Negative regulation of the osteoblast function in multiple myeloma through the repressor gene E4BP4 activated by malignant plasma cells

The role of the circadian timing system on drug metabolism and detoxification: an update

INTRODUCTION

The 24-hour variations in drug absorption, distribution, metabolism, and elimination, collectively known as pharmacokinetics, are fundamentally influenced by rhythmic physiological processes regulated by the molecular clock. Recent advances have elucidated the intricacies of the circadian timing system and the molecular interplay between biological clocks, enzymes and transporters in preclinical level.

AREA COVERED

Circadian rhythm of the drug metabolizing enzymes and carrier efflux functions possess a major role for drug metabolism and detoxification. The efflux and metabolism function of intestines and liver seems important. The investigations revealed that the ABC and SLC transporter families, along with cytochrome p-450 systems in the intestine, liver, and kidney, play a dominant role in the circadian detoxification of drugs. Additionally, the circadian control of efflux by the blood-brain barrier is also discussed.

EXPERT OPINION

The influence of the circadian timing system on drug pharmacokinetics significantly impacts the efficacy, adverse effects, and toxicity profiles of various drugs. Moreover, the emergence of sex-related circadian changes in the metabolism and detoxification processes has underscored the importance of considering gender-specific differences in drug tolerability and pharmacology. A better understanding of coupling between central clock and circadian metabolism/transport contributes to the development of more rational drug utilization and the implementation of chronotherapy applications.

The role of basic leucine zipper transcription factor E4BP4 in cancer: a review and update

Mutations in the genes of tumor cells and the disorder of immune microenvironment are the main factors of tumor development. The sensitivity of tumor cells to chemotherapy drugs affect the treatment of tumor. Nuclear transcription factor E4BP4 is dysregulated in a variety of malignant tumors. It can suppress the transcription of NFKBIA, RASSF8, SOSTDC1, FOXO-induced genes (TRAIL, FAS, GADD45a and GADD45b) and Hepcidin, up-regulate RCAN1-1 and PRNP, activate mTOR and p38 in cancer cells. Also, E4BP4 can regulate tumor immune microenvironment. TGFb1/Smad3/E4BP4/ IFNγ axis in NK cells plays an important role in antitumor immunotherapy. Over expression of E4BP4 inhibited the development of Th17 cells by directly binding to the RORγt promoter. Moreover, recent studies have shown that E4BP4 inhibited the expression of multidrug resistance genes. In this review, we summarize the molecular mechanism of E4BP4 in cancer cellular process, the effects of E4BP4 in cancer immunotherapy and antitumor drug resistance, to provide theoretical basis for tumor treatment strategies targeting E4BP4.

Myeloma Bone Disease: A Comprehensive Review

Multiple myeloma (MM) is a neoplastic clonal proliferation of plasma cells in the bone marrow microenvironment, characterized by overproduction of heavy- and light-chain monoclonal proteins (M-protein). These proteins are mainly found in the serum and/or urine. Reduction in normal gammaglobulins (immunoparesis) leads to an increased risk of infection. The primary site of origin is the bone marrow for nearly all patients affected by MM with disseminated marrow involvement in most cases. MM is known to involve bones and result in myeloma bone disease. Osteolytic lesions are seen in 80% of patients with MM which are complicated frequently by skeletal-related events (SRE) such as hypercalcemia, bone pain, pathological fractures, vertebral collapse, and spinal cord compression. These deteriorate the patient's quality of life and affect the overall survival of the patient. The underlying pathogenesis of myeloma bone disease involves uncoupling of the bone remodeling processes. Interaction of myeloma cells with the bone marrow microenvironment promotes the release of many biochemical markers including osteoclast activating factors and osteoblast inhibitory factors. Elevated levels of osteoclast activating factors such as RANK/RANKL/OPG, MIP-1-α., TNF-α, IL-3, IL-6, and IL-11 increase bone resorption by osteoclast stimulation, differentiation, and maturation, whereas osteoblast inhibitory factors such as the Wnt/DKK1 pathway, secreted frizzle related protein-2, and runt-related transcription factor 2 inhibit osteoblast differentiation and formation leading to decreased bone formation. These biochemical factors also help in development and utilization of appropriate anti-myeloma treatments in myeloma patients. This review article summarizes the pathophysiology and the recent developments of abnormal bone remodeling in MM, while reviewing various approved and potential treatments for myeloma bone disease.

Bone Marrow Mesenchymal Stromal Cells in Multiple Myeloma: Their Role as Active Contributors to Myeloma Progression

Multiple myeloma (MM) is a hematological malignancy of plasma cells that proliferate and accumulate within the bone marrow (BM). Work from many groups has made evident that the complex microenvironment of the BM plays a crucial role in myeloma progression and response to therapeutic agents. Within the cellular components of the BM, we will specifically focus on mesenchymal stromal cells (MSCs), which are known to interact with myeloma cells and the other components of the BM through cell to cell, soluble factors and, as more recently evidenced, through extracellular vesicles. Multiple structural and functional abnormalities have been found when characterizing MSCs derived from myeloma patients (MM-MSCs) and comparing them to those from healthy donors (HD-MSCs). Other studies have identified differences in genomic, mRNA, microRNA, histone modification, and DNA methylation profiles. We discuss these distinctive features shaping MM-MSCs and propose a model for the transition from HD-MSCs to MM-MSCs as a consequence of the interaction with myeloma cells. Finally, we review the contribution of MM-MSCs to several aspects of myeloma pathology, specifically to myeloma growth and survival, drug resistance, dissemination and homing, myeloma bone disease, and the induction of a pro-inflammatory and immunosuppressive microenvironment.

Therapeutic targets in myeloma bone disease

Multiple myeloma (MM) is the second most common haematological malignancy and is characterized by a clonal proliferation of neoplastic plasma cells within the bone marrow. MM is the most frequent cancer involving the skeleton, causing osteolytic lesions, bone pain and pathological fractures that dramatically decrease MM patients' quality of life and survival. MM bone disease (MBD) results from uncoupling of bone remodelling in which excessive bone resorption is not compensated by new bone formation, due to a persistent suppression of osteoblast activity. Current management of MBD includes antiresorptive agents, bisphosphonates and denosumab, that are only partially effective due to their inability to repair the existing lesions. Thus, research into agents that prevent bone destruction and more importantly repair existing lesions by inducing new bone formation is essential. This review discusses the mechanisms regulating the uncoupled bone remodelling in MM and summarizes current advances in the treatment of MBD. LINKED ARTICLES: This article is part of a themed issue on The molecular pharmacology of bone and cancer-related bone diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.9/issuetoc.

CCN1 stimulated the osteoblasts via PTEN/AKT/GSK3β/cyclinD1 signal pathway in Myeloma Bone Disease

BACKGROUNDS

Myeloma-related bone disease (MBD) is a common complication of multiple myeloma (MM), which can both decrease life quality and influence the prognosis of the patients. We have found that CCN1 stimulated proliferation and differentiation of osteoblasts in MM in vitro and in vivo, while its mechanism still remains unknown.

METHOD

Bone marrow mononuclear cells were collected from MM patients and differentiated into the osteoblasts. After co-culture with CCN1 in vitro, the intracellular signaling antibody array and western blot were performed to explore the signaling pathway. Furthermore, GSK3β inhibitor TWS119 was used to check the pathway of CCN1 might have on osteoblasts in vitro.

RESULTS

For the protein array kit, the expressions of GSK3β, 4E-BP1, and PTEN are decreased in CCN1 group. For western blots, the CCN1 group also has lower expression comparing to the control group in PTEN (P = .031). Meanwhile p-AKT and cyclinD1 levels have increased in the CCN1 group (P = .002, P = .039). After adding TWS119 as another group, western blot was performed again to verify the pathway. For upstream proteins PTEN and p-AKT, TWS119 group has higher expression level compared to that in CCN1 group (P = .003, P = .001). And for downstream protein cyclinD1, TWS119 group also presented higher level than the control group (P = .02). CCN1 could have almost the same effect on GSK3β as the specific inhibitor TWS119 had.

CONCLUSIONS

CCN1 can stimulate osteoblasts through PTEN/AKT/GSK3β/cyclinD1 pathway in MBD, which has the potential to be a novel therapy of MBD.

Multiple Myeloma and Bone: The Fatal Interaction

Multiple myeloma (MM) is the second-most-common hematologic malignancy and the most frequent cancer to involve bone. MM bone disease (MMBD) has devastating consequences for patients, including dramatic bone loss, severe bone pain, and pathological fractures that markedly decrease the quality of life and impact survival of MM patients. MMBD results from excessive osteoclastic bone resorption and persistent suppressed osteoblastic bone formation, causing lytic lesions that do not heal, even when patients are in complete and prolonged remission. This review discusses the cellular and molecular mechanisms that regulate the uncoupling of bone remodeling in MM, the effects of MMBD on tumor growth, and potential therapeutic approaches that may prevent severe bone loss and repair damaged bone in MM patients.

The first invertebrate NFIL3 transcription factor with role in immune defense identified from the Hong Kong oyster, Crassostrea hongkongensis

NFIL3 (nuclear factor interleukin 3-regulated) is a basic leucine zipper type transcription factor that mediates a variety of immune responses in vertebrates. However, the sequence information and function of NFIL3 homologs in invertebrates, especially mollusks, remains unknown. In the present study, the first NFIL3 homolog was identified in a marine mollusk, Crassostrea hongkongensis (designated as ChNFIL3), followed by its functional characterization. The full-length cDNA of ChNFIL3 is 2221 bp and consists of an open reading frame (ORF) of 1536 bp that encodes a polypeptide of 551 amino acids. Simple Modular Architecture Research Tool (SMART) analysis indicated that ChNFIL3 has two basic leucin zipper domains, similar to the other known NFIL3 family proteins. Tissue distribution analysis of NFIL3 in this mollusk revealed high expression in digestive glands and hemocytes. A significant induction in the mRNA level of ChNFIL3 was observed following bacterial stimulation. ChNFIL3 was found to be localized in the nucleus and over expression of ChNIFL3 led to upregulation of transcriptional activity of an NF-κB reporter gene in HEK 293T cells, indicating its role in innate immunity. Furthermore, addition of exogenous recombinant ChNFIL3 proteins resulted in enhanced mRNA level of hemocyte interleukin 17 in vitro. In conclusion, our findings revealed that NFIL3 in molluscs, plays a conserved role in host defense, similar to its mammalian homolog.

Chromothripsis in Treatment Resistance in Multiple Myeloma

Multiple myeloma (MM) is a malignant disease caused by an abnormal proliferation of plasma cells, of which the prognostic factors include chromosomal abnormality, β-2 microglobulin, and albumin. Recently, the term chromothripsis has emerged, which is the massive but highly localized chromosomal rearrangement in response to a one-step catastrophic event. Many studies have shown an association of chromothripsis with the prognosis in several cancers; however, few studies have investigated it in MM. Here, we studied the association between chromothripsis-like patterns and treatment resistance or prognosis. First, we analyzed nine MM cell lines (U266, MM.1S, RPMI8226, KMS-11, KMS-12-BM, KMS-12-PE, KMS-28-BM, KMS-28-PE, and NCI-H929) and bone marrow samples of four patients who were diagnosed with MM by next-generation sequencing-based copy number variation analysis. The frequency of the chromothripsis-like pattern was observed in seven cell lines. We analyzed the treatment-induced chromothripsis-like patterns in KMS-12-BM and KMS-12-PE cells. As a result, breakpoints and chromothripsis-like patterns were increased after drug treatment in the relatively resistant KMS-12-BM. We further analyzed the patients’ results according to the therapeutic response, which was divided into sensitive and resistant, as suggested by the International Myeloma Working Group. The chromothripsis-like pattern was more frequently observed in the resistant group. In the sensitive group, the frequency of the chromothripsis-like pattern decreased after treatment, whereas the resistant group showed increased chromothripsis-like patterns after the treatment. These results suggest that the chromothripsis-like pattern is associated with treatment response in MM.

Regulation of Clock Genes by Adrenergic Receptor Signaling in Osteoblasts

The clock system has been identified as one of the major mechanisms controlling cellular functions. Circadian clock gene oscillations also actively participate in the functions of various cell types including bone-related cells. Previous studies demonstrated that clock genes were expressed in bone tissue and also that their expression exhibited circadian rhythmicity. Recent findings have shown that sympathetic tone plays a central role in biological oscillations in bone. Adrenergic receptor (AR) signaling regulates the expression of clock genes in cancellous bone. Furthermore, α₁-AR signaling in osteoblasts is known to negatively regulate the expression of bone morphogenetic protein-4 (Bmp4) by up-regulating nuclear factor IL-3 (Nfil3)/e4 promoter-binding protein 4 (E4BP4). The ablation of α_1B-AR signaling also increases the expression of the Bmp4 gene in bone. The findings of transient overexpression and siRNA experiments have supported the involvement of the transcription factor CCAAT/enhancer-binding protein delta (C/EBPδ, Cebpd) in Nfil3 and Bmp4 expression in MC3T3-E1 cells. These findings suggest that the effects of Cebpd are due to the circadian regulation of Bmp4 expression, at least in part, by the up-regulated expression of the clock gene Nfil3 in response to α_1B-AR signaling in osteoblasts. Therefore, AR signaling appears to modulate cellular functionality through the expression of clock genes that are circadian rhythm regulators in osteoblasts. The expression of clock genes regulated by the sympathetic nervous system and clock-controlled genes that affect bone metabolism are described herein.

Molecular mechanisms, current management and next generation therapy in myeloma bone disease

Multiple myeloma (MM) bone disease is a major cause of morbidity and mortality in MM patients and persists even in patients in remission. This bone disease is caused by an uncoupling of bone remodeling, with increased osteoclast and decreased osteoblast activity and formation, culminating in lytic bone destruction. Bisphosphonates are the current standard of care but new therapies are needed. As the molecular mechanisms controlling MM bone disease are increasingly well understood, new therapeutic targets are extensively explored in the preclinical setting and initial clinical trials with novel compounds now show promising results. In this review, we will provide a comprehensive overview of the biology of MM bone disease, summarize its current clinical management and discuss preclinical and clinical data on next generation therapies.

CYR61/CCN1 stimulates proliferation and differentiation of osteoblasts in vitro and contributes to bone remodeling in vivo in myeloma bone disease

Cysteine-rich 61 (CYR61/CCN1), a secreted protein in bone marrow (BM) microenvironment, has diverse effects on many cellular activities such as growth and differentiation. However, the effect of CCN1 on osteoblasts (OBs) in myeloma bone disease remains unclear. In our study, the level of CCN1 in multiple myeloma (MM) patients was detected by ELISA and RT-PCR. The proliferation and differentiation of OBs from MM patients were observed after stimulated by CCN1 in vitro. The myeloma cells transduced with CYR61 gene (RPMI‑8226/CYR61) were injected in a mouse model to evaluate the efficacy of CCN1 in vivo and compare with zoledronic acid. The results showed that CYR61/CCN1 levels in BM supernatant and OBs both elevated significantly in all newly diagnosed MM patients, especially in patients without bone disease (P=0.001 and P<0.001). After 30 ng/l CCN1 stimulation for 24 h, the quantity and mineralization of OBs increased significantly in vitro (P=0.046 and 0.048). The transcription factors of Wnt pathway, runt-related transcription factor 2 (Runx2) and β-catenin were upregulated in OBs after CCN1 stimulation (P=0.012 and 0.011). After injection of RPMI‑8226 cells, bone lesions were observed obviously by microCT and histochemistry at 7 weeks. Radiographic analysis of the bones showed decreased resorption in CCN1 overexpression group and zoledronic acid group, while severe resorption in negative control. Furthermore, trabecular bone volume in CCN1 overexpression group (1.7539±0.16949) was significantly higher than zoledronic acid group (1.2839±0.077) (P=0.012). In conclusion, CCN1 can stimulate the proliferation and differentiation of OBs in vitro and contribute to bone remodeling in vivo in MBD.

Osteoblast inhibition by chemokine cytokine ligand3 in myeloma-induced bone disease

Background

Multiple myeloma is a hematologic malignancy characterized by the accumulation of monoclonal plasma cells in the bone marrow. A common manifestation of the disease is myeloma bone disease (MBD), which is caused by increased osteoclastic bone resorption and decreased bone formation. The chemokine cytokine ligand 3 (CCL3) is a pro-inflammatory protein and chemokine that stimulates osteoclasts in MBD. However, little is known about the effect of CCL3 on osteoblasts (OB).

Methods

The OBs are induced from patients with MBD and healthy donors, cultured in vitro, and identified by histochemistry. The effects of CCL3 and CCL3 antibody on the OBs in vitro are observed. The CCL3 receptor (CCR1), osteocalcin (OCN), runt-related transcription factor 2 (Runx2), and osterix (Osx) are detected using flow cytometry, enzyme-linked immunosorbent assay, and real-time PCR.

Results

Proliferation and osteogenic potential of the OB in patients with MBD are suppressed. Moreover, the CCR1 expression is significantly higher in patients with MBD than in normal controls. The OCN level, quantity of calcium nodules, and Runx2 and Osx levels decrease after CCL3 stimulation, which indicates that CCL3 inhibits OB function. Furthermore, CCL3 antibody partially restores OB activity through the upregulation of the OCN, Runx2, and Osx.

Conclusions

CCL3 contributes to the OB/OC imbalance by inhibiting OB differentiation and function in MBD.

Bone disease in multiple myeloma: pathophysiology and management

Myeloma bone disease (MBD) is a devastating complication of multiple myeloma (MM). More than 80% of MM patients suffer from destructive bony lesions, leading to pain, fractures, mobility issues, and neurological deficits. MBD is not only a main cause of disability and morbidity in MM patients but also increases the cost of management. Bone destruction and lack of bone formation are main factors in the development of MBD. Some novel factors are found to be involved in the pathogenesis of MBD, eg, receptor activator of nuclear factor kappa-B ligand (RANKL), osteoprotegerin (OPG) system (RANKL/OPG), Wingless (Wnt), dickkopf-1 (Wnt/DKK1) pathway. The addition of novel agents in the treatment of MM, use of bisphosphonates and other supportive modalities such as radiotherapy, vertebroplasty/kyphoplasty, and surgical interventions, all have significant roles in the treatment of MBD. This review provides an overview on the pathophysiology and management of MBD.

Multiple myeloma mesenchymal stromal cells: Contribution to myeloma bone disease and therapeutics

Multiple myeloma is a hematological malignancy in which clonal plasma cells proliferate and accumulate within the bone marrow. The presence of osteolytic lesions due to increased osteoclast (OC) activity and suppressed osteoblast (OB) function is characteristic of the disease. The bone marrow mesenchymal stromal cells (MSCs) play a critical role in multiple myeloma pathophysiology, greatly promoting the growth, survival, drug resistance and migration of myeloma cells. Here, we specifically discuss on the relative contribution of MSCs to the pathophysiology of osteolytic lesions in light of the current knowledge of the biology of myeloma bone disease (MBD), together with the reported genomic, functional and gene expression differences between MSCs derived from myeloma patients (pMSCs) and their healthy counterparts (dMSCs). Being MSCs the progenitors of OBs, pMSCs primarily contribute to the pathogenesis of MBD because of their reduced osteogenic potential consequence of multiple OB inhibitory factors and direct interactions with myeloma cells in the bone marrow. Importantly, pMSCs also readily contribute to MBD by promoting OC formation and activity at various levels (i.e., increasing RANKL to OPG expression, augmenting secretion of activin A, uncoupling ephrinB2-EphB4 signaling, and through augmented production of Wnt5a), thus further contributing to OB/OC uncoupling in osteolytic lesions. In this review, we also look over main signaling pathways involved in the osteogenic differentiation of MSCs and/or OB activity, highlighting amenable therapeutic targets; in parallel, the reported activity of bone-anabolic agents (at preclinical or clinical stage) targeting those signaling pathways is commented.

New Frontiers for the NFIL3 bZIP Transcription Factor in Cancer, Metabolism and Beyond

The bZIP transcription factor NFIL3 (Nuclear factor Interleukin 3 regulated, also known as E4 binding protein 4, E4BP4) regulates diverse biological processes from circadian rhythm to cellular viability. Recently, a host of novel roles have been identified for NFIL3 in immunological signal transduction, cancer, aging and metabolism. Elucidating the signaling pathways that are impacted by NFIL3 and the regulatory mechanisms that it targets, inhibits or activates will be critical for developing a clearer picture of its physiological roles in disease and normal processes. This review will discuss the recent advances and emerging issues regarding NFIL3-mediated transcriptional regulation of CEBPb and FOXO1 activated genes and signal transduction.

Glucocorticoid induced osteoblast apoptosis by increasing E4BP4 expression via up-regulation of Bim

It is well known that glucocorticoid (GC)-induced bone loss is caused primarily by hypofunction and apoptosis of osteoblasts. However, the precise molecular events underlying the effect of GC on osteoblast apoptosis are not fully understood. Recent studies implicated an important role of E4BP4 in the regulation of osteoblast apoptosis and differentiation. Furthermore, E4BP4 is a GC-regulated gene required for GC-induced apoptosis in many cells. Therefore, we hypothesize that E4BP4 may be implicated in the process of GC-induced osteoblast apoptosis. Western blot, reverse-transcription-PCR, flow cytometry, and Hoechst 33258 staining were employed to investigate the role of E4BP4 in dexamethasone (DEX)-induced osteoblast apoptosis. We found that the expression of E4BP4 is significantly up-regulated in osteoblasts exposed to DEX. Furthermore, the depletion of E4BP4 significantly decreased DEX-induced osteoblast apoptosis. In addition, E4BP4 plays a crucial role in GC-evoked apoptosis of osteoblasts by enabling induction of Bim. On the basis of these results above, we can draw the conclusion that E4BP4 may contribute to the process of DEX-induced osteoblast apoptosis.

PTHrP produced by myeloma plasma cells regulates their survival and pro-osteoclast activity for bone disease progression

To promote their survival and progression in the skeleton, osteotropic malignancies of breast, lung, and prostate produce parathyroid hormone-related protein (PTHrP), which induces hypercalcemia. PTHrP serum elevations have also been described in multiple myeloma (MM), although their role is not well defined. When we investigated MM cells from patients and cell lines, we found that PTHrP and its receptor (PTH-R1) are highly expressed, and that PTHrP is secreted both as a full-length molecule and as small subunits. Among these subunits, the mid-region, including the nuclear localization sequence (NLS), exerted a proliferative effect because it was accumulated in nuclei of MM cells surviving in starvation conditions. This was confirmed by increased transcription of several genes enrolled in proliferation and apoptosis control. PTHrP was also found to stimulate PTH-R1 in MM cells. PTH-R1's selective activation by the full-length PTHrP molecule or the NH2 -terminal fragment resulted in a significant increase of intracellular Ca(2+) influx, cyclic adenosine monophosphate (cAMP) content, and expression of receptor activator of NF-κB ligand (RANKL) and monocyte chemoattractant protein-1 (MCP-1). Our data definitely clarify the role of PTHrP in MM. The PTHrP peptide is functionally secreted by malignant plasma cells and contributes to MM tumor biology and progression, both by intracrine maintenance of cell proliferation in stress conditions and by autocrine or paracrine stimulation of PTH-R1, which in turn reinforces the production of osteoclastogenic factors. © 2014 American Society for Bone and Mineral Research.

E4BP4: an unexpected player in the immune response

Until recently, the basic leucine zipper transcription factor E4BP4 (also known as NFIL3) was of little interest to immunologists, being best known for its role in regulating circadian rhythm in chick pineal gland. However, characterisation of E4bp4(-/-) mice, independently generated in four different laboratories, has revealed roles for E4BP4 in diverse haematopoietic lineages. E4BP4 is essential for the development of NK cells and CD8α(+) conventional dendritic cells, and is also involved in macrophage activation, polarisation of CD4(+) T cell responses and B cell class switching to IgE. Here, we discuss the role of E4BP4 as a regulator of the immune response and highlight future questions for the field.

Gfi1 expressed in bone marrow stromal cells is a novel osteoblast suppressor in patients with multiple myeloma bone disease

Protracted inhibition of osteoblast (OB) differentiation characterizes multiple myeloma (MM) bone disease and persists even when patients are in long-term remission. However, the underlying pathophysiology for this prolonged OB suppression is unknown. Therefore, we developed a mouse MM model in which the bone marrow stromal cells (BMSCs) remained unresponsive to OB differentiation signals after removal of MM cells. We found that BMSCs from both MM-bearing mice and MM patients had increased levels of the transcriptional repressor Gfi1 compared with controls and that Gfi1 was a novel transcriptional repressor of the critical OB transcription factor Runx2. Trichostatin-A blocked the effects of Gfi1, suggesting that it induces epigenetic changes in the Runx2 promoter. MM-BMSC cell-cell contact was not required for MM cells to increase Gfi1 and repress Runx2 levels in MC-4 before OBs or naive primary BMSCs, and Gfi1 induction was blocked by anti-TNF-α and anti-IL-7 antibodies. Importantly, BMSCs isolated from Gfi1(-/-) mice were significantly resistant to MM-induced OB suppression. Strikingly, siRNA knockdown of Gfi1 in BMSCs from MM patients significantly restored expression of Runx2 and OB differentiation markers. Thus, Gfi1 may have an important role in prolonged MM-induced OB suppression and provide a new therapeutic target for MM bone disease.

Spatial segregation of BMP/Smad signaling affects osteoblast differentiation in C2C12 cells

BACKGROUND

Bone morphogenetic proteins (BMPs) are involved in a plethora of cellular processes in embryonic development and adult tissue homeostasis. Signaling specificity is achieved by dynamic processes involving BMP receptor oligomerization and endocytosis. This allows for spatiotemporal control of Smad dependent and non-Smad pathways. In this study, we investigate the spatiotemporal regulation within the BMP-induced Smad transcriptional pathway.

METHODOLOGY/PRINCIPAL FINDINGS

Here we discriminate between Smad signaling events that are dynamin-dependent (i.e., require an intact endocytic pathway) and dynamin-independent. Inhibition of dynamin-dependent endocytosis in fluorescence microscopy and fractionation studies revealed a delay in Smad1/5/8 phosphorylation and nuclear translocation after BMP-2 stimulation of C2C12 cells. Using whole genome microarray and qPCR analysis, we identified two classes of BMP-2 induced genes that are differentially affected by inhibition of endocytosis. Thus, BMP-2 induced gene expression of Id1, Id3, Dlx2 and Hey1 is endocytosis-dependent, whereas BMP-2 induced expression of Id2, Dlx3, Zbtb2 and Krt16 is endocytosis-independent. Furthermore, we demonstrate that short term inhibition of endocytosis interferes with osteoblast differentiation as measured by alkaline phosphatase (ALP) production and qPCR analysis of osteoblast marker gene expression.

CONCLUSIONS/SIGNIFICANCE

Our study demonstrates that dynamin-dependent endocytosis is crucial for the concise spatial activation of the BMP-2 induced signaling cascade. Inhibition of endocytic processes during BMP-2 stimulation leads to altered Smad1/5/8 signaling kinetics and results in differential target gene expression. We show that interfering with the BMP-2 induced transcriptional network by endocytosis inhibition results in an attenuation of osteoblast differentiation. This implies that selective sensitivity of gene expression to endocytosis provides an additional mechanism for the cell to respond to BMP in a context specific manner. Moreover, we suggest a novel Smad dependent signal cascade induced by BMP-2, which does not require endocytosis.

Ascorbic acid regulates osterix expression in osteoblasts by activation of prolyl hydroxylase and ubiquitination-mediated proteosomal degradation pathway

Mouse genetic studies reveal that ascorbic acid (AA) is essential for osteoblast (OB) differentiation and that osterix (Osx) was a key downstream target of AA action in OBs. To determine the molecular pathways for AA regulation of Osx expression, we evaluated if AA regulates Osx expression by regulating production and/or actions of local growth factors and extracellular matrix (ECM) proteins. Inhibition of actions of IGFs by inhibitory IGFBP-4, BMPs by noggin, and ECM-mediated integrin signaling by RGD did not block AA effects on Osx expression in OBs. Furthermore, blockade of components of MAPK signaling pathway had no effect on AA-induced Osx expression. Because AA is required for prolyl hydroxylase domain (PHD) activity and because PHD-induced prolyl-hydroxylation targets proteins to proteosomal degradation, we next tested if AA effect on Osx expression involves activation of PHD to hydroxylate and induce ubiquitin-proteosome-mediated degradation of transcriptional repressor(s) of Osx gene. Treatment of OBs with dimethyloxallyl glycine and ethyl 3, 4-dihydroxybenzoate, known inhibitors of PHD, completely blocked AA effect on Osx expression and OB differentiation. Knockdown of PHD2 expression by Lentivirus-mediated shRNA abolished AA-induced Osx induction and alkaline phosphatase activity. Furthermore, treatment of OBs with MG115, inhibitor of proteosomal degradation, completely blocked AA effects on Osx expression. Based on these data, we conclude that AA effect on Osx expression is mediated via a novel mechanism that involves PHD2 and proteosomal degradation of a yet to be identified transcriptional repressor that is independent of BMP, IGF-I, or integrin-mediated signaling in mouse OBs.

A role for nuclear factor interleukin-3 (NFIL3), a critical transcriptional repressor, in down-regulation of periovulatory gene expression

The LH surge triggers dramatic transcriptional changes in genes associated with ovulation and luteinization. The present study investigated the spatiotemporal expression of nuclear factor IL-3 (NFIL3), a transcriptional regulator of the basic leucine zipper transcription factor superfamily, and its potential role in the ovary during the periovulatory period. Immature female rats were injected with pregnant mare's serum gonadotropin, treated with human chorionic gonadotropin (hCG), and ovaries or granulosa cells were collected at various times after hCG. Nfil3 mRNA was highly induced both in intact ovaries and granulosa cells after hCG treatment. In situ hybridization demonstrated that Nfil3 mRNA was highly induced in theca-interstitial cells at 4-8 h after hCG, localized to granulosa cells at 12 h, and decreased at 24 h. Overexpression of NFIL3 in granulosa cells inhibited the induction of prostaglandin-endoperoxide synthase 2 (Ptgs2), progesterone receptor (Pgr), epiregulin (Ereg), and amphiregulin (Areg) and down-regulated levels of prostaglandin E2. The inhibitory effect on Ptgs2 induction was reversed by NFIL3 small interfering RNA treatment. In theca-interstitial cells the expression of hydroxyprostaglandin dehydrogenase 15-(nicotinamide adenine dinucleotide) (Hpgd) was also inhibited by NFIL3 overexpression. Data from luciferase assays demonstrated that NFIL3 overexpression decreased the induction of the Ptgs2 and Areg promoter activity. EMSA and chromatin immunoprecipitation analyses indicated that NFIL3 binds to the promoter region containing the DNA-binding sites of cAMP response element binding protein and CCAAT enhancer binding protein-β. In summary, hCG induction of NFIL3 expression may modulate the process of ovulation and theca-interstitial and granulosa cell differentiation by regulating expression of PTGS2, PGR, AREG, EREG, and HPGD, potentially through interactions with cAMP response element binding protein and CCAAT enhancer binding protein-β on their target gene promoters.

Tumor-host cell interactions in the bone disease of myeloma

Multiple myeloma is a hematological malignancy that is associated with the development of a destructive osteolytic bone disease, which is a major cause of morbidity for patients with myeloma. Interactions between myeloma cells and cells of the bone marrow microenvironment promote both tumor growth and survival and bone destruction, and the osteolytic bone disease is now recognized as a contributing component to tumor progression. Since myeloma bone disease is associated with both an increase in osteoclastic bone resorption and a suppression of osteoblastic bone formation, research to date has largely focused upon the role of the osteoclast and osteoblast. However, it is now clear that other cell types within the bone marrow, including cells of the immune system, mesenchymal stem cells and bone marrow stromal cells, can contribute to the development of myeloma bone disease. This review discusses the cellular mechanisms and potential therapeutic targets that have been implicated in myeloma bone disease.

Molecular genetic studies of gene identification for osteoporosis: the 2009 update

Osteoporosis is a complex human disease that results in increased susceptibility to fragility fractures. It can be phenotypically characterized using several traits, including bone mineral density, bone size, bone strength, and bone turnover markers. The identification of gene variants that contribute to osteoporosis phenotypes, or responses to therapy, can eventually help individualize the prognosis, treatment, and prevention of fractures and their adverse outcomes. Our previously published reviews have comprehensively summarized the progress of molecular genetic studies of gene identification for osteoporosis and have covered the data available to the end of September 2007. This review represents our continuing efforts to summarize the important and representative findings published between October 2007 and November 2009. The topics covered include genetic association and linkage studies in humans, transgenic and knockout mouse models, as well as gene-expression microarray and proteomics studies. Major results are tabulated for comparison and ease of reference. Comments are made on the notable findings and representative studies for their potential influence and implications on our present understanding of the genetics of osteoporosis.

Constitutive down-regulation of Osterix in osteoblasts from myeloma patients: in vitro effect of Bortezomib and Lenalidomide

Bortezomib and Lenalidomide have been shown to be effective in the control of multiple myeloma (MM) progression. We have investigated their role in the in vitro expression of Osterix by primary osteoblast cultures from MM patients and found that Osterix RNA was constitutively down-regulated in these cells. Treatment of osteoblasts with Bortezomib resulted in an increase of Osterix RNA and in enhanced activity of both BMP-2 and Runx2. Instead, Lenalidomide was unable to modify Osterix transcription. These findings provide additional evidence suggesting that, at least in vitro, Bortezomib promotes the osteoblast maturation whereas Lenalidomide is ineffective.