STIM2 is involved in the regulation of apoptosis and the cell cycle in normal and malignant monocytic cells

Calcium is a ubiquitous messenger that regulates a wide range of cellular functions, but its involvement in the pathophysiology of acute myeloid leukemia (AML) is not widely investigated. Here, we identified, from an analysis of The Cancer Genome Atlas and genotype-tissue expression databases, stromal interaction molecule 2 (STIM2) as being highly expressed in AML with monocytic differentiation and negatively correlated with overall survival. This was confirmed on a validation cohort of 407 AML patients. We then investigated the role of STIM2 in cell proliferation, differentiation, and survival in two leukemic cell lines with monocytic potential and in normal hematopoietic stem cells. STIM2 expression increased at the RNA and protein levels upon monocyte differentiation. Phenotypically, STIM2 knockdown drastically inhibited cell proliferation and induced genomic stress with DNA double-strand breaks, as shown by increased levels of phosphorylate histone H2AXγ (p-H2AXγ), followed by activation of the cellular tumor antigen p53 pathway, decreased expression of cell cycle regulators such as cyclin-dependent kinase 1 (CDK1)-cyclin B1 and M-phase inducer phosphatase 3 (CDC25c), and a decreased apoptosis threshold with a low antiapoptotic/proapoptotic protein ratio. Our study reports STIM2 as a new actor regulating genomic stability and p53 response in terms of cell cycle and apoptosis of human normal and malignant monocytic cells.

Aortic valve calcification is promoted by interleukin-8 and restricted through antagonizing CXC motif chemokine receptor 2

AIMS

Inflammatory cytokines play a critical role in the progression of calcific aortic valve disease (CAVD), for which there is currently no pharmacological treatment. The aim of this study was to test the hypothesis that interleukin-8 (IL-8), known to be involved in arterial calcification, also promotes aortic valve calcification (AVC) and to evaluate whether pharmacologically blocking the IL-8 receptor, CXC motif chemokine receptor 2 (CXCR2), could be effective in preventing AVC progression.

METHODS AND RESULTS

A cohort of 195 patients (median age 73, 74% men) diagnosed with aortic valve stenosis (severe in 16.9% of cases) were prospectively followed by CT for a median time of 2.6 years. A Cox proportional hazards regression analysis indicated that baseline IL-8 serum concentrations were associated with rapid progression of AVC, defined as an annualized change in the calcification score by CT ≥ 110 AU/year, after adjustment for age, gender, bicuspid anatomy, and baseline disease severity. In vitro, exposure of primary human aortic valvular interstitial cells (hVICs) to 15 pg/mL IL-8 induced a two-fold increase in inorganic phosphate (Pi)-induced calcification. IL-8 promoted NFκB pathway activation, MMP-12 expression, and elastin degradation in hVICs exposed to Pi. These effects were prevented by SCH527123, an antagonist of CXCR2. The expression of CXCR2 was confirmed in hVICs and samples of aortic valves isolated from patients with CAVD, in which the receptor was mainly found in calcified areas, along with MMP-12 and a degraded form of elastin. Finally, in a rat model of chronic kidney disease-associated CAVD, SCH527123 treatment (1 mg/kg/day given orally for 11 weeks) limited the decrease in aortic cusp separation, the increase in maximal velocity of the transaortic jet, and the increase in aortic mean pressure gradient measured by echocardiography, effects that were associated with a reduction in hydroxyapatite deposition and MMP-12 expression in the aortic valves.

CONCLUSION

Overall, these results highlight, for the first time, a significant role for IL-8 in the progression of CAVD by promoting calcification via a CXCR2- and MMP-12-dependent mechanism that leads to elastin degradation, and identify CXCR2 as a promising therapeutic target for the treatment of CAVD.

