Extracellular HMGB1 promotes differentiation of nurse-like cells in chronic lymphocytic leukemia. Blood. 2014;123:1709-1719. [PMID: 24464016 DOI: 10.1182/blood-2013-10-529610]

High Mobility Group Box 1 (HMGB1): Molecular Signaling and Potential Therapeutic Strategies

High Mobility Group Box 1 (HMGB1) is a highly conserved non-histone chromatin-associated protein across species, primarily recognized for its regulatory impact on vital cellular processes, like autophagy, cell survival, and apoptosis. HMGB1 exhibits dual functionality based on its localization: both as a non-histone protein in the nucleus and as an inducer of inflammatory cytokines upon extracellular release. Pathophysiological insights reveal that HMGB1 plays a significant role in the onset and progression of a vast array of diseases, viz., atherosclerosis, kidney damage, cancer, and neurodegeneration. However, a clear mechanistic understanding of HMGB1 release, translocation, and associated signaling cascades in mediating such physiological dysfunctions remains obscure. This review presents a detailed outline of HMGB1 structure-function relationship and its regulatory role in disease onset and progression from a signaling perspective. This review also presents an insight into the status of HMGB1 druggability, potential limitations in understanding HMGB1 pathophysiology, and future perspective of studies that can be undertaken to address the existing scientific gap. Based on existing paradigm of various studies, HMGB1 is a critical regulator of inflammatory cascades and drives the onset and progression of a broad spectrum of dysfunctions. Studies focusing on HMGB1 druggability have enabled the development of biologics with potential clinical benefits. However, deeper understanding of post-translational modifications, redox states, translocation mechanisms, and mitochondrial interactions can potentially enable the development of better courses of therapy against HMGB1-mediated physiological dysfunctions.

Targeting the tumor microenvironment for treating double-refractory chronic lymphocytic leukemia

ABSTRACT

The introduction of BTK inhibitors and BCL2 antagonists to the treatment of chronic lymphocytic leukemia (CLL) has revolutionized therapy and improved patient outcomes. These agents have replaced chemoimmunotherapy as standard of care. Despite this progress, a new group of patients is currently emerging, which has become refractory or intolerant to both classes of agents, creating an unmet medical need. Here, we propose that the targeted modulation of the tumor microenvironment provides new therapeutic options for this group of double-refractory patients. Furthermore, we outline a sequential strategy for tumor microenvironment-directed combination therapies in CLL that can be tested in clinical protocols.

Impact of leukemia-associated macrophages on the progression and therapy response of chronic lymphocytic leukemia

The treatment landscape of chronic lymphocytic leukemia (CLL) has advanced remarkably over the past decade. The advent and approval of the BTK inhibitor ibrutinib and BCL-2 inhibitor venetoclax, as well as monoclonal anti-CD20 antibodies rituximab and obinutuzumab, have resulted in deep remissions and substantially improved survival outcomes for patients. However, CLL remains a complex disease with many patients still experiencing relapse and unsatisfactory treatment responses. CLL cells are highly dependent on their pro-leukemic tumor microenvironment (TME), which comprises different cellular and soluble factors. A large body of evidence suggests that CLL-associated macrophages shaped by leukemic cells play a pivotal role in maintaining CLL cell survival. In this review, we summarize the pro-survival interactions between CLL cells and macrophages, as well as the impact of the current first-line treatment agents, including ibrutinib, venetoclax, and CD20 antibodies on leukemia-associated macrophages.

Role of the tumor microenvironment in CLL pathogenesis

Chronic lymphocytic leukemia (CLL) cells extensively interact with and depend on their surrounding tumor microenvironment (TME). The TME encompasses a heterogeneous array of cell types, soluble signals, and extracellular vesicles, which contribute significantly to CLL pathogenesis. CLL cells and the TME cooperatively generate a chronic inflammatory milieu, which reciprocally reprograms the TME and activates a signaling network within CLL cells, promoting their survival and proliferation. Additionally, the inflammatory milieu exerts chemotactic effects, attracting CLL cells and other immune cells to the lymphoid tissues. The intricate CLL-TME interactions also facilitate immune evasion and compromise leukemic cell surveillance. We also review recent advances that have shed light on additional aspects that are substantially influenced by the CLL-TME interplay.

Mesenchymal stem cells-macrophages crosstalk and myeloid malignancy

As major components of the tumor microenvironment, both mesenchymal stem cells (MSCs) and macrophages can be remodelled and exhibit different phenotypes and functions during tumor initiation and progression. In recent years, increasing evidence has shown that tumor-associated macrophages (TAMs) play a crucial role in the growth, metastasis, and chemotherapy resistance of hematological malignancies, and are associated with poor prognosis. Consequently, TAMs have emerged as promising therapeutic targets. Notably, MSCs exert a profound influence on modulating immune cell functions such as macrophages and granulocytes, thereby playing a crucial role in shaping the immunosuppressive microenvironment surrounding tumors. However, in hematological malignancies, the cellular and molecular mechanisms underlying the interaction between MSCs and macrophages have not been clearly elucidated. In this review, we provide an overview of the role of TAMs in various common hematological malignancies, and discuss the latest advances in understanding the interaction between MSCs and macrophages in disease progression. Additionally, potential therapeutic approaches targeting this relationship are outlined.

B-1 derived anti-Thy-1 B cells in old aged mice develop lymphoma/leukemia with high expression of CD11b and Hamp2 that different from TCL1 transgenic mice

Human old aged unmutated chronic lymphocytic leukemia U-CLL are the TCL1+ZAP70+CD5+ B cells. Since CD5 makes the BCR signaling tolerance, ZAP70 increased in U-CLL not only TCL1+ alone. In mice, TCL1 (TCL1A) is the negative from neonate to old aged, as TC-. VH8-12/Vk21-5 is the anti-thymocyte/Thy-1 autoreactive ATA B cell. When ATA μκTg generation in mice, ATA B cells are the neonate generated CD5+ B cells in B-1, and in the middle age, CD5+ can be down or continuously CD5+, then, old aged CLL/lymphoma generation with increased CD11b in TC-ZAP70-CD5- or TC-ZAP70+CD5+. In this old aged TC-ATA B microarray analysis showed most similar to human CLL and U-CLL, and TC-ZAP70+CD5+ showed certain higher present as U-CLL. Original neonate ATA B cells showed with several genes down or further increase in old aged tumor, and old aged T-bet+CD11c+, CTNNB1hi, HMGBhi, CXCR4hi, DPP4hi and decreased miR181b. These old aged increased genes and down miR181b are similar to human CLL. Also, in old age ATA B cell tumor, high CD38++CD44++, increased Ki67+ AID+, and decreased CD180- miR15Olow are similar to U-CLL. In this old aged ATA B, increased TLR7,9 and Wnt10b. TC+Tg generated with ATAμκTg mice occurred middle age tumor as TC+ZAP70-CD5+ or TC+ZAP70+CD5+, with high NF-kB1, TLR4,6 and Wnt5b,6 without increased CD11b. Since neonatal state to age with TC+Tg continuously, middle age CLL/lymphoma generation is not similar to old aged generated, however, some increased in TC+ZAP70+ are similar to the old age TC- ATA B tumor. Then, TC- ATA B old age tumor showed some difference to human CLL. ATA B cells showed CD11b+CD22++, CD24 down, and hepcidin Hamp2++ with iron down. This mouse V8-12 similar to human V2-5, and V2-5 showed several cancers with macrophages/neutrophils generated hepcidin+ ironlow or some showed hepcidin- iron+ with tumor, and mouse V8-12 with different Vk19-17 generate MZ B cells strongly increased macrophage++ in old aged and generated intestine/colon tumor. Conclusion, neonate generated TC-ATA B1 cells in old aged tumor generation are CD11b+ in the leukemia CLL together with lymphoma cancer with hepcidin-related Hamp2++ in B-1 cell generation to control iron.

