Functional and structural diversity of the human Dickkopf gene family

Identification of a progenitor cell population destined to form fracture fibrocartilage callus in Dickkopf-related protein 3-green fluorescent protein reporter mice

Fracture healing is a complex biological process involving the proliferation of mesenchymal progenitor cells, and chondrogenic, osteogenic, and angiogenic differentiation. The mechanisms underlying the proliferation and differentiation of mesenchymal progenitor cells remain unclear. Here, we demonstrate Dickkopf-related protein 3 (Dkk3) expression in periosteal cells using Dkk3-green fluorescent protein reporter mice. We found that proliferation of mesenchymal progenitor cells began in the periosteum, involving Dkk3-positive cell proliferation near the fracture site. In addition, Dkk3 was expressed in fibrocartilage cells together with smooth muscle α-actin and Col3.6 in the early phase of fracture healing as a cell marker of fibrocartilage cells. Dkk3 was not expressed in mature chondrogenic cells or osteogenic cells. Transient expression of Dkk3 disappeared in the late phase of fracture healing, except in the superficial periosteal area of fracture callus. The Dkk3 expression pattern differed in newly formed type IV collagen positive blood vessels and the related avascular tissue. This is the first report that shows Dkk3 expression in the periosteum at a resting state and in fibrocartilage cells during the fracture healing process, which was associated with smooth muscle α-actin and Col3.6 expression in mesenchymal progenitor cells. These fluorescent mesenchymal lineage cells may be useful for future studies to better understand fracture healing.

Wnt/β-catenin signaling via Axin2 is required for myogenesis and, together with YAP/Taz and Tead1, active in IIa/IIx muscle fibers

Canonical Wnt/β-catenin signaling plays an important role in myogenic differentiation, but its physiological role in muscle fibers remains elusive. Here, we studied activation of Wnt/β-catenin signaling in adult muscle fibers and muscle stem cells in an Axin2 reporter mouse. Axin2 is a negative regulator and a target of Wnt/β-catenin signaling. In adult muscle fibers, Wnt/β-catenin signaling is only detectable in a subset of fast fibers that have a significantly smaller diameter than other fast fibers. In the same fibers, immunofluorescence staining for YAP/Taz and Tead1 was detected. Wnt/β-catenin signaling was absent in quiescent and activated satellite cells. Upon injury, Wnt/β-catenin signaling was detected in muscle fibers with centrally located nuclei. During differentiation of myoblasts expression of Axin2, but not of Axin1, increased together with Tead1 target gene expression. Furthermore, absence of Axin1 and Axin2 interfered with myoblast proliferation and myotube formation, respectively. Treatment with the canonical Wnt3a ligand also inhibited myotube formation. Wnt3a activated TOPflash and Tead1 reporter activity, whereas neither reporter was activated in the presence of Dkk1, an inhibitor of canonical Wnt signaling. We propose that Axin2-dependent Wnt/β-catenin signaling is involved in myotube formation and, together with YAP/Taz/Tead1, associated with reduced muscle fiber diameter of a subset of fast fibers.

Kremen1 regulates mechanosensory hair cell development in the mammalian cochlea and the zebrafish lateral line

Here we present spatio-temporal localization of Kremen1, a transmembrane receptor, in the mammalian cochlea, and investigate its role in the formation of sensory organs in mammal and fish model organisms. We show that Kremen1 is expressed in prosensory cells during cochlear development and in supporting cells of the adult mouse cochlea. Based on this expression pattern, we investigated whether Kremen1 functions to modulate cell fate decisions in the prosensory domain of the developing cochlea. We used gain and loss-of-function experiments to show that Kremen1 is sufficient to bias cells towards supporting cell fate, and is implicated in suppression of hair cell formation. In addition to our findings in the mouse cochlea, we examined the effects of over expression and loss of Kremen1 in the zebrafish lateral line. In agreement with our mouse data, we show that over expression of Kremen1 has a negative effect on the number of mechanosensory cells that form in the zebrafish neuromasts, and that fish lacking Kremen1 protein develop more hair cells per neuromast compared to wild type fish. Collectively, these data support an inhibitory role for Kremen1 in hair cell fate specification.

Expression of Cancer Testis Antigens in Colorectal Cancer: New Prognostic and Therapeutic Implications

Background. While cancer/testis antigens (CTAs) are restricted in postnatal tissues to testes and germ line-derived cells, their role in cancer development and the clinical significance of their expression still remain to be better defined. Objective. The aim of this study was to investigate the level of CTA expression in colon samples from patients with colorectal cancer (CRC) in relation to patient clinical status. Methods. Forty-five patients with newly diagnosed colorectal cancer were included in the study. We selected a panel of 18 CTAs that were previously detected in CRC as well as some new gene candidates, and their expression was detected at the mRNA level by employing RQ-PCR. Additionally, we evaluated CTA expression in three colon cancer cell lines (CL-188, HTB-39, and HTB-37) after exposure to the DNA methylation-modifying drug 5-azacytidine. Results. We report that 6 out of 18 (33%) CTAs tested (MAGEA3, OIP5, TTK, PLU1, DKKL1, and FBXO39) were significantly (p < 0.05) overexpressed in tumor tissue compared with healthy colon samples isolated from the same patients. Conclusions. Moreover, we found that MAGEA3, PLU-1, and DKKL expression positively correlated with disease progression, evaluated according to the Dukes staging system. Finally, 5-azacytidine exposure significantly upregulated expression of CTAs on CRC cells, which indicates that this demethylation agent could be employed therapeutically to enhance the immune response against tumor cells.

The Effect of Altered Loading on Mandibular Condylar Cartilage

OBJECTIVE

The purpose of this study was to delineate the cellular, mechanical and morphometric effects of altered loading on the mandibular condylar cartilage (MCC) and subchondral bone. We hypothesized that altered loading will induce differentiation of cells by accelerating the lineage progression of the MCC.

MATERIALS AND METHODS

Four-week-old male Dkk3 XCol2A1XCol10A1 mice were randomly divided into two groups: (1) Loaded-Altered loading of MCC was induced by forced mouth opening using a custom-made spring; (2) Control-served as an unloaded group. Mice were euthanized and flow cytometery based cell analysis, micro-CT, gene expression analysis, histology and morphometric measurements were done to assess the response.

RESULTS

Our flow cytometery data showed that altered loading resulted in a significant increase in a number of Col2a1-positive (blue) and Col10a1-positive (red) expressing cells. The gene expression analysis showed significant increase in expression of BMP2, Col10a1 and Sox 9 in the altered loading group. There was a significant increase in the bone volume fraction and trabecular thickness, but a decrease in the trabecular spacing of the subchondral bone with the altered loading. Morphometric measurements revealed increased mandibular length, increased condylar length and increased cartilage width with altered loading. Our histology showed increased mineralization/calcification of the MCC with 5 days of loading. An unexpected observation was an increase in expression of tartrate resistant acid phosphatase activity in the fibrocartilaginous region with loading.

CONCLUSION

Altered loading leads to mineralization of fibrocartilage and drives the lineage towards differentiation/maturation.