Indoxyl sulfate impairs erythropoiesis at BFU-E stage in chronic kidney disease

Chronic kidney disease (CKD) is a global health condition characterized by a progressive deterioration of kidney function. It is associated with high serum levels of uremic toxins (UT), such as Indoxyl Sulfate (IS), which may participate in the genesis of several uremic complications. Anemia is one of the major complications in CKD patients that contribute to cardiovascular disease, increase morbi-mortality, and is associated with a deterioration of kidney failure in these patients. Our study aimed to characterize the impact of IS on CKD-related erythropoiesis. Using cellular and pre-clinical models, we studied cellular and molecular effects of IS on the growth and differentiation of erythroid cells. First, we examined the effect of clinically relevant concentrations of IS (up to 250 μM) in the UT7/EPO cell line. IS at 250 μM increased apoptosis of UT7/EPO cells at 48 h compared to the control condition. We confirmed this apoptotic effect of IS in erythropoiesis in human primary CD34⁺ cells during the later stages of erythropoiesis. Then, in IS-treated human primary CD34⁺ cells and in a (5/6 Nx) mice model, a blockage at the burst-forming unit-erythroid (BFU-E) stage of erythropoiesis was also observed. Finally, IS deregulates a number of erythropoietic related genes such as GATA-1, Erythropoietin-Receptor (EPO-R), and β-globin. Our findings suggest that IS could affect cell viability and differentiation of erythroid progenitors by altering erythropoiesis and contributing to the development of anemia in CKD.

Red blood cell proteomics reveal remnant protein biosynthesis and folding pathways in PIEZO1-related hereditary xerocytosis

Hereditary xerocytosis is a dominant red cell membrane disorder characterized by an increased leak of potassium from the inside to outside the red blood cell membrane, associated with loss of water leading to red cell dehydration and chronic hemolysis. 90% of cases are related to heterozygous gain of function mutations in PIEZO1, encoding a mechanotransductor that translates a mechanical stimulus into a biological signaling. Data are still required to understand better PIEZO1-HX pathophysiology. Recent studies identified proteomics as an accurate and high-input tool to study erythroid progenitors and circulating red cell physiology. Here, we isolated red blood cells from 5 controls and 5 HX patients carrying an identified and pathogenic PIEZO1 mutation and performed a comparative deep proteomic analysis. A total of 603 proteins were identified among which 56 were differentially expressed (40 over expressed and 16 under expressed) between controls and HX with a homogenous expression profile within each group. We observed relevant modifications in the protein expression profile related to PIEZO1 mutations, identifying two main "knots". The first contained both proteins of the chaperonin containing TCP1 complex involved in the assembly of unfolded proteins, and proteins involved in translation. The second contained proteins involved in ubiquitination. Deregulation of proteins involved in protein biosynthesis was also observed in in vitro-produced reticulocytes after Yoda1 exposure. Thus, our work identifies significant changes in the protein content of PIEZO1-HX erythrocytes, revealing a "PIEZO1 signature" and identifying potentially targetable pathways in this disease characterized by a heterogeneous clinical expression and contra-indication of splenectomy.

Histone Deacetylases Function in the Control of Early Hematopoiesis and Erythropoiesis

Numerous studies have highlighted the role of post-translational modifications in the regulation of cell proliferation, differentiation and death. Among these modifications, acetylation modifies the physicochemical properties of proteins and modulates their activity, stability, localization and affinity for partner proteins. Through the deacetylation of a wide variety of functional and structural, nuclear and cytoplasmic proteins, histone deacetylases (HDACs) modulate important cellular processes, including hematopoiesis, during which different HDACs, by controlling gene expression or by regulating non-histone protein functions, act sequentially to provide a fine regulation of the differentiation process both in early hematopoietic stem cells and in more mature progenitors. Considering that HDAC inhibitors represent promising targets in cancer treatment, it is necessary to decipher the role of HDACs during hematopoiesis which could be impacted by these therapies. This review will highlight the main mechanisms by which HDACs control the hematopoietic stem cell fate, particularly in the erythroid lineage.

