Plasma Rhenium and Selenium Concentrations After Repeated Daily Oral Administration of Rhenium(I)-diselenoether in 4T1 Breast Tumor-bearing Mice.

BACKGROUND/AIM: Rhenium(I)-diselenoether (Re-diSe) is a compound combining a rhenium tricarbonyl(I) core with a diselenide ligand. A high dose of 60 mg/kg had a pro-tumor effect in a previous study, in non-immune deficient 4T1 tumor-bearing mice, while doses of 1 and 10 mg/kg did not affect tumor growth, after repeated oral administrations. This study aimed to examine the tumor effects of a lower dose of 0.1 mg/kg with the same experimental design and to assay plasma Re and Se concentrations. MATERIALS AND METHODS: Syngenic BALB/cByJ (JAX) mice were orthotopically inoculated with 4T1 mammary breast cancer cells. Re-diSe was daily administered orally for 23 days at doses of 0.1, 1, and 10 mg/kg, whereas controls received no treatment. Tumor and mice weights were measured at the end of the experiment. Plasma Re and Se concentrations were assayed by an inductively coupled plasma sector field mass spectrometry instrument (ICP-sf-MS). RESULTS: The weight of the tumors did not vary in treated versus non-treated mice. The limit of detection (LOD) of Re was 0.34 nmol/l. Plasma Re concentrations were 14±20 nmol/l at doses of 0.1 mg/kg, and increased at higher doses, up to 792±167 nmol/l at doses of 10 mg/kg. Plasma Se concentrations were significantly increased in mice treated with the dose of 0.1 mg/kg (4,262±1,511 nmol/l) versus controls (1,262±888 nmol/l), but not from 0.1 to 1 mg/kg, nor from 1 to 10 mg/kg. CONCLUSION: The 0.1 mg/kg dose of Re-diSe resulted in detectable plasma Re concentrations and significantly increased plasma Se concentrations. In the future, doses as low as 0.1 mg/kg of Re-diSe will be tested, exploring its potential immune interest as a metronomic schedule of treatment, but in mouse models that readily develop extensive metastatic disease.

Environmental signals perceived by the brain abate pro-metastatic monocytes by dampening glucocorticoids receptor signaling.

While positive social-behavioral factors predict longer survival in cancer patients, the underlying mechanisms are unknown. Since tumor metastasis are the major cancer mortality factor, we investigated how an enriched environment (EE) conductive to enhanced sensory, cognitive and motor stimulation impact metastatic progression in lungs following intravasation in the circulation. We find that mice housed in EE exhibited reduced number of lung metastatic foci compared to control mice housed in a standard environment (SE). Compared to SE mice, EE mice increased lung inflammation as early as 4 days after circulating tumor cells extravasation. The impact of environmental signals on lung metastasis is independent of adrenergic receptors signaling. By contrast, we find that serum corticosterone levels are lower in EE mice and that glucocorticoid receptor (GR) antagonist reduces the number of lung metastasis in SE mice. In addition, the difference of the number of lung metastasis between SE and EE mice is abolished when inflammatory monocytes are rendered deficient in GR signaling. This decreased GR signaling in inflammatory monocytes of SE mice results in an exacerbated inflammatory profile in the lung. Our study shows that not only EE reduces late stages of metastatic progression in lungs but disclose a novel anti-tumor mechanism whereby GR-dependent reprogramming of inflammatory monocytes can inhibit metastatic progression in lungs. Moreover, while inflammatory monocytes have been shown to promote cancer progression, they also have an anti-tumor effect, suggesting that their role is more complex than currently thought.

Relationship between the oxidative status and the tumor growth in transplanted triple-negative 4T1 breast tumor mice after oral administration of rhenium(I)-diselenoether.

