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Elevated activity of bone-degrading osteoclasts (OC) contributes to pathological bone degradation in diseases such as multiple myeloma. Several proinflammatory cytokines, including TNF, contribute to osteoclastogenesis. The receptor-interacting protein kinase 1 (RIPK1) regulates inflammation and cell death. It is recruited to the TNF-receptor complex, where it is ubiquitinated, and activates transcription factor NF-κB and mitogen-activated protein kinases (MAPK). Smac-mimetics (SM) is a group of drugs that block RIPK1 ubiquitination and shifts RIPK1 to activation of apoptosis or necroptosis. In this manuscript, we show that the two SM birinapant and LCL-161 reduced the number and viability of primary human OC, and induced TNF-dependent cell death in OC precursors (pre-OC). Birinapant was more cytotoxic than LCL-161 and induced predominantly apoptosis and to some degree necroptosis. Both inhibitors restrained osteoclastogenesis induced by myeloma patient bone-marrow aspirates. SM has gained attention as novel treatment strategies both for cancer and chronic inflammatory pathologies, but limited information has been available on interactions with primary human immune cells. As LCL-161 is in phase 2 clinical studies for multiple myeloma, we propose that SM might possess additional benefits in reducing bone degradation in myeloma patients. Taken together, we show that SM reduces human osteoclastogenesis, and that these compounds may represent promising drug candidates for pathological bone degradation.

Background The majority of patients with advanced cancer develop cachexia, a weight loss syndrome that severely reduces quality of life and limits survival. Our understanding of the underlying mechanisms that cause the condition is limited, and there are currently no treatment options that can completely reverse cachexia. Several tumour‐derived factors and inflammatory mediators have been suggested to contribute to weight loss in cachectic patients. However, inconsistencies between studies are recurrent. Activin A and interleukin 6 (IL‐6) are among the best studied factors that seem to be important, and several studies support their individual role in cachexia development. Methods We investigated the interplay between activin A and IL‐6 in the cachexia‐inducing TOV21G cell line, both in culture and in tumours in mice. We previously found that the human TOV21G cells secrete IL‐6 that induces autophagy in reporter cells and cachexia in mice. Using this established cachexia cell model, we targeted autocrine activin A by genetic, chemical, and biological approaches. The secretion of IL‐6 from the cancer cells was determined in both culture and tumour‐bearing mice by a species‐specific ELISA. Autophagy reporter cells were used to monitor the culture medium for autophagy‐inducing activities, and muscle mass changes were evaluated in tumour‐bearing mice. Results We show that activin A acts in an autocrine manner to promote the synthesis and secretion of IL‐6 from cancer cells. By inhibiting activin A signalling, the production of IL‐6 from the cancer cells is reduced by 40–50% (up to 42% reduction on protein level, P = 0.0048, and 48% reduction on mRNA level, P = 0.0308). Significantly reduced IL‐6 secretion (P < 0.05) from the cancer cells is consistently observed when using biological, chemical, and genetic approaches to interfere with the autocrine activin A loop. Inhibiting activin signalling also reduces the ability of the cancer cells to accelerate autophagy in non‐cancerous cells (up to 43% reduced autophagy flux, P = 0.0006). Coherent to the in vitro data, the use of an anti‐activin receptor 2 antibody in cachectic tumour‐bearing mice reduces serum levels of cancer cell‐derived IL‐6 by 62% (from 417 to 159 pg/mL, P = 0.03), and, importantly, it reverses cachexia and counteracts loss of all measured muscle groups (P < 0.0005). Conclusions Our data support a functional link between activin A and IL‐6 signalling pathways and indicate that interference with activin A‐induced IL‐6 secretion from the tumour has therapeutic potential for cancer‐induced cachexia. © 2019 The Authors. Journal of Cachexia, Sarcopenia and Muscle published by John Wiley & Sons Ltd on behalf of Society on Sarcopenia, Cachexia and Wasting Disorders Journal of Cachexia, Sarcopenia and Muscle (2019) Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/jcsm.12489 This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