IL-8 promotes the calcification of human aortic valve interstitial cells, which is prevented through antagonizing CXCR1 and CXCR2 receptors

Background/Introduction

Inflammation is a key feature of calcific aortic valve stenosis (CAVS) against which there is currently no pharmacological treatment.

Purpose

To verify the hypothesis that interleukin-8 (IL-8), a pro-inflammatory factor involved in arterial calcifications, also promotes the calcification of human aortic valve interstitial cells (hVICs).

Methods

Primary hVICs were isolated from healthy pieces of aortic valves harvested from patients undergoing surgical valve replacement. They were cultured in a pro-calcifying condition (Pi-3.8mM) with or without IL-8 (5 to 50 pg/ml) for up to 21 days. Calcification was analysed by alizarin red staining and calcium content was measured with the o-cresolphthalein complexone method. The viability of hVICs was verified by the MTT assay. The expression of osteogenic (BMP2, OPN, osterix and ALP) and myofibrotic (alpha-SMA, collagen-1, collagen-3 and elastin) markers as well as that of metalloproteases (MMP-2, -9 and -12) was analysed by RT-qPCR. The expression of IL-8 receptors, CXCR-1 and CXCR-2 was evaluated by Western blot and flow cytometry, and the effects of IL-8 were tested in the presence or absence of SCH527123, an antagonist of CXCR-1 and CXCR-2. Finally, the expression of CXCR-1 and -2 and elastin was analysed by immunohistochemistry in the calcified and non-calcified areas of human aortic valve samples. All of these experiments were carried out from valves of at least 5 different donors and a P<0.05 was considered statistically significant.

Results

IL-8 (15 pg/mL) caused a significant ∼2-fold increase in the calcification of hVICs in the Pi condition, compared to the Pi-only condition, without modulation of cell viability. In the presence of Pi, IL-8 exposure significantly stimulated the expression of the transcripts of elastin and MMP-12, an elastase, and reduced that of OPN, a well-known inhibitor of calcification. The effects of IL-8 on hVICs calcification and on the expression of MMP-12, elastin and OPN transcripts were significantly prevented by the addition of SCH527123. In addition, the expression of CXCR-1 and -2 was confirmed in histological samples of human aortic valves. This expression was more pronounced in calcified areas compared to non-calcified areas and co-localized with degraded elastin.

Conclusion

IL-8 promoted the calcification of hVICs in culture. This effect was significantly prevented by antagonizing CXCR-1 and CXCR-2 IL-8 receptors, which we showed for the first time to be expressed by human VICs and aortic valves of patients with CAVS. Further studies are underway to clarify the cellular mechanisms involved.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Fédération Hospitalo-Universitaire REMOD-VHF

MO550INDOXYL SULFATE AFFECTS ERYTHROPOIESIS DURING THE COURSE OF CHRONIC KIDNEY DISEASE: A MOLECULAR STUDY

Background and Aims

Chronic kidney disease (CKD) is a global health condition characterized by a progressive deterioration of renal function due to high serum levels of uremic toxins. Anemia is a major trouble in CKD patients that contributes to a faster deterioration of renal failure, leading to cardiovascular disease and increasing morbimortality. Erythropoietin (EPO) is known to contribute to CKD-associated anemia. Thus, accumulation of uremic toxins in blood impairs EPO synthesis, leading to a subsequent impairment of erythropoiesis in the bone marrow. Very few molecular clues explain why erythropoiesis is affected in CKD or explain why erythropoiesis-stimulating agents (ESA) are not efficient in some patients with CKD. The current study aims to characterize the impact of one of the most representative uremic toxins, Indoxyl Sulfate (IS), in CKD-related anemia. IS is a protein-bound uremic toxin derived from the tryptophan dietary metabolism which is difficult to remove by dialysis. Our study demonstrates the molecular effects of IS on the growth and the differentiation of red blood cells in an erythroid cell line and in primary cell cultures CD34+.