BACKGROUND: Selective inhibitory effects of rhenium(I)-diselenoether (Re-diSe) were observed in cultured breast malignant cells. They were attributed to a decrease in Reactive Oxygen Species (ROS) production. A concomitant decrease in the production of Transforming Growth Factor-beta (TGFß1), Insulin Growth Factor 1 (IGF1), and Vascular Endothelial Growth Factor A (VEGFA) by the malignant cells was also observed. AIM: The study aimed to investigate the anti-tumor effects of Re-diSe on mice bearing 4T1 breast tumors, an experimental model of triple-negative breast cancer, and correlate them with several biomarkers. MATERIAL AND METHODS: 4T1 mammary breast cancer cells were orthotopically inoculated into syngenic BALB/c Jack mice. Different doses of Re-diSe (1, 10, and 60 mg/kg) were administered orally for 23 consecutive days to assess the efficacy and toxicity. The oxidative status was evaluated by assaying Advanced Oxidative Protein Products (AOPP), and by the dinitrophenylhydrazone (DNPH) test in plasma of healthy mice, non-treated tumor-bearing mice (controls), treated tumor-bearing mice, and tumors in all tumor-bearing mice. Tumor necrosis factor (TNFα), VEGFA, VEGFB, TGFß1, Interferon, and selenoprotein P (selenoP) were selected as biomarkers. RESULTS: Doses of 1 and 10 mg/kg did not affect the tumor weights. There was a significant increase in the tumor weights in mice treated with the maximum dose of 60 mg/kg, concomitantly with a significant decrease in AOPP, TNFα, and TGFß1 in the tumors. SelenoP concentrations increased in the plasma but not in the tumors. CONCLUSION: We did not confirm the anti-tumor activity of the Re-diSe compound in this experiment. However, the transplantation of the tumor cells did not induce an expected pro-oxidative status without any increase of the oxidative biomarkers in the plasma of controls compared to healthy mice. This condition could be essential to evaluate the effect of an antioxidant drug. The choice of the experimental model will be primordial to assess the effects of the Re-diSe compound in further studies.

Idiopathic CD4 T Cell Lymphocytopenia: A Case of Overexpression of PD-1/PDL-1 and CTLA-4.

Idiopathic CD4 T cell lymphocytopenia (ICL) is a rare entity characterized by CD4 T cell count of <300 cells/mm3 along with opportunistic infection for which T cell marker expression remains to be fully explored. We report an ICL case for which T lymphocyte phenotype and its costimulatory molecules expression was analyzed both ex vivo and after overnight stimulation through CD3/CD28. The ICL patient was compared to five healthy controls. We observed higher expression of inhibitory molecules PD-1/PDL-1 and CTLA-4 on CD4 T cells and increased regulatory T cells in ICL, along with high activation and low proliferation of CD4 T cells. The alteration in the expression of both the costimulatory pathway and the apoptotic pathway might participate to down-regulate both CD4 T cell functions and numbers observed in ICL.

Immunosuppressive Tumor Microenvironment Status and Histological Grading of Endometrial Carcinoma.

The recent successes of new cancer immunotherapy approaches have led to investigate their relevance in the context of the Endometrial Carcinoma (EC). These therapies, that take the tumor-induced immunosuppressive microenvironment into account, target the tumor immune escape, in particular the inhibitory receptors involved in the regulation of the effector T cells' activity (immune checkpoints). The aim of this study was to identify, in ECs, differences in intergrades immune status that could contribute to the differences in tumor aggressiveness, and could also be used as theranostic tools. The immune status of tumors was assessed by quantitative real-time PCR. We analyzed the expression of specific genes associated to specific leukocytes subpopulations and the expression of reporting genes associated with the tumor escape/resistance. This study highlights significant differences in the EC intergrades immune status especially the tumor-infiltrating cell types and their activation status as well as in the molecular factors produced by the environment. The immune microenvironment of grade 1 ECs hints at a robust tumoricidal milieu while that of higher grades is more evocative of a tolerogenic milieu. This genes-based immunological monitoring of tumors that easily highlights significant intergrade differences relating to the density, composition and functional state of the leukocyte infiltrate, could give solid arguments for choosing the best therapeutic options, especially those targeting immune checkpoints. Moreover it could enable an easy adaptation of individual treatment approaches for each patient.

