reduced frequencies of Ly6C^- monocytes, which were associated with altered proliferation and apoptosis of non-classical monocytes from bone marrow and altered heterogeneity of interstitial macrophages in lung. Myeloid-specific LAIR1 deficiency promoted metastatic growth in a melanoma model and LAIR1 expression associated with improved clinical outcomes in human metastatic melanoma. Thus, monocytes and macrophages rely on LAIR1 sensing of stromal determinants for fitness and function, with relevance in homeostasis and disease.

Ca2+/calmodulin-dependent Protein Kinases in Leukemia Development

Ca²⁺/calmodulin (CaM) signaling is important for a wide range of cellular functions. It is not surprised the role of this signaling has been recognized in tumor progressions, such as proliferation, invasion, and migration. However, its role in leukemia has not been well appreciated. The multifunctional Ca²⁺/CaM-dependent protein kinases (CaMKs) are critical intermediates of this signaling and play key roles in cancer development. The most investigated CaMKs in leukemia, especially myeloid leukemia, are CaMKI, CaMKII, and CaMKIV. The function and mechanism of these kinases in leukemia development are summarized in this study.

Expression of leukocyte immunoglobulin-like receptor subfamily B expression on immune cells in hepatocellular carcinoma

BACKGROUND

Leukocyte immunoglobulin-like receptor subfamily B (LILRB) is a group of inhibitory receptors involved in innate immune mainly expressed on lymphoid and myelomonocytic cells. LILRB is proposed to serve as immune checkpoint like PD-1 and CTLA-4 for tumor treatment. We recently reported that the expression of LILRB2 in CD1c⁺ mDC from tumor tissue might suppress immune for HCC patients. However, the expression of all the LILRB family on other immune cells in peripheral blood and tumor microenvironment of HCC patients has not been systematically studied.

METHODS

The expression of LILRB family (LILRB1, LILRB2, LILRB3, LILRB4 and LILRB5) on immune cells, including granulocytes, NK cells, NKT cells, monocyte subsets, TAMs, B cells, γδ T cells, CD4⁺ T cells, CD8⁺ T cells and MDSC subsets, was analyzed by flow cytometry in the peripheral blood of 20 HCC patients and 20 healthy donors as well as in the tumor and tumor free tissues of 10 HCC patients.

RESULTS

LILRB1, LILRB2 and LILRB3 in granulocytes from peripheral blood were expressed increased in HCC patients compared with healthy donors. The expression of LILRB5 in NK cells and NKT cells from HCC blood were higher compared with healthy donors` blood. CD14⁺CD16⁺ monocyte subsets in blood of HCC patients expressed increased LILRB1 and LILRB4 than that in healthy donors. CD14⁺CD16^- monocyte subsets in blood of HCC patients expressed increased LILRB3 than that in healthy donors. Compared to corresponding TFL, LILRB3, LILRB4 and LILRB5 were expressed enhanced in TAMs from HCC tumors. LILRB1 expressed on the B cells both in the blood and tumor had significantly increased compared with healthy donors or corresponding TFL. Different from peripheral blood, in the HCC microenvironment, CD4⁺ T cells expressed lower LILRB2, LILRB3 and LILRB4 than that from TFL and CD8⁺ T cells expressed decreased LILRB2. And γδ T cells expressed LILRB1 in HCC blood and microenvironment. Surprisingly, the percentage of LILRB1 expressed on MDSC from HCC peripheral blood and tumors was lower than that from healthy donors and corresponding TFL.

CONCLUSIONS

This is the first systemically examination of the LILRB family expression on a variety of immune cells from both peripheral blood and microenvironment in HCC patients. The specific increasing expression of LILRB on immune cells may regulate innate and adaptive immune and impact on HCC progression. Our findings justify further investigation of LILRB function in HCC.

Megakaryocyte progenitor cell function is enhanced upon aging despite the functional decline of aged hematopoietic stem cells

Age-related morbidity is associated with a decline in hematopoietic stem cell (HSC) function, but the mechanisms of HSC aging remain unclear. We performed heterochronic HSC transplants followed by quantitative analysis of cell reconstitution. Although young HSCs outperformed old HSCs in young recipients, young HSCs unexpectedly failed to outcompete the old HSCs of aged recipients. Interestingly, despite substantial enrichment of megakaryocyte progenitors (MkPs) in old mice in situ and reported platelet (Plt) priming with age, transplanted old HSCs were deficient in reconstitution of all lineages, including MkPs and Plts. We therefore performed functional analysis of young and old MkPs. Surprisingly, old MkPs displayed unmistakably greater regenerative capacity compared with young MkPs. Transcriptome analysis revealed putative molecular regulators of old MkP expansion. Collectively, these data demonstrated that aging affects HSCs and megakaryopoiesis in fundamentally different ways: whereas old HSCs functionally decline, MkPs gain expansion capacity upon aging.

