Characterization of a new IL-6-dependent human B-lymphoma cell line in long term culture

Lessons learned from the preclinical discovery and development of sarilumab for the treatment of rheumatoid arthritis

INTRODUCTION

Rheumatoid arthritis (RA) pathogenesis is driven by a complex network of proinflammatory cytokines, among which interleukin-6 (IL-6) plays a key role in inducing and perpetuating chronic inflammation. Targeting the IL-6 pathway has shown to be an invaluable treatment strategy, as demonstrated by the results accrued in the last decade with the first IL-6 inhibitor, tocilizumab. More recently, a second monoclonal antibody blocking IL-6, sarilumab, has enriched our armamentarium by proving outstanding efficacy in RA treatment.

AREAS COVERED

After exploring the IL-6 pathway under physiological conditions and in the RA pathogenesis, in this review we discuss the pharmacologic properties of sarilumab and the clinical trials that constitute the sarilumab development program and have enabled its licensed application.

EXPERT OPINION

Results from clinical trials confirmed the efficacy and safety of sarilumab for the treatment of RA, similar to its precursor tocilizumab. Blocking IL-6 pathway results in comprehensive control of the disease, from both physician's and patient's perspective, and of RA comorbidities and extra-articular manifestations which are largely IL-6 driven. Finally, the proven efficacy of sarilumab as monotherapy arises the drug as a required therapeutic alternative considering the large proportion of patients intolerant or inadequate to receive conventional synthetic disease-modifying drugs (csDMARDs).

Chimeric antigen receptor-T cells with cytokine neutralizing capacity

Infusion of T lymphocytes expressing chimeric antigen receptors (CARs) can produce extraordinary antitumor activity in patients with leukemia, lymphoma, and myeloma. The signaling mechanisms activating T cells and provoking tumor cell killing also trigger cytokine secretion and macrophage activation, leading to cytokine release syndrome (CRS). CRS is a serious side effect of CAR-T cells, and proinflammatory interleukin-6 (IL-6) is central to its pathogenesis. To endow T cells with anti-CRS activity, we designed a nonsignaling membrane-bound IL-6 receptor (mbaIL6) constituted by a single chain variable fragment derived from an anti-IL-6 antibody linked to a transmembrane anchoring peptide. We found that mbaIL6 expressed on the surface of T cells could rapidly remove IL-6 from the culture supernatant. IL-6 removal was proportional to the number of mbaIL6+ cells, increased with T-cell proliferation, and neutralized IL-6 signaling and function. A construct encoding for mbaIL6 and an anti-CD19-41BB-CD3ζ CAR allowed simultaneous expression of both receptors. T cells with mbaIL6 and CAR neutralized macrophage-derived IL-6 while exerting powerful antitumor activity. Cytotoxicity and proliferation were identical to those of cells expressing CAR alone in vitro, and CAR-T cells were effective in xenograft models regardless of mbaIL6 expression. Levels of human IL-6 in mice, however, were greatly reduced if T cells expressed both receptors instead of CAR alone. Thus, CAR-T cells with on-board capacity to extinguish IL-6 represent a new approach to prevent CRS and suppress its severity without affecting the antitumor potential of CAR-T cells.

Long-term stimulation of trout head kidney cells with the cytokines MCSF, IL-2 and IL-6: gene expression dynamics

The production of salmonid leukocyte cell lines from primary cell cultures has been attempted on several occasions, however, to date only monocyte/macrophage like cell lines exist (e.g. RTS-11 and SHK-1 cells). With the increasing number of cytokines discovered in fish in recent years, many of which are growth factors for leukocytes, we now have the possibility of using these molecules to promote leukocyte development and differentiation in culture. We have generated stable cell lines transfected with a variety of plasmids expressing cytokines (Interleukin (IL)-2, IL-6 and Macrophage Colony Stimulating Factor (MCSF)), in order to produce conditioned media rich in these cytokines. The cytokine-conditioned media were used to assess their activity and ability to support the growth of primary head kidney (HK) leukocyte cultures. Here, we describe a series of experiments aimed to determine which cell population(s) of primary HK cultures is supported and will grow in conditioned media containing MCSF, IL-2 or IL-6. For a period of 5 weeks, cells were incubated at 22°C and media were changed every 3-4 days. Samples were taken at different time points, from freshly isolated HK cells (T0), one week post-stimulation (1-WPS), 3-WPS and 5-WPS for RNA extraction. A variety of cell lineage markers (MCSF Receptor 2 (MCSFR2) for macrophages, CD4 and CD8a for T cells and IgM heavy chain for B cells) were then analysed by real-time qPCR to study the cell population dynamics as influenced by the different recombinant cytokines in the cultures. We show here that whilst MCSF appears to drive macrophage differentiation and maintenance, IL-2 and IL-6 seem to preferentially drive lymphocyte differentiation.