Method

Firstly, we examined in vitro the time-courses of IS under clinically relevant concentrations of IS (250 µM -1 mM) in a human leukemic cell line in which proliferation is induced by EPO, the UT7/EPO cell line. Cell apoptosis, proliferation, differentiation and cell cycle analysis were assessed by the MACSQuant flow cytometry. Erythroid gene expression analysis was assessed by RT-qPCR (Quantstudio 7 flex). The ratio A260/280 assessed the quality of nucleic acids. Western blotting experiments were performed to study protein expression. Human primary CD34+ cells were obtained from mobilized peripheral blood mononuclear cells (MNC) of healthy subjects and were isolated by magnetic microbeads separation on MACS columns.

Results

IS at 250 µM and 1 mM increased apoptosis of UT7/EPO cell line at 48h compared to control condition. On the other hand, we found no significant effect of IS on the phenotype of UT7/EPO, when using CD235a (Glycophorin A), as a marker for the detection of the erythroid cell lineage.

Ki67 cellular levels, a cell proliferation marker, was not altered between control and IS experiments. This indicated that IS did not affect proliferation in UT7/EPO. At 48h, at the clinically relevant concentration of IS (250 µM), we observed an increase of the cell phase cycle Sub-G1. The analysis of erythropoiesis related genes shows that HIF2α was deregulated with IS (250 µM). Finally, in the Epo-EpoR signalling pathway, we studied the activation of the Jak2/Stat5 proteins.

Results in human primary CD34+ cells confirmed the apoptotic effect of IS observed in UT7/EPO.

Conclusion

Our findings suggest that IS, a representative protein-bound uremic toxin, could affect cell viability, apoptosis and the cell cycle. This study suggests clues to develop new therapies for CKD-associated anemia.

Optical genome mapping, a promising alternative to gold standard cytogenetic approaches in a series of acute lymphoblastic leukemias

Acute lymphoblastic leukemias (ALL) are characterized by a large number of cytogenetic abnormalities of clinical interest that require the use of several complementary techniques. Optical genome mapping (OGM) is based on analysis of ultra-high molecular weight DNA molecules that provides a high-resolution genome-wide analysis highlighting copy number and structural anomalies, including balanced translocations. We compared OGM to standard techniques (karyotyping, fluorescent in situ hybridization, single nucleotide polymorphism-array and reverse transcription multiplex ligation-dependent probe amplification) in 10 selected B or T-ALL. Eighty abnormalities were found using standard techniques of which 72 (90%) were correctly detected using OGM. Eight discrepancies were identified, while 12 additional anomalies were found by OGM. Among the discrepancies, four were detected in raw data but not retained because of filtering issues. However, four were truly missed, either because of a low variant allele frequency or because of a low coverage of some regions. Of the additional anomalies revealed by OGM, seven were confirmed by another technique, some of which are recurrent in ALL such as LMO2-TRA and MYC-TRB fusions. Despite false positive anomalies due to background noise and a case of inter-sample contamination secondarily identified, the OGM technology was relatively simple to use with little practice. Thus, OGM represents a promising alternative to cytogenetic techniques currently performed for ALL characterization. It enables a time and cost effective analysis allowing identification of complex cytogenetic events, including those currently inaccessible to standard techniques.

Ascorbic acid (vitamin C) synergistically enhances the therapeutic effect of targeted therapy in chronic lymphocytic leukemia

Background

Novel, less toxic, cost-effective and safe therapeutic strategies are needed to improve treatment of chronic lymphocytic leukemia (CLL). Ascorbic acid (AA, vitamin C) has shown a potential anti-cancer therapeutic activity in several cancers. However, the anti-cancer effects of ascorbic acid on CLL B-cells have not been extensively studied. We aimed in this study to evaluate the in vitro therapeutic activity using clinically relevant conditions.

Methods

Primary CLL B-cells and two CLL cell lines were exposed to a dose that is clinically achievable by AA oral administration (250 μM), and cell death and potential mechanisms were assessed. The role of the protective CLL microenvironment was studied. Synergistic interaction between AA and CLL approved drugs (Ibrutinib, Idelalisib and Venetoclax) was also evaluated.

