CD44-ligation induces, through ERK1/2 pathway, synthesis of cytokines TNF-alpha and IL-6 required for differentiation of THP-1 monoblastic leukemia cells

Structural characterization and biological evaluation of a new O-acetyl-1,4-linked-β-d-mannan possessed potential application in hydrophilic polymer materials from Dendrobium devonianum

To explore the active polysaccharides from Dendrobium devonianum, a novel O-acetylmannan (DDP-1) with molecular weight of 117 kDa was isolated from D. devonianum. The chemical and instrumental analysis indicated that the DDP-1 was a homopolysaccharide containing a backbone chain composed of →4)-β-d-Manp-(1 → (71.4%) residue with internal →4)-2-O-acetyl-β-d-Manp-(1 → (14.2%), →4)-3-O-acetyl-β-d-Manp-(1 → (7.1%), and non-reducing end β-d-Manp-(1 → (7.3%) residues. Anticancer assay in vitro revealed that DDP-1 had anticancer activity against the growth of HepG2 and MCF-7 cancer cells. Moreover, cytokine secretion assays also presented that DDP-1 can promote cytokine production of TNF-α and IL-6 in THP-1 macrophage stimulated by PMA. Finally, the effects of isolation and purification on the microstructure of DDP-1 was studied by scanning electron microscope. The morphological features of DDP-1 indicated that DDP-1 hold high potential application in hydrophilic polymer materials.

Oroxylin A, a natural compound, mitigates the negative effects of TNFα-treated acute myelogenous leukemia cells

Tumor necrosis factor alpha (TNFα) is a complicated cytokine which is involved in proliferation and differentiation of acute myelogenous leukemia (AML) cells through a poorly understood mechanism. Mechanistic studies indicate that TNFα induced binding of PI3K subunit p85α to N-terminal truncated nuclear receptor RXRα (tRXRα) proteins, and activated AKT. The activated PI3K/AKT pathway negatively regulated differentiation of AML cells through the upregulation of c-Myc. In addition, TNFα also induced activation of nuclear factor κB (NF-κB), a nuclear transcription factor which was shown to promote cell proliferation. The present study demonstrates that oroxylin A, a natural compound isolated from Scutellariae radix, sensitizes leukemia cells to TNFα and markedly enhances TNFα-induced growth inhibition and differentiation of AML cell including human leukemia cell lines and primary AML cells. Activation of PI3K/AKT pathway could be inhibited by oroxylin A through inhibiting expression of tRXRα in NB4 and HL-60-resistant cells. Furthermore, we found that oroxylin A inhibited the activation of NF-κB and the DNA binding activity by TNFα proved by EMSA in these two AML cell lines. Moreover, in vivo studies showed that treatment with oroxylin A in combination with TNFα decreased AML cell population and prolonged survival in NOD/SCID mice with xenografts of primary AML cells. Overall, our results indicate that oroxylin A is able to inhibit the negative effects of TNFα for AML therapy, suggesting that combination of oroxylin A and TNFα have the potential to delay growth or eliminate the abnormal leukemic cells, thus representing a promising strategy for AML treatment.

1,4-β-d-Glucomannan from Dendrobium officinale Activates NF-кB via TLR4 to Regulate the Immune Response