Translocated HMGB3 is involved in papillary thyroid cancer progression by activating cytoplasmic TLR3 and transmembrane TREM1

The family of high mobility group box (HMGB) proteins participates in various biological processes including immunity, inflammation, as well as cancer formation and progression. However, its role in thyroid cancer remains to be clarified. We performed quantitative RT-PCR (qRT-PCR), western blot, enzyme-linked immunosorbent, immunohistochemistry, and immunofluorescence assays to evaluate the expression level and subcellular location of HMGB3. The effects of HMGB3 knockdown on malignant biological behaviors of thyroid cancer were determined by cell proliferation assays, cell cycle and apoptosis assays, and transwell chamber migration and invasion assays. Differential expression genes (DEGs) altered by HMGB3 were analyzed using the Ingenuity Pathway Analysis (IPA) and TRRUST v2 database. HMGB3 correlated pathways predicted by bioinformatic analysis were then confirmed using western blot, co-immunoprecipitation, dual-luciferase reporter assay, and flow cytometry. We found that HMGB3 is overexpressed and its downregulation inhibits cell viability, promotes cell apoptosis and cell cycle arrest, and suppresses cell migration and invasion in thyroid cancer. In PTC, both tissue and serum levels of HMGB3 are elevated and are correlated with lymph node metastasis and advanced tumor stage. Mechanistically, we observed the translocation of HMGB3 in PTC, induced at least partially by hypoxia. Cytoplasmic HMGB3 activates nucleic-acid-mediated TLR3/NF-κB signaling and extracellular HMGB3 interacts with the transmembrane TREM1 receptor in PTC. This study demonstrates the oncogenic role of HMGB3 cytoplasmic and extracellular translocation in papillary thyroid cancers; we recommend its future use as a potential circulating biomarker and therapeutic target for PTC.

Role of HMGB1 and its associated signaling pathways in human malignancies

The High-Mobility Group Box-1 (HMGB1), a non-histone chromatin-associated protein, plays a crucial role in cancer growth and response to therapy as it retains a pivotal role in promoting both cell death and survival. HMGB1 has been reported to regulate several signaling pathways engaged in inflammation, genome stability, immune function, cell proliferation, cell autophagy, metabolism, and apoptosis. However, the association between HMGB1 and cancer is complex and its mechanism in tumorigenesis needs to be further elucidated. This review aims to understand the role of HMGB1 in human malignancies and discuss the signaling pathways linked to this process to provide a comprehensive understanding on the association of HMGB1 with carcinogenesis. Further, we will review the role of HMGB1 as a target/biomarker for cancer therapy, the therapeutic strategies used to target this protein, and its potential role in preventing or treating cancers. In light of the recent growing evidence linking HMGB1 to cancer progression, we think that it may be suggested as a novel and emergent therapeutic target for cancer therapy. Hence, HMGB1 warrants paramount investigation to comprehensively map its role in tumorigenesis.

The Role of the Microenvironment and Cell Adhesion Molecules in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is a B-cell malignancy whose progression largely depends on the lymph node and bone marrow microenvironment. Indeed, CLL cells actively proliferate in specific regions of these anatomical compartments, known as proliferation centers, while being quiescent in the blood stream. Hence, CLL cell adhesion and migration into these protective niches are critical for CLL pathophysiology. CLL cells are lodged in their microenvironment through a series of molecular interactions that are mediated by cellular adhesion molecules and their counter receptors. The importance of these adhesion molecules in the clinic is demonstrated by the correlation between the expression levels of some of them, in particular CD49d, and the prognostic likelihood. Furthermore, novel therapeutic agents, such as ibrutinib, impair the functions of these adhesion molecules, leading to an egress of CLL cells from the lymph nodes and bone marrow into the circulation together with an inhibition of homing into these survival niches, thereby preventing disease progression. Several adhesion molecules have been shown to participate in CLL adhesion and migration. Their importance also stems from the observation that they are involved in promoting, directly or indirectly, survival signals that sustain CLL proliferation and limit the efficacy of standard and novel chemotherapeutic drugs, a process known as cell adhesion-mediated drug resistance. In this respect, many studies have elucidated the molecular mechanisms underlying cell adhesion-mediated drug resistance, which have highlighted different signaling pathways that may represent potential therapeutic targets. Here, we review the role of the microenvironment and the adhesion molecules that have been shown to be important in CLL and their impact on transendothelial migration and cell-mediated drug resistance. We also discuss how novel therapeutic compounds modulate the function of this important class of molecules.

Characterization of the Intraclonal Complexity of Chronic Lymphocytic Leukemia B Cells: Potential Influences of B-Cell Receptor Crosstalk with Other Stimuli

Chronic lymphocytic leukemia (CLL) clones contain subpopulations differing in time since the last cell division ("age"): recently born, proliferative (PF; CXCR4DimCD5Bright), intermediate (IF; CXCR4IntCD5Int), and resting (RF; CXCR4BrightCD5Dim) fractions. Herein, we used deuterium (2H) incorporation into newly synthesized DNA in patients to refine the kinetics of CLL subpopulations by characterizing two additional CXCR4/CD5 fractions, i.e., double dim (DDF; CXCR4DimCD5Dim) and double bright (DBF; CXCR4BrightCD5Bright); and intraclonal fractions differing in surface membrane (sm) IgM and IgD densities. Although DDF was enriched in recently divided cells and DBF in older cells, PF and RF remained the most enriched in youngest and oldest cells, respectively. Similarly, smIgMHigh and smIgDHigh cells were the youngest, and smIgMLow and smIgDLow were the oldest, when using smIG levels as discriminator. Surprisingly, the cells closest to the last stimulatory event bore high levels of smIG, and stimulating via TLR9 and smIG yielded a phenotype more consistent with the in vivo setting. Finally, older cells were less sensitive to in vivo inhibition by ibrutinib. Collectively, these data define additional intraclonal subpopulations with divergent ages and phenotypes and suggest that BCR engagement alone is not responsible for the smIG levels found in vivo, and the differential sensitivity of distinct fractions to ibrutinib might account, in part, for therapeutic relapse.