Directed evolution of a three-finger neurotoxin by using cDNA display yields antagonists as well as agonists of interleukin-6 receptor signaling

Background

Directed evolution of biomolecules such as DNA, RNA and proteins containing high diversity has emerged as an effective method to obtain molecules for various purposes. In the recent past, proteins from non-immunoglobulins have attracted attention as they mimic antibodies with respect to binding potential and provide further potential advantages. In this regard, we have attempted to explore a three-finger neurotoxin protein (3F). 3F proteins are small (~7 kDa), structurally well defined, thermally stable and resistant to proteolysis that presents them as promising candidates for directed evolution.

Results

We have engineered a snake α-neurotoxin that belongs to the 3F family by randomizing the residues in the loops involved in binding with acetylcholine receptors and employing cDNA display to obtain modulators of interleukin-6 receptor (IL-6R). Selected candidates were highly specific for IL-6R with dissociation constants and IC50s in the nanomolar range. Antagonists as well as agonists were identified in an IL-6 dependent cell proliferation assay. Size minimization yielded peptides of about one-third the molecular mass of the original proteins, without significant loss of activities and, additionally, lead to the identification of the loops responsible for function.

Conclusions

This study shows 3F protein is amenable to introduce amino acid changes in the loops that enable preparation of a high diversity library that can be utilized to obtain ligands against macromolecules. We believe this is the first report of protein engineering to convert a neurotoxin to receptor ligands other than the parent receptor, the identification of an agonist from non-immunoglobulin proteins, the construction of peptide mimic of IL-6, and the successful size reduction of a single-chain protein.

N-linked glycosylation is required for optimal function of Kaposi's sarcoma herpesvirus-encoded, but not cellular, interleukin 6

Kaposi's sarcoma-associated herpesvirus interleukin-6 (vIL-6) is a structural and functional homologue of the human cytokine IL-6 (hIL-6). hIL-6 and vIL-6 exhibit similar biological functions and both act via the gp130 receptor subunit to activate the Janus tyrosine kinase (JAK)1 and signal transducer and activator of transcription (STAT)1/3 pathway. Here we show that vIL-6 is N-linked glycosylated at N78 and N89 and demonstrate that N-linked glycosylation at site N89 of vIL-6 markedly enhances binding to gp130, signaling through the JAK1-STAT1/3 pathway and functions in a cytokine-dependent cell proliferation bioassay. Although hIL-6 is also N-glycosylated at N73 and multiply O-glycosylated, neither N-linked nor O-linked glycosylation is necessary for IL-6 receptor alpha-dependent binding to gp130 or signaling through JAK1-STAT1/3. As distinct from vIL-6, unglycosylated hIL-6 is as potent as glycosylated hIL-6 in stimulating B cell proliferation. These findings highlight distinct functional roles of N-linked glycosylation in viral and cellular IL-6.

Quantitative proteomic and transcriptional analysis of the response to the p38 mitogen-activated protein kinase inhibitor SB203580 in transformed follicular lymphoma cells