Loss of Dickkopf 3 Promotes the Tumorigenesis of Basal Breast Cancer

Dickkopf 3 (DKK3) has been associated with tumor suppression of various tumor entities including breast cancer. However, the functional impact of DKK3 on the tumorigenesis of distinct molecular breast cancer subtypes has not been considered so far. Therefore, we initiated a study analyzing the subtype-specific DKK3 expression pattern as well as its prognostic and functional impact with respect to breast cancer subtypes. Based on three independent tissue cohorts including one in silico dataset (n = 30, n = 463 and n = 791) we observed a clear down-regulation of DKK3 expression in breast cancer samples compared to healthy breast tissue controls on mRNA and protein level. Interestingly, most abundant reduction of DKK3 expression was detected in the highly aggressive basal breast cancer subtype. Analyzing a large in silico dataset comprising 3,554 cases showed that low DKK3 mRNA expression was significantly associated with reduced recurrence free survival (RFS) of luminal and basal-like breast cancer cases. Functionally, DKK3 re-expression in human breast cancer cell lines led to suppression of cell growth possibly mediated by up-regulation of apoptosis in basal-like but not in luminal-like breast cancer cell lines. Moreover, ectopic DKK3 expression in mesenchymal basal breast cancer cells resulted in partial restoration of epithelial cell morphology which was molecularly supported by higher expression of epithelial markers like E-Cadherin and down-regulation of mesenchymal markers such as Snail 1. Hence, we provide evidence that down-regulation of DKK3 especially promotes tumorigenesis of the aggressive basal breast cancer subtype. Further studies decoding the underlying molecular mechanisms of DKK3-mediated effects may help to identify novel targeted therapies for this clinically highly relevant breast cancer subtype.

Dickkopf 2 promotes proliferation and invasion via Wnt signaling in prostate cancer

Wnt/β-catenin signaling dysregulation is involved in tumorigenesis. Furthermore, epigenetic modification of the Dickkopf (DKK) family (DKK1‑4) has been shown to be important in the regulation of Wnt signaling. However, the functions and mechanism of DKK2 in the development and progression of prostate cancer remain unclear. Therefore, the present study investigated the role of DKK2 in prostate cancer. The mRNA and protein expression levels of DKK2 in prostate cancer tissues and cells were assessed by reverse transcription‑quantitative polymerase chain reaction and western blotting, respectively. The biological function of DKK2 in prostate cancer was investigated using 3‑(4,5‑dimethylthiazol‑2‑yl)-2,5‑diphenyltetrazolium bromide and transwell invasion assays. DKK2 was demonstrated to be upregulated in prostate cancer tissues and cells, and knockdown of DKK2 suppressed cell proliferation and invasion. Furthermore, small interfering RNA targeting DKK2 inhibited the expression of β‑catenin, cyclin D1 and c‑Myc in prostate cancer cells. The present report suggested that DKK2 downregulation suppressed the proliferation and invasion of prostate cancer cells by inhibiting the Wnt/β‑catenin signaling pathway.

Modulating Dickkopf-1: A Strategy to Monitor or Treat Cancer?

Dickkopf-1 (DKK1) is a secreted Wnt/β-catenin pathway antagonist involved in embryogenesis. It was first described 25 years ago for its function in head induction and limb morphogenesis. Since then, this protein has been widely studied in the context of active Wnt/β-catenin signalling during cellular differentiation and development. Dysregulation of DKK1 has been associated with bone pathologies and has now emerged as a potential biomarker of cancer progression and prognosis for several types of malignancies. Reducing the amount of circulating DKK1 may reveal a simple and efficient strategy to limit or reverse cancer growth. This review will provide an overview of the role of Dickkopf-1 in cancer and explore its potential use as a biomarker and therapeutic target.

Glucose induced activation of canonical Wnt signaling pathway in hepatocellular carcinoma is regulated by DKK4

Elevated glycemic index, an important feature of diabetes is implicated in an increased risk of hepatocellular carcinoma (HCC). However, the underlying molecular mechanisms of this association are relatively less explored. Present study investigates the effect of hyperglycemia over HCC proliferation. We observed that high glucose culture condition (HG) specifically activates canonical Wnt signaling in HCC cells, which is mediated by suppression of DKK4 (a Wnt antagonist) expression and enhanced β-catenin level. Functional assays demonstrated that a normoglycemic culture condition (NG) maintains constitutive expression of DKK4, which controls HCC proliferation rate by suppressing canonical Wnt signaling pathway. HG diminishes DKK4 expression leading to loss of check at G0/G1/S phases of the cell cycle thereby enhancing HCC proliferation, in a β-catenin dependent manner. Interestingly, in NOD/SCID mice supplemented with high glucose, HepG2 xenografted tumors grew rapidly in which elevated levels of β-catenin, c-Myc and decreased levels of DKK4 were detected. Knockdown of DKK4 by shRNA promotes proliferation of HCC cells in NG, which is suppressed by treating cells exogenously with recombinant DKK4 protein. Our in vitro and in vivo results indicate an important functional role of DKK4 in glucose facilitated HCC proliferation.

DKK1 inhibits proliferation and migration in human retinal pigment epithelial cells via the Wnt/β-catenin signaling pathway

Retinal pigment epithelial (RPE) cells play important roles in diabetic retinopathy (DR). Dickkopf 1 (DKK1) has been reported to be important in the regulation of cell proliferation and migration. However, there are few previous studies regarding DKK1 in RPE cells. Therefore, in the present study, we investigated the effect of DKK1 on the proliferation and migration of human RPE cells, and the signaling mechanisms underlying these effects. The results showed that the overexpression of DKK1 significantly inhibited the proliferation and migration of ARPE-19 cells. In addition, overexpression of DKK1 markedly inhibited the expression of β-catenin and cyclin D1 in ARPE-19 cells. Collectively, the present findings suggest that the overexpression of DKK1 inhibited the proliferation and migration of RPE cells by suppressing the Wnt/β-catenin signaling pathway. Therefore, DKK1 are able to augment the growth of human RPE, and further studies are warranted to investigate the effects of DKK1 effects on DR.

Association of Wnt signaling pathway genetic variants in gallbladder cancer susceptibility and survival

Gallbladder cancer (GBC) is the most common malignancy of the biliary tract with adverse prognosis and poor survival. Wnt signaling plays an important role in embryonic development and regeneration of tissues in all the species. Deregulation of expression and mutations in this pathway may lead to disease state such as cancer. In this study, we assessed the association of common germline variants of Wnt pathway genes (SFRP2, SFRP4, DKK2, DKK3, WISP3, APC, β-catenin, AXIN-2, GLI-1) to evaluate their contribution in predisposition to GBC and treatment outcomes. The study included 564 GBC patients and 250 controls. Out of 564, 200 patients were followed up for treatment response and survival. Tumor response (RECIST 1.1) was recorded in 116 patients undergoing non-adjuvant chemotherapy (NACT). Survival was assessed by Kaplan-Meier curve and Cox-proportional hazard regression. Single locus analysis showed significant association of SFRP4 rs1802073G > T [p value = 0.0001], DKK2 rs17037102C > T [p value = 0.0001], DKK3 rs3206824C > T [p value = 0.012], APC rs4595552 A/T [p value = 0.021], APC rs11954856G > T [p value = 0.047], AXIN-2 rs4791171C > T [p value = 0.001], β-catenin rs4135385A > G [p value = 0.031], and GLI-1 rs222826C > G [p value = 0.001] with increased risk of GBC. Gene-gene interaction using GMDR analysis predicted APC rs11954856 and AXIN2 rs4791171 as significant in conferring GBC susceptibility. Cox-proportional hazard model showed GLI-1 rs2228226 CG/GG and AXIN-2 rs4791171 TT genotype higher hazard ratio. In recursive partitioning, AXIN-2 rs4791171 TT genotype showed higher mortality and hazard. Most of studied genetic variants influence GBC susceptibility. APC rs11954856, GLI-1 rs2228226, and AXIN-2 rs4791171 were found to be associated with poor survival in advanced GBC patients.