Results

Ascorbic acid is cytotoxic for CLL B-cells at low dose (250 μM) but spares healthy B-cells. Ascorbic-acid-induced cytotoxicity involved pro-oxidant damage through the generation of reactive oxygen species in the extracellular media and in CLL cells, and induced caspase-dependent apoptosis. We also found that AA treatment overcame the supportive survival effect provided by microenvironment including bone marrow mesenchymal stem cells, T-cell cues (CD40L + IL-4), cytokines and hypoxia. Our data suggest that resistance to AA could be mediated by the expression of the enzyme catalase in some CLL samples and by the glucose metabolite pyruvate. We also demonstrated that AA synergistically potentiates the cytotoxicity of targeted therapies used in or being developed for CLL.

Conclusion

These preclinical results point to AA as an adjuvant therapy with potential to further improve CLL treatments in combination with targeted therapies.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s13046-020-01738-0.

TRIM37 is highly expressed during mitosis in CHON-002 chondrocytes cell line and is regulated by miR-223

Multiple molecular disorders can affect mechanisms regulating proliferation and differentiation of growth plate chondrocytes. Mutations in the TRIM37 gene cause the Mulibrey nanism, a heritable growth disorder. Since chondrocytes are instrumental in long bone growth that is deficient in nanism, we hypothesized that TRIM37 defect could contribute to dysregulation of the chondrocyte cell cycle. Western blotting, confocal microscopy and imaging flow cytometry determined TRIM37 expression in CHON-002 cell lineage. We showed that TRIM37 is expressed during mitosis of chondrocytes and directly impacted their proliferation. During the chondrocyte cell cycle, TRIM37 was present in both nucleus and cytoplasm. During M phase we observed an increase of the TRIM37-Tubulin co-localization in comparison with G1, S and G2 phases. TRIM37 knock down inhibited proliferation, together with cell cycle anomalies and increased autophagy, while overexpression accordingly enhanced cell proliferation. We demonstrated that microRNA-223 directly targets TRIM37, and suggest that miR-223 regulates TRIM37 gene expression during the cell cycle. In summary, our results give clues to explain why TRIM37 deficiency in chondrocytes impacts bone growth. Modulating TRIM37 using miR-223 could be an approach to increase chondrogenesis.

PIEZO1 activation delays erythroid differentiation of normal and hereditary xerocytosis-derived human progenitor cells

Hereditary xerocytosis is a dominantly inherited red cell membrane disorder caused in most cases by gain-of-function mutations in PIEZO1, encoding a mechanosensitive ion channel that translates a mechanic stimulus into calcium influx. We found that PIEZO1 was expressed early in erythroid progenitor cells, and investigated whether it could be involved in erythropoiesis, besides having a role in the homeostasis of mature red cell hydration. In UT7 cells, chemical PIEZO1 activation using YODA1 repressed glycophorin A expression by 75%. This effect was PIEZO1-dependent since it was reverted using specific short hairpin-RNA knockdown. The effect of PIEZO1 activation was confirmed in human primary progenitor cells, maintaining cells at an immature stage for longer and modifying the transcriptional balance in favor of genes associated with early erythropoiesis, as shown by a high GATA2/GATA1 ratio and decreased α/β-globin expression. The cell proliferation rate was also reduced, with accumulation of cells in G0/G1 of the cell cycle. The PIEZO1-mediated effect on UT7 cells required calcium-dependent activation of the NFAT and ERK1/2 pathways. In primary erythroid cells, PIEZO1 activation synergized with erythropoietin to activate STAT5 and ERK, indicating that it may modulate signaling pathways downstream of erythropoietin receptor activation. Finally, we studied the in-vitro erythroid differentiation of primary cells obtained from 14 PIEZO1-mutated patients, from 11 families, carrying ten different mutations. We observed a delay in erythroid differentiation in all cases, ranging from mild (n=3) to marked (n=8). Overall, these data demonstrate a role for PIEZO1 during erythropoiesis, since activation of PIEZO1 - both chemically and through activating mutations - delays erythroid maturation, providing new insights into the pathophysiology of hereditary xerocytosis.