The majority of cancer patients with advanced disease experience weight loss, including loss of lean body mass. Severe weight loss is characteristic for cancer cachexia, a condition that significantly impairs functional status and survival. The underlying causes of cachexia are incompletely understood, and currently no therapeutic approach can completely reverse the condition. Autophagy coordinates lysosomal destruction of cytosolic constituents and is systemically induced by starvation. We hypothesized that starvation-mimicking signaling compounds secreted from tumor cells may cause a systemic acceleration of autophagy during cachexia. We found that IL-6 secreted by tumor cells accelerates autophagy in myotubes when complexed with soluble IL-6 receptor (trans-signaling). In lung cancer patients, were cachexia is prevalent, there was a significant correlation between elevated IL-6 expression in the tumor and poor prognosis of the patients. We found evidence for an autophagyinducing bioactivity in serum from cancer patients and that this is clearly associated with weight loss. Importantly, the autophagy-inducing bioactivity was reduced by interference with IL-6 trans-signaling. Together, our findings suggest that IL-6 trans-signaling may be targeted in cancer cachexia. © The Author(s) 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/)

Lipoteichoic acid (LTA) is a central inducer of inflammatory responses caused by Gram-positive bacteria, such as Staphylococcus aureus, via activation of TLR2. Localization of TLR2 in relation to its coreceptors may be important for function. This study explores the signaling, uptake, and trafficking pattern of LTA in relation to expression of TLR2 and its coreceptors CD36 and CD14 in human monocytes. We found TLR2 expressed in early endosomes, late endosomes/lysosomes, and in Rab-11-positive compartments but not in the Golgi apparatus or endoplasmic reticulum (ER). Rapid internalization of fluorescently labeled LTA was observed in human monocytes, colocalizing with markers for early and late endosomes, lysosomes, ER, and Golgi network. Blocking CD14 and CD36 with antibodies inhibited LTA binding and LTA-induced TNF release from monocytes, emphasizing an important role for both molecules as coreceptors for TLR2. Importantly, blocking CD36 did not affect TNF release induced by N-palmitoyl-S-[2,3-bis(palmitoyloxy)-(2R,S)-propyl]-(R)-cysteinyl-seryl-(lysyl)3-lysine or LPS. Expression of CD14 markedly enhanced LTA binding to the plasma membrane and also enhanced NF-κB activation. LTA internalization, but not NF-κB activation, was inhibited in Dynamin-I K44A dominant-negative transfectants, suggesting that LTA is internalized by receptor-mediated endocytosis but that internalization is not required for signaling. In fact, immobilizing LTA and thereby inhibiting internalization resulted in enhanced TNF release from monocytes. Our results suggest that LTA signaling preferentially occurs at the plasma membrane, is independent of internalization, and is facilitated by CD36 and CD14 as coreceptors for TLR2.

Toll-like receptor 2 (TLR2) is a signaling receptor for a variety of microbial products, including bacterial lipoproteins and peptidoglycan, and is central in initiating immune responses toward Gram-positive bacteria, spirochetes, and mycobacteria. The mechanisms behind regulation of TLR2 protein expression are still not well understood. By using a newly developed monoclonal antibody against mouse TLR2, we detected TLR2 protein expression on macrophages, neutrophils, and dendritic cells. Endogenous macrophage TLR2 localized mostly to the cell membrane, with particular accumulation around phagosomes containing zymosan. Treatment of macrophages with the TLR2 antibody diminished cellular response to lipoproteins and down-regulated membrane TLR2. Marked up-regulation of surface TLR2 was observed on macrophages in response to whole bacteria, lipoproteins, lipopolysaccharide, poly(I-C) (double-stranded RNA), R848, and CpG DNA, and this up-regulation appeared to be a very sensitive marker for the presence of microbial products. Up-regulation of TLR2 in response to stimuli correlated with an increased response to secondary lipoprotein exposure following a low concentration of primary lipoprotein challenge. By comparison, exposure to a larger primary challenge induced a hyporeactive state. Most interestingly, lipopolysaccharide- and double-stranded RNA-induced up-regulation of surface TLR2 in macrophages was found to be MyD88-independent, whereas the up-regulation in response to lipoproteins, R848, and CpG DNA was absent in MyD88-deficient cells. We conclude that complex mechanisms regulate expression and signaling via TLR2. Up-regulation of TLR2 in the presence of low, yet clinically relevant amounts of microbial products may be an important mechanism by which the immune system boosts its response to a beginning infection.