HMGB1: a potential new target for tendinopathy treatment

Tendinopathy describes a complex pathology of the tendon characterized by abnormalities in the microstructure, composition, and cellularity of the tendon, leading to pain, limitation of activity and reduced function. Nevertheless, the mechanism of tendinopathy has not been fully elucidated, and the treatment of tendinopathy remains a challenge. High mobility group box 1 (HMGB1), a highly conserved and multifaceted nuclear protein, exerts multiple roles and high functional variability and is involved in many biological and pathological processes. In recent years, several studies have suggested that HMGB1 is associated with tendinopathy and may play a key role in the pathogenesis of tendinopathy. Therefore, this review summarizes the expression and distribution of HMGB1 in tendinopathy, focuses on the roles of HMGB1 and HMGB1-based potential mechanisms involved in tendinopathy, and finally summarizes the findings on HMGB1-based therapeutic approaches in tendinopathy, probably providing new insight into the mechanism and further potential therapeutic targets of tendinopathy.

An agent-based model of monocyte differentiation into tumour-associated macrophages in chronic lymphocytic leukemia

Monocyte-derived macrophages help maintain tissue homeostasis and defend the organism against pathogens. In tumors, recent studies have uncovered complex macrophage populations, including tumor-associated macrophages, which support tumorigenesis through cancer hallmarks such as immunosuppression, angiogenesis, or matrix remodeling. In the case of chronic lymphocytic leukemia, these macrophages are known as nurse-like cells (NLCs) and they protect leukemic cells from spontaneous apoptosis, contributing to their chemoresistance. We propose an agent-based model of monocyte differentiation into NLCs upon contact with leukemic B cells in vitro. We performed patient-specific model optimization using cultures of peripheral blood mononuclear cells from patients. Using our model, we were able to reproduce the temporal survival dynamics of cancer cells in a patient-specific manner and to identify patient groups related to distinct macrophage phenotypes. Our results show a potentially important role of phagocytosis in the polarization process of NLCs and in promoting cancer cells' enhanced survival.

NF-kB and the CLL microenvironment

Chronic lymphocytic leukemia (CLL) is the most prevalent type of leukemia in the western world. Despite the positive clinical effects of new targeted therapies, CLL still remains an incurable and refractory disease and resistance to treatments are commonly encountered. The Nuclear Factor-Kappa B (NF-κB) transcription factor has been implicated in the pathology of CLL, with high levels of NF-κB associated with disease progression and drug resistance. This aberrant NF-κB activation can be caused by genetic mutations in the tumor cells and microenvironmental factors, which promote NF-κB signaling. Activation can be induced via two distinct pathways, the canonical and non-canonical pathway, which result in tumor cell proliferation, survival and drug resistance. Therefore, understanding how the CLL microenvironment drives NF-κB activation is important for deciphering how CLL cells evade treatment and may aid the development of novel targeting therapeutics. The CLL microenvironment is comprised of various cells, including nurse like cells, mesenchymal stromal cells, follicular dendritic cells and CD4+ T cells. By activating different receptors, including the B cell receptor and CD40, these cells cause overactivity of the canonical and non-canonical NF-κB pathways. Within this review, we will explore the different components of the CLL microenvironment that drive the NF-κB pathway, investigating how this knowledge is being translated in the development of new therapeutics.

Macrophage- and BCR-derived but not TLR-derived signals support the growth of CLL and Richter syndrome murine models in vivo

A large amount of circumstantial evidence has accumulated suggesting that Toll-like receptor (TLR) signals are involved in driving chronic lymphocytic leukemia (CLL) cell proliferation, but direct in vivo evidence for this is still lacking. We have now further addressed this possibility by pharmacologically inhibiting or genetically inactivating the TLR pathway in murine CLL and human Richter syndrome (RS) patient-derived xenograft (PDX) cells. Surprisingly, we show that pharmacologic inhibition of TLR signaling by treatment with an IRAK1/4 inhibitor delays the growth of the transplanted malignant cells in recipient mice, but genetic inactivation of the same pathway by CRISPR/Cas9-mediated disruption of IRAK4 or its proximal adaptor MyD88 has no effect. We further show that treatment with the IRAK1/4 inhibitor results in depletion of macrophages and demonstrate that these cells can support the survival and enhance the proliferation of both murine Eμ-TCL1 leukemia and human RS cells. We also show that genetic disruption of the B-cell receptor (BCR) by CRISPR/Cas9 editing of the immunoglobulin M constant region gene inhibits the growth of human RS-PDX cells in vivo, consistent with our previous finding with murine Eμ-TCL1 leukemia cells. Finally, we show that genetic disruption of IRAK4 does not result in negative selection of human CLL cell lines xenografted in immunodeficient mice. The obtained data suggest that TLR signals are unlikely to represent a major driver of CLL/RS cell proliferation and provide further evidence that signals from macrophages and the BCR promote the growth and survival of CLL and RS cells in vivo.

Disruption of Nurse-like Cell Differentiation as a Therapeutic Strategy for Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is the most common adult leukemia, but, despite advances in treatment, many patients still experience relapse. CLL cells depend on interactions with supportive cells, and nurse-like cells (NLCs) are the major such cell type. However, little is known about how NLCs develop. Here, we performed DNA methylation analysis of CLL patient-derived NLCs using the 850K Illumina array, comparing CD14+ cells at day 1 (monocytes) versus day 14 (NLCs). We found a strong loss of methylation in AP-1 transcription factor binding sites, which may be driven by MAPK signaling. Testing of individual MAPK pathways (MEK, p38, and JNK) revealed a strong dependence on MEK/ERK for NLC development, because treatment of patient samples with the MEK inhibitor trametinib dramatically reduced NLC development in vitro. Using the adoptive transfer Eµ-TCL1 mouse model of CLL, we found that MEK inhibition slowed CLL progression, leading to lower WBC counts and to significantly longer survival time. There were also lower numbers of mouse macrophages, particularly within the M2-like population. In summary, NLC development depends on MEK signaling, and inhibition of MEK leads to increased survival time in vivo. Hence, targeting the MEK/ERK pathway may be an effective treatment strategy for CLL.

Hypoxia-induced HMGB1 promotes glioma stem cells self-renewal and tumorigenicity via RAGE

Glioma stem cells (GSCs) in the hypoxic niches contribute to tumor initiation, progression, and recurrence in glioblastoma (GBM). Hypoxia induces release of high-mobility group box 1 (HMGB1) from tumor cells, promoting the development of tumor. Here, we report that HMGB1 is overexpressed in human GBM specimens. Hypoxia promotes the expression and secretion of HMGB1 in GSCs. Furthermore, silencing HMGB1 results in the loss of stem cell markers and a reduction in self-renewal ability of GSCs. Additionally, HMGB1 knockdown inhibits the activation of RAGE-dependent ERK1/2 signaling pathway and arrests the cell cycle in GSCs. Consistently, FPS-ZM1, an inhibitor of RAGE, downregulates HMGB1 expression and the phosphorylation of ERK1/2, leading to a reduction in the proliferation of GSCs. In xenograft mice of GBM, HMGB1 knockdown inhibits tumor growth and promotes mouse survival. Collectively, these findings uncover a vital function for HMGB1 in regulating GSC self-renewal potential and tumorigenicity.