Hepatocyte SLAMF3 reduced specifically the multidrugs resistance protein MRP-1 and increases HCC cells sensitization to anti-cancer drugs

Multidrug resistance MDR proteins (MRPs) are members of the C family of a group of proteins named ATP binding cassette (ABC) transporters. MRPs can transport drugs including anticancer drugs, nucleoside analogs, antimetabolites and tyrosine kinase inhibitors. Drugs used in HCC therapy, such as tyrosine kinase inhibitor sorafenib, are substrates of uptake and/or efflux transporters. Variable expression of MRPs at the plasma membrane of tumor cells may contribute to drug resistance and subsequent clinical response. Recently, we reported that the hepatocyte SLAMF3 expression (Signaling Lymphocytic Activation Molecule Family member 3) was reduced in tumor cells from hepatocellular carcinoma (HCC) compared to its high expression in adjacent tissues. In the present study, we make a strong correlation between induced SLAMF3 overexpression and the specific loss of MRP-1 expression and its functionalities as a drugs resistance transporter. No changes were observed on expression of ABCG2 and MDR. More importantly, we highlight a strong inverse correlation between MRP-1 and SLAMF3 expression in patients with HCC. We propose that the SLAMF3 overexpression in cancerous cells could represent a potential therapeutic strategy to improve the drugs sensibility of resistant cells and thus control the therapeutic failure in HCC patients.

DHEA prevents ribavirin-induced anemia via inhibition of glucose-6-phosphate dehydrogenase

Ribavirin has been widely used for antiviral therapy. Unfortunately, ribavirin-induced anemia is often a cause of limiting or interrupting treatment. Our team has observed that dehydroepiandrosterone (DHEA) has a protective effect against in vitro and in vivo ribavirin-induced hemolysis. The aim of this study was to better understand this effect as well as the underlying mechanism(s). DHEA was able to reduce in vitro intraerythrocytic ATP depletion induced by ribavirin. Only 1% of ATP remained after incubation with ribavirin (2 mM) at 37 °C for 24 h vs. 37% if DHEA (200 μM) was added (p < 0.01). DHEA also helped erythrocytes conserve their size, with a shrinkage of only 10% vs 40% at 24 h with ribavirin alone (p < 0.01), and reduced phosphatidylserine exposure at the outer membrane, i.e. 27% vs 40% at 48 h, (p < 0.05). DHEA also inhibits ribavirin-induced hemolysis, i.e. 34% vs 46.5% at 72 h (p < 0.01). DHEA is an inhibitor of glucose-6-phosphate dehydrogenase (G6PD), a key enzyme in the hexose monophosphate shunt connected to the glycolytic pathway which is the only energy supplier of the red blood cell in the form of ATP. We have confirmed this inhibitory effect in the presence of ribavirin. All these observations suggest that ribavirin-induced hemolysis was initiated by ATP depletion, and that the inhibitory effect of DHEA on G6PD was able to rescue enough ATP to limit this hemolysis. This mechanism could be important for improving the therapeutic management of patients treated with ribavirin.

Factors involved in CLL pathogenesis and cell survival are disrupted by differentiation of CLL B-cells into antibody-secreting cells

Recent research has shown that chronic lymphocytic leukemia (CLL) B-cells display a strong tendency to differentiate into antibody-secreting cells (ASCs) and thus may be amenable to differentiation therapy. However, the effect of this differentiation on factors associated with CLL pathogenesis has not been reported. In the present study, purified CLL B-cells were stimulated to differentiate into ASCs by phorbol myristate acetate or CpG oligodeoxynucleotide, in combination with CD40 ligand and cytokines in a two-step, seven-day culture system. We investigated (i) changes in the immunophenotypic, molecular, functional, morphological features associated with terminal differentiation into ASCs, (ii) the expression of factors involved in CLL pathogenesis, and (iii) the expression of pro- and anti-apoptotic proteins in the differentiated cells. Our results show that differentiated CLL B-cells are able to display the transcriptional program of ASCs. Differentiation leads to depletion of the malignant program and deregulation of the apoptosis/survival balance. Analysis of apoptosis and the cell cycle showed that differentiation is associated with low cell viability and a low rate of cell cycle entry. Our findings shed new light on the potential for differentiation therapy as a part of treatment strategies for CLL.