The effect of guluronate oligomers on the barrier properties of mucous matrices was investigated in terms of the mobility of nanoparticles in mucous matrices by fluorescence recovery after photobleaching (FRAP), cellular uptake of nanoparticles in mucus secreting cells (HT29-MTX), and mucin matrix architecture by scanning electron microscopy (SEM). Guluronate oligomers improved nanoparticle mobility in both native and highly purified mucus matrices and improved cellular uptake of nanoparticles through a mucus layer. Addition of guluronate oligomers to mucin matrices resulted in a decrease in the density of network cross-links and an increase in matrix pore size. Based on these data, we conclude that guluronate oligomers are able to improve nanoparticle mobility in several mucus matrices and alter network architecture in mucin matrices in a manner that suggests a reduction in barrier function. As such, there may be a potential application for guluronate oligomers in mucosal delivery of nanomedicines.

Based on the thieno[2,3-d]pyrimidine scaffold, a series of new 4-amino-6-aryl thienopyrimidines have been prepared and evaluated as EGFR tyrosine kinase inhibitors. The in vitro activity was found to depend strongly on the substitution pattern in the 6-aryl ring, the stereochemistry, and the basicity at the secondary 4-amino group. A stepwise optimization by combination of active fragments led to the discovery of three structures with EGFR IC50 < 1 nM. The most potent drug candidate had an IC50 of 0.3 nM towards EGFR and its mutants L858R and L861Q. Studies using human cancer cell lines and an EGFR-L858R reporter cell system revealed good cellular potency, verifying the identified thienopyrimidines as promising lead structures.

Lipopolysaccharide (LPS), a part of the Gram-negative bacteria cell wall, is a potent inducer of tumor necrosis factor (TNF). TNF is an important mediator in Gram-negative infections such as meningococcal septic shock, but its harmful action can be prevented by the natural occurring soluble (s) TNF receptors (sTNFR) sp55 and sp75. In this study, the effect of LPS on release of sTNFR was investigated. First, we found a selective increase in human whole-blood sp75 TNFR levels following LPS stimulation, accompanied by no increase in sp55. Separating the different blood cell populations, mononuclear cells (PBMC) selectively released sp75 upon LPS stimulation, while LPS induced a minor increase in sp75 release from polymorphonuclear granulocytes. Interestingly, in co-cultures of PBMC and granulocytes, the release of LPS-induced sp75 TNFR was enhanced. Second, adherent monocytes were also found to selectively release sp75 TNFR upon LPS stimulation, where Neisseria meningitidis LPS was found to be 100-1000 times more potent in inducing sp75 release than Escherichia coli LPS. Using flow cytometry, the monocyte membrane distribution of both TNFR were found to be increased after LPS stimulation. Third, human umbilical vein endothelial cells selectively released sp55 TNFR after stimulation with LPS. We conclude that mononuclear and endothelial cells might be the main sources of soluble p75 and p55 TNFR, respectively, observed in Gram-negative sepsis, although these receptors are released in vivo more rapidly than they are in vitro.

The functional role of human tumor necrosis factor receptor (TNFR) p75 was studied by the use of TNFR p75-specific agonistic antibodies. Human SW480T adenocarcinoma cells, stably transfected with a reporter construct containing beta-galactosidase under the control of human cytomegalovirus immediate early enhancer, were stimulated with anti-TNFR p75 polyclonal antiserum or monoclonal antibodies followed by measurement of beta-galactosidase activity and analysis by electrophoretic mobility shift assays. It was found that cross-linking of TNFR p75 led to strong induction of the human cytomegalovirus enhancer as well as activation of nuclear factor-kappa B (NF-kappa B). Stimulation of TNFR p75 also mediated activation of NF-kappa B in human KYM-1 rhabdomyosarcoma cells but not in other cell types such as U937 and HL-60 monocytic cells or in Eahy 926 endothelial cells. NF-kappa B activation induced by TNFR p75 was delayed approximately 15 min compared with NF-kappa B activation induced by TNFR p55, indicating that the two TNFRs activate NF-kappa B through different signaling pathways. The data presented in this study identify intracellular responses mediated by TNFR p75 which have not been reported previously and suggest that TNFR p75-induced activation of NF-kappa B is strictly cell type-specific.