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Glioma stem cells overexpress HMGB1 in human glioblastoma

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Hypoxia induces the upregulation and release of HMGB1 in glioma stem cells

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HMGB1 promotes the self-renewal of glioma stem cells via RAGE

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Targeting HMGB1 inhibits the tumorigenesis of glioma stem cells

Focus on the tumor microenvironment: A seedbed for neuroendocrine prostate cancer

The tumor microenvironment (TME) is a microecology consisting of tumor and mesenchymal cells and extracellular matrices. The TME plays important regulatory roles in tumor proliferation, invasion, metastasis, and differentiation. Neuroendocrine differentiation (NED) is a mechanism by which castration resistance develops in advanced prostate cancer (PCa). NED is induced after androgen deprivation therapy and neuroendocrine prostate cancer (NEPC) is established finally. NEPC has poor prognosis and short overall survival and is a major cause of death in patients with PCa. Both the cellular and non-cellular components of the TME regulate and induce NEPC formation through various pathways. Insights into the roles of the TME in NEPC evolution, growth, and progression have increased over the past few years. These novel insights will help refine the NEPC formation model and lay the foundation for the discovery of new NEPC therapies targeting the TME.

Regulation of S100As Expression by Inflammatory Cytokines in Chronic Lymphocytic Leukemia

The calcium-binding proteins S100A4, S100A8, and S100A9 are upregulated in chronic lymphocytic leukemia (CLL), while the S100A9 promotes NF-κB activity during disease progression. The S100-protein family has been involved in several malignancies as mediators of inflammation and proliferation. The hypothesis of our study is that S100A proteins are mediators in signaling pathways associated with inflammation-induced proliferation, such as NF-κB, PI3K/AKT, and JAK/STAT. The mononuclear cells (MNCs) of CLL were treated with proinflammatory IL-6, anti-inflammatory IL-10 cytokines, inhibitors of JAK1/2, NF-κB, and PI3K signaling pathways, to evaluate S100A4, S100A8, S100A9, and S100A12 expression as well as NF-κB activation by qRT-PCR, immunocytochemistry, and immunoblotting. The quantity of S100A4, S100A8, and S100A9 positive cells (p < 0.05) and their protein expression (p < 0.01) were significantly decreased in MNCs of CLL patients compared to healthy controls. The S100A levels were generally increased in CD19+ cells compared to MNCs of CLL. The S100A4 gene expression was significantly stimulated (p < 0.05) by the inhibition of the PI3K/AKT signaling pathway in MNCs. IL-6 stimulated S100A4 and S100A8 protein expression, prevented by the NF-κB and JAK1/2 inhibitors. In contrast, IL-10 reduced S100A8, S100A9, and S100A12 protein expressions in MNCs of CLL. Moreover, IL-10 inhibited activation of NF-κB signaling (4-fold, p < 0.05). In conclusion, inflammation stimulated the S100A protein expression mediated via the proliferation-related signaling and balanced by the cytokines in CLL.

IL-10 Rescues CLL Survival through Repolarization of Inflammatory Nurse-like Cells

Simple Summary

In in vitro co-cultures of CLL cells and nurse-like cells (NLC), protection against apoptosis is only provided by M2-like NLC, and not M1-like NLC. In this study, we propose that fine-tuning of NLC polarization (and therefore survival of leukemic cells) is dictated by a balance between IL-10 and TNF.

Abstract

Tumor-associated macrophages (TAMs) in chronic lymphocytic leukemia (CLL) are also called nurse-like cells (NLC), and confer survival signals through the release of soluble factors and cellular contacts. While in most patient samples the presence of NLC in co-cultures guarantees high viability of leukemic cells in vitro, in some cases this protective effect is absent. These macrophages are characterized by an “M1-like phenotype”. We show here that their reprogramming towards an M2-like phenotype (tumor-supportive) with IL-10 leads to an increase in leukemic cell survival. Inflammatory cytokines, such as TNF, are also able to depolarize M2-type protective NLC (decreasing CLL cell viability), an effect which is countered by IL-10 or blocking antibodies. Interestingly, both IL-10 and TNF are implied in the pathophysiology of CLL and their elevated level is associated with bad prognosis. We propose that the molecular balance between these two cytokines in CLL niches plays an important role in the maintenance of the protective phenotype of NLCs, and therefore in the survival of CLL cells.

Enhanced IL-9 secretion by p66Shc-deficient CLL cells modulates the chemokine landscape of the stromal microenvironment

The stromal microenvironment is central to chronic lymphocytic leukemia (CLL) pathogenesis. How leukemic cells condition the stroma to enhance its chemoattractant properties remains elusive. Here, we show that mouse and human CLL cells promote the contact-independent stromal expression of homing chemokines. This function was strongly enhanced in leukemic cells from Eμ-TCL1 mice lacking the pro-oxidant p66Shc adaptor, which develop an aggressive disease with organ infiltration. We identified interleukin-9 (IL-9) as the soluble factor, negatively modulated by p66Shc, that is responsible for the chemokine-elevating activity of leukemic cells on stromal cells. IL-9 blockade in Eμ-TCL1/p66Shc-/- mice resulted in a decrease in the nodal expression of homing chemokines, which correlated with decreased leukemic cell invasiveness. IL-9 levels were found to correlate inversely with residual p66Shc in p66Shc-deficient human CLL cells (n = 52 patients). p66Shc reconstitution in CLL cells normalized IL-9 expression and neutralized their chemokine-elevating activity. Notably, high IL-9 expression in CLL cells directly correlates with lymphadenopathy, liver infiltration, disease severity, and overall survival, emerging as an independent predictor of disease outcome. Our results demonstrate that IL-9 modulates the chemokine landscape in the stroma and that p66Shc, by regulating IL-9 expression, fine tunes the ability of leukemic cells to shape the microenvironment, thereby contributing to CLL pathogenesis.

Nurse-Like Cells and Chronic Lymphocytic Leukemia B Cells: A Mutualistic Crosstalk inside Tissue Microenvironments

Chronic lymphocytic leukemia (CLL) is the most common adult leukemia in Western countries and is an example of hematological disease where cooperation between genetic defects and tumor microenvironmental interaction is involved in pathogenesis. CLL is a disease that is considered as "addicted to the host"; indeed, the crosstalk between leukemic cells and the tumor microenvironment is essential for leukemic clone maintenance supporting CLL cells' survival, proliferation, and protection from drug-induced apoptosis. CLL cells are not innocent bystanders but actively model and manipulate the surrounding microenvironment to their own advantage. Besides the different players involved in this crosstalk, nurse-like cells (NLC) resemble features related to leukemia-associated macrophages with an important function in preserving CLL cell survival and supporting an immunosuppressive microenvironment. This review provides a comprehensive overview of the role played by NLC in creating a nurturing and permissive milieu for CLL cells, illustrating the therapeutic possibilities in order to specifically target and re-educate them.