2,3-O-acetylated-1,4-β-d-glucomannan (DOP-1-1) is a polysaccharide isolated from the stem of Dendrobium officinale. DOP-1-1 has been demonstrated to have remarkable immunomodulatory properties, but little is known about the influence of its structural diversity on bioactivity (and even less about the exact mechanism underlying its immune responses). First, DOP-1-1 was stabilized at different temperatures and pH conditions based on differential scanning calorimetry and size exclusion-chromatography–high-performance liquid chromatography. Then, a detailed study on the effects of DOP-1-1 on a human leukemia monocytic cell line (THP-1) under normal conditions was undertaken. DOP-1-1 promoted the translocation of nuclear factor-kappa B (NF-κB) and degradation of IκB proteins. The expression of genes and proteins closely associated with the immune, survival and apoptotic functions of NF-κB were analyzed by quantitative real-time RT-PCR. Furthermore, CCL4 and IP10 were confirmed to be the novel targets of the immune response stimulated by DOP-1-1. The phosphorylation of NF-кB was inhibited by treatment with a toll-like receptor 4 (TLR4) antagonist (TAK-242) and myeloid differentiation factor 88 (MyD88) inhibitor (ST2825). These data suggested: (i) the O-acetylated glucomannan DOP-1-1 is present in the steady state in low-pH solutions; (ii) DOP-1-1 can induce an immune response through NF-кB mediated by a TLR4 signaling pathway; and (iii) CCL4 and IP10 could be the novel targets of the immune response stimulated by O-acetylated glucomannan.

BTKCys481Ser drives ibrutinib resistance via ERK1/2 and protects BTKwild-type MYD88-mutated cells by a paracrine mechanism

Acquired ibrutinib resistance due to BTK^Cys481 mutations occurs in B-cell malignancies, including those with MYD88 mutations. BTK^Cys481 mutations are usually subclonal, and their relevance to clinical progression remains unclear. Moreover, the signaling pathways that promote ibrutinib resistance remain to be clarified. We therefore engineered BTK^Cys481Ser and BTK^WT expressing MYD88-mutated Waldenström macroglobulinemia (WM) and activated B-cell (ABC) diffuse large B-cell lymphoma (DLBCL) cells and observed reactivation of BTK-PLCγ2-ERK1/2 signaling in the presence of ibrutinib in only the former. Use of ERK1/2 inhibitors triggered apoptosis in BTK^Cys481Ser-expressing cells and showed synergistic cytotoxicity with ibrutinib. ERK1/2 reactivation in ibrutinib-treated BTK^Cys481Ser cells was accompanied by release of many prosurvival and inflammatory cytokines, including interleukin-6 (IL-6) and IL-10 that were also blocked by ERK1/2 inhibition. To clarify if cytokine release by ibrutinib-treated BTK^Cys481Ser cells could protect BTK^WT MYD88-mutated malignant cells, we used a Transwell coculture system and showed that nontransduced BTK^WT MYD88-mutated WM or ABC DLBCL cells were rescued from ibrutinib-induced killing when cocultured with BTK^Cys481Ser but not their BTK^WT-expressing counterparts. Use of IL-6 and/or IL-10 blocking antibodies abolished the protective effect conferred on nontransduced BTK^WT by coculture with BTK^Cys481Ser expressing WM or ABC DLBCL cell counterparts. Rebound of IL-6 and IL-10 serum levels also accompanied disease progression in WM patients with acquired BTK^Cys481 mutations. Our findings show that the BTK^Cys481Ser mutation drives ibrutinib resistance in MYD88-mutated WM and ABC DLBCL cells through reactivation of ERK1/2 and can confer a protective effect on BTK^WT cells through a paracrine mechanism.

Hyaluronan size alters chondrogenesis of adipose-derived stem cells via the CD44/ERK/SOX-9 pathway