Dkk3 prevents familial dilated cardiomyopathy development through Wnt pathway

To date, the role of Dickkopf 3 (Dkk3) on the pathogenesis of familial dilated cardiomyopathy (FDCM), and whether and how Dkk3 interferes with Wnt signaling in heart tissues remains unknown. Here, we demonstrate that strong Dkk3 expression was markedly downregulated in adult hearts from WT mice, and Dkk3 expression was upregulated suddenly in hearts from DCM mouse models. Using Dkk3 transgenic and knockout mice, as well as cTnT(R141W) transgenic mice, which manifests progressive chamber dilation and contractile dysfunction and has pathologic phenotypes similar to human DCM patients, we determined that transgenic expression of Dkk3 increased survival rate, improved cardiac morphology breakage and dysfunction, and ameliorated cardiac pathological changes in the cTnT(R141W) mice. In contrast, Dkk3 knockout reduced the survival rate and aggravated the pathological phenotypes of the cTnT(R141W) mice. The protective effects of Dkk3 appeared clearly at 3 months of age, peaked at 6 months of age, and decreased at 10 months of age in the cTnT(R141W) mice. Furthermore, we determined that Dkk3 upregulated Dvl1 (Dishevelled 1) and key proteins of the canonical Wnt pathway (cytoplasmic and nuclear β-catenin, c-Myc, and Axin2) and downregulated key proteins of the noncanonical Wnt pathway (c-Jun N-terminal kinase (JNK), Ca(2+)/calmodulin-dependent protein kinase II (CAMKII), and histone deacetylase 4 (HDAC4)). In contrast, Dkk3 knockout reversed these changes in the cTnT(R141W) mice. In summary, Dkk3 could prevent FDCM development in mice, especially in the compensatory stage, and probably through activation of the canonical and inhibition of the noncanonical Wnt pathway, which suggested that Dkk3 could serve as a therapeutic target for the treatment of cardiomyopathy and heart failure.

Photoperiodic and Diurnal Regulation of WNT Signaling in the Arcuate Nucleus of the Female Djungarian Hamster, Phodopus sungorus

The WNT pathway was shown to play an important role in the adult central nervous system. We previously identified the WNT pathway as a novel integration site of the adipokine leptin in mediating its neuroendocrine control of metabolism in obese mice. Here we investigated the implication of WNT signaling in seasonal body weight regulation exhibited by the Djungarian hamster (Phodopus sungorus), a seasonal mammal that exhibits profound annual changes in leptin sensitivity. We furthermore investigated whether crucial components of the WNT pathway are regulated in a diurnal manner. Gene expression of key components of the WNT pathway in the hypothalamus of hamsters acclimated to either long day (LD) or short day (SD) photoperiod was analyzed by in situ hybridization. We detected elevated expression of the genes WNT-4, Axin-2, Cyclin-D1, and SFRP-2, in the hypothalamic arcuate nucleus, a key energy balance integration site, during LD compared with SD as well as a diurnal regulation of Axin-2, Cyclin-D1, and DKK-3. Investigating the effect of photoperiod as well as leptin on the activation (phosphorylation) of the WNT coreceptor LRP-6-(Ser1490) by immunohistochemistry, we found elevated activity in the arcuate nucleus during LD relative to SD as well as after leptin treatment (2 mg/kg body weight). These findings indicate that differential WNT signaling may be associated with seasonal body weight regulation and is partially regulated in a diurnal manner in the adult brain. Furthermore, they suggest that this pathway plays a key role in the neuroendocrine regulation of body weight and integration of the leptin signal.

Role of the Wnt/β-catenin signaling pathway in the response of chondrocytes to mechanical loading

In order to better understand the mechanisms by which chondrocytes respond to mechanical stimulation, ATDC5 mouse embryonic carcinoma cells were induced to differentiate into chondrocytes and then exposed to mechanical loading. To specifically elucidate the role of this pathway, the localization and expression of proteins involved in the Wnt/β-catenin signaling pathway were observed. Chondrogenic-differentiated ATDC5 cells were exposed to a 12% cycle tension load for 1, 2, 4, or 8 h. At each time point, immunofluorescence staining, western blot analysis, and qPCR were used to track the localization of β-catenin and glycogen synthase kinase-3β (GSK-3β) expression. In addition, the mRNA expression of Wnt3a, disheveled homolog 1 (Dvl-1), GSK-3β, and collagen type II were also detected. Activation of the Wnt/β-catenin signaling pathway was investigated in cells treated with Dickkopf-related protein 1 (DKK-1). β-catenin and GSK-3β protein expression increased initially and then decreased over the mechanical loading period, and the corresponding mRNA levels followed a similar trend. After application of the inhibitor DKK-1, Wnt/β‑catenin signaling was suppressed, and the mRNA expression of collagen II was also reduced. Thus, stimulation of chondrocytes with mechanical strain loading is associated with the translocation of active β-catenin from the cytoplasm to the nucleus.

Tubular Dickkopf-3 promotes the development of renal atrophy and fibrosis

Renal tubular atrophy and interstitial fibrosis are common hallmarks of etiologically different progressive chronic kidney diseases (CKD) that eventually result in organ failure. Even though these pathological manifestations constitute a major public health problem, diagnostic tests, as well as therapeutic options, are currently limited. Members of the dickkopf (DKK) family, DKK1 and -2, have been associated with inhibition of Wnt signaling and organ fibrosis. Here, we identify DKK3 as a stress-induced, tubular epithelia-derived, secreted glycoprotein that mediates kidney fibrosis. Genetic as well as antibody-mediated abrogation of DKK3 led to reduced tubular atrophy and decreased interstitial matrix accumulation in two mouse models of renal fibrosis. This was facilitated by an amplified, antifibrogenic, inflammatory T cell response and diminished canonical Wnt/β-catenin signaling in stressed tubular epithelial cells. Moreover, in humans, urinary DKK3 levels specifically correlated with the extent of tubular atrophy and interstitial fibrosis in different glomerular and tubulointerstitial diseases. In summary, our data suggest that DKK3 constitutes an immunosuppressive and a profibrotic epithelial protein that might serve as a potential therapeutic target and diagnostic marker in renal fibrosis.

Serum Dickkopf-1 as a Biomarker for the Diagnosis of Hepatocellular Carcinoma

PURPOSE

Dickkopf-1 (DKK-1) is a Wnt/β-catenin signaling pathway inhibitor. We investigated whether DKK-1 is related to progression in hepatocellular carcinoma (HCC) cells and HCC patients.

MATERIALS AND METHODS

In vitro reverse-transcription polymerase chain reaction (RT-PCR), wound healing assays, invasion assays, and ELISAs of patient serum samples were employed. The diagnostic accuracy of the serum DKK-1 ELISA was assessed using receiver operating characteristic (ROC) curves and area under ROC (AUC) analyses.

RESULTS

RT-PCR showed high DKK-1 expression in Hep3B and low in 293 cells. Similarly, the secreted DKK-1 concentration in the culture media was high in Hep3B and low in 293 cells. Wound healing and invasion assays using 293, Huh7, and Hep3B cells showed that DKK-1 overexpression promoted cell migration and invasion, whereas DKK-1 knock-down inhibited them. When serum DKK-1 levels were assessed in 370 participants (217 with HCC and 153 without), it was significantly higher in HCC patients than in control groups (median 1.48 ng/mL vs. 0.90 ng/mL, p<0.001). The optimum DKK-1 cutoff level was 1.01 ng/mL (AUC=0.829; sensitivity 90.7%; specificity 62.0%). Although DKK-1 had a higher AUC than alpha-fetoprotein (AFP) and des-gamma-carboxy prothrombin (DCP) (AUC=0.829 vs. 0.794 and 0.815, respectively), they were statistically similar (all p>0.05). When three biomarkers were combined (DKK-1 plus AFP plus DCP), they showed significantly higher AUC (AUC=0.952) than single marker, DKK-1 plus AFP, or DKK-1 plus DCP (all p<0.001).