The p38 mitogen-activated protein kinase (MAPK) is a key mediator of stress, extracellular-, growth factor-, and cytokine-induced signaling, and has been implicated in the development of cancer. Our previous work showed evidence for p38 MAPK activation in a subset of transformed follicular lymphomas (Elenitoba-Johnson et al. (2003) Proc. Natl. Acad. Sci. U.S.A. 100, 7259). We demonstrated that inhibition of p38 MAPK by SB203580 resulted in dose- and time-dependent caspase-3-mediated apoptosis. In order to further elucidate the basis of the cellular effects of SB203580, we have employed a systems biologic approach involving cDNA microarray and quantitative proteomic analysis of transformed follicular lymphoma derived-cells (OCI Ly-1) treated with SB203580. Gene expression profiling revealed differential expression (>/=1.5-fold) of 374 genes/ESTs in cells treated for 3 h and 515 genes/ESTs in cells treated for 21 h. The majority (52% at 3 h and 91% at 21 h) were down-regulated, including genes encoding growth cytokines, transcriptional regulators and cytoskeletal proteins. Quantitative proteomic analysis using ICAT-LC-MS/MS identified 277 differentially expressed proteins at 3 h and 350 proteins at 21 h of treatment with SB203580, the majority of which were also down-regulated. Analysis of functional groups of the differentially expressed proteins implicated components of diverse overlapping pathways including the IL-6/phosphatidylinositol 3-kinase, insulin-like growth factor 2/Ras/Raf, WNT8d/Frizzled, MAPK-activated protein kinase 2, and nuclear factor kappaB. The differential phosphorylation status of selected kinase-active proteins was validated by Western blotting analysis. Our complementary genomic and proteomic approach reveal the global cellular consequences of SB203580 treatment and provide insights into its growth inhibitory effect on transformed follicular lymphoma cells.

Kaposi's sarcoma-associated herpesvirus-infected primary effusion lymphoma has a plasma cell gene expression profile

Kaposi's sarcoma-associated herpesvirus is associated with three human tumors: Kaposi's sarcoma, and the B cell lymphomas, plasmablastic lymphoma associated with multicentric Castleman's disease, and primary effusion lymphoma (PEL). Epstein-Barr virus, the closest human relative of Kaposi's sarcoma-associated herpesvirus, mimics host B cell signaling pathways to direct B cell development toward a memory B cell phenotype. Epstein-Barr virus-associated B cell tumors are presumed to arise as a consequence of this virus-mediated B cell activation. The stage of B cell development represented by PEL, how this stage relates to tumor pathology, and how this information may be used to treat the disease are largely unknown. In this study we used gene expression profiling to order a range of B cell tumors by stage of development. PEL gene expression closely resembles that of malignant plasma cells, including the low expression of mature B cell genes. The unfolded protein response is partially activated in PEL, but is fully activated in plasma cell tumors, linking endoplasmic reticulum stress to plasma cell development through XBP-1. PEL cells can be defined by the overexpression of genes involved in inflammation, cell adhesion, and invasion, which may be responsible for their presentation in body cavities. Similar to malignant plasma cells, all PEL samples tested express the vitamin D receptor and are sensitive to the vitamin D analogue drug EB 1089 (Seocalcitol).

Establishment and characterization of a Kaposi's sarcoma-associated herpesvirus- and Epstein-Barr virus-negative malignant lymphoma cell line (OHK) with primary effusion lymphoma immunophenotype

A novel cell line, designated OHK, was established from ascites of a 59-year-old Japanese woman with diffuse large B-cell lymphoma showing a peculiar serosal tropism, as seen in primary effusion lymphomas (PEL). OHK exhibited a large pleomorphic morphology with irregular nuclei and distinct nucleoli, and included immunoblastic and Reed-Sternberg-like giant cells. On ultrastructural examination, rich intermediate filaments, and well-developed Golgi apparati and rough endoplasmic reticulum, were seen. Immunophenotypically, OHK lacked T and B cell-associated antigens, and had CD10, CD30, CD33 and CD138 antigens. Although OHK cells did not express immunoglobulin (Ig) protein, Southern blot analysis demonstrated clonal rearrangements of Ig heavy and light chain genes. These observations suggest that OHK cells are derived from preterminally differentiated B cells, and that they have features of PEL. Kaposi's sarcoma-associated herpesvirus and Epstein-Barr virus were not detected. OHK displayed hyperploid karyotypes with multiple structural abnormalities, and produced some cytokines such as macrophage-colony-stimulating factor (M-CSF), granulocyte-CSF, interleukin 6 and transforming growth factor beta 1. In particular, vascular endothelial growth factor (VEGF), whose stimulation of vascular permeability is thought to be critical to the pathogenesis of PEL, was also produced in large quantities. These results indicate that OHK may be a useful tool for the investigation of PEL.