Three different antibodies against a human TNF receptor (htr-1, htr-5, and htr-9) have been examined for their binding pattern to U937 cells and ability to mimic TNF-alpha activity in U937 cells, Fs4 fibroblasts, and human endothelial cells. Flow cytometric analysis revealed that htr-5 and htr-9 bound specifically to a TNF receptor on U937 cells that could be blocked by pretreatment with rTNF-alpha. Pretreatment of U937 cells with rTNF-beta blocked the binding of htr-9, but to a lesser extent htr-5 binding. Pretreatment with htr-5 inhibited the binding of htr-9 to U937 cells while pretreatment with htr-9 did not inhibit htr-5 binding. These results indicate that htr-5 and htr-9 recognize distinct but overlapping epitopes of a human TNF receptor on U937 cells and that htr-5 may be close to a TNF-alpha-specific domain of the binding site. Pretreatment with htr-5 or htr-9 only minimally reduced binding of BrTNF-alpha to U937 cells; however, these antibodies were much more effective in inhibiting BrTNF-alpha binding to HL-60 cells. Furthermore, it was found that htr-1 and htr-9, but not htr-5, had TNF-alpha activity on U937 cells, Fs4 fibroblasts, and endothelial cells and that the TNF-alpha activity induced by htr-9 was completely inhibited by htr-5. However, the cytotoxic activity of TNF-alpha was only partially inhibited by htr-5 on U937 cells while htr-5 had no effect on TNF-alpha activity on Fs4 cells. The data suggest that a common epitope is involved in inducing TNF-alpha activity in three different cell systems.

Apo-2L is a new member of the tumour necrosis factor (TNF) family shown to induce apoptosis in a number of tumour cell lines. Apo-2L mRNA is expressed by numerous human tissues. Here we report that Apo-2L is expressed and utilized by human Natural Killer (NK) cells. NK cells were shown to express surface Apo-2L in response to interleukin 2 (IL-2) activation, and this response was restricted to the CD3 − population of the NK cells. Apo-2L mRNA and intracellular Apo-2L were present in both CD3 − and CD3 + NK cells; however, increased expression in response to IL-2 was only observed in CD3 − CD56 + cells. Also, IL-2-activated NK cells were shown to utilize membrane-bound Apo-2L in mediating lysis of Jurkat cells. Furthermore, Apo-2L-induced apoptosis of Jurkat cells was more rapid than FasL-induced apoptosis, indicating an important and distinct role for Apo-2L in apoptotic cell destruction. In conclusion, we report that NK cells express Apo-2L and that IL-2 activated CD3 − NK cells utilize the Apo-2L pathway in mediating target cell lysis.

The present study describes the immunomagnetic isolation of human natural killer (NK) and lymphokine activated killer (LAK) cells. Antibodies against CD56 and sheep anti-mouse IgG-coated magnetic monodisperse particles (Dynabeads M-450) were used for the positive isolation of CD56+ cells from unstimulated mononuclear cells (PBMC). A highly enriched population of CD56+ cells (less than or equal to 3% contaminating cells) was obtained with this method. The cellular yield of CD56+ cells was high (5.3% of the unseparated PBMC). The CD56+ cells remained unactivated after separation and preserved their functional characteristics, as measured by cytotoxic activity against the NK sensitive K562 cells. Incubating the CD56+ cells with IL-2 resulted in high LAK activity, as measured by cytotoxic activity against Daudi cells. Large numbers of functionally active CD56+ cells were obtained from IL-2 stimulated lymphocytes using anti-CD56 coated Dynabeads 450. A further enrichment of effector cells with LAK activity was accomplished by depleting the CD56+ cells for T-cells by anti-CD3 coated Dynabeads M450. The immunomagnetic isolation technique described was easy to perform, did not require expensive equipment and yielded NK and LAK cells of satisfactory purity.

The production and localization of tumor necrosis factor (TNF) in human monocytes were investigated by using monoclonal and polyclonal antibodies against recombinant human TNF together with flow cytometry and immunofluorescence microscopy. Lipopolysaccharide (LPS) induced a rapid and transient accumulation of TNF in perinuclear vesicles which was detected 20 min after the addition of LPS. The fluorescence intensity of the vesicles peaked at 40 min of LPS exposure, concomitantly with the release of TNF into the medium. Thus, our results indicate that the secretion of TNF is typical for secretory proteins as it involves passage through the secretory apparatus. Additional studies demonstrated that plasma membrane-associated TNF could not be detected in live monocytes not exposed to LPS. However, after 90 min with LPS, a small population of monocytes expressed membrane-associated TNF, and by 24 hr approximately 50% of the monocytes displayed TNF on the plasma membrane. Furthermore, our results indicate that plasma membrane-associated TNF does not represent released TNF bound back to its own receptor. Thus, our findings support the view that TNF exists as a surface transmembrane protein in LPS-stimulated monocytes.