Hyaluronan (HA) is a natural linear polymer that is one of the main types of extracellular matrix during the early stage of chondrogenesis. We found that the chondrogenesis of adipose-derived stem cells (ADSCs) can be initiated and promoted by the application of HA to mimic the chondrogenic niche. The aim of this study is to investigate the optimal HA molecular weight (Mw) for chondrogenesis of ADSCs and the detailed mechanism. In this study, we investigated the relationships among HA Mw, CD44 clustering, and the extracellular signal-regulated kinase (ERK)/SOX-9 pathway during chondrogenesis of ADSCs. Human ADSCs (hADSCs) and rabbit ADSCs (rADSCs) were isolated and expanded. Chondrogenesis was induced in rADSCs by culturing cells in HA-coated wells (HA Mw: 80 kDa, 600 kDa and 2000 kDa) and evaluated by examining cell aggregation, chondrogenic gene expression (collagen type II and aggrecan) and sulfated glycosaminoglycan (sGAG) deposition in vitro. Cartilaginous tissue formation in vivo was confirmed by implanting HA/rADSCs into joint cavities. CD44 clustering, ERK phosphorylation, SOX-9 expression and SOX-9 phosphorylation in cultured hADSCs were further evaluated. Isolated and expanded rADSCs showed multilineage potential and anchorage-independent growth properties. Cell aggregation, chondrogenic gene expression, and sGAG deposition increased with increasing HA Mw in rADSCs. The 2000 kDa HA had the most pronounced chondrogenic effect on rADSCs in vitro, and implanted 2000 kDa HA/rADSCs exhibited marked cartilaginous tissue formation in vivo. CD44 clustering and cell aggregation of hADSCs were enhanced by an increase in HA Mw. In addition, higher HA Mws further enhanced CD44 clustering, ERK phosphorylation, and SOX-9 expression and phosphorylation in hADSCs. Inhibiting CD44 clustering in hADSCs reduced HA-induced chondrogenic gene expression. Inhibiting ERK phosphorylation also simultaneously attenuated HA-induced SOX-9 expression and phosphorylation and chondrogenic gene expression in hADSCs. Our results indicate that HA initiates ADSC chondrogenesis and that higher Mw HAs exhibit stronger effects, with 2000 kDa HA having the strongest effect. These effects may be mediated through increased CD44 clustering and the ERK/SOX-9 signaling pathway.

STATEMENT OF SIGNIFICANCE

HA-based biomaterials have been studied in stem cell-based articular cartilage tissue engineering. However, little is known about the optimal HA size for stem cell chondrogenesis and the mechanism of how HA size modulates stem cell chondrogenesis. Accordingly, we used HAs with various Mws (80-2000 kDa) as culture substrates and tested their chondrogenic effect on ADSCs. Our results demonstrated that HAs with a Mw of 2000 kDa showed the optimal effect for chondrogenesis of ADSCs. Moreover, we found that HA size can regulate ADSC chondrogenesis via the CD44/ERK/SOX-9 pathway. This finding provides new information regarding the biochemical control of chondrogenesis by HA substrates that may add value to the development of HA-based biomaterials for articular cartilage regeneration.

The activation of EGFR promotes myocardial tumor necrosis factor-α production and cardiac failure in endotoxemia

To study the effect of EGFR activation on the generation of TNF-α and the occurrence of cardiac dysfuncetion during sepsis, PD168393 and erlotinib (both are EGFR inhibitors) were applied to decreased the production of TNF-α and phosphrylation of ERK1/2 and p38 induced by LPS in cardiomyocytes. These results were further proved by specifically knocked down the expression of EGFR in vitro. Both TAPI-1, a TNF-α converting enzyme (TACE) inhibitor, and TGF-α neutralizing antibody could inhibit the activation of EGFR and the generation of TNF-α mRNA after LPS treatment. The increase of TGF-α in response to LPS could also be suppressed by TAPI-1. On the other hand, exogenous TGF-α increased the expression of TNF-α mRNA and partially reversed the inhibitory effect of TAPI-1 on expression of TNF-α mRNA in response to LPS indicating that the transactivation of EGFR by LPS in cardiomyocytes needs the help of TACE and TGF-α. In endotoxemic mice, inhibition the activation of EGFR not only decreased TNF-α production in the myocardium but also improved left ventricular pump function and ameliorated cardiac dysfunction and ultimately improved survival rate. All these results provided a new insight of how EGFR regulation the production of TNF-α in cardiomyocytes and a potential new target for the treatment of cardiac dysfunction in sepsis.