Percutaneous vertebroplasty in tumoral spinal fractures with posterior vertebral wall involvement: Feasibility and safety.

PURPOSE: to evaluate the technical feasibility and safety of CT and fluoroscopy guided percutaneous vertebroplasty in the treatment of tumoral vertebral fractures with posterior wall involvement. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained for this study. Sixty-three consecutive adult patients (35 women, 28 men; mean age+/- standard deviation: 69 years+/- 14) with tumoral spinal fractures that compromised the posterior wall were treated by means of percutaneous vertebroplasty with CT and fluoroscopy guidance. Only local anesthesia was used during these procedures. Postoperative outcome was assessed using the Kostuik index. RESULTS: Sixty-three vertebroplasties were performed on thirty-four thoracic (54%), twenty-six lumbar (41%), and three (5%) cervical vertebrae. The etiologies of the fractures were metastasis in twenty-eight (44%), myeloma in twenty-five (40%) and hemangioma in ten (16%). Almost all fractures (94%) were consolidated after vertebroplasty (score of Kostuik <3) (p < 0.001). No major complications were reported in our series of cases. CONCLUSION: This study suggests that tumoral spinal fractures with posterior vertebral wall involvement can be successfully and safely treated by CT- and fluoroscopy-guided percutaneous vertebroplasty.

Understanding the Progression of Bone Metastases to Identify Novel Therapeutic Targets.

Bone is one of the most preferential target site for cancer metastases, particularly for prostate, breast, kidney, lung and thyroid primary tumours. Indeed, numerous chemical signals and growth factors produced by the bone microenvironment constitute factors promoting cancer cell invasion and aggression. After reviewing the different theories proposed to provide mechanism for metastatic progression, we report on the gene expression profile of bone-seeking cancer cells. We also discuss the cross-talk between the bone microenvironment and invading cells, which impacts on the tumour actions on surrounding bone tissue. Lastly, we detail therapies for bone metastases. Due to poor prognosis for patients, the strategies mainly aim at reducing the impact of skeletal-related events on patients' quality of life. However, recent advances have led to a better understanding of molecular mechanisms underlying bone metastases progression, and therefore of novel therapeutic targets.

Gallium, a promising candidate to disrupt the vicious cycle driving osteolytic metastases.

Bone metastases of breast cancer typically lead to a severe osteolysis due to an excessive osteoclastic activity. On the other hand, the semi-metallic element gallium (Ga) displays an inhibitory action on osteoclasts, and therefore on bone resorption, as well as antitumour properties. Thus, we explored in vitro Ga effects on osteoclastogenesis in an aggressive bone metastatic environment based on the culture of pre-osteoclast RAW 264.7 cells with conditioned medium from metastatic breast tumour cells, i.e. the breast tumour cell line model MDA-MB-231 and its bone-seeking clone MDA-231BO. We first observed that Ga dose-dependently inhibited the tumour cells-induced osteoclastic differentiation of RAW 264.7 cells. To mimic a more aggressive environment where pro-tumourigenic factors are released from bone matrix due to osteoclastic resorption, metastatic breast tumour cells were stimulated with TGF-ß, a mayor cytokine in bone metastasis vicious cycle. In these conditions, we observed that Ga still inhibited cancer cells-driven osteoclastogenesis. Lastly, we evidenced that Ga affected directly and strongly the proliferation/viability of both cancer cell lines, as well as the expression of major osteolytic factors in MDA-231BO cells. With the exception of two small scale clinical studies from 1980s, this is the first time that antitumour properties of Ga have been specifically studied in the context of bone metastases. Our data strongly suggest that, through its action against the vicious cycle involving bone cells and tumour cells, Ga represents a relevant and promising candidate for the local treatment of bone metastases in patients with breast cancer.