RB/PLK1-dependent induced pathway by SLAMF3 expression inhibits mitosis and control hepatocarcinoma cell proliferation

Polo-like kinase PLK1 is a cell cycle protein that plays multiple roles in promoting cell cycle progression. Among the many roles, the most prominent role of PLK1 is to regulate the mitotic spindle formation checkpoint at the M-phase. Recently we reported the expression of SLAMF3 in Hepatocytes and show that it is down regulated in tumor cells of hepatocellular carcinoma (HCC). We also show that the forced high expression level of SLAMF3 in HCC cells controls proliferation by inhibiting the MAPK ERK/JNK and the mTOR pathways. In the present study, we provide evidence that the inhibitory effect of SLAMF3 on HCC proliferation occurs through Retinoblastoma (RB) factor and PLK1-dependent pathway. In addition to the inhibition of MAPK ERK/JNK and the mTOR pathways, expression of SLAMF3 in HCC retains RB factor in its hypophosphorylated active form, which in turn inactivates E2F transcription factor, thereby repressing the expression and activation of PLK1. A clear inverse correlation was also observed between SLAMF3 and PLK expression in patients with HCC. In conclusion, the results presented here suggest that the tumor suppressor potential of SLAMF3 occurs through activation of RB that represses PLK1. We propose that the induction of a high expression level of SLAMF3 in cancerous cells could control cellular mitosis and block tumor progression.

TLR9 Ligand (CpG Oligodeoxynucleotide) Induces CLL B-Cells to Differentiate into CD20(+) Antibody-Secreting Cells

B-cell chronic lymphocytic leukemia (CLL) is the most frequent adult leukemia in the Western world. It is a heterogeneous disease characterized by clonal proliferation and the accumulation of CD5⁺ mature B lymphocytes. However, the normal counterpart from which the latter cells arise has not yet been identified. CD27 expression and gene expression profiling data suggest that CLL cells are related to memory B-cells. In vitro, memory B-cells differentiate into plasma cells when stimulated with CpG oligodeoxynucleotide (CpG). The objective of the present study was therefore to investigate the ability of CpG, in the context of CD40 ligation, to induce the differentiation of CLL B-cells into antibody-secreting cells (ASCs). CD20⁺CD38⁻ CLL B-cells were stimulated with a combination of CpG, CD40 ligand and cytokines (CpG/CD40L/c) in a two-step, 7-day culture system. We found that the CpG/CD40L/c culture system prompted CLL B-cells to differentiate into CD19⁺CD20⁺CD27⁺CD38⁻ASCs. These cells secreted large amounts of IgM and had the same shape as plasma cells. However, only IgMs secreted by ASCs that had differentiated from unmutated CLL B-cells were poly/autoreactive. Class-switch recombination (CSR) to IgG and IgA was detected in cells expressing the activation-induced cytidine deaminase gene (AICDA). Although these ASCs expressed high levels of the transcription factors PRDM1 (BLIMP1), IRF4, and XBP1s, they did not downregulate expression of PAX5. Our results suggest that CLL B-cells can differentiate into ASCs, undergo CSR and produce poly/autoreactive antibodies. Furthermore, our findings may be relevant for (i) identifying the normal counterpart of CLL B-cells and (ii) developing novel treatment strategies in CLL.

Phorbol myristate acetate, but not CD40L, induces the differentiation of CLL B cells into Ab-secreting cells

In this study, we investigated the capacity of chronic lymphocytic leukemia (CLL) B cells to undergo terminal differentiation into Ig-secreting plasma cells in T cell-independent and T cell-dependent responses. We used a two-step model involving stimulation with phorbol myristate acetate (PMA) and CD40L, together with cytokines (PMA/c and CD40L/c), for 7 days. We describe immunophenotypic modifications, changes in the levels of mRNA and protein for transcription factors and morphological and functional events occurring during the differentiation of CLL B cells into antibody-secreting cells (ASCs). The induction of differentiation differed significantly between the CD40L/c and PMA/c culture systems. The PMA/c culture system allowed CLL B cells to differentiate into IgM-secreting cells with an immunophenotype and molecular profile resembling those of preplasmablasts. By contrast, CD40L/c-stimulated cells had a phenotype and morphology similar to those of activated B cells and resembling those of the CLL B cells residing in the lymph node and bone marrow. These data suggest that the CLL B cells are not frozen permanently at a stage of differentiation and are able to differentiate into ASCs as appropriate stimulation are provided. The data presented here raise questions about the molecular processes and stimulation required for CLL B-cell differentiation and about the inability of CD40 ligand to induce differentiation of the CLL B cells.

Characterization of a new V gene replacement in the absence of activation-induced cytidine deaminase and its contribution to human B-cell receptor diversity

In B cells, B-cell receptor (BCR) immunoglobulin revision is a common route for modifying unwanted antibody specificities via a mechanism called VH replacement. This in vivo process, mostly affecting heavy-chain rearrangement, involves the replacement of all or part of a previously rearranged IGHV gene with another germline IGHV gene located upstream. Two different mechanisms of IGHV replacement have been reported: type 1, involving the recombination activating genes complex and requiring a framework region 3 internal recombination signal; and type 2, involving an unidentified mechanism different from that of type 1. In the case of light-chain loci, BCR immunoglobulin editing ensures that a second V-J rearrangement occurs. This helps to maintain tolerance, by generating a novel BCR with a new antigenic specificity. We report that human B cells can, surprisingly, undergo type 2 replacement associated with κ light-chain rearrangements. The de novo IGKV-IGKJ products result from the partial replacement of a previously rearranged IGKV gene by a new germline IGKV gene, in-frame and without deletion or addition of nucleotides. There are wrcy/rgyw motifs at the 'IGKV donor-IGKV recipient chimera junction' as described for type 2 IGHV replacement, but activation-induced cytidine deaminase (AID) expression was not detected. This unusual mechanism of homologous recombination seems to be a variant of gene conversion-like recombination, which does not require AID. The recombination phenomenon described here provides new insight into immunoglobulin locus recombination and BCR immunoglobulin repertoire diversity.

Identification of SLAMF3 (CD229) as an inhibitor of hepatocellular carcinoma cell proliferation and tumour progression

Although hepatocellular carcinoma (HCC) is one of the most common malignancies and constitutes the third leading cause of cancer-related deaths, the underlying molecular mechanisms are not fully understood. In the present study, we demonstrate for the first time that hepatocytes express signalling lymphocytic activation molecule family member 3 (SLAMF3/CD229) but not other SLAMF members. We provide evidence to show that SLAMF3 is involved in the control of hepatocyte proliferation and in hepatocellular carcinogenesis. SLAMF3 expression is significantly lower in primary human HCC samples and HCC cell lines than in human healthy primary hepatocytes. In HCC cell lines, the restoration of high levels of SLAMF3 expression inhibited cell proliferation and migration and enhanced apoptosis. Furthermore, SLAMF3 expression was associated with inhibition of HCC xenograft progression in the nude mouse model. The restoration of SLAMF3 expression levels also decreased the phosphorylation of MAPK ERK1/2, JNK and mTOR. In samples from resected HCC patients, SLAMF3 expression levels were significantly lower in tumorous tissues than in peritumoral tissues. Our results identify SLAMF3 as a specific marker of normal hepatocytes and provide evidence for its potential role in the control of proliferation of HCC cells.