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Reconstitution deficit by old HSCs was observed by chimerism and absolute cell numbers

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Young HSCs did not outcompete resident HSCs in aged recipient mice

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Old MkPs display remarkable capacity to engraft, expand, and reconstitute platelets

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Aging is associated with changes in MkP genome-wide expression signatures

Leukocyte immunoglobulin-like receptor subfamily B: therapeutic targets in cancer

Inhibitory leukocyte immunoglobulin-like receptors (LILRBs 1–5) transduce signals via intracellular immunoreceptor tyrosine-based inhibitory motifs that recruit phosphatases to negatively regulate immune activation. The activation of LILRB signaling in immune cells may contribute to immune evasion. In addition, the expression and signaling of LILRBs in cancer cells especially in certain hematologic malignant cells directly support cancer development. Certain LILRBs thus have dual roles in cancer biology—as immune checkpoint molecules and tumor-supporting factors. Here, we review the expression, ligands, signaling, and functions of LILRBs, as well as therapeutic development targeting them. LILRBs may represent attractive targets for cancer treatment, and antagonizing LILRB signaling may prove to be effective anti-cancer strategies.

Immunosuppressive receptor LILRB1 acts as a potential regulator in hepatocellular carcinoma by integrating with SHP1

BACKGROUND

Immunosuppressive receptor LILRB1 regulates tumors progression by transducing immune inhibitory signals via intracellular immunoreceptor tyrosine-based inhibitory motifs. However, its role in Hepatocellular Carcinoma (HCC) remains vague.

OBJECTIVE

This study is aimed to disclose the association between LILRB1 and HCC.

METHODS

Immunoblotting and qRT-PCR were employed to evaluate the level of LILRB1 in hepatocarcinoma cells. LILRB1-positive cells in tissue array were measured using immunohistochemistry staining. The relation among LILRB1, SHP1 and SHP2 and survival rates were analyzed using Gene Expression Profiling Interactive Analysis (GEPIA) and Oncomine database.

RESULTS

LILRB1 was robustly reduced in hepatocarcinoma cells compared to normal cells. Clinically, LILRB1 was significantly higher in 49 of 75 (65%) paired paracarcinoma tissues than that in paired HCC samples. 48 of 75 (64%) HCC subjects in tissue microarray showed low level of LILRB1, compared to 25 of 75 (33%) in paired-adjacent tissues. Oncomine database and GEPIA analysis confirmed that LILRB1 was lower in HCC than normal tissues. Additionally, lowLILRB1 had a significant association with clinicopathological characteristics and Disease Free Survival, but no association with Overall Survival in HCC patients. Mechanismly, positive correlation between LILRB1 and SHP1, but not SHP2 was observed in HCC.

CONCLUSIONS

LILRB1 possibly plays an antitumor effect in hepatocarcinoma cells by integrating SHP1, providing evidence that LILRB1 might be involved in the pathologic progression of HCC.

The Clot Thickens: Recent Clues on Hematopoietic Stem Cell Contribution to Age-Related Platelet Biology Open New Questions

Platelets provide life-saving functions by halting external and internal bleeding. There is also a dark side to platelet biology, however. Recent reports provide evidence for increased platelet reactivity during aging of mice and humans, making platelets main suspects in the most prevalent aging-related human pathologies, including cardiovascular diseases, stroke, and cancer. What drives this platelet hyperreactivity during aging? Here, we discuss how hematopoietic stem cell differentiation pathways into the platelet lineage offer avenues to understand the fundamental differences between young and old platelets. Recent advances begin to unravel how the cellular and molecular regulation of the parent hematopoietic stem and progenitor cells likely imbue aging characteristics on the resulting Plt progeny. The resulting mechanistic insights into intrinsic platelet reactivity will provide strategies for selectively targeting age-related pathways. This brief viewpoint focuses on current concepts on aging hematopoiesis and the implications for platelet hyperactivity during aging.

New strategies to treat AML: novel insights into AML survival pathways and combination therapies

The effective treatment of acute myeloid leukemia (AML) is very challenging. Due to the immense heterogeneity of this disease, treating it using a "one size fits all" approach is ineffective and only benefits a subset of patients. Instead, there is a shift towards more personalized treatment based on the patients' genomic signature. This shift has facilitated the increased revelation of novel insights into pathways that lead to the survival and propagation of AML cells. These AML survival pathways are involved in drug resistance, evasion of the immune system, reprogramming metabolism, and impairing differentiation. In addition, based on the reports of enhanced clinical efficiencies when combining drugs or treatments, deeper investigation into possible pathways, which can be targeted together to increase treatment response in a wider group of patients, is warranted. In this review, not only is a comprehensive summary of targets involved in these pathways provided, but also insights into the potential of targeting these molecules in combination therapy will be discussed.

Immunotherapy in Hematologic Malignancies: Emerging Therapies and Novel Approaches

Immunotherapy is extensively investigated for almost all types of hematologic tumors, from preleukemic to relapse/refractory malignancies. Due to the emergence of technologies for target cell characterization, antibody design and manufacturing, as well as genome editing, immunotherapies including gene and cell therapies are becoming increasingly elaborate and diversified. Understanding the tumor immune microenvironment of the target disease is critical, as is reducing toxicity. Although there have been many successes and newly FDA-approved immunotherapies for hematologic malignancies, we have learned that insufficient efficacy due to disease relapse following treatment is one of the key obstacles for developing successful therapeutic regimens. Thus, combination therapies are also being explored. In this review, immunotherapies for each type of hematologic malignancy will be introduced, and novel targets that are under investigation will be described.