Adaptive immune response inhibits ectopic mature bone formation induced by BMSCs/BCP/plasma composite in immune-competent mice.

A combination of autologous bone marrow stromal cells (BMSCs) and biomaterials is a strategy largely developed in bone tissue engineering, and subcutaneous implantation in rodents or large animals is often a first step to evaluate the potential of new biomaterials. This study aimed at investigating the influence of the immune status of the recipient animal on BMSCs-induced bone formation. BMSCs prepared from C57BL/6 mice, composed of a mixture of mesenchymal stromal and monocytic cells, were combined with a biomaterial that consisted of biphasic calcium phosphate (BCP) particles and plasma clot. This composite was implanted subcutaneously either in syngenic C57BL/6 immune-competent mice or in T-lymphocyte-deficient Nude (Nude) mice. Using histology, immunohistochemistry, and histomorphometry, we show here that this BMSC/BCP/plasma clot composite implanted in Nude mice induces the formation of mature lamellar bone associated to hematopoietic areas and numerous vessels. Comparatively, implantation in C57BL/6 results in the formation of woven bone without hematopoietic tissue, a lower number of new vessels, and numerous multinucleated giant cells (MNGCs). In situ hybridization, which enabled to follow the fate of the BMSCs, revealed that BMSCs implanted in Nude mice survived longer than BMSCs implanted in C57BL/6 mice. Quantitative expression analysis of 280 genes in the implants indicated that the differences between C57BL/6 and Nude implants corresponded almost exclusively to genes related to the immune response. Gene expression profile in C57BL/6 implants was consistent with a mild chronic inflammation reaction characterized by Th1, Th2, and cytotoxic T-lymphocyte activation. In the implants retrieved from T-deficient Nude mice, Mmp14, Il6st, and Tgfbr3 genes were over-expressed, suggesting their putative role in bone regeneration and hematopoiesis. In conclusion, we show here that the T-mediated inflammatory microenvironment is detrimental to BMSCs-induced bone formation and shortens the survival of implanted cells. Conversely, the lack of T-lymphocyte reaction in T-deficient animals is beneficial to BMSCs-induced mature bone formation. This should be taken into account when evaluating cell/biomaterial composites in these models.

Therapeutic strategies for treating osteolytic bone metastases.

The recent progress in oncologic management of patients with localized cancer or metastatic disease has permitted a significant improvement in life expectancy. Nevertheless, bone metastases and their consequent skeletal-related events (SREs) are still associated with unfavorable prognosis and greatly affect quality of life. Global management of these bone metastases includes traditional local approaches (surgery, radiotherapy, etc.) and systemic administration of chemotherapeutic agents. This review focuses on treatments specific for bone metastases and, in particular, on inhibitors of bone resorption that are effective for preventing and delaying the development of SREs.

Monocytes differentiation upon treatment with a peptide corresponding to the C-terminus of activated T cell-expressed Tirc7 protein.

Atp6v0a3 gene encodes for two alternative products, Tirc7 and a3 proteins, which are differentially expressed in activated T cells and resorbing osteoclasts, respectively. Tirc7 plays a central role in T cell activation, while a3 protein is critical for osteoclast-mediated bone matrix resorption. Based on the large body of evidences documenting the relationships between T cells and osteoclasts, we hypothesized that the extracellular C-terminus of Tirc7 protein could directly interact with osteoclast precursor cells. To address this issue, we performed the molecular cloning of a mouse Atp6v0a3 cDNA segment encoding the last 40 amino acids of Tirc7 protein, and we used this peptide as a ligand added to mouse osteoclast precursor cells. We evidenced that Tirc7-Cter peptide induced the differentiation of RAW264.7 cells into osteoclast-like cells, stimulated an autocrine/paracrine regulatory loop potentially involved in osteoclastic differentiation control, and strongly up-regulated F4/80 protein expression within multinucleated osteoclast-like cells. Using a mouse bone marrow-derived CD11b(+) cell line, or total bone marrow primary cells, we observed that similarly to Rankl, Tirc7-Cter peptide induced the formation of TRACP-positive large multinucleated cells. At last, using mouse primary monocytes purified from total bone marrow, we determined that Tirc7-Cter peptide induced the appearance of small multinucleated cells (3-4 nuclei), devoid of resorbing activity, and which displayed modulations of dendritic cell marker genes expression. In conclusion, we report for the first time on biological effects mediated by a peptide corresponding to the C-terminus of Tirc7 protein, which interfere with monocytic differentiation pathways.