The Trypanosoma cruzi trans-sialidase, through its COOH-terminal tandem repeat, upregulates interleukin 6 secretion in normal human intestinal microvascular endothelial cells and peripheral blood mononuclear cells

The Trypanosoma cruzi trans-sialidase can sensitize mice to become highly susceptible to T. cruzi invasion, through mechanisms that remain unknown. In pursuing this observation, we found that purified trans-sialidase induces the selective release of biologically active interleukin (IL)-6 in naive human intestinal microvascular endothelial cells (HIMECs), peripheral blood mononuclear cells (PBMCs), and bladder carcinoma cells. The trans-sialidase action was independent of its catalytic activity, as demonstrated with a genetically engineered trans-sialidase mutant, an enzymatically active polypeptide, and cocultures of PBMCs with epimastigotes and trypomastigotes. Instead, the trans-sialidase action was reproduced with a recombinant COOH-terminal tandem repeat and with synthetic peptides modeled on the tandem repeat. Most interesting, HIMECs infected with a trypomastigote population expressing trans-sialidase effectively released IL-6, but did not upon infection with the counterpart trypomastigote population expressing low trans-sialidase levels. IL-6 is a key factor in the regulation and symptom formation of infection caused by several types of viruses, such as HIV and influenza A virus. However, the function of IL-6 in protozoan and other parasitic diseases remains unclear. The unique findings presented here suggest that trans-sialidase is a major inducer of IL-6 secretion in T. cruzi infection, independently of immune cell activation. Such IL-6 secretion might underlie some features of Chagas's disease, such as pyrexia, neuroprotection, and fibrosis, and might result in the undermining of normal acquired immunity against T. cruzi.

Role of Vascular Endothelial Growth Factor/Vascular Permeability Factor in the Pathogenesis of Kaposi's Sarcoma-Associated Herpesvirus-Infected Primary Effusion Lymphomas

Primary effusion lymphomas (PELs), which are rare lymphomas associated with Kaposi's sarcoma-associated herpesvirus (or human herpesvirus-8) infection, present as malignant lymphomatous effusions in body cavities. Because PELs prefer liquid growth, we hypothesized that increased vascular permeability would be required for effusions to form. We found that the PEL cell lines BC-1, BCP-1, and BCBL-1 produce high levels of vascular endothelial growth factor/vascular permeability factor (VEGF/VPF). Reverse transcriptase-polymerase chain reaction analysis of RNA from the PEL cell lines amplified the 3 VEGF-secreted isoforms: VEGF/VPF121, VEGF/VPF145, and VEGF/VPF165. Two of the PEL cell lines expressed the VEGF/VPF receptor Flt-1, but VEGF/VPF did not stimulate proliferation in these cells. Most (13/14) control SCID/beige mice inoculated intraperitoneally with BCBL-1 cells and subsequently observed or treated with control antibodies developed effusion lymphoma of human cell origin with prominent bloody ascites. In contrast, none (0/9) of the mice treated with a neutralizing antihuman VEGF/VPF antibody developed ascites and effusion lymphoma. These results demonstrate that VEGF/VPF is critical to BCBL-1 growth as effusion lymphoma in mice and suggest that VEGF/VPF stimulation of vascular permeability may be critical to the pathogenesis of PELs.

Role of Vascular Endothelial Growth Factor/Vascular Permeability Factor in the Pathogenesis of Kaposi's Sarcoma-Associated Herpesvirus-Infected Primary Effusion Lymphomas

Primary effusion lymphomas (PELs), which are rare lymphomas associated with Kaposi's sarcoma-associated herpesvirus (or human herpesvirus-8) infection, present as malignant lymphomatous effusions in body cavities. Because PELs prefer liquid growth, we hypothesized that increased vascular permeability would be required for effusions to form. We found that the PEL cell lines BC-1, BCP-1, and BCBL-1 produce high levels of vascular endothelial growth factor/vascular permeability factor (VEGF/VPF). Reverse transcriptase-polymerase chain reaction analysis of RNA from the PEL cell lines amplified the 3 VEGF-secreted isoforms: VEGF/VPF121, VEGF/VPF145, and VEGF/VPF165. Two of the PEL cell lines expressed the VEGF/VPF receptor Flt-1, but VEGF/VPF did not stimulate proliferation in these cells. Most (13/14) control SCID/beige mice inoculated intraperitoneally with BCBL-1 cells and subsequently observed or treated with control antibodies developed effusion lymphoma of human cell origin with prominent bloody ascites. In contrast, none (0/9) of the mice treated with a neutralizing antihuman VEGF/VPF antibody developed ascites and effusion lymphoma. These results demonstrate that VEGF/VPF is critical to BCBL-1 growth as effusion lymphoma in mice and suggest that VEGF/VPF stimulation of vascular permeability may be critical to the pathogenesis of PELs.