CONCLUSION

DKK-1 might be a key regulator in HCC progression and a potential therapeutic target in HCC. Serum DKK-1 could complement the diagnostic accuracy of AFP and DCP.

Dickkopf-3 (DKK-3) obstructs VEGFR-2/Akt/mTOR signaling cascade by interacting of β2-microglobulin (β2M) in ovarian tumorigenesis

In this study, we investigated a possible mechanism of β2-microglobulin (β2M) function in cancer metastases in vitro, using a human ovarian carcinoma cell line. β2M, a modulator acts as a cell growth-promoting and cellular signaling factors, was identified as a dickkopf-3 (DKK-3) interacting protein. We also observed that DKK-3 suppresses endothelial cell angiogenesis of β2M through vascular endothelial growth factor receptor-2 (VEGFR-2) in tumorigenesis. Luciferase activity was remarkably reduced by the transfection of DKK-3 in a dose-dependent manner. In addition, over-expression of β2M activates cell growth by suppressing DKK-3-induced apoptosis. The effect of β2M on cell cycle and apoptosis-regulatory components was also confirmed through the silencing of β2M expression. Furthermore, induction of β2M-mediated VEGFR-2/Akt/mTOR phosphorylation and tumor angiogenesis was significantly suppressed by over-expression of DKK-3. Taken together, our results suggest an underlying mechanism for an increase of β2M-related activity in ovarian tumor cells.

Dickkopf-related protein 3 is a potential Aβ-associated protein in Alzheimer's Disease

Amyloid-β (Aβ) is the most prominent protein in Alzheimer's disease (AD) senile plaques. In addition, Aβ interacts with a variety of Aβ-associated proteins (AAPs), some of which can form complexes with Aβ and influence its clearance, aggregation or toxicity. Identification of novel AAPs may shed new light on the pathophysiology of AD and the metabolic fate of Aβ. In this study, we aimed to identify new AAPs by searching for proteins that may form soluble complexes with Aβ in CSF, using a proteomics approach. We identified the secreted Wnt pathway protein Dickkopf-related protein 3 (Dkk-3) as a potential Aβ-associated protein. Using immunohistochemistry on human AD brain tissue, we observed that (i) Dkk-3 co-localizes with Aβ in the brain, both in diffuse and classic plaques. (ii) Dkk-3 is expressed in neurons and in blood vessel walls in the brain and (iii) is secreted by leptomeningeal smooth muscle cells in vitro. Finally, measurements using ELISA revealed that (iv) Dkk-3 protein is abundantly present in both cerebrospinal fluid and serum, but its levels are similar in non-demented controls and patients with AD, Lewy body dementia, and frontotemporal dementia. Our study demonstrates that Dkk-3 is a hitherto unidentified Aβ-associated protein which, given its relatively high cerebral concentrations and co-localization with Aβ, is potentially involved in AD pathology. In this study, we propose that Dickkopf-related protein-3 (Dkk-3) might be a novel Amyloid-β (Aβ) associated protein. We demonstrate that Dkk-3 is expressed in the brain, especially in vessel walls, and co-localizes with Aβ in senile plaques. Furthermore, Dkk-3 levels in cerebrospinal fluid strongly correlate with Aβ40 levels, but were not suitable to discriminate non-demented controls and patients with dementia.

High level of serum protein DKK1 predicts poor prognosis for patients with hepatocellular carcinoma after hepatectomy

AIM

To evaluate prognostic significance of DKK1 for hepatocelluar carcinoma.

MATERIALS & METHODS

We enrolled a test cohort consisting of 266 hepatitis virus B-related hepatocelluar carcinoma patients who had undergone hepatectomy and a validation cohort of 95. Associations of DKK1 with overall survival and time to recurrence were determined by Cox proportional hazards regression model.

RESULTS

High levels of preoperative serum DKK1 were associated with poor overall survival and higher recurrence rate and DKK1 was an independent prognostic predictor. Moreover, DKK1 maintained ability to predict recurrence for patients with low recurrence risk. Double positives of DKK1 and AFP indicated the worst overall survival and the highest recurrence rate compared with either used alone. Patients with preoperatively and 1-day postoperatively positive DKK1 had higher recurrence rates than those whose values were both negative. Similar results were found in the validation cohort.

CONCLUSION

Serum DKK1 could predict prognosis of hepatocelluar carcinoma after hepatectomy.

Dickkopf Homolog 3 Induces Stem Cell Differentiation into Smooth Muscle Lineage via ATF6 Signalling

Smooth muscle cells (SMCs) are a key component of healthy and tissue engineered vessels and play a crucial role in vascular development and the pathogenic events of vascular remodeling i.e. restenosis. However, the cell source from which they can be isolated is limited. Embryonic stem (ES) cells that have the remarkable capability to differentiate into vascular SMCs in response to specific stimuli provide a useful model for studying SMC differentiation. Previous studies suggested that dickkopf homolog 3 (DKK3) has a role in human partially induced pluripotent stem cell to SMC differentiation. Here, we demonstrate that the expression of DKK3 is essential for the expression of SMC markers and myocardin at both the mRNA and protein levels during mouse ES cell differentiation into SMCs (ESC-SMC differentiation). Overexpression of DKK3 leads to further up-regulation of the aforementioned markers. Further investigation indicates that DKK3 added as a cytokine activates activating transcription factor 6 (ATF6), leading to the increased binding of ATF6 on the myocardin promoter and increased its expression. In addition, inhibition of extracellular signal-regulated kinases 1/2 (ERK1/2) promotes the expression of ATF6 and leads to further increase of myocardin transcription. Our findings offer a novel mechanism by which DKK3 regulates ESC-SMC differentiation by activating ATF6 and promoting myocardin expression.

Immunotherapy strategies in multiple myeloma

Multiple myeloma (MM) is a B-cell malignancy characterized by the clonal proliferation of malignant plasma cells in the bone marrow and the development of osteolytic bone lesions. MM has emerged as a paradigm within the cancers for the success of drug discovery and translational medicine. This article discusses immunotherapy as an encouraging option for the goal of inducing effective and long-lasting therapeutic outcome. Divided into two distinct approaches, passive or active, immunotherapy, which targets tumor-associated antigens has shown promising results in multiple preclinical and clinical studies.

The role of Dickkopf-3 overexpression in esophageal adenocarcinoma

OBJECTIVES

Ninety percent of patients with esophageal adenocarcinoma ultimately die of their disease, highlighting the need for novel therapeutic targets. The goal of this study was to define the functional significance of overexpression of Dickkopf-3 (DKK3) in esophageal adenocarcinoma.

METHODS

DKK3 expression was analyzed by real-time polymerase chain reaction in 95 chemonaive and 21 chemoresistant esophageal adenocarcinomas. The esophageal adenocarcinoma cell line OE33 was stably transfected with DKK3 (OE33/DKK3) and evaluated using WST-1 (Roche, Basel, Switzerland), Matrigel (BD Biosciences, San Jose, Calif), endothelial tube formation, and chemosensitivity assays. Tumorigenesis was evaluated by injecting 1 × 10(6) OE33/DKK3 and vector cells in NOD/SCIDγ mice.