CCL5 neutralization restricts cancer growth and potentiates the targeting of PDGFRß in colorectal carcinoma.

Increased CCL5 levels are markers of an unfavourable outcome in patients with melanoma, breast, cervical, prostate, gastric or pancreatic cancer. Here, we have assessed the role played by CCL5/CCR5 interactions in the development of colon cancer. To do so, we have examined a number of human colorectal carcinoma clinical specimens and found CCL5 and its receptors over-expressed within primary as well as liver and pulmonary metastases of patients compared to healthy tissues. In vitro, CCL5 increased the growth and migratory responses of colon cancer cells from both human and mouse origins. In addition, systemic treatment of mice with CCL5-directed antibodies reduced the extent of development of subcutaneous colon tumors, of liver metastases and of peritoneal carcinosis. Consistently, we found increased numbers of CD45-immunoreactive cells within the stroma of the remaining lesions as well as at the interface with the healthy tissue. In contrast, selective targeting of CCR5 through administration of TAK-779, a CCR5 antagonist, only partially compromised colon cancer progression. Furthermore, CCL5 neutralization rendered the tumors more sensitive to a PDGFRß-directed strategy in mice, this combination regimen offering the greatest protection against liver metastases and suppressing macroscopic peritoneal carcinosis. Collectively, our data demonstrate the involvement of CCL5 in the pathogenesis of colorectal carcinoma and point to its potential value as a therapeutic target.

Xg expression in Ewing's sarcoma is of prognostic value and contributes to tumor invasiveness.

Ewing's sarcoma (EWS) is an aggressive tumor of children and young adults that requires intensive treatment. The search for new prognostic factors is very important to choose the most appropriate therapy and to better understand the biology of the disease for the development of new therapeutic tools. We found that Xg, a thus far poorly described molecule and member of the CD99 family, is expressed in EWS cell lines and EWS primary tumors. Immunohistochemical analysis confirmed the expression of Xg in 24% of patients. We found that Xg expression in EWS defines a subgroup of patients with worse prognosis compared with those with Xg-negative localized tumors, indicating a clinical relevance of Xg expression in EWS. Forced expression of Xg in an EWS cell line upregulated cell migration and invasion in vitro. Furthermore, knockdown of Xg expression with specific short hairpin RNA significantly reduced migration and invasion of EWS cells. Consistent with these data, in vivo xenotransplant studies in nude mice revealed that Xg expression increased the incidence and the number of metastases of EWS cells. Thus, Xg expression is associated with lower overall survival in EWS patients with localized tumors and is implicated in metastasis.

Antagonism of chemokine receptor CXCR3 inhibits osteosarcoma metastasis to lungs.

Metastasis continues to be the leading cause of mortality for patients with cancer. Several years ago, it became clear that chemokines and their receptors could control the tumor progress. CXCR3 has now been identified in many cancers including osteosarcoma and CXCR3 ligands were expressed by lungs that are the primary sites to which this tumor metastasize. This study tested the hypothesis that disruption of the CXCR3/CXCR3 ligands complexes could lead to a decrease in lungs metastasis. The experimental design involved the use of the CXCR3 antagonist, AMG487 and 2 murine models of osteosarcoma lung metastases. After tail vein injection of osteosarcoma cells, mice that were systematically treated with AMG487 according to preventive or curative protocols had a significant reduction in metastatic disease. Treatment of osteosarcoma cells in vitro with AMG487 led to decreased migration, decreased matrix metalloproteinase activity, decreased proliferation/survival and increased caspase-independent death. Taken together, our results support the hypothesis that CXCR3 and their ligands intervene in the initial dissemination of the osteosarcoma cells to the lungs and stimulate the growth and expansion of the metastatic foci in later stages. Moreover, these studies indicate that targeting CXCR3 may specifically inhibit tumor metastasis without adversely affecting antitumoral host response.