The Regulatory Effect of SIRT1 on Extracellular Microenvironment Remodeling

The sirtuins family is well known by its unique nicotinamide adenine dinucleotide (NAD⁺)-dependent deacetylase function. The most-investigated member of the family, Sirtuin 1 (SIRT1), accounts for deacetylating a broad range of transcription factors and coregulators, such as p53, the Forkhead box O (FOXO), and so on. It serves as a pivotal regulator in various intracellular biological processes, including energy metabolism, DNA damage response, genome stability maintenance and tumorigenesis. Although the most attention has been focused on its intracellular functions, the regulatory effect on extracellular microenvironment remodeling of SIRT1 has been recognized by researchers recently. SIRT1 can regulate cell secretion process and participate in glucose metabolism, neuroendocrine function, inflammation and tumorigenesis. Here, we review the advances in the understanding of SIRT1 on remodeling the extracellular microenvironment, which may provide new ideas for pathogenesis investigation and guidance for clinical treatment.

Expression profiles of HMGB1 on B-CLL related leukocytes contribute to prediction of relapse

BACKGROUND

The High Mobility Group Box 1 (HMGB1) is a nuclear protein that is frequently overexpressed in hematologic diseases and might be of relevance in immunogenic cancer control thus correlating with patients' (pts.) prognosis in diseases such as acute myeloid, acute lymphatic and chronic lymphocytic leukemia.

MATERIALS AND METHODS

Expression profiles of blasts from AML (n = 21), ALL (n = 16) and of B-lymphocytes of CLL (n = 9) pts. were analyzed for surface expression of HMGB1 using flow cytometry. Expression was quantified and correlated with clinically and prognostically relevant markers.

RESULTS

Expression profiling of HMGB1 in blasts of AML and ALL subtypes did not show differences between primary vs. secondary disease development and gender related differences. In ALL pts. however, age groups at initial diagnosis between ≥20 vs. <20 years were compared and showed significant differences (≥20 vs. <20 years; 89% vs. 49%, p  <0.05) with higher expression in higher age. In AML and CLL these differences were not visible. To evaluate the prognostic significance of HMGB1 expression, expression quantity was correlated with established and prognostic classification systems (in AML ELN, in ALL GMALL) and probability to relapse. No significant correlation was seen in these entities. However, when AML pts. were analyzed for remission rates after first anthracycline based induction therapy, in those who did not experience a complete remission significantly enhanced HMGB1 surface expression was seen (98 vs. 94%; p < 0.05; n = 20). Furthermore, for CLL it was shown that higher HMGB1 expression was found in pretreated patients with relapsed or/and refractory disease (1 vs. more relapses; 94 vs. 98%; p  <0.05; n = 9).

CONCLUSION

HMGB1 is frequently expressed in hematologic malignancies. In this study it was shown that HMGB1 surface expression on AML blasts can be used as predictors for treatment response. In CLL it may be a marker for advanced disease. In order to implement this marker in FACS routine it could be a useful and practical tool for prognostic assessment and treatment planning.

Internalization of HMGB1 (High Mobility Group Box 1) Promotes Angiogenesis in Endothelial Cells

OBJECTIVE

In patients with peripheral artery disease, blockages in arterioles <1 mm cannot be treated surgically, and there are currently few effective medicines. Studies have shown that inflammation in ischemic tissue is related to injury recovery and angiogenesis, but insufficient attention has been paid to this area. Studies have suggested that HMGB1 (high mobility group protein 1), which is released by ischemic tissue, promotes angiogenesis, but the mechanism is not entirely clear. In this study, we tested the internalization of HMGB1 in endothelial cells and investigated a novel proangiogenic pathway. Approach and Results: Using green fluorescent protein-tagged HMGB1 to stimulate endothelial cells, we demonstrated HMGB1 internalization via dynamin and RAGE (receptor for advanced glycation end products)-dependent signaling. Using a fluorescence assay, we detected internalized protein fusion to lysosomes, followed by activation of CatB (cathepsin B) and CatL (cathepsin L). The latter promoted the release of VEGF (vascular endothelial growth factor)-A and endoglin and upregulated the capacities of cell migration, proliferation, and tube formation in endothelial cells. We identified that the cytokine-induced fragment-a key functional domain in HMGB1-mediates the internalization and angiogenic function of HMGB1. We further confirmed that HMGB1 internalization also occurs in vivo in endothelial cells and promotes angiogenesis in mouse femoral artery ligation.

CONCLUSIONS

In this study, we identified a novel pathway of HMGB1 internalization-induced angiogenesis in endothelial cells. This finding sheds light on the regulatory role of inflammatory factors in angiogenesis through cell internalization and opens a new door to understand the relationship between inflammation and angiogenesis in ischemic diseases.

Development of a cell-line model to mimic the pro-survival effect of nurse-like cells in chronic lymphocytic leukemia

The interaction between Chronic lymphocytic leukemia (CLL) cells and monocyte-derived nurse-like cells (NLCs) is fundamentally important to CLL biology. However, studies of how CLL cells and NLCs interact have been hampered by the need for freshly obtained CLL blood samples, coupled with wide variation in the number of monocytes present in the blood of individual patients. Here, we report the development and validation of a cell-line model of NLCs which overcomes these difficulties. Co-culture of primary CLL cells with THP-1 cells induced to differentiate into macrophages by phorbol 12-myristate 13-acetate (PMA) significantly reduced both spontaneous and fludarabine-induced cell death of leukemic cells. Furthermore, compared with their M1-polarized counterparts, M2-polarized macrophages derived from PMA-differentiated THP-1 cells conferred to CLL cells greater protection from spontaneous and fludarabine-induced apoptosis. Since NLCs resemble M2 tumor-associated macrophages, this cell-line model could be useful for investigating the mechanisms through which NLCs protect CLL cells from spontaneous and drug-induced apoptosis.

High mobility group box 1 (HMGB1): a pivotal regulator of hematopoietic malignancies

High mobility group box 1 (HMGB1) is a nonhistone chromatin-associated protein that has been widely reported to play a pivotal role in the pathogenesis of hematopoietic malignancies. As a representative damage-associated molecular pattern (DAMP), HMGB1 normally exists inside cells but can be secreted into the extracellular environment through passive or active release. Extracellular HMGB1 binds with several different receptors and interactors to mediate the proliferation, differentiation, mobilization, and senescence of hematopoietic stem cells (HSCs). HMGB1 is also involved in the formation of the inflammatory bone marrow (BM) microenvironment by activating proinflammatory signaling pathways. Moreover, HMGB1-dependent autophagy induces chemotherapy resistance in leukemia and multiple myeloma. In this review, we systematically summarize the emerging roles of HMGB1 in carcinogenesis, progression, prognosis, and potential clinical applications in different hematopoietic malignancies. In summary, targeting the regulation of HMGB1 activity in HSCs and the BM microenvironment is highly beneficial in the diagnosis and treatment of various hematopoietic malignancies.