RESULTS

DKK3 was overexpressed (>2-fold) in 75.8% (72/95) of esophageal adenocarcinomas. DKK3 protein was present at moderate to high levels in 46.8% (29/62) of esophageal adenocarcinomas on tissue microarray. Stable transfection of DKK3 significantly increased proliferation (P < .05) and Matrigel invasion (P < .001). Levels of SMAD4, a key mediator of the transforming growth factor-ß pathway, increased after activin treatment of OE33/DKK3, and siSMAD4 significantly decreased Matrigel invasion, suggesting that DKK3 acts through the transforming growth factor-β pathway. OE33/DKK3 cells increased endothelial tube formation and were significantly more resistant to 5-fluorouracil and cisplatin, and DKK3 expression was significantly higher in chemoresistant esophageal adenocarcinomas (P < .005). In NOD/SCIDγ mice, OE33/DKK3 cells resulted in tumors at all sites (8/8), whereas vector cells grew in only 1 of 8 sites. Nodal metastases were also significantly increased in patients with esophageal adenocarcinomas highly overexpressing DKK3, 28 of 32 (88%) versus 42 of 63 (68%) (P < .05).

CONCLUSIONS

These findings suggest that DKK3 may be important in mediating invasion in esophageal adenocarcinoma and could be a novel target in the treatment and prevention of metastatic disease.

Baicalin can attenuate the inhibitory effects of mifepristone on Wnt pathway during peri-implantation period in mice

Wnts are considered as important factors in uterus developmental process and embryo implantation. Baicalin has been demonstrated to possess tocolytic properties. In order to investigate the effect of baicalin on the Wnt signaling pathway during the peri-implantation, pregnant Kuming mice were randomly divided into four groups: control group, baicalin group administered with 40mg/kg BW of baicalin through an intragastric gavage on day 2 to 7 of the pregnancy (Pd2-Pd7), mifepristone group treated with 4mg/kg BW of mifepristone, an abortifacient agent, via subcutaneous administration on Pd4, and baicalin+mifepristone group treated with their combination. The concentrations of the implantation-related steroid hormones (progesterone and estradiol) in the blood serum were measured with RIA. The gene and protein expression levels of the important molecules of the Wnt pathway (Wnt4, LRP6, Dkk1 and β-catenin) in the endometrium were detected with RT-PCR and western blot, respectively. The results showed that baicalin decreased (P<0.05) the estradiol levels on Pd4-Pd8 and increased (P<0.05) the progesterone levels on Pd3-Pd8. Mifepristone increased (P<0.05) the estradiol levels on Pd5-Pd8 and decreased (P<0.05) the progesterone levels on Pd6-Pd8. Compared with the control group, baicalin increased the gene and protein expression levels of Wnt4, LRP6 and β-catenin (P<0.05) and decreased the gene and protein expression levels of Dkk1 (P<0.05) during the middle-to-late stage of the experiment in mice uterine tissue. Baicalin alleviated the mifepristone-induced increase or decrease in the serum levels of progesterone and estradiol, and the gene or protein expression levels of Wnt4, LRP6 and β-catenin. The tocolytic properties tocolysis of baicalin may be realized through regulating the levels of estrogen/progesterone and the important components of canonical Wnt signaling pathway during the embryo implantation process intervened with the subcutaneous administration of mifepristone in the mice.

Global gene expression during early differentiation of Xenopus (Silurana) tropicalis gonad tissues

African clawed frog Xenopus sp. is used extensively for developmental biology and toxicology research. Amid concerns of environmental pollutants disrupting endocrine systems and causing altered reproductive development in wildlife, eco-toxicology research has led to a focus on linking molecular initiating events to population-level effects. As such, efforts to better understand reproductive development at the molecular level in these model species are warranted. To that end, transcriptomes were characterized in differentiating Xenopus tropicalis gonad tissues at Nieuwkoop and Faber (NF) stage 58 (pro-metamorphosis), NF66 (completion of metamorphosis), 1week post-metamorphosis (1WPM), and 2weeks post-metamorphosis (2WPM). Differential expression analysis between tissue types at each developmental stage revealed a substantial divergence of ovary and testis transcriptomes starting between NF58 and NF66; transcriptomes continued to diverge through 2WPM. Generally, testis-enriched transcripts were expressed at relatively constant levels, while ovary-enriched transcripts were up-regulated within this developmental period. Functional analyses of differentially expressed transcripts allowed linkages to be made between their putative human orthologues and specific cellular processes associated with differentiating gonad tissues. In ovary tissue, genetic programs direct germ cells through meiosis to the diplotene stage when maternal mRNAs are transcribed and trafficked to oocytes for translation following fertilization. In the testis, gene expression is consistent with connective tissue development, tubule formation, and germ cell support (Leydig and Sertoli cells). This dataset exhibited remarkable consistency with transcript profiles previously described in gonad tissues across species, and emphasizes the universal importance of certain transcripts for germ cell development and preparation of these tissues for reproduction.

The cysteine-rich core domain of REIC/Dkk-3 is critical for its effect on monocyte differentiation and tumor regression

Reduced expression in immortalized cells (REIC)/Dickkopf (Dkk)-3 is a tumor-suppressor gene and has been studied as a promising therapeutic gene for cancer gene therapy. Intratumoral injection of an adenovirus vector carrying the human REIC/Dkk-3 gene (Ad-REIC) elicits cancer cell-specific apoptosis and anticancer immune responses. The cytokine-like effect of secretory REIC/Dkk-3 on the induction of dendritic cell (DC)-like cell differentiation from monocytes plays a role in systemic anticancer immunity. In the present study, we generated recombinant full-length and N-terminally truncated REIC/Dkk-3 to characterize the biological activity of the protein. During the purification procedure, we identified a 17 kDa cysteine-rich stable product (C17-REIC) showing limited degradation. Further analysis showed that the C17-REIC domain was sufficient for the induction of DC-like cell differentiation from monocytes. Concomitant with the differentiation of DCs, the REIC/Dkk-3 protein induced the phosphorylation of glycogen synthase kinase 3β (GSK-3β) and signal transducers and activators of transcription (STAT) at a level comparable to that of granulocyte/macrophage colony-stimulating factor. In a mouse model of subcutaneous renal adenocarcinoma, intraperitoneal injection of full-length and C17-REIC proteins exerted anticancer effects in parallel with the activation of immunocompetent cells such as DCs and cytotoxic T lymphocytes in peripheral blood. Taken together, our results indicate that the stable cysteine-rich core region of REIC/Dkk-3 is responsible for the induction of anticancer immune responses. Because REIC/Dkk-3 is a naturally circulating serum protein, the upregulation REIC/Dkk-3 protein expression could be a promising option for cancer therapy.

Musashi1 regulates survival of hepatoma cell lines by activation of Wnt signalling pathway

BACKGROUND & AIMS

Musashi1 (MSI1) belongs to the RNA-binding protein (RBP) family, with functions as translational activator or suppressor of specifically bound mRNA. However, its function in hepatocellular carcinoma (HCC) has been deeply unexplored. Here, we investigated the role of MSI1 for proliferation and tumourigenesis in HCC.

METHODS

The expression of MSI1 in HCC tissues was examined by immunohistochemistry and western blotting. The effects of MSI1 overexpression and silencing on cell proliferation, cell viability, tumoursphere and tumour formation of HCC were explored.

RESULTS

In this study, we initially reported that MSI1 was upregulated in HCC. Overexpression of MSI1 in HepG2 cell lines resulted in significantly promoted cell growth, tumour formation and cell cycle progression. Consistently, knockdown of MSI1 in Huh7 cell lines remarkably inhibited cell growth and tumour formation, and caused cell cycle arrest at the G1/S transition. Dual-luciferase assays indicated that MSI1 activated Wnt signal pathway, and APC and DKK1 were direct targets of MSI1.

CONCLUSION

Taken together, these findings indicate that an oncogenic role of MSI1 in HCC may be through modulation of cell growth and cell cycle by activating Wnt pathway via direct downregulation of APC and DKK1.