Silencing of hSlo potassium channels in human osteosarcoma cells promotes tumorigenesis.

Potassium channels, the most diverse superfamily of ion channels, have recently emerged as regulators of carcinogenesis, thus introducing possible new therapeutic strategies in the fight against cancer. In particular, the large conductance Ca(2+)-activated K(+) channels, often referred to as BK channels, are at the crossroads of several tumor-associated processes such as cell proliferation, survival, secretion and migration. Despite the high BK channel expression in osteosarcoma (OS), their function has not yet been investigated in this malignant bone pathology. Here, using stable RNA interference to reduce the expression of hSlo, the human pore-forming alpha-subunit of the BK channel, in human Cal72 OS cells, we show that BK channels play a functional role in carcinogenesis. Our results reveal for the first time that BK channels exhibit antitumoral properties in OS in vivo and affect the tumor microenvironment through the modulation of both chemokine expression and leukocyte infiltration.

Soluble fractalkine prevents monocyte chemoattractant protein-1-induced monocyte migration via inhibition of stress-activated protein kinase 2/p38 and matrix metalloproteinase activities.

In this study, we address the question of the cross-talk between two chemokines that are cosecreted during inflammation, namely monocyte chemoattractant protein-1 (MCP-1) and soluble fractalkine (s-FKN), toward monocyte migration. We found that s-FKN fails to induce MonoMac6 cell migration per se. Interestingly, this chemokine antagonizes transendothelial migration and chemotaxis of MonoMac6 cells and freshly isolated human monocytes induced by MCP-1, indicating a direct effect of s-FKN on monocytic cells. In this study, we found that stress-activated protein kinase (SAPK)1/c-Jun N-terminal kinase 1 and SAPK2/p38 are involved in the control of MCP-1-induced MonoMac6 cell migration. We demonstrated that s-FKN abrogates the MCP-1-induced SAPK2/p38 activation as well as the upstream Pyk2 activity. Furthermore, we observed that s-FKN also inhibits the activity of a major matrix metalloproteinase (MMP), namely MMP-2. Taken collectively, our results indicate that the s-FKN antagonizes the chemoattractant effect of MCP-1 on monocytes, likely by inhibiting crucial signaling pathways, like SAPK2/p38 and MMP-2 activities.

Focal adhesion kinase pp125FAK interacts with the large conductance calcium-activated hSlo potassium channel in human osteoblasts: potential role in mechanotransduction.