C-reactive protein serum level is a valuable and simple prognostic marker in non Hodgkin's lymphoma

Interleukin-6 plays a central role in normal B-cell maturation and in proliferation of some B-cell malignancies including multiple myeloma and some non Hodgkin's lymphomas (NHL). Furthermore, this cytokine also plays a major role in acute phase response by mediating synthesis of acute phase proteins such as C-reactive protein (CRP). In order to evaluate the exact role of CRP serum level as a simple prognostic factor, we analyzed CRP and IL-6 serum levels in 39 patients with NHL. Eleven patients had low grade NHL, 15 intermediate grade NHL, and 13 high grade NHL. Thirty percent of the patients presented detectable IL-6 serum levels (mean+/-SD: 33.6+/-95.2 U/ml, range: 0 to 500). Increased serum CRP levels were found in 42% of the patients with a mean of 29.2+/-41.97 mg/l] (range: 0 to 129). Thirty seven patients were studied for both markers. Three groups of patients were determined. One with low IL-6 and CRP serum levels (N=21), a second with high level of both markers (N=10), and the third with high serum CRP levels alone (N = 5). Only one patient had high level of serum IL-6 with no detectable CRP. The correlation of serum IL-6 and CRP levels with patient survival was investigated. Median survival in the group with low IL-6 level was not reached. 67% of patients of this group were still alive at 32 months from diagnosis. The group of patients with detectable IL-6 had a median of survival of 12 months (p<0.025). The survival of patients with a CRP<10 mg/l was not reached. 75% of patients survive at 32 months from diagnosis, whereas the group with higher CRP level reached a median survival at 8.5 months (p<0.009). As expected, on univariate analysis, there is a significant relationship between CRP and IL-6 levels (p<0.00017), and CRP levels and B symptoms (p<0.001). Furthermore there is a significant relationship between CRP and LDH levels (p<0.042).These results indicated that CRP may be considered as a valuable and easy prognostic biomarker of NHL.

Interaction between interleukin 10 and interleukin 6 in human B-cell differentiation

Contrary to their opposing action on human T-lymphocytes and monocytes, both Interleukin (IL-)10 and IL-6 are potent differentiation factors of human B-cells. Both are known to induce immunoglobulin (Ig) production. The precise mechanism of this converging effect of IL-6 and IL-10 remains elusive, however. Here we investigated the role of IL-6 in the IL-10 dependent B-cell differentiation into Ig secreting cells. We found that co-stimulation of SAC-stimulated human peripheral B-lymphocytes with IL-10 and IL-6 exhibited no additive effect on Ig production over stimulation with IL-10 alone, and that IL-6 receptor blockade only mildly inhibited IL-10 induced Ig synthesis. In fact, we could show that stimulation of B-cells with IL-10 somewhat suppressed SAC induced autocrine IL-6 production. Despite this suppression IL-6 levels remained sufficiently high to stimulate its receptor, and IL-6 binding to the B-cell surface was not affected. The failure of IL-6 to exert an additional effect on SAC+IL-10 induced Ig production suggests that IL-10 may recruit components of the IL-6 intracellular pathway for Ig induction. In conclusion we could demonstrate that IL-10 acts on B-cell differentiation independently of autocrine IL-6 and that it had a considerably mild effect on B lymphocytic autocrine IL-6 secretion. This still allows an IL-6 effect in the presence of IL-10 which appears adaptive with a view to the converging effects of these two cytokines on human B lymphocytes. Our study thus adds to the appreciation of the complex cytokine regulation of the immune system.