A Review of Biomarkers in Mood and Psychotic Disorders: A Dissection of Clinical vs. Preclinical Correlates

Despite significant research efforts aimed at understanding the neurobiological underpinnings of mood (depression, bipolar disorder) and psychotic disorders, the diagnosis and evaluation of treatment of these disorders are still based solely on relatively subjective assessment of symptoms as well as psychometric evaluations. Therefore, biological markers aimed at improving the current classification of psychotic and mood-related disorders, and that will enable patients to be stratified on a biological basis into more homogeneous clinically distinct subgroups, are urgently needed. The attainment of this goal can be facilitated by identifying biomarkers that accurately reflect pathophysiologic processes in these disorders. This review postulates that the field of psychotic and mood disorder research has advanced sufficiently to develop biochemical hypotheses of the etiopathology of the particular illness and to target the same for more effective disease modifying therapy. This implies that a "one-size fits all" paradigm in the treatment of psychotic and mood disorders is not a viable approach, but that a customized regime based on individual biological abnormalities would pave the way forward to more effective treatment. In reviewing the clinical and preclinical literature, this paper discusses the most highly regarded pathophysiologic processes in mood and psychotic disorders, thereby providing a scaffold for the selection of suitable biomarkers for future studies in this field, to develope biomarker panels, as well as to improve diagnosis and to customize treatment regimens for better therapeutic outcomes.

Blocking of the interaction between Wnt proteins and their co-receptors contributes to the anti-tumor effects of adenovirus-mediated DKK3 in glioblastoma

The effect of the third member of the Dickkopf family (DKK3) in the Wnt pathway in glioblastoma remains unclear. We first demonstrated the non-specific interaction of Wnt3a and Wnt5a with the receptors LRP6 and ROR2 and the up-regulation of the Wnt pathway in glioblastoma cells. We used an adenovirus vector and found that an increase in DKK3 protein attenuated the expression of Wnt3a, Wnt5a and LRP6, but not of ROR2, and their interaction, thereby affecting both canonical- and non-canonical Wnt downstream cascades. This produced anti-tumor effects in GBM xenograft models. The suppression of Wnt pathways upstream by DKK3 may have promise for the treatment of glioblastoma.

T cell-based targeted immunotherapies for patients with multiple myeloma

Despite high-dose chemotherapy followed by autologs stem-cell transplantation as well as novel therapeutic agents, multiple myeloma (MM) remains incurable. Following the general trend towards personalized therapy, targeted immunotherapy as a new approach in the therapy of MM has emerged. Better progression-free survival and overall survival after tandem autologs/allogeneic stem cell transplantation suggest a graft versus myeloma effect strongly supporting the usefulness of immunological therapies for MM patients. How to induce a powerful antimyeloma effect is the key issue in this field. Pivotal is the definition of appropriate tumor antigen targets and effective methods for expansion of T cells with clinical activity. Besides a comprehensive list of tumor antigens for T cell-based approaches, eight promising antigens, CS1, Dickkopf-1, HM1.24, Human telomerase reverse transcriptase, MAGE-A3, New York Esophageal-1, Receptor of hyaluronic acid mediated motility and Wilms' tumor gene 1, are described in detail to provide a background for potential clinical use. Results from both closed and on-going clinical trials are summarized in this review. On the basis of the preclinical and clinical data, we elaborate on three encouraging therapeutic options, vaccine-enhanced donor lymphocyte infusion, chimeric antigen receptors-transfected T cells as well as vaccines with multiple antigen peptides, to pave the way towards clinically significant immune responses against MM.

Myeloma bone disease: pathogenesis, current treatments and future targets

INTRODUCTION

Patients with myeloma develop localized and generalized bone loss leading to hypercalcaemia, accelerated osteoporosis, vertebral wedge fractures, other pathological fractures, spinal cord compression and bone pain. Bone loss is mediated by a variety of biological modifiers including osteoclast-activating factors (OAF) and osteoblast (OB) inhibitory factors produced either directly by malignant plasma cells (MPCs) or as a consequence of their interaction with the bone marrow microenvironment (BMM). Raised levels of OAFs such as receptor activator of nuclear factor-kappa B ligand (RANKL), macrophage inflammatory protein 1 alpha, tumour necrosis factor-alpha and interleukin 6 stimulate bone resorption by recruiting additional osteoclasts. Via opposing mechanisms, increases in OB inhibitory factors, such as dickkopf-1 (Dkk-1), soluble frizzled-related protein-3 and hepatocyte growth factor (HGF), suppress bone formation by inhibiting the differentiation and recruitment of OBs. These changes result in an uncoupling of physiological bone remodelling, leading to myeloma bone disease (MBD). Moreover, the altered BMM provides a fertile ground for the growth and survival of MPCs. Current clinical management of MBD is both reactive (to pain and fractures) and preventive, with bisphosphonates (BPs) being the mainstay of pharmacological treatment. However, side effects and uncertainties associated with BPs warrant the search for more targeted treatments for MBD. This review will summarize recent developments in understanding the intimate relationship between MBD and the BMM and the novel ways in which they are being therapeutically targeted.

SOURCES OF DATA

All data included were sourced and referenced from PubMed.

AREAS OF AGREEMENT

The clinical utility of BP therapy is well established. However, there is general acknowledgement that BPs are only partially successful in the treatment of MBD. The number of skeletal events attributable to myeloma are reduced by BPs but not totally eliminated. Furthermore, existing damage is not repaired. It is widely recognized that more effective treatments are needed.

AREAS OF CONTROVERSY

There remains controversy concerning the duration of BP therapy. Whether denosumab is a viable alternative to BP therapy is also contested. Many of the new therapeutic strategies discussed are yet to translate to clinical practice and demonstrate equal efficacy or superiority to BP therapy. It also remains controversial whether reported anti-tumour effects of bone-modulating therapies are clinically significant.

GROWING POINTS

The potential clinical utility of bone anabolic therapies including agents such as anti-Dkk-1, anti-sclerostin and anti-HGF is becoming increasingly recognized.

AREAS TIMELY FOR DEVELOPING RESEARCH

Further research effectively targeting the mediators of MBD, targeting both bone resorption and bone formation, is urgently needed. This should translate promptly to clinical trials of combination therapy comprising anti-resorptives and bone anabolic therapies to demonstrate efficacy and improved outcomes over BPs.

Serum Dickkopf-1 expression level positively correlates with a poor prognosis in breast cancer

BACKGROUND

The different expression level of Dickkopf-1 (DKK-1) in different cancers shows that the function of DKK-1 depends on the histological type of the cancer cells and the tissue microenvironment. To our knowledge, the serum expression level of DKK-1 in breast cancer is little known.

METHODS

Blood samples from 125 consecutive patients diagnosed with breast cancer and 53 control subjects from March 2008 to August 2013 were investigated. Serum DKK-1 expression levels were measured by enzyme-linked immunosorbent assay (ELISA). The overall survival (OS) and relapse-free survival (RFS) analyzed by log-rank test, and survival curves were plotted according to Kaplan-Meier.

RESULTS

The mean serum level of DKK-1 in patients with breast cancer was 4.99 ± 1.50 ng/mL, and was significantly higher than that in healthy individuals (1.88 ± 0.81 ng/mL, P < 0.001). DKK-1 level correlated significantly with TNM stage (P = 0.009), tumor grade (P = 0.02), lymph node metastasis (P = 0.001), and expression of HER2 (P = 0.002). The DKK-1 expression level was classified as high or low in relation to the median value, and patients with breast cancer (n = 125) were divided into a high expression group (n = 63) and a low expression group (n = 62). The Kaplan-Meier method for survival analysis showed that the patients with a high serum DKK-1 level had a poorer OS (48.7% vs. 81.3%, p = 0.01) and RFS (24.3% vs. 71.6%, p = 0.003) than those with a low expression level. The multivariate Cox regression analysis indicated that serum DKK-1 level was independent prognostic factors for OS and RFS.