UNLABELLED: Molecular events of mechanotransduction in osteoblasts are poorly defined. We show that the mechanosensitive BK channels open and recruit the focal adhesion kinase FAK in osteoblasts on hypotonic shock. This could convert mechanical signals in biochemical events, leading to osteoblast activation. INTRODUCTION: Mechanical strains applied to the skeleton influence bone remodeling and architecture mainly through the osteoblast lineage. The molecular mechanisms involved in osteoblastic mechanotransduction include opening of mechanosensitive cation channels and the activation of protein tyrosine kinases, notably FAK, but their interplay remains poorly characterized. The large conductance K+ channel (BK) seems likely as a bone mechanoreceptor candidate because of its high expression in osteoblasts and its ability to open in response to membrane stretch or hypotonic shock. Propagation of the signals issued from the mechanosensitivity of BK channels inside the cell likely implies complex interactions with molecular partners involved in mechanotransduction, notably FAK. METHODS: Interaction of FAK with the C terminus of the hSlo alpha-subunit of BK was investigated using the yeast two-hybrid system as well as immunofluorescence microscopy and coimmunoprecipitation experiments with a rabbit anti-hslo antibody on MG63 and CAL72 human osteosarcoma cell lines and on normal human osteoblasts. Mapping of the FAK region interacting with hSlo was approached by testing the ability of hSlo to recruit mutated ot truncated FAK proteins. RESULTS: To the best of our knowledge, we provide the first evidence of the physical association of FAK with the intracellular part of hslo. We show that FAK/hSlo interaction likely takes place through the Pro-1-rich domain situated in the C-terminal region of the kinase. FAK/hSlo association occurs constitutively at a low, but appreciable, level in human osteosarcoma cells and normal human osteoblasts that express endogenous FAK and hSlo. In addition, we found that application of an hypo-osmotic shock to these cells induced a sustained activation of BK channels associated to a marked increase in the recruitment of FAK on hSlo. CONCLUSIONS: Based on these data, we propose that BK channels might play a triggering role in the signaling cascade induced by mechanical strains in osteoblasts.

The receptor activator of nuclear factor (NF)-kappaB ligand (RANKL) is a new chemotactic factor for human monocytes.

Bone resorption is regulated by the immune system, where receptor activator of nuclear factor (NF)kappaB ligand (RANKL), a new member of the tumor-necrosis factor family, may contribute to pathological conditions. Due to the role of RANKL in the maturation of monocyte-derived osteoclasts, we hypothesized that RANKL could exert chemotactic properties toward monocytic cells. Our results demonstrate that RANKL induces the migration of MonoMac-6 monocytic cells as well as human freshly isolated total peripheral blood mononuclear cells (PBMC) and CD14+ purified PBMC. RANKL induces the migration of MonoMac-6 cells in a dose-dependent manner and with an efficacy similar to MCP-1. After an 8-h incubation, the soluble form of RANKL (sRANKL) started to exhibit a chemoattractive effect on MonoMac-6 cells, with an increased effect observed up to 24 h. RANKL elicits an additive chemotactic effect to MCP-1. Furthermore, addition of the RANKL decoy receptor osteoprotegerin in the lower well or RANKL in the upper well abrogates the RANKL-induced migration of MonoMac-6 cells, hallmarking a true specific activity. RNase protection assay experiments indicate that exposure of MonoMac-6 cells to RANKL had no significant effect on the expression of a variety of chemokines, known to attract monocytes. This study provides evidence that RANKL behaves as a chemotactic factor for monocytic cells, emphazing the cross-talk between bone and immune systems.

Prostaglandin E2 induces interaction between hSlo potassium channel and Syk tyrosine kinase in osteosarcoma cells.

Prostaglandins (PGs) are important mediators of bone response to growth factors, hormones, inflammation, or mechanical strains. In this study, we show that in MG63 osteosarcoma cells, prostaglandin E2 (PGE2) produces the opening of a large conductance Ca2+-dependent K+ channel (BK). This PGE2-mediated channel opening induces the recruitment of various tyrosine-phosphorylated proteins on the hSlo alpha-subunit of BK. Because the C-terminal domain of hSlo encompasses an immunoreceptor tyrosine-based activation motif (ITAM), we show that the Syk nonreceptor tyrosine kinase, reported yet to be expressed mainly in hematopoietic cells, is expressed also in osteoblastic cells, and recruited on this ITAM after a PGE2-induced docking/activation process. We show that Syk/hSlo association is dependent of an upstream Src-related tyrosine kinase activity, in accord with the classical two-step model described for immune receptors. Finally, we provide evidence that this Syk/hSlo interaction does not affect the electrical features of BK channels in osteosarcoma cells. With these data, we would like to suggest the new notion that besides its conductance function, hSlo channel can behave in bone cells, as a true transduction protein intervening in the bone remodeling induced by PGE2.