A novel role of breast cancer-derived hyaluronan on inducement of M2-like tumor-associated macrophages formation

Microenvironmental signals determine the differentiation types and distinct functions of macrophages. Tumor-associated macrophages (TAM) constitute major infiltrates around solid tumor cells and accelerate tumor progression due to their immunosuppressive functions. However, the mechanisms through which tumor microenvironment modulates macrophages transition are not completely elucidated. Hyaluronan (HA), a prominent component in tumor microenvironment, is a notable immunoregulator and its high level is often related to poor prognosis. Herein, we found that the number of M2 macrophages was highly correlated with HA expression in tumor tissues from breast cancer patients. Experimental data showed that breast cancer-derived HA stimulated M2-like TAM formation in a mouse model and had multiple effects on macrophages transformation in vitro, including upregulating CD204, CD206, IL-10 and TGF-β, activating STAT3 signal, and suppressing killing capacity. These data indicate that HA derived from breast cancer activates macrophages in an alternative manner. Further mechanism study revealed that HA-CD44-ERK1/2-STAT3 pathway served as an important regulator in M2-like TAM formation. Therefore, targeting TAM by abrogating HA-CD44 interaction may be a potential strategy for breast cancer immunotherapy.

Structural characterization and immunomodulating activity of polysaccharide from Dendrobium officinale

A neutral heteropolysaccharide (DOP-1-1) consisted by mannose and glucose (5.9:1) with an average molecular weight at about 1.78×10(5) Da was purified from Dendrobium officinale. Based on Fourier transform infrared spectrum (FT-IR) and nuclear magnetic resonance (NMR) spectra, it suggested that partial structure of DOP-1-1 is an O-acetylated glucomannan with β-d configuration in pyranose sugar forms. The immunomodulatory activity of DOP-1-1 was evaluated by secretion level of cytokine (interleukin (IL)-1β and IL-10) and tumor necrosis factor (TNF)-α in vitro. Our results suggested that DOP-1-1 could stimulate cytokine production (TNF-α, IL-1β) in cells. These findings demonstrated that the purified polysaccharide from D. officinale presented significant immune-modulating activities. Furthermore, by Western-blot we can found that the signaling pathways of DOP-1-1 induced immune activities involving ERK1/2 and NF-кB. As to antioxidant activity, DOP-1-1 hadn't showed remarkable scavenging capacity of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) in contrast with other studies of polysaccharides from D. officinale.

CD44 clustering is involved in monocyte differentiation

Differentiation of monocytes into macrophages is an important process under physiological and pathological conditions, but the underlying mechanism of monocyte differentiation is not completely clear. Some adhesion molecules have been reported to play an important role in cell differentiation. CD44 is an important adhesion molecule that mediates cell-cell and cell-matrix interaction, and participates in a wide variety of cellular functions. As CD44 has been reported to show different activated states between monocytes and macrophages, we propose that CD44 may be involved in monocyte differentiation. In this study, we explored the role of CD44 in monocyte differentiation and further studied the mechanisms that were involved in. THP-1 cells (human monocytic leukemia cell line) were induced with phorbol 12-myristate 13-acetate (PMA) to establish the model of monocyte differentiation in vitro. It was found that CD44 expression and binding capacity to hyaluronic acid were increased significantly, and the distribution of CD44 was converted into clusters during differentiation. The PMA-induced CD44 clustering and CD44 high expression were suppressed by blocking CD44, which resulted in the inhibition of CD14 expression. PMA-induced phosphorylation of ERK1/2 signal was also suppressed by blocking CD44. Our results suggested that CD44 was involved in monocyte differentiation. The mechanisms of monocyte differentiation following CD44 activation may include CD44 high expression and clustering which in turn lead to phosphorylation of ERK1/2.