Nitrative DNA damage in lung epithelial cells exposed to indium nanoparticles and indium ions

Indium compounds have been widely used in manufacturing displays of mobile phones, computers and televisions. However, inhalation exposure to indium compounds causes interstitial pneumonia in exposed workers and lung cancer in experimental animals. 8-Nitroguanine (8-nitroG) is a mutagenic DNA lesion formed under inflammatory conditions and may participate in indium-induced carcinogenesis. In this study, we examined 8-nitroG formation in A549 cultured human lung epithelial cells treated with indium compounds, including nanoparticles of indium oxide (In₂O₃) and indium-tin oxide (ITO), and indium chloride (InCl₃). We performed fluorescent immunocytochemistry to examine 8-nitroG formation in indium-exposed A549 cells. All indium compounds significantly increased 8-nitroG formation in A549 cells at 5 ng/ml after 4 h incubation. 8-NitroG formation was largely reduced by 1400 W, methyl-β-cyclodextrin (MBCD) and monodansylcadaverine (MDC), suggesting the involvement of nitric oxide synthase and endocytosis. 8-NitroG formation in A549 cells was also largely suppressed by small interfering RNA (siRNA) for high-mobility group box-1 (HMGB1), receptor for advanced glycation and end products (AGER, RAGE) and Toll-like receptor 9 (TLR9). These results suggest that indium compounds induce inflammation-mediated DNA damage in lung epithelial cells via the HMGB1-RAGE-TLR9 pathway. This mechanism may contribute to indium-induced genotoxicity in the respiratory system.

Role of Non-Coding RNAs in the Development of Targeted Therapy and Immunotherapy Approaches for Chronic Lymphocytic Leukemia

In the past decade, novel targeted therapy approaches, such as BTK inhibitors and Bcl2 blockers, and innovative treatments that regulate the immune response against cancer cells, such as monoclonal antibodies, CAR-T cell therapy, and immunomodulatory molecules, have been established to provide support for the treatment of patients. However, drug resistance development and relapse are still major challenges in CLL treatment. Several studies revealed that non-coding RNAs have a main role in the development and progression of CLL. Specifically, microRNAs (miRs) and tRNA-derived small-RNAs (tsRNAs) were shown to be outstanding biomarkers that can be used to diagnose and monitor the disease and to possibly anticipate drug resistance and relapse, thus supporting physicians in the selection of treatment regimens tailored to the patient needs. In this review, we will summarize the most recent discoveries in the field of targeted therapy and immunotherapy for CLL and discuss the role of ncRNAs in the development of novel drugs and combination regimens for CLL patients.

Novel HDAC inhibitor Chidamide synergizes with Rituximab to inhibit diffuse large B-cell lymphoma tumour growth by upregulating CD20

Loss of CD20 is a major obstacle for the retreatment of relapsed/refractory diffuse large B cell lymphoma (DLBCL) with Rituximab-associated regimens. Histone deacetylation causes gene silencing and inhibits CD20 expression. Chidamide is a novel inhibitor for histone deacetylases (HDACs). We hypothesize that Chidamide could overcome Rituximab-mediated down-regulation of CD20 and facilitate Rituximab-induced killing. In this study, we determine the mechanism of synergy of Chidamide with Rituximab in DLBCL using in vitro and in vivo models. We found that the levels of CD20 protein surface expression on five DLBCL cell lines were significantly and positively correlated with the sensitivities of cells to Rituximab. Treatment with Rituximab significantly reduced CD20 surface expression at the protein levels. RNA sequencing showed that Chidamide significantly increased expression of more than 2000 transcriptomes in DLBCL cells, around 1000 transcriptomes belong to the cell membrane and cell periphery pathways, including MS4A1. Chidamide significantly increased CD20 surface expression in DLBCL cell lines. Combination with Chidamide significantly synergized Rituximab-induced cell death in vitro and significantly inhibited tumour growth in DLBCL-bearing xenograft mice. A patient with relapsed/refractory DLBCL achieved a complete response after three cycles combined treatment with Chidamide and Rituximab. In conclusion, our data demonstrate for the first time that inhibition of HDACs by Chidamide significantly enhanced Rituximab-induced tumour growth inhibition in vitro and in vivo. We propose that CD20 surface expression should be used clinically to evaluate treatment response in patients with DLBCL. Chidamide is a promising sensitizer for the retreatment of DLBCL with Rituximab.

The BET inhibitor GS-5829 targets chronic lymphocytic leukemia cells and their supportive microenvironment

Despite major improvements in treatment outcome with novel targeted therapies, such as the Bruton tyrosine kinase (BTK) inhibitor ibrutinib, chronic lymphocytic leukemia (CLL) remains incurable in the majority of patients. Activation of PI3K, NF-κB, and/or MYC has been linked to residual disease and/or resistance in ibrutinib-treated patients. These pathways can be targeted by inhibitors of bromodomain and extra-terminal (BET) proteins. Here we report about the preclinical activity of GS-5829, a novel BET inhibitor, in CLL. GS-5829 inhibited CLL cell proliferation and induced leukemia cell apoptosis through deregulation of key signaling pathways, such as BLK, AKT, ERK1/2, and MYC. IκBα modulation indicates that GS-5829 also inhibited NF-κB signaling. GS-5829-induced apoptosis resulted from an imbalance between positive (BIM) and negative regulators (BCL-X_L) of the intrinsic apoptosis pathway. The antileukemia activity of GS-5829 increased synergistically in combinations with B-cell receptor signaling inhibitors, the BTK inhibitor ibrutinib, the PI3Kδ inhibitor idelalisib, and the SYK inhibitor entospletinib. In cocultures that mimic the lymph node microenvironment, GS-5829 inhibited signaling pathways within nurselike cells and their growth, indicating that BET inhibitors also can target the supportive CLL microenvironment. Collectively, these data provide a rationale for the clinical evaluation of BET inhibitors in CLL.

Effect of high mobility group box 1 on Toll-like receptor 9 in B cells in myeloperoxidase-ANCA-associated vasculitis

High mobility group box 1 (HMGB1) played pathogenic role in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Recent findings demonstrated that Toll-like receptor 9 (TLR9) was involved in B cell tolerance breaking of autoimmune disease, including AAV. Here, we investigated the effect of HMGB1 on TLR9 in B cells of AAV. In the present work, patients with myeloperoxidase (MPO)-AAV in active stage were recruited. Intracellular TLR9 expression in various B cell subpopulations of the whole blood was detected by flow cytometry and the correlation with clinical data was analysed. Our results showed that intracellular TLR9 expression in B cells, memory B cells and plasmablasts correlated with erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP). In particular, TLR9 expression in plasma cells correlated with ESR, CRP, serum creatinine, eGFR, and Birmingham Vasculitis Activity Score. To further explore the effect of HMGB1 on B cell, peripheral blood mononuclear cells (PBMCs) from AAV patients were isolated. After stimulated with HMGB1, TLR9 expression in various B cell subpopulations and proliferation ratio of live B cells were analysed by flow cytometry. We found that TLR9 expression in plasma cells and the proliferation ratio of live B cells by HMGB1 stimulation were significantly upregulated compared with the control group. Therefore, TLR9 expression in plasma cells was associated with disease activity of MPO-AAV. HMGB1 could enhance TLR9 expression in plasma cells and B cell proliferation. These indicated a role of HMGB1 on TLR9 in B cells in MPO-AAV, which would provide potential clues for intervention strategies.