CONCLUSIONS

Serum DKK-1 level can be used as a noninvasive biomarker for the prognosis of breast cancer.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_161.

Dysregulated expression of dickkopfs for potential detection of hepatocellular carcinoma

The prognosis for hepatocellular carcinoma (HCC) remains dismal due to the lack of diagnostic markers for early detection. This review will discuss the clinical potential of the dickkopf (DKK) family members as diagnostic and/or prognostic markers for HCC. In comparison to serum α-fetoprotein (AFP) level, which remains the gold standard for HCC diagnosis, high serum DKK1 levels have higher diagnostic value for HCC, especially for AFP-negative HCC, and can distinguish HCC from non-malignant chronic liver diseases. Additionally, the combination of serum DKK1 and AFP levels enhances diagnostic accuracy for HCC compared to serum DKK1 or AFP levels alone. Although DKK1 offers potential for its use in HCC diagnosis this review will discuss the challenges facing DKK1 and also shed some light on recent developments on the remaining DKK family members: DKK2, DKK3 and DKK4.

Potential of adenovirus-mediated REIC/Dkk-3 gene therapy for use in the treatment of pancreatic cancer

BACKGROUND AND AIM

The reduced expression in immortalized cells REIC/the dickkopf 3 (Dkk-3) gene, tumor suppressor gene, is downregulated in various malignant tumors. In a prostate cancer study, an adenovirus vector carrying the REIC/Dkk-3 gene (Ad-REIC) induces apoptosis. In the current study, we examined the effects of REIC/Dkk-3 gene therapy in pancreatic cancer.

METHODS

REIC/Dkk-3 expression was assessed by immunoblotting and immunohistochemistry in the pancreatic cancer cell lines (ASPC1, MIAPaCa2, Panc1, BxPC3, SUIT-2, KLM1, and T3M4) and pancreatic cancer tissues. The Ad-REIC agent was used to investigate the apoptotic effect in vitro and antitumor effects in vivo. We also assessed the therapeutic effects of Ad-REIC therapy with gemcitabine.

RESULTS

The REIC/Dkk-3 expression was lost in the pancreatic cancer cell lines and decreased in pancreatic cancer tissues. Ad-REIC induced apoptosis and inhibited cell growth in the ASPC1 and MIAPaCa2 lines in vitro, and Ad-REIC inhibited tumor growth in the mouse xenograft model using ASPC1 cells. The antitumor effect was further enhanced in combination with gemcitabine. This synergistic effect may be caused by the suppression of autophagy via the enhancement of mammalian target of rapamycin signaling.

CONCLUSIONS

Ad-REIC induces apoptosis and inhibits tumor growth in pancreatic cancer cell lines. REIC/Dkk-3 gene therapy is an attractive therapeutic tool for pancreatic cancer.

CD58, a novel surface marker, promotes self-renewal of tumor-initiating cells in colorectal cancer

Colorectal tumor-initiating cells (CT-ICs) have self-renewal capabilities and have an important role in tumorigenesis, metastasis, recurrence and treatment resistance in colorectal cancer. Multiple cell-surface molecules targeting CT-ICs, possibly representing different CT-IC subpopulations, have been reported. However, whether new surface markers exist, as well as the mechanisms by which the markers regulate self-renewal, remain unclear. In this study, we enriched a CT-IC population through a serum-free low-adhesion system in vitro. Within this population, we found that CD58 and CD44 were upregulated using a cDNA GeneChip, and CD44(high)CD58(high) cancer cells, the common existence of which was demonstrated by flow cytometry in multiple colon cancer cell lines and primary specimens, exhibited enhanced self-renewal ability, epithelial-mesenchymal transition ability and tumorigenicity, both in vitro and in vivo. Furthermore, activated CD58 upregulated the Wnt/β-catenin pathway and thus promoted self-renewal of CT-ICs; conversely, knockdown of CD58 significantly impaired sphere formation and tumor growth. With immunoprecipitation and western blotting approaches, CD58 was found to upregulate the Wnt pathway by degradation of Dickkopf 3. These results indicate that CD58 is a novel cell-surface marker that functionally regulates self-renewal of CT-ICs, which may provide an intriguing therapeutic target for the efficient killing and elimination of CT-ICs.

Dickkopf-3 attenuates pressure overload-induced cardiac remodelling

AIMS

Dickkopf-3 (DKK3), a secreted protein in the Dickkopf family, is expressed in various tissues, including the heart, and has been shown to play an important role in tissue development. However, the biological function of DKK3 in the heart remains largely unexplored. This study aimed to examine the role of DKK3 in pathological cardiac hypertrophy.

METHODS AND RESULTS

We performed gain-of-function and loss-of-function studies using DKK3 cardiac-specific transgenic (TG) mice and DKK3 knockout (KO) mice (C57BL/6J background). Cardiac hypertrophy was induced by aortic banding. Cardiac hypertrophy was evaluated by echocardiographic, haemodynamic, pathological, and molecular analyses. Our results demonstrated that the loss of DKK3 exaggerated pressure overload-induced cardiac hypertrophy, fibrosis, and dysfunction, whereas the overexpression of DKK3 protected the heart against pressure overload-induced cardiac remodelling. These beneficial effects were associated with the inhibition of the ASK1-JNK/p38 (apoptosis signal-regulating kinase 1-c-Jun N-terminal kinase/p38) signalling cascade. Parallel in vitro experiments confirmed these in vivo observations. Co-immunoprecipitation experiments suggested that physical interactions occurred between DKK3 and ASK1. Moreover, rescue experiments indicated that, in DKK3 TG mice, the activation of ASK1 using a cardiac-specific conditional ASK1 transgene reduced the functionality of DKK3 in response to pressure overload; furthermore, the inactivation of ASK1 by dominant-negative ASK1 rescued pressure overload-induced cardiac abnormalities in DKK3 KO mice.

CONCLUSION

Taken together, our findings indicate that DKK3 acts as a cardioprotective regulator of pathological cardiac hypertrophy and that this function largely occurs via the regulation of ASK1-JNK/p38 signalling.

Bidirectional effect of Wnt signaling antagonist DKK1 on the modulation of anthrax toxin uptake

LRP6, a co-receptor for the morphogen Wnt, aids endocytosis of anthrax complexes. Here we report that Dickkopf1 (DKK1) protein, a secreted LRP6 ligand and antagonist, is also a modulator of anthrax toxin sensitivity. shRNA-mediated gene silencing or TALEN-mediated gene knockout of DKK1 reduced sensitivity of cells to PA-dependent hybrid toxins. However, unlike the solely inhibitory effect on Wnt signaling, the effects of DKK1 overexpression on anthrax toxicity were bidirectional, depending on its endogenous expression and cell context. Fluorescence microscopy and biochemical analyses showed that DKK1 facilitates internalization of anthrax toxins and their receptors, an event mediated by DKK1-LRP6-Kremen2 complex. Monoclonal antibodies against DKK1 provided dose-dependent protection to macrophages from killing by anthrax lethal toxin (LT). Our discovery that DKK1 forms ternary structure with LRP6 and Kremen2 in promoting PA-mediated toxin internalization provides a paradigm for bacterial exploitation of mechanisms that host cells use to internalize signaling proteins.