Growth modulation of freshly isolated non-Hodgkin's B-lymphoma cells induced by various cytokines and all-trans-retinoic-acid

We investigated the potential of ten cytokines (IL2, IL3, IL4, IL6, IL10, IL13, G-CSF, GM-CSF, interferon alpha, interferon gamma) and all-trans-retinoic acid to modulate the spontaneous proliferative response in vitro of purified B-non Hodgkin's lymphoma cells of various histological subtypes. 19 malignant lymph nodes were studied. In each case the growth could be influenced by several of these modulators. Cytokines most often implicated were interferon gamma (14/19 cases, 73.7%), IL4 (13/19 cases, 68.4%), interferon alpha (12/19 cases, 63.1%). IL2 (9/19 cases, 47.3%), IL6, IL10, IL13 and ATRA were less frequently involved (6/19 cases, 31.6%) and hematopoietic growth factors (IL3, GM-CSF, G-CSF) were rarely implicated (2/19 cases, 10.5%). The values of growth stimulation ranged from a 1.1-fold to a 6.1-fold increase, and the values of growth inhibition ranged from 15% to 98%. Each cytokine could be either inhibitory or stimulatory depending on the sample analyzed, and no relationship could be found with the histological subtype. Two notable exceptions were IL2, displaying exclusively a positive effect, and ATRA displaying exclusively a negative effect. Overall, these results may have strong implications for future clinical studies using cytokines in the treatment of lymphomas. Ideally, the pattern of in vitro growth response to cytokines or ATRA should be determined individually before undertaking any cytokine treatment.

Studies of the expression of the Wiskott-Aldrich syndrome protein

The Wiskott-Aldrich syndrome (WAS) is an X-linked disorder characterized by thrombocytopenia, eczema, disorders in cell-mediated and humoral immunity, and a proclivity to lymphoproliferative disease. The gene responsible encodes a 53-kD proline-rich protein of unknown function (WASP). We produced a FLAG-WASP fusion protein that was used to immunize mice and produce mAbs against WASP. Using monoclonal anti-WASP in Western immunoblots, we have determined that WASP is present in the cytoplasmic but not nuclear fraction of normal human peripheral blood mononuclear cells, in normal human platelets, in T lymphocytes, non-T lymphocytes, and monocytes. The protein is produced in the B cell immunoblastic cell line DS-1, in normal EBV-transformed B cell lines, and in HEL92.1.7, but is barely detectable in MOLT-4 and not detectable in K562. WASP was present in two of four EBV-transformed cell lines from WAS patients. Splenic tissue immunostaining was performed in two patients, and the results correlated with the results of the Western blots. Sequence analysis of WASP cDNA from two patients who produce WASP show mutations causing amino acid substitutions. These studies establish a foundation for further studies aimed at understanding the function of WASP.

Interleukin-10 directly inhibits the interleukin-6 production in T-cells

IL-6 is a potent regulator of T-cell activation, proliferation and differentiation. Since IL-10 inhibits cytokine production by T cells, the effect of IL-10 on IL-6 production by T cells was investigated. IL-6 production by purified monocytes or T cells was detected from cell-free culture supernatants by ELISA after stimulation of the cells with LPS or an anti-CD3 monoclonal antibody for 3 days. Although the main source of IL-6 are LPS activated monocytes (29.6 +/- 10 ng/ml), T cells secreted sufficiently high levels of IL-6 (790 +/- 200 pg/ml) to stimulate the high affinity IL-6 receptor. IL-10 decreased anti-CD3 induced IL-6 mRNA expression by up to 80%. In addition, IL-10 significantly inhibited IL-6 release from T-cells. Highly purified, anti-CD3 activated T-cells secreted 600 +/- 150 pg/ml IL-6 compared to 21 +/- 2 pg/ml IL-6 following addition of IL-10 (10 ng/ml; P < 0.001). FACS analysis revealed a monocyte contamination of the T-cell preparations of less than 0.5%. In addition, no IL-1 production was detectable. Thus, in our experiments the effect of IL-10 on IL-6 production was independent of the presence of monocytes. Finally, inhibition of IL-6 production was not reversed by IL-2 (100 U/ml). In conclusion, IL-10 suppressed the synthesis of IL-6 by T-cells via a monocyte- and IL-2-independent mechanism. These results may help to understand the complex regulation of T-cell mediated cytokine production by IL-10.