Tumor-Associated Macrophages in Hematologic Malignancies: New Insights and Targeted Therapies

The growth of hematologic malignant cells can be facilitated by other non-tumor cells within the same microenvironment, including stromal, vascular, immune and mesenchymal stem cells. Macrophages are an integral part of the human innate immune system and the tumor microenvironment. Complex interplays between the malignant hematologic cells and the infiltrating macrophages promote the formation of leukemia, lymphoma or myeloma-associated macrophages. These pro-tumorigenic macrophages in turn play an important part in facilitating tumor growth, metastasis and chemotherapeutic resistance. Previous reports have highlighted the association between tumor-associated macrophages (TAMs) and disease progression in hematologic malignancies. This review summarizes the role of TAMs in different subtypes of leukemia, lymphoma and myeloma, focusing on new insights and targeted therapies.

Targeting the Immune Microenvironment in Lymphomas of B-Cell Origin: From Biology to Clinical Application

In lymphomas of B-cell origin, cancer cells orchestrate an inflammatory microenvironment of immune and stromal cells that sustain the tumor cell survival and growth, known as a tumor microenvironment (TME). The features of the TME differ between the different lymphoma types, ranging from extremely inflammatory, such as in Hodgkin lymphoma, to anergic, leading to immune deficiency and susceptibility to infections, such as in chronic lymphocytic leukemia. Understanding the characteristic features of the TME as well as the interactions between cancer and TME cells has given insight into the pathogenesis of most lymphomas and contributed to identify novel therapeutic targets. Here, we summarize the preclinical data that contributed to clarifying the role of the immune cells in the TME of different types of lymphomas of B-cell origin, and explain how the understanding of the biological background has led to new clinical applications. Moreover, we provide an overview of the clinical results of trials that assessed the safety and efficacy of drugs directly targeting TME immune cells in lymphoma patients.

Study of gene expressions' correlation structures in subgroups of Chronic Lymphocytic Leukemia Patients

In chronic lymphocytic leukemia (CLL) the interaction of leukemic cells with the microenvironment ultimately affects patient outcome. CLL cases can be divided in two subgroups with different clinical course based on the mutational status of the immunoglobulin heavy variable (IGHV) genes: mutated CLL (M-CLL) and unmutated CLL (U-CLL). Since in CLL, the differentiated relation of genes between the two subgroups is of greater importance than the individual gene behavior, this paper investigates the differences between the groups' gene interactions, by comparing their correlation structures. Fisher's test and Zou's confidence intervals are employed to detect differences of correlation coefficients. Afterwards, networks created by the genes participating in most differences are estimated with the use of structural equation models (SEM). The analysis is enhanced with graph modeling in order to visualize the between group differences in the gene structures of the two subgroups. The applied methodology revealed stronger correlations between genes in U-CLL patients, a finding in line with related biomedical literature. Using SEM for multigroup analysis, different gene structures between the two groups of patients were confirmed. The study of correlation structures can facilitate the detection of differential gene expression profiles in CLL subgroups, with potential applications in other diseases. Comparison of correlations can be very useful in understanding the complex internal structural differences which signify the variations of a disease.

Blockade of HMGB1 signaling pathway by ethyl pyruvate inhibits tumor growth in diffuse large B-cell lymphoma

High mobility group box 1 (HMGB1) protein in the tumor microenvironment actively contributes to tumor progression but its role in diffuse large B-cell lymphoma (DLBCL) is unknown. The aim of this study was to determine the mechanism by which HMGB1 promotes tumor growth in DLBCL and whether blockade of HMGB1 signaling pathway could inhibit tumorigenesis. We report that HMGB1 promotes proliferation of DLBCL cells by activation of AKT, extracellular signal-regulated kinases 1/2 (ERK1/2), signal transducer and activator of transcription 3 (STAT3) and SRC Proto-Oncogene, Non-Receptor Tyrosine Kinase (Src). Ethyl pyruvate (EP), an anti-inflammatory agent, inhibits HMGB1 active release from DLBCL cells and significantly inhibited proliferation of DLBCL cells in vitro. Treatment with EP significantly prevented and inhibited tumor growth in vivo and prolonged DLBCL-bearing mice survival. EP significantly downregulated HMGB1 expression and phosphorylation of Src and ERK1/2 in mice lymphoma tissue. EP induced accumulation of the cell cycle inhibitor p27 but downregulated expression of cyclin-dependent kinase 2 (CDK2). Increased nuclear translocation of p27 interacted with CDK2 and cyclin A, which led to blockade of cell cycle progression at the G1 to S phase transition. In conclusion, we demonstrated for the first time that blockade of HMGB1-mediated signaling pathway by EP effectively inhibited DLBCL tumorigenesis and disease progression.

Increased autocrine interleukin-6 production is significantly associated with worse clinical outcome in patients with chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) remains incurable with current standard therapy. We have previously reported that an increased expression of interleukin‐6 (IL‐6) receptor CD126 leads to resistance of CLL cells to chemotherapy and worse prognosis for patients with CLL. In this study, we determine whether autocrine IL‐6 production by CLL B cells is associated with poor clinical outcome and explore IL‐6‐mediated survival mechanism in primary CLL cells. Our results demonstrate that higher levels of autocrine IL‐6 are significantly associated with shorter absolute lymphocyte doubling time, patients received treatment, without complete remission, advanced Binet stages, 17p/11q deletion, and shorter time to first time treatment and progression‐free survival. IL‐6 activated both STAT3 and nuclear factor kappa B (NF‐κB) in primary CLL cells. Blocking IL‐6 receptor and JAK2 inhibited IL‐6‐mediated activation of STAT3 and NF‐κB. Our study demonstrates that an increased autocrine IL‐6 production by CLL B‐cells are associated with worse clinical outcome for patients with CLL. IL‐6 promotes CLL cell survival by activating both STAT3 and NF‐κB through diverse signaling cascades. Neutralizing IL‐6 or blocking IL‐6 receptor might contribute overcoming the resistance of CLL cells to chemotherapy. We propose that the measurement of autocrine IL‐6 could be a useful approach to predict clinical outcome.

Lower expression of Bax predicts poor clinical outcome in patients with glioma after curative resection and radiotherapy/chemotherapy

BACKGROUND

The prognosis in patients with gliomas after surgical resection followed by radiotherapy and/or chemotherapy is still very poor. The pro-apoptotic protein Bax, a short-lived protein in cancers, plays important roles in the sensitivity of glioma cells to spontaneous and therapy-induced apoptosis but and its prognostic value in gliomas is unknown.

METHODS

By an immunohistochemical method, we determined Bax protein expression from 96 patients with gliomas after curative resection. Two statistical analyses were performed to evaluate the prognostic significance of Bax protein: an independent continuous and a multivariate categorical analysis, with test/validation set-defined cut points, and Kaplan-Meier estimated outcome measures of overall survival (OS) and relapse-free survival (RFS).