CD44 ligation with A3D8 antibody induces apoptosis in acute myeloid leukemia cells through binding to CD44s and clustering lipid rafts

CD44 is a cell surface antigen expressed on acute myeloid leukemia cells and is used as a marker to isolate leukemia stem cells. CD44 ligation with the antibody A3D8 has been found to induce apoptosis in human acute promyelocytic leukemia (APL) cells via activation of caspase-8. The mechanism of A3D8-induced caspase-8 activation was studied in APL NB4 cells. A3D8 induces lipid raft clustering which causes Fas aggregation as determined with a confocal microscope. A3D8-induced apoptosis is abrogated by the lipid raft disrupting agent methyl-β-cyclodextrin and the caspase-8 inhibitor Z-IETD-fmk. Western blot analysis reveals that A3D8 binds to the standard form of CD44 (CD44s). HL-60 cells without detectable CD44s protein are not responsive to A3D8-induced apoptosis. SKNO-1 cells containing higher level of CD44s protein are more sensitive to A3D8-induced apoptosis than NB4 cells. These results indicate that A3D8 induces apoptosis in leukemia cells through caspase-8 activation by binding to CD44s protein and inducing lipid raft clustering.

The biology of CD44 and HCELL in hematopoiesis: the 'step 2-bypass pathway' and other emerging perspectives

PURPOSE OF REVIEW

The homing and egress of hematopoietic stem and progenitor cells (HSPCs) to and from marrow, respectively, and the proliferation and differentiation of HSPCs within marrow are complex processes critically regulated by the ordered expression and function of adhesion molecules that direct key cell-cell and cell-matrix interactions. The integral membrane molecule CD44, known primarily for its role in binding hyaluronic acid, is characteristically expressed on HSPCs. Conspicuously, human HSPCs uniquely display a specialized glycoform of CD44 known as hematopoietic cell E-/L-selectin ligand (HCELL), which is the most potent ligand for both E-selectin and L-selectin expressed on human cells. This review focuses on recent advances in our understanding of the biology of CD44 and HCELL in hematopoiesis.

RECENT FINDINGS

New data indicate that CD44-mediated events in hematopoiesis are more complex than previously imagined. Ex-vivo glycan engineering has established that HCELL serves as a 'bone marrow homing receptor'. Moreover, biochemical studies now show that CD44 forms bimolecular complexes with a variety of membrane proteins, one of which is VLA-4. Engagement of CD44 or of HCELL directly induces VLA-4 activation via G-protein-dependent signaling, triggering a 'step 2-bypass pathway' of cell migration, and extravascular lodgment, in absence of chemokine receptor engagement.

SUMMARY

Recent studies have further clarified the roles of CD44 and its glycoform HCELL in hematopoietic processes, providing key insights on how targeting these molecules may be beneficial in promoting hematopoiesis and in treating hematologic malignancies.

CD44 in hematological neoplasias

The CD44 protein family spans a large group of transmembrane glycoproteins acquired by alternative splicing and post-translational modifications. The great heterogeneity in molecular structure is reflected in its various important functions: CD44 mediates (1) interaction between cell and extracellular matrix, (2) signal submission, e.g., by acting as co-receptor for membrane-spanning receptor tyrosine kinases or by association with intracellular molecules initiating several signaling pathways, and (3) anchor function connecting to the cytoskeleton via the ezrin-radixin-moesin protein family. The expression pattern of the different CD44 isoforms display strong variations dependent on cell type, state of activation, and differentiation stage. In hematopoietic cells, CD44 mediates interaction of progenitor cells and bone marrow stroma during hematopoiesis, regulates maturation, and activation-induced cell death in T cells, influences neutrophil and macrophage migration as well as cytokine production, and participates in lymphocyte extravasation and migration. CD44 is involved in development and progress of hematological neoplasias by enhancement of apoptotic resistance, invasiveness, as well as regulation of bone marrow homing, and mobilization of leukemia-initiating cells into the peripheral blood. Thereby altered CD44 expression functions as marker for worse prognosis in most hematological malignancies. Additionally, CD44 expression levels can be used to distinguish between different hematological neoplasias and subtypes. Concerning new treatment strategies, CD44 displays promising potential either by direct targeting of CD44 expressed on the malignant cells or reversing an acquired resistance to primary treatment mediated through altered CD44 expression. The former can be achieved by antibody or hyaluronan-based immunotherapy.