High expression of the secreted protein dickkopf homolog 4: roles in invasion and metastasis of renal cell carcinoma and its association with Von Hippel-Lindau gene

The aim of this study was to investigate the effects of the dickkopf homolog 4 (DKK4)/Wnt/β-catenin signaling pathway on tumorigenesis and metastasis in clear cell renal cell carcinoma (ccRCC), as well as to elucidate the underlying mechanisms. We examined the expression of DKK4 in 30 cases of ccRCC and matched adjacent normal tissues, and investigated its correlation with clinicopathological characteristics. Stable DKK4-transfected cells were established, and DKK4 functional analyses were performed, including a T-cell factor/lymphoid enhancer factor (TCF/LEF) reporter assay, and experiments on cell viability, apoptosis, invasive capability and tumor growth in vivo. Finally, western blot analysis was performed to detect Von Hippel-Lindau (VHL) expression in 50 clinical specimens. The expression levels of the DKK4, β-catenin and β-catenin downstream target genes, cyclin D1 and c-myc, were determined in the these specimens, as well as in RCC4(-), T3-14(+) cell lines by qRT-PCR and western blot analysis. The same tests were also performed in human embryonic kidney (HEK)293 cells which were transfected with the pCDH-DKK4 plasmid. After 6 weeks the tumor weight significantly increased in the mice transfected with the tumor cells. DKK4 mRNA and protein expression levels were significantly upregulated (p<0.001). DKK4 was distinctly overexpressed (68.0%) in all patient tissues. VHL(-) samples accounted for 60.0% of all samples, while DKK4 expression was significantly upregulated in 50% of these samples, indicating a correlation with VHL(-) expression (r=0.403, p<0.05). We also observed reduced expression levels of cyclin D1, c-myc and β-catenin (to a greater extent) in the VHL(-), RCC4(-) and T3-14(+) cells, as well as in the stably transfected HEK293 cells. DKK4 may be an oncogene, and its upregulated expression may be involved in the pathogenesis of ccRCC as a downstream gene of VHL. By activating other pathways apart from the Wnt/β-catenin pathway, DKK4 may play an important role in ccRCC tumorigenesis and metastasis.

Anti-cancer effects of REIC/Dkk-3-encoding adenoviral vector for the treatment of non-small cell lung cancer

Objectives

REIC/Dkk-3 is down-regulated in a broad range of human cancer cells and is considered to function as a tumor suppressor. We previously reported that REIC/Dkk-3-expressing adenovirus vector (Ad-REIC) induced endoplasmic reticulum (ER) stress and cancer-specific apoptosis in human prostate cancer. In this study, we examined the therapeutic impact of Ad-REIC on non-small cell lung cancer (NSCLC).

Materials and Methods

We examined the anti-tumor effect of Ad-REIC on 25 NSCLC cell lines in vitro and A549 cells in vivo. Two of these cell lines were artificially established as EGFR-tyrosine kinase inhibitor (TKI) resistant sublines.

Results

Ad-REIC-treatment inhibited the cell viability by 40% or more in 13 (52%) of the 25 cell lines at multiplicity of infection (MOI) of 20 (20 MOI). These cell lines were regarded as being highly sensitive cells. The cell viability of a non-malignant immortalized cell line, OUMS-24, was not inhibited at 200 MOI of Ad-REIC. The effects of Ad-REIC on EGFR-TKI resistant sublines were equivalent to those in the parental cell lines. Here, we demonstrated that Ad-REIC treatment activated c-Jun N-terminal kinase (JNK) in NSCLC cell lines, indicating the induction of ER stress with GRP78/BiP (GRP78) up-regulation and resulting in apoptosis. A single intratumoral injection of Ad-REIC significantly inhibited the tumorigenic growth of A549 cells in vivo. As predictive factors of sensitivity for Ad-REIC treatment in NSCLC, we examined the expression status of GRP78 and coxsackievirus and adenovirus receptor (CAR). We found that the combination of the GRP78 and CAR expressional statuses may be used as a predictive factor for Ad-REIC sensitivity in NSCLC cells.

Conclusion

Ad-REIC induced JNK activation and subsequent apoptosis in NSCLC cells. Our study indicated that Ad-REIC has therapeutic potential against NSCLC and that the expression statuses of GRP78 and CAR may predict a potential therapeutic benefit of Ad-REIC.

Clusterin regulates β-amyloid toxicity via Dickkopf-1-driven induction of the wnt-PCP-JNK pathway

Although the mechanism of Aβ action in the pathogenesis of Alzheimer's disease (AD) has remained elusive, it is known to increase the expression of the antagonist of canonical wnt signalling, Dickkopf-1 (Dkk1), whereas the silencing of Dkk1 blocks Aβ neurotoxicity. We asked if clusterin, known to be regulated by wnt, is part of an Aβ/Dkk1 neurotoxic pathway. Knockdown of clusterin in primary neurons reduced Aβ toxicity and DKK1 upregulation and, conversely, Aβ increased intracellular clusterin and decreased clusterin protein secretion, resulting in the p53-dependent induction of DKK1. To further elucidate how the clusterin-dependent induction of Dkk1 by Aβ mediates neurotoxicity, we measured the effects of Aβ and Dkk1 protein on whole-genome expression in primary neurons, finding a common pathway suggestive of activation of wnt-planar cell polarity (PCP)-c-Jun N-terminal kinase (JNK) signalling leading to the induction of genes including EGR1 (early growth response-1), NAB2 (Ngfi-A-binding protein-2) and KLF10 (Krüppel-like factor-10) that, when individually silenced, protected against Aβ neurotoxicity and/or tau phosphorylation. Neuronal overexpression of Dkk1 in transgenic mice mimicked this Aβ-induced pathway and resulted in age-dependent increases in tau phosphorylation in hippocampus and cognitive impairment. Furthermore, we show that this Dkk1/wnt-PCP-JNK pathway is active in an Aβ-based mouse model of AD and in AD brain, but not in a tau-based mouse model or in frontotemporal dementia brain. Thus, we have identified a pathway whereby Aβ induces a clusterin/p53/Dkk1/wnt-PCP-JNK pathway, which drives the upregulation of several genes that mediate the development of AD-like neuropathologies, thereby providing new mechanistic insights into the action of Aβ in neurodegenerative diseases.

Dkk3 levels in patients with myeloproliferative neoplasms

INTRODUCTION

Dickkopf-3 (Dkk3) has been proposed as tumor suppressor gene and a marker for tumor blood vessels and has pro-angiogenic properties. Dkk3 is expressed in platelets and megakaryocytes from healthy controls and patients with BCR-ABL1-negative myeloproliferative neoplasms (MPN). The aim of this study is, to find out whether patients with MPN have higher Dkk3 serum levels than normal controls.

MATERIAL & METHODS

We analyzed Dkk3 serum levels with ELISA in patients with newly diagnosed and untreated MPN, including 10 essential thrombocythemia (ET), 10 polycythemia vera (PV), 10 primary meylofibrosis (PMF) and 10 healthy blood donors and correlated these findings with biological and clinical key data and the JAK2-V617F status. Dkk3 levels were corrected to platelet count, Dkk3c, as patients with MPN have higher platelet counts than controls.

RESULTS

As expected, patients with MPN have higher platelet counts than normal controls. Dkk3 serum levels of patients with MPN (5.4 ± 6.1 ng/ml) showed no significant difference compared to normal controls (4.4 ± 3.8 ng/ml). Regarding Dkk3c, a significant difference to controls was found in PV (8.5 ± 8.7 ng/ml; p=0.04), but not in ET and PMF (5.7 ± 3.8 ng/ml; p=0.07 and 2.7 ± 3.6 ng/ml; p=0.9; respectively. Dkk3c correlated with the JAK2-V617F mutational burden (p=0.014, Rho=0.445).

CONCLUSION

Dkk3 levels corrected to platelet count showed higher levels in PV than normal controls. Elevated Dkk3c level could possibly correlate to platelet activation in PV patients and increased Dkk3 release. Whether this remains a surrogate marker of platelet release or it contributes to the thrombophilic state through its pro-angiogenic properties remains to be shown.

The effects of Dickkopf-4 on