RESULTS

Bax protein levels in glioblastoma were significantly decreased compared with grade II gliomas. Lower levels of Bax expression confer worse OS (continuous P = 0.025; categorical P = 0.003) and RFS (continuous P = 0.014; categorical P < 0.0001) and negatively correlate with the grades of gliomas. Patients underwent radiotherapy followed by surgical resection showed significantly increased OS (median = 45 vs. 17 months) and RFS (median = 39 vs. 16 months). Patients with higher levels of Bax and radiotherapy showed greatly increased survival rates (median OS = 66 months and median RFS = 105 months). Lower expression of Bax also confers inferior clinical outcome for gliomas patients after chemotherapy with temozolomide (OS and RFS P < 0.0001).

CONCLUSION

Decreased expression of Bax correlates with poor clinical outcome in patients with gliomas. We propose that Bax protein levels can be used as a reliable prognostic marker for risk-stratify patients with gliomas after curative resection and radiotherapy and/or chemotherapy.

Hepatitis B virus-X protein regulates high mobility group box 1 to promote the formation of hepatocellular carcinoma

Hepatitis B virus (HBV) infection is a risk factor for hepatocellular carcinoma (HCC). HBV X protein (HBx) is an important carcinogen for HBV-induced HCC. When the HBx gene is integrated into the host cell genome, it is difficult to eradicate. The identification of an effective target to inhibit the oncogenic function of HBx is therefore critically important. The present study demonstrated that HBx, particularly truncated HBx, was expressed in several HBV-derived cell lines (e.g., Hep3B and SNU423). By analyzing data from The Cancer Genome Atlas, it was revealed that high expression of high mobility group box 1 (HMGB1) was associated with the process and prognosis of HCC. In vitro experiments confirmed that HBx could regulate the expression of HMGB1 and knockdown of HMGB1 could decrease the ability of HBx to promote cellular proliferation. HBx could also upregulate six transcription factors (GATA binding protein 3, Erb-B2 receptor tyrosine kinase 3, heat shock transcription factor 1, nuclear factor κB subunit 1, TATA-box binding protein and Kruppel-like factor 4), which could directly regulate HMGB1. By analyzing genes that are co-expressed with HMGB1, several signaling pathways associated with the development of HCC were identified. HBx and HMGB1 were revealed to be involved in these pathways, which may be the mechanism by which HBx promotes HCC by regulating HMGB1. These findings suggested that HMGB1 may be an effective target for inhibiting HBV-induced HCC.

The role of high-mobility group protein box 1 in lung cancer

High-mobility group protein box 1(HMGB1)is a ubiquitous highly conserved nuclear protein. Acting as a chromatin-binding factor, HMGB1 binds to DNA and plays an important role in stabilizing nucleosome formation, facilitating gene transcription, DNA repairing, inflammation, cell differentiation, and regulating the activity of steroid hormone receptors. Currently, HMGB1 is discovered to be related to development, progression, and targeted therapy of lung cancer, which makes it an attractive biomarker, and therapeutic target. This review aims to encapsulate the relationship between HMGB1 and lung cancer, suggesting that HMGB1 plays a pivotal role in initiation, development, invasion, metastasis, and prognosis of lung cancer.

Ibrutinib modifies the function of monocyte/macrophage population in chronic lymphocytic leukemia

In lymphoid organs, nurse-like cells (NLCs) show properties of tumor-associated macrophages, playing a crucial role in chronic lymphocytic leukemia (CLL) cell survival. Ibrutinib, a potent inhibitor of Bruton's tyrosine kinase (BTK), is able to counteract pro-survival signals in CLL cells. Since the effects on CLL cells have been studied in the last years, less is known about the influence of ibrutinib on NLCs properties. We sought to determine how ibrutinib modifies NLCs functions focusing on the balance between immunosuppressive and inflammatory features. Our data show that ibrutinib targets BTK expressed by NLCs modifying their phenotype and function. Treatment with ibrutinib reduces the phagocytic ability and increases the immunosuppressive profile of NLCs exacerbating the expression of M2 markers. Accordingly, ibrutinib hampers LPS-mediated signaling, decreasing STAT1 phosphorylation, while allows IL-4-mediated STAT6 phosphorylation. In addition, NLCs treated with ibrutinib are able to protect CLL cells from drug-induced apoptosis partially through the secretion of IL-10. Results from patient samples obtained prior and after 1 month of treatment with ibrutinib show an accentuation of CD206, CD11b and Tie2 in the monocytic population in the peripheral blood. Our study provides new insights into the immunomodulatory action of ibrutinib on monocyte/macrophage population in CLL.

STAT3 and NF-κB cooperatively control in vitro spontaneous apoptosis and poor chemo-responsiveness in patients with chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is an adult disease characterized by in vivo accumulation of mature CD5/CD19/CD23 triple positive B cells and is currently incurable. CLL cells undergo spontaneous apoptosis in response to in vitro cell culture condition but the underlying mechanism is unclear. We hypothesize that the sensitivity of CLL cells to spontaneous apoptosis may be associated with the constitutive activities of transcription factors STAT3 and/or NF-κB. We now show that the sensitivity of fresh CLL cells to spontaneous apoptosis is highly variable among different patients during 48 hours’ cell culture and inversely correlated with in vivo constitutively activated STAT3 and NF-κB (p < 0.001). Both activated STAT3 and NF-κB maintain the levels of anti-apoptotic protein Mcl-1/Bcl-xL and autocrine IL-6 production. CLL cells with higher susceptibility to in vitro spontaneous apoptosis show the greatest chemosensitivity (p < 0.001), which is reflected clinically as achieving a complete response (CR) (p < 0.001), longer lymphocyte doubling times (p < 0.01), time to first treatment (p < 0.01), and progression free survival (p < 0.05). Our data suggest that the sensitivity of CLL cells to in vitro spontaneous apoptosis is co-regulated by constitutively activated STAT3 and NF-κB and reflects the in vivo chemo-responsiveness and clinical outcomes.

Revisiting the role of interleukin-8 in chronic lymphocytic leukemia

The proliferation and survival of malignant B cells in chronic lymphocytic leukemia (CLL) depend on signals from the microenvironment in lymphoid tissues. Among a plethora of soluble factors, IL-8 has been considered one of the most relevant to support CLL B cell progression in an autocrine fashion, even though the expression of IL-8 receptors, CXCR1 and CXCR2, on leukemic B cells has not been reported. Here we show that circulating CLL B cells neither express CXCR1 or CXCR2 nor they respond to exogenous IL-8 when cultured in vitro alone or in the presence of monocytes/nurse-like cells. By intracellular staining and ELISA we show that highly purified CLL B cells do not produce IL-8 spontaneously or upon activation through the B cell receptor. By contrast, we found that a minor proportion (<0.5%) of contaminating monocytes in enriched suspensions of leukemic cells might be the actual source of IL-8 due to their strong capacity to release this cytokine. Altogether our results indicate that CLL B cells are not able to secrete or respond to IL-8 and highlight the importance of methodological details in in vitro experiments.