Transcriptional silencing of the Wnt-antagonist DKK1 by promoter methylation is associated with enhanced Wnt signaling in advanced multiple myeloma

Powerful and accurate detection of temporal gene expression patterns from multi-sample multi-stage single-cell transcriptomics data with TDEseq

We present a non-parametric statistical method called TDEseq that takes full advantage of smoothing splines basis functions to account for the dependence of multiple time points in scRNA-seq studies, and uses hierarchical structure linear additive mixed models to model the correlated cells within an individual. As a result, TDEseq demonstrates powerful performance in identifying four potential temporal expression patterns within a specific cell type. Extensive simulation studies and the analysis of four published scRNA-seq datasets show that TDEseq can produce well-calibrated p-values and up to 20% power gain over the existing methods for detecting temporal gene expression patterns.

Lucidin 3-methyl ether from Rubia philippinensis suppresses the proliferation of multiple myeloma cells through the promotion of β-catenin degradation

BACKGROUND

Constitutive accumulation of β-catenin has been frequently observed in multiple myeloma. Extracts from genus Rubia plants exhibit cytotoxic activity against several types of cancer cells; however, little is known about their chemopreventive mechanisms and bioactive metabolites.

PURPOSE

Purpose: The study aimed to identify the underlying antiproliferative mechanisms of Rubia philippinensis extract in multiple myeloma cells and the major active metabolites responsible for cytotoxic activity of R. philippinensis.

METHODS

The effects of R. philippinensis extracts and lucidin 3-methyl ether on the Wnt/β-catenin pathway were determined by cell-based reporter assay, Western blot analysis, and RT-PCR. The antiproliferative activity was evaluated by cell viability assay and apoptosis analysis in RPMI8226 and MM.1S multiple myeloma cells.

RESULTS

R. philippinensis extracts inhibited Wnt/β-catenin signaling and lucidin 3-methyl ether, an anthraquinone derivative, was identified as the major active metabolite responsible for the inhibition of Wnt/β-catenin signaling. Lucidin 3-methyl ether induced β-catenin phosphorylation at Ser33/Ser37/Thr41 residues and promoted proteasomal degradation of β-catenin via a GSK-3β-independent mechanism, thereby downregulating Wnt3a-induced β-catenin response transcription (CRT). Moreover, lucidin 3-methyl ether repressed the expression of β-catenin/T-cell factor (TCF)-dependent genes, such as cyclin D1, c-myc, and axin-2, thus inhibiting MM cell proliferation. Apoptosis was also elicited by lucidin 3-methyl ether, as indicated by the increase in the population of annexin V-FITC positive cells and caspase-3/7 activity in MM cells.

CONCLUSION

These findings indicate that R. philippinensis and its active metabolite lucidin 3-methyl ether prevent cell proliferation through the suppression of the Wnt/β-catenin pathway and exhibit potential as chemopreventive agents for the treatment of MM.

The role of Wnt/β-catenin signaling pathway in the pathogenesis and treatment of multiple myeloma (review)

Multiple myeloma (MM) is a refractory hematological malignancy characterized by aberrant accumulation of plasma cells. Patients with MM are susceptible to becoming resistant to chemotherapy, eventually leading to relapse. Progression of MM is largely dependent on the bone marrow microenvironment. Stromal cells in the bone marrow microenvironment secrete Wnt ligands to activate Wnt signaling in MM, which is mediated through the transcription regulator β-catenin. In addition, Wnt/β-catenin pathway encourages osteoblast differentiation and bone formation, dysregulation of which is responsible for proliferation and drug resistance of MM cells. As a result, direct inhibition or silencing of β-catenin or associated genes in the Wnt/β-catenin pathway has been proposed to be an effective therapeutic anti-MM strategy. However, the underlying regulatory mechanism of the Wnt/β-catenin pathway in MM remains to be fully elucidated. Herein, we summarized research advances on the specific genes and molecular biology process of Wnt/β-catenin pathway involved in tumorigenesis of MM, as well as the interaction with bone marrow microenvironment. Additionally, comprehensive summaries of drugs or small molecule inhibitors acting on Wnt/β-catenin pathway and targeting MM were introduced. This review intends to provide an overview of theoretical supports for novel Wnt/β-catenin pathway based treatment strategies in MM.

Targeting signalling pathways and the immune microenvironment of cancer stem cells - a clinical update

Cancer stem cells (CSCs) have important roles in tumour development, relapse and metastasis; the intrinsic self-renewal characteristics and tumorigenic properties of these cells provide them with unique capabilities to resist diverse forms of anticancer therapy, seed recurrent tumours, and disseminate to and colonize distant tissues. The findings of several studies indicate that CSCs originate from non-malignant stem or progenitor cells. Accordingly, inhibition of developmental signalling pathways that are crucial for stem and progenitor cell homeostasis and function, such as the Notch, WNT, Hedgehog and Hippo signalling cascades, continues to be pursued across multiple cancer types as a strategy for targeting the CSCs hypothesized to drive cancer progression - with some success in certain malignancies. In addition, with the renaissance of anticancer immunotherapy, a better understanding of the interplay between CSCs and the tumour immune microenvironment might be the key to unlocking a new era of oncological treatments associated with a reduced propensity for the development of resistance and with enhanced antimetastatic activity, thus ultimately resulting in improved patient outcomes. Herein, we provide an update on the progress to date in the clinical development of therapeutics targeting the Notch, WNT, Hedgehog and Hippo pathways. We also discuss the interactions between CSCs and the immune system, including the potential immunological effects of agents targeting CSC-associated developmental signalling pathways, and provide an overview of the emerging approaches to CSC-targeted immunotherapy.

Aberrant Wnt signaling in multiple myeloma: molecular mechanisms and targeting options

Aberrant activation of Wnt/β-catenin signaling plays a central role in the pathogenesis of a wide variety of malignancies and is typically caused by mutations in core Wnt pathway components driving constitutive, ligand-independent signaling. In multiple myelomas (MMs), however, these pathway intrinsic mutations are rare despite the fact that most tumors display aberrant Wnt pathway activity. Recent studies indicate that this activation is caused by genetic and epigenetic lesions of Wnt regulatory components, sensitizing MM cells to autocrine Wnt ligands and paracrine Wnts emanating from the bone marrow niche. These include deletion of the tumor suppressor CYLD, promotor methylation of the Wnt antagonists WIF1, DKK1, DKK3, and sFRP1, sFRP2, sFRP4, sFRP5, as well as overexpression of the co-transcriptional activator BCL9 and the R-spondin receptor LGR4. Furthermore, Wnt activity in MM is strongly promoted by interaction of both Wnts and R-spondins with syndecan-1 (CD138) on the MM cell-surface. Functionally, aberrant canonical Wnt signaling plays a dual role in the pathogenesis of MM: (I) it mediates proliferation, migration, and drug resistance of MM cells; (II) MM cells secrete Wnt antagonists that contribute to the development of osteolytic lesions by impairing osteoblast differentiation. As discussed in this review, these insights into the causes and consequences of aberrant Wnt signaling in MM will help to guide the development of targeting strategies. Importantly, since Wnt signaling in MM cells is largely ligand dependent, it can be targeted by drugs/antibodies that act upstream in the pathway, interfering with Wnt secretion, sequestering Wnts, or blocking Wnt (co)receptors.

EBV miR-BART10-3p Promotes Cell Proliferation and Migration by Targeting DKK1

In Epstein-Barr virus (EBV)-infected epithelial cancers, BamHI A rightward transcript (BART) miRNAs are highly expressed. However, only a few target genes of BART miRNAs have been investigated. Our mRNA microarray data showed that DKK1 was markedly down-regulated in EBV-associated gastric carcinoma (EBVaGC) cells. Using luciferase reporter assay we tested whether miR-BART10-3p regulates DKK1 by directly targeting the 3'-UTR of DKK1 mRNA. We observed that miR-BART10-3p transfection decreased DKK1 expression, while an LNA inhibitor of miR-BART10-3p (LNA-miR-BART10-3p(i)) increased DKK1 expression. Furthermore, miR-BART10-3p and siDKK1 promoted cell proliferation and migration. In contrast, transfecting GC cells with LNA-miR-BART10-3p(i) or DKK1 over expression vector suppressed cell proliferation and migration. Our results suggest that miR-BART10-3p may be involved in the tumor progression of EBVaGC by targeting DKK1.

A large scale high-throughput screen identifies chemical inhibitors of phosphatidylinositol 4-kinase type II alpha

The minor phospholipid, phosphatidylinositol 4-phosphate (PI4P), is emerging as a key regulator of lipid transfer in ER-membrane contact sites. Four different phosphatidylinositol 4-kinase (PI4K) enzymes generate PI4P in different membrane compartments supporting distinct cellular processes, many of which are crucial for the maintenance of cellular integrity but also hijacked by intracellular pathogens. While type III PI4Ks have been targeted by small molecular inhibitors, thus helping decipher their importance in cellular physiology, no inhibitors are available for the type II PI4Ks, which hinders investigations into their cellular functions. Here, we describe the identification of small molecular inhibitors of PI4K type II alpha (PI4K2A) by implementing a large scale small molecule high-throughput screening. A novel assay was developed that allows testing of selected inhibitors against PI4K2A in intact cells using a bioluminescence resonance energy transfer approach adapted to plate readers. The compounds disclosed here will pave the way to the optimization of PI4K2A inhibitors that can be used in cellular and animal studies to better understand the role of this enzyme in both normal and pathological states.

WNT Signaling in Cancer Immunosurveillance

Deregulated WNT signaling has been shown to favor malignant transformation, tumor progression, and resistance to conventional cancer therapy in a variety of preclinical and clinical settings. Accumulating evidence suggests that aberrant WNT signaling may also subvert cancer immunosurveillance, hence promoting immunoevasion and resistance to multiple immunotherapeutics, including immune checkpoint blockers. Here, we discuss the molecular and cellular mechanisms through which WNT signaling influences cancer immunosurveillance and present potential therapeutic avenues to harness currently available WNT modulators for cancer immunotherapy.

Cancer Metastases to Bone: Concepts, Mechanisms, and Interactions with Bone Osteoblasts

The skeleton is a unique structure capable of providing support for the body. Bone resorption and deposition are controlled in a tightly regulated balance between osteoblasts and osteoclasts with no net bone gain or loss. However, under conditions of disease, the balance between bone resorption and deposition is upset. Osteoblasts play an important role in bone homeostasis by depositing new bone osteoid into resorption pits. It is becoming increasingly evident that osteoblasts additionally play key roles in cancer cell dissemination to bone and subsequent metastasis. Our laboratory has evidence that when osteoblasts come into contact with disseminated breast cancer cells, the osteoblasts produce factors that initially reduce breast cancer cell proliferation, yet promote cancer cell survival in bone. Other laboratories have demonstrated that osteoblasts both directly and indirectly contribute to dormant cancer cell reactivation in bone. Moreover, we have demonstrated that osteoblasts undergo an inflammatory stress response in late stages of breast cancer, and produce inflammatory cytokines that are maintenance and survival factors for breast cancer cells and osteoclasts. Advances in understanding interactions between osteoblasts, osteoclasts, and bone metastatic cancer cells will aid in controlling and ultimately preventing cancer cell metastasis to bone.

Wnt signaling in multiple myeloma: a central player in disease with therapeutic potential

Multiple myeloma is the second most frequent hematological malignancy in the western world and remains incurable, predominantly due to acquired drug resistance and disease relapse. The highly conserved Wnt signal transduction pathway, which plays a key role in regulating cellular processes of proliferation, differentiation, migration, and stem cell self-renewal, is associated with multiple aspects of disease. Bone homeostasis is severely disturbed by Wnt antagonists that are secreted by the malignant plasma cells in the bone marrow. In the vast majority of patients, this results in osteolytic bone disease, which is associated with bone pain and pathological fractures and was reported to facilitate disease progression. More recently, cumulative evidence also indicates the importance of intrinsic Wnt signaling in the survival of multiple myeloma cells. However, Wnt pathway-activating gene mutations could not be identified. The search for factors or processes responsible for Wnt pathway activation currently focuses on aberrant ligand levels in the bone marrow microenvironment, increased expression of Wnt transcriptional co-factors and associated micro-RNAs, and disturbed epigenetics and post-translational modification processes. Furthermore, Wnt pathway activation is associated with acquired cell adhesion-mediated resistance of multiple myeloma cells to conventional drug therapies, including doxorubicin and lenalidomide. In this review, we present an overview of the relevance of Wnt signaling in multiple myeloma and highlight the Wnt pathway as a potential therapeutic target for this disease.

DKK1 and Kremen Expression Predicts the Osteoblastic Response to Bone Metastasis

Bone metastasis is a complication of advanced breast and prostate cancer. Tumor-secreted Dickkopf homolog 1 (DKK1), an inhibitor of canonical Wnt signaling and osteoblast differentiation, was proposed to regulate the osteoblastic response to metastatic cancer in bone. The objectives of this study were to compare DKK1 expression with the in vivo osteoblastic response in a panel of breast and prostate cancer cell lines, and to discover mechanisms that regulate cancer DKK1 expression. DKK1 expression was highest in MDA-MB-231 and PC3 cells that produce osteolytic lesions, and hence a suppressed osteoblastic response, in animal models of bone metastasis. LnCaP, C4-2B, LuCaP23.1, T47D, ZR-75-1, MCF-7, ARCaP and ARCaP_M cancer cells that generate osteoblastic, mixed or no bone lesions had the lowest DKK1 expression. The cell lines with negligible expression, LnCaP, C4-2B and T47D, exhibited methylation of the DKK1 promoter. Canonical Wnt signaling activity was then determined and found in all cell lines tested, even in the MDA-MB-231 and PC3 cell lines despite sizeable amounts of DKK1 protein expression expected to block canonical Wnt signaling. A mechanism of DKK1 resistance in the osteolytic cell lines was investigated and determined to be at least partially due to down-regulation of the DKK1 receptors Kremen1 and Kremen2 in the MDA-MB-231 and PC3 cell lines. Combined DKK1 and Kremen expression in cancer cells may serve as predictive markers of the osteoblastic response of breast and prostate cancer bone metastasis.

Syndecan-1 promotes Wnt/β-catenin signaling in multiple myeloma by presenting Wnts and R-spondins

HS chains decorating syndecan-1 promote autocrine and paracrine Wnt signaling in MM. Loss of HS inhibits MM cell growth by attenuating Wnt signaling.

Anti-proliferative activity of CGK012 against multiple myeloma cells via Wnt/β-catenin signaling attenuation

The aberrant activation of Wnt/β-catenin signaling is involved in the development of multiple myeloma; thus, this signaling pathway is a potential target for the development of therapeutics for this malignancy. Here, we performed cell-based chemical screening and found that CGK012, a pyranocoumarin compound, suppressed the Wnt3a-CM-mediated activation of β-catenin response transcription. CGK012 induced β-catenin phosphorylation at Ser33/Ser37/Thr41, leading to proteasomal degradation and reducing the level of intracellular β-catenin. Furthermore, CGK012 consistently decreased the amount of β-catenin and repressed the expression of cyclin D1, c-myc, and axin-2 (downstream target genes of β-catenin) in RPMI-8226 multiple myeloma cells. In addition, CGK012 inhibited the proliferation of RPMI-8226 cells and promoted apoptosis, as indicated by the increase in the population of Annexin V-FITC-stained cells and caspase-3/7 activity. These findings suggest that CGK012 could exert antiproliferative activity against multiple myeloma cells by attenuating the Wnt/β-catenin pathway; thus, it may have potential as a therapeutic agent for multiple myeloma treatment.

Epigenetic modifications in multiple myeloma: recent advances on the role of DNA and histone methylation

INTRODUCTION

Multiple Myeloma (MM) is a clonal late B-cell disorder accounting for about 13% of hematological cancers and 1% of all neoplastic diseases. Recent studies on the molecular pathogenesis and biology of MM have highlighted a complex epigenomic landscape contributing to MM onset, prognosis and high individual variability. Areas covered: We describe here the current knowledge on epigenetic events characterizing MM initiation and progression, focusing on the role of DNA and histone methylation and on the most promising epi-therapeutic approaches targeting the methylation pathway. Expert opinion: Data published so far indicate that alterations of the epigenetic framework, which include aberrant global or gene/non-coding RNA specific methylation profiles, feature prominently in the pathobiology of MM. Indeed, the aberrant expression of components of the epigenetic machinery as well as the reversibility of the epigenetic marks make this pathway druggable, providing the basis for the design of epigenetic therapies against this still fatal malignancy.

Aberrantly expressed LGR4 empowers Wnt signaling in multiple myeloma by hijacking osteoblast-derived R-spondins

The unrestrained growth of tumor cells is generally attributed to mutations in essential growth control genes, but tumor cells are also affected by, or even addicted to, signals from the microenvironment. As therapeutic targets, these extrinsic signals may be equally significant as mutated oncogenes. In multiple myeloma (MM), a plasma cell malignancy, most tumors display hallmarks of active Wnt signaling but lack activating Wnt-pathway mutations, suggesting activation by autocrine Wnt ligands and/or paracrine Wnts emanating from the bone marrow (BM) niche. Here, we report a pivotal role for the R-spondin/leucine-rich repeat-containing G protein-coupled receptor 4 (LGR4) axis in driving aberrant Wnt/β-catenin signaling in MM. We show that LGR4 is expressed by MM plasma cells, but not by normal plasma cells or B cells. This aberrant LGR4 expression is driven by IL-6/STAT3 signaling and allows MM cells to hijack R-spondins produced by (pre)osteoblasts in the BM niche, resulting in Wnt (co)receptor stabilization and a dramatically increased sensitivity to auto- and paracrine Wnts. Our study identifies aberrant R-spondin/LGR4 signaling with consequent deregulation of Wnt (co)receptor turnover as a driver of oncogenic Wnt/β-catenin signaling in MM cells. These results advocate targeting of the LGR4/R-spondin interaction as a therapeutic strategy in MM.

Loss of CYLD expression unleashes Wnt signaling in multiple myeloma and is associated with aggressive disease

Deletion or mutation of the gene encoding the deubiquitinating enzyme CYLD is a common genomic aberration in multiple myeloma (MM). However, the functional consequence of CYLD loss and the mechanism underlying its putative role as a tumor suppressor gene in the pathogenesis of MM has not been established. Here, we show that CYLD expression is highly variable in myeloma cell lines and primary MMs and that low CYLD expression is associated with disease progression from monoclonal gammopathy of undetermined significance to MM, and with poor overall and progression free-survival of MM patients. Functional assays revealed that CYLD represses MM cell proliferation and survival. Furthermore, CYLD acts as a negative regulator of NF-κB and Wnt/β-catenin signaling and loss of CYLD sensitizes MM cells to NF-κB-stimuli and Wnt ligands. Interestingly, in primary MMs, low CYLD expression strongly correlated with a proliferative and Wnt signaling-gene expression signature, but not with an NFκB target gene signature. Altogether, our findings identify CYLD as a negative regulator of NF-κB and Wnt/β-catenin signaling in MM and indicate that loss of CYLD enhances MM aggressiveness through Wnt pathway activation. Thus, targeting the Wnt pathway could be a promising therapeutic strategy in MM with loss of CYLD activity.

Identification of candidate genes for myeloma-induced osteocyte death based on microarray data

Background

The study was aimed to investigate the molecular mechanisms of osteocyte death in multiple myeloma (MM) patients.

Methods

GSE27372 was downloaded from Gene Expression Omnibus, including three HOB-01 (osteocyte cell line) control samples and three HOB-01 samples co-cultured with JJN3 (human MM cell line). After the differentially expressed genes (DEGs) were identified by Student’s t test method, enrichment analyses were performed for them using DAVID software. Using TRANSFAC, TSGene, and tumor-associated gene (TAG) databases, functional annotation was conducted for the DEGs. Additionally, protein-protein interaction (PPI) network and sub-network analyses were performed using STRING database and Cytoscape software.

Results

Total 393 DEGs were identified, including 22 transcription factors (e.g., KLF4 and IRF8) and 37 TAGs. Enrichment analysis suggested that EGF, S1PR1, and NPY1R were enriched in the function of circulatory system development. EGF (degree = 31) and EGR1 (degree = 19) had high degrees and interactions in the PPI network. In the sub-network, S1PR1, C3AR1, and NPY1R could interact with each other.

Conclusions

These DEGs might participate in the osteocyte apoptosis induced by myeloma cells. These findings might provide a theoretical basis for a better understanding of the osteolysis in MM patients.

Wnt Signaling in Cancer Stem Cell Biology

Aberrant regulation of Wnt signaling is a common theme seen across many tumor types. Decades of research have unraveled the epigenetic and genetic alterations that result in elevated Wnt pathway activity. More recently, it has become apparent that Wnt signaling levels identify stem-like tumor cells that are responsible for fueling tumor growth. As therapeutic targeting of these tumor stem cells is an intense area of investigation, a concise understanding on how Wnt activity relates to cancer stem cell traits is needed. This review attempts at summarizing the intricacies between Wnt signaling and cancer stem cell biology with a special emphasis on colorectal cancer.

Global measures of peripheral blood-derived DNA methylation as a risk factor in the development of mature B-cell neoplasms

AIM

To examine whether peripheral blood methylation is associated with risk of developing mature B-cell neoplasms (MBCNs).

MATERIALS & METHODS

We conducted a case-control study nested within a large prospective cohort. Peripheral blood was collected from healthy participants. Cases of MBCN were identified by linkage to cancer registries. Methylation was measured using the Infinium(®) HumanMethylation450.

RESULTS

During a median of 10.6-year follow-up, 438 MBCN cases were evaluated. Global hypomethylation was associated with increased risk of MBCN (odds ratio: 2.27, [95% CI: 1.59-3.25]). Within high CpG promoter regions, hypermethylation was associated with increased risk (odds ratio: 1.76 [95% CI: 1.25-2.48]). Promoter hypermethylation was observed in HOXA9 and CDH1 genes.

CONCLUSION

Aberrant global DNA methylation is detectable in peripheral blood collected years before diagnosis and is associated with increased risk of MBCN, suggesting changes to DNA methylation are an early event in MBCN development.

Expression and prognostic value of SFRP1 and β-catenin in patients with glioblastoma

The roles of secreted frizzled-related protein-1 (SFRP1) and β-catenin in human cancer have been widely studied, and it has recently been demonstrated that these proteins are associated with numerous human carcinomas. However, their clinical significance in glioblastoma multiforme (GBM) has not been examined. The current study aimed to analyze the correlation between the expression of SFRP1 and β-catenin, and clinicopathological characteristics in GBM patients. The expression of SFRP1 and β-catenin was assessed by immunohistochemistry in 113 samples of GBM and 40 normal brain tissues. Compared with normal brain tissues, GBM tissues exhibited significantly lower expression of SFRP1, and higher expression of β-catenin (both P<0.05). A Kaplan-Meier analysis revealed that patients with positive SFRP1 expression had a significantly longer overall survival (OS) time relative to those with negative SFRP1 expression (P<0.000), and that patients with positive β-catenin expression had a shorter OS time than those with negative β-catenin expression (P<0.000). A multivariate Cox regression analysis indicated that adjuvant treatment, SFRP1 expression and β-catenin expression were independent prognostic factors for OS (P<0.000, P=0.008 and P=0.001, respectively) in patients with GBM. The current data suggest that expression of SFRP1 and β-catenin may be considered significant prognostic indicators for patients with GBM.

Drug resistance in multiple myeloma: latest findings and new concepts on molecular mechanisms

In the era of new and mostly effective therapeutic protocols, multiple myeloma still tends to be a hard-to-treat hematologic cancer. This hallmark of the disease is in fact a sequel to drug resistant phenotypes persisting initially or emerging in the course of treatment. Furthermore, the heterogeneous nature of multiple myeloma makes treating patients with the same drug challenging because finding a drugable oncogenic process common to all patients is not yet feasible, while our current knowledge of genetic/epigenetic basis of multiple myeloma pathogenesis is outstanding. Nonetheless, bone marrow microenvironment components are well known as playing critical roles in myeloma tumor cell survival and environment-mediated drug resistance happening most possibly in all myeloma patients. Generally speaking, however; real mechanisms underlying drug resistance in multiple myeloma are not completely understood. The present review will discuss the latest findings and concepts in this regard. It reviews the association of important chromosomal translocations, oncogenes (e.g. TP53) mutations and deranged signaling pathways (e.g. NFκB) with drug response in clinical and experimental investigations. It will also highlight how bone marrow microenvironment signals (Wnt, Notch) and myeloma cancer stem cells could contribute to drug resistance in multiple myeloma.

Endometrial stromal cells and decidualized stromal cells: origins, transformation and functions

Decidualization of endometrium, which is characterized by endometrial stromal cell (ESC) decidualization, vascular reconstruction, immune cell recruitment, and plentiful molecule production, is a crucial step for uterus to become receptive for embryo. When implantation takes place, ESCs surround and directly interact with embryo. Decidualized stromal cells (DSCs) are of great importance in endometrial decidualization, having a broad function in regulating immune activity and vascular remodeling of uterus. DSCs are shown to have a higher metabolic level and looser cytoskeleton than ESCs. What's the origin of ESCs and how ESCs successfully transform into DSCs had puzzled scientists in the last decades. Breakthrough had been achieved recently, and many studies had elucidated some of the characters and functions of DSCs. However, several questions still remain unclear. This paper reviews current understanding of where ESCs come from and how ESCs differentiate into DSCs, summarizes some characters and functions of DSCs, analyzes current studies and their limitations and points out research areas that need further investigation.

The putative promoters of germ cell-specific genes and Nanog are hypomethylated in chicken sperm

Germ cell-specific genes such as Ddx4, Dnd1, and Dazl play critical roles in the proliferation and survival of germ cells. However, the methylation state of the promoter in mature germ cells is still unknown. Here, we investigated the methylation levels of these genes and the pluripotency marker gene Nanog in chicken sperm as compared with the Alb gene in the liver. CpG islands and/or promoter motifs such as TATA box, GC box and CAAT box were found within the putative promoter regions that we identified. By using the bisulfite reaction, CpG sites in the putative promoters were converted, and they were analyzed by sequencing. The putative promoters of Ddx4, Dnd1, Dazl and Nanog showed very low methylation levels in sperm, but they were highly methylated in the liver. Conversely, the Alb gene promoter was highly methylated in sperm and hypomethylated in the liver. However, no transcripts of Ddx4, Dnd1, Dazl and Nanog were detected in sperm or the liver. Also, no transcripts of Dnmt1 and Dnmt3a were detected in sperm. Our present results may indicate that these germ cell-specific genes and the pluripotency marker gene are ready to express any time after fertilization. Our findings showing that low methylation and selective DNA methylation of specific genes are present in chicken sperm contribute to our understanding of fertilization and embryogenesis of birds.

Piceatannol exhibits selective toxicity to multiple myeloma cells and influences the Wnt/ beta-catenin pathway

Aberrant activation of Wnt/β-catenin signaling promotes development and progression of various malignant neoplasms. Recent studies observed that the Wnt pathway is constitutively active in myeloma cells and promotes an exaggerated proliferation. Thus, the Wnt signaling pathway might be an attractive therapeutic target for multiple myeloma. In this study, we identified piceatannol as an inhibitor of the Wnt/β-catenin pathway and as a potent inducer of apoptosis in myeloma cells. Interestingly, healthy cells remained mainly unaffected. These results reveal a significant selective induction of apoptosis by piceatannol and suggest a significant in vivo effect against multiple myeloma.

Genetic determinants of heel bone properties: genome-wide association meta-analysis and replication in the GEFOS/GENOMOS consortium

Quantitative ultrasound of the heel captures heel bone properties that independently predict fracture risk and, with bone mineral density (BMD) assessed by X-ray (DXA), may be convenient alternatives for evaluating osteoporosis and fracture risk. We performed a meta-analysis of genome-wide association (GWA) studies to assess the genetic determinants of heel broadband ultrasound attenuation (BUA; n = 14 260), velocity of sound (VOS; n = 15 514) and BMD (n = 4566) in 13 discovery cohorts. Independent replication involved seven cohorts with GWA data (in silico n = 11 452) and new genotyping in 15 cohorts (de novo n = 24 902). In combined random effects, meta-analysis of the discovery and replication cohorts, nine single nucleotide polymorphisms (SNPs) had genome-wide significant (P < 5 × 10(-8)) associations with heel bone properties. Alongside SNPs within or near previously identified osteoporosis susceptibility genes including ESR1 (6q25.1: rs4869739, rs3020331, rs2982552), SPTBN1 (2p16.2: rs11898505), RSPO3 (6q22.33: rs7741021), WNT16 (7q31.31: rs2908007), DKK1 (10q21.1: rs7902708) and GPATCH1 (19q13.11: rs10416265), we identified a new locus on chromosome 11q14.2 (rs597319 close to TMEM135, a gene recently linked to osteoblastogenesis and longevity) significantly associated with both BUA and VOS (P < 8.23 × 10(-14)). In meta-analyses involving 25 cohorts with up to 14 985 fracture cases, six of 10 SNPs associated with heel bone properties at P < 5 × 10(-6) also had the expected direction of association with any fracture (P < 0.05), including three SNPs with P < 0.005: 6q22.33 (rs7741021), 7q31.31 (rs2908007) and 10q21.1 (rs7902708). In conclusion, this GWA study reveals the effect of several genes common to central DXA-derived BMD and heel ultrasound/DXA measures and points to a new genetic locus with potential implications for better understanding of osteoporosis pathophysiology.

Decoding the pathophysiology and the genetics of multiple myeloma to identify new therapeutic targets

In recent years, significant progress has been achieved in the characterization of the transcriptional profiles, gene mutations and structural chromosomal lesions in myeloma cells. These studies have identified many candidate therapeutic targets, which are recurrently deregulated in myeloma cells. However, these targets do not appear, at least individually, to represent universal driver(s) of this disease. Furthermore, evaluation of these recurrent lesions does not suggest that they converge to a single molecular pathway. Detailed integration of molecular and functional data for these candidate targets and pathways will hopefully dissect which of them play more critical roles for each of the different individual molecular defined subtypes of this disease. This review focuses on how recent updates in our understanding of myeloma pathogenesis and molecular characterization may impact ongoing and future efforts to develop new therapeutics for this disease.

Contribution of genetic and epigenetic mechanisms to Wnt pathway activity in prevalent skeletal disorders

We reported previously that the expression of Wnt-related genes is lower in osteoporotic hip fractures than in osteoarthritis. We aimed to confirm those results by analyzing β-catenin levels and explored potential genetic and epigenetic mechanisms involved. β-Catenin gene expression and nuclear levels were analyzed by real time PCR and confocal immunofluorescence. Increased nuclear β-catenin was found in osteoblasts isolated from patients with osteoarthritis (99 ± 4 units vs. 76 ± 12, p=0.01, n=10), without differences in gene transcription, which is consistent with a post-translational down-regulation of β-catenin and decreased Wnt pathway activity. Twenty four single nucleotide polymorphisms (SNPs) of genes showing differential expression between fractures and osteoarthritis (WNT4, WNT10A, WNT16 and SFRP1) were analyzed in DNA isolated from blood of 853 patients. The genotypic frequencies were similar in both groups of patients, with no significant differences. Methylation of Wnt pathway genes was analyzed in bone tissue samples (15 with fractures and 15 with osteoarthritis) by interrogating a CpG-based methylation array. Six genes showed significant methylation differences between both groups of patients: FZD10, TBL1X, CSNK1E, WNT8A, CSNK1A1L and SFRP4. The DNA demethylating agent 5-deoxycytidine up-regulated 8 genes, including FZD10, in an osteoblast-like cell line, whereas it down-regulated other 16 genes. In conclusion, Wnt activity is reduced in patients with hip fractures, in comparison with those with osteoarthritis. It does not appear to be related to differences in the allele frequencies of the Wnt genes studied. On the other hand, methylation differences between both groups could contribute to explain the differences in Wnt activity.

Effects of constitutive β-catenin activation on vertebral bone growth and remodeling at different postnatal stages in mice

Background and Objective

The Wnt/β-catenin signaling pathway is essential for controlling bone mass; however, little is known about the variable effects of the constitutive activation of β-catenin (CA-β-catenin) on bone growth and remodeling at different postnatal stages. The goal of the present study was to observe the effects of CA-β-catenin on vertebral bone growth and remodeling in mice at different postnatal stages. In particular, special attention was paid to whether CA-β-catenin has detrimental effects on these processes.

Methods

Catnblox(ex 3) mice were crossed with mice expressing the TM-inducible Cre fusion protein, which could be activated at designated time points via injection of tamoxifen. β-catenin was stabilized by tamoxifen injection 3 days, and 2, 4, 5, and 7 months after birth, and the effects lasted for one month. Radiographic imaging, micro-computed tomography, immunohistochemistry, and safranin O and tartrate-resistant acid phosphatase staining were employed to observe the effects of CA-β-catenin on vertebral bone growth and remodeling.

Results

CA-β-catenin in both early (3 days after birth) and late stages (2, 4, 5, and 7 months after birth) increased bone formation and decreased bone resorption, which together increased vertebral bone volume. However, when β-catenin was stabilized in the early stage, vertebral linear growth was retarded, and the mice demonstrated shorter statures. In addition, the newly formed bone was mainly immature and located close to the growth plate. In contrast, when β-catenin was stabilized in the late stage, vertebral linear growth was unaffected, and the newly formed bone was mainly mature and evenly distributed throughout the vertebral body.

Conclusions

CA-β-catenin in both early and late stages of growth can increase vertebral bone volume, but β-catenin has differential effects on vertebral growth and remodeling when activated at different postnatal stages.

Lysine-specific demethylase 1 (LSD1/KDM1A) contributes to colorectal tumorigenesis via activation of the Wnt/β-catenin pathway by down-regulating Dickkopf-1 (DKK1) [corrected]

We collected paired samples of tumor and adjacent normal colorectal tissues from 22 patients with colorectal carcinoma to compare the differences in the expression of lysine specific demethylase 1 (LSD1) in these two tissues. The results showed that in 19 paired samples (86.4%), LSD1 is more highly expressed in tumor tissue than in normal tissue. To explore the role of LSD1 in colorectal tumorigenesis, we used somatic cell gene targeting to generate an LSD1 knockout (KO) HCT 116 human colorectal cancer cell line as a research model. The analysis of phenotypic changes showed that LSD1 KO colorectal cancer cells are less tumorigenic, both in vivo and in vitro. The differential expression analysis of the cells by mRNA sequencing (RNA-Seq) yielded 2,663 differentially expressed genes, and 28 of these genes had highly significant differences (Q <0.01). We then selected the 4 colorectal cancer-related genes ADM, DKK1, HAS3 and SMURF2 for quantitative real-time PCR verification. The results showed that the differences in the expression of ADM, DKK1 and HAS3 were consistent with those measured using the RNA-Seq data. As DKK1 was the gene with the most significant differential expression, we analyzed the key proteins of the DKK1-related Wnt/β-catenin signaling pathway and found that, after knocking out LSD1, the amount of free β-catenin translocated to the nucleus was significantly reduced and that the transcription of the signaling pathway target gene c-Myc was down-regulated. Our studies show that LSD1 activates the Wnt/β-catenin signaling pathway by down-regulating the pathway antagonist DKK1, which may be one of the mechanisms leading to colorectal tumorigenesis.

Genomic instability in multiple myeloma: mechanisms and therapeutic implications

INTRODUCTION

Clonal plasma cells in multiple myeloma (MM) are typified by their nearly universal aneuploidy and the presence of recurrent chromosomal aberrations reflecting their chromosomal instability. Multiple myeloma is also recognized to be heterogeneous with distinct molecular subgroups. Deep genome sequencing studies have recently revealed an even wider heterogeneity and genomic instability with the identification of a complex mutational landscape and a branching pattern of clonal evolution.

AREAS COVERED

Despite the lack of full understanding of the exact mechanisms driving the genomic instability in MM, recent observations have correlated these abnormalities with impairments in the DNA damage repair machinery as well as epigenetic changes. These mechanisms and the resulting therapeutic implications will be the subject of this review.

EXPERT OPINION

By providing growth advantage of the fittest clone and promoting the acquisition of drug resistance, genomic instability is unarguably beneficial to MM cells, however, it may also well be its Achilles heal by creating exploitable vulnerabilities. As such, targeting presumptive DNA repair defects and other oncogenic addictions represent a promising area of clinical investigation. In particular, by inducing gene or pathway dependencies not present in normal cells, genomic instability can generate targets of contextual synthetic lethality in MM cells.

Epigenetic modulating agents as a new therapeutic approach in multiple myeloma

Multiple myeloma (MM) is an incurable B-cell malignancy. Therefore, new targets and drugs are urgently needed to improve patient outcome. Epigenetic aberrations play a crucial role in development and progression in cancer, including MM. To target these aberrations, epigenetic modulating agents, such as DNA methyltransferase inhibitors (DNMTi) and histone deacetylase inhibitors (HDACi), are under intense investigation in solid and hematological cancers. A clinical benefit of the use of these agents as single agents and in combination regimens has been suggested based on numerous studies in pre-clinical tumor models, including MM models. The mechanisms of action are not yet fully understood but appear to involve a combination of true epigenetic changes and cytotoxic actions. In addition, the interactions with the BM niche are also affected by epigenetic modulating agents that will further determine the in vivo efficacy and thus patient outcome. A better understanding of the molecular events underlying the anti-tumor activity of the epigenetic drugs will lead to more rational drug combinations. This review focuses on the involvement of epigenetic changes in MM pathogenesis and how the use of DNMTi and HDACi affect the myeloma tumor itself and its interactions with the microenvironment.

Galectin-3 accelerates the progression of oral tongue squamous cell carcinoma via a Wnt/β-catenin-dependent pathway

The purpose of this study was to elucidate the clinicopathological significance and mechanism of action of galectin-3 in oral tongue squamous cell carcinoma (OTSCC). Here, the expression of galectin-3 was quantified in OTSCC (n = 68) and paired OTSCC and normal surrounding tissues (n = 10) using immunohistochemical staining. Tca8113 OTSCC cells were transfected with a plasmid expressing galectin-3 cDNA or siRNA against galectin-3. Cell proliferation, migration and invasion were measured using the MTT assay, Matrigel-coated Transwell migration assay and wound healing assay. The effect of galectin-3 on the Wnt/β-catenin signaling pathway and epithelial mesenchymal transition (EMT) were investigated using a plasmid expressing the Wnt antagonist dickkopf 1 (DKK1) and Western blotting. Galectin-3 was expressed at significantly higher levels in OTSCC than the normal adjacent tissues; galectin-3 expression correlated strongly with pathological stage, pathological grade and lymph node invasion in OTSCC. Overexpression of galectin-3 promoted Tca8113 cell proliferation, migration and invasion, upregulated Wnt protein expression, activated β-catenin and induced the EMT; knockdown of galectin-3 had the opposite effects. Co-transfection of Tca8113 cells overexpressing galectin-3 with the Wnt antagonist DKK1 reduced the ability of galectin-3 to increase cell proliferation, migration and invasion, reduced upregulation of Wnt, inhibited β-catenin activation and abrogated the EMT, demonstrating that the Wnt/β-catenin signaling pathway mediated the effects of galectin-3. Galectin-3 plays an important role in the progression of OTSCC via activation of the Wnt/β-catenin signaling pathway.

On the origin and destination of cancer stem cells: a conceptual evaluation

Despite remaining uncertainties and ongoing research it is possible to draw up a model for the role of (cancer) stem cells in both the initiation and progression of cancer towards metastasis. The cancer stem cell of origin and the cancer stem cell are, despite phenotypic similarities, genotypically different entities. Given the right circumstances provided by a combination of genomic changes and biochemical and physical interactions with its microenvironment, an epithelial cancer cell may undergo a phenotypic epithelial mesenchymal transition (EMT) towards a cancer stem cell. This transition conveys upon the cell crucial stem cell-like abilities which facilitate migration into the blood circulation as an individual circulating tumor cell, survive there, and subsequently seed into organ tissue where, once more in close interaction with its microenvironment, the process of clonal self renewal may start, leading to a metastatic tumor. Both in the primary tumor as well as in the metastatic tumor, partial differentiation of the cancer stem cell progeny leads to phenotypic heterogeneity. Throughout this complex process of cancer metastasis similarities with the way stem cells function during embryonic development, including the signaling pathways that mediate these functions, are evident. Deeper insight in the EMT process, plasticity of the resulting cancer stem cells, and the role of cancer stem cells in the metastatic process is expected to lead to novel anti-metastatic cancer therapies. Emerging human in vitro cancer models in the form of "organ-on-a-chip" may contribute valuable novel research tools to achieve this aim.

The effects of promoter methylation on downregulation of DAZAP2 in multiple myeloma cell lines

Our previous studies had shown that DAZAP2 was profoundly downregulated in bone marrow mononuclear cells from multiple myeloma patients. In this report, we analyzed epigenetic changes in multiple myeloma cell lines to understand the molecular mechanisms underlying the downregulation of DAZAP2. Four multiple myeloma cell lines, KM3, MM.1S, OPM-2 and ARH-77, were studied. The results of methylation specific PCR (MSP) showed that the promoter of DAZAP2 was methylated for KM3, MM.1S, OPM-2 and unmethylated for ARH-77. The DAZAP2 promoter region was amplified to obtain a series of different length sequences. All of the amplified sequences were inserted to luciferase reporter vector. The constructs were transfected into COS-7 cells and the luciferase activities were measured to search for the core region of DAZAP2 promoter. Two CpG islands were found in DAZAP2 promoter region. The results of luciferase assay showed that CpG island 1 displayed weak transcriptional activity, whereas CpG island 2 exhibited strong transcriptional activity (273 folds) compared to the control. The sequence that covered both CpG islands 1 and 2 showed higher activity (1,734 folds) compared to the control, suggesting that the two islands had synergistic effect on regulating DAZAP2 expression. We also found that M. Sss I methylase could inhibit the luciferase activity, whereas demethylation using 5-aza-2′-deoxycytidine treatment rescued the expression of DAZAP2 for multiple myeloma cell lines. These data revealed that methylation of DAZAP2 promoter was involved in downregulation of DAZAP2 in multiple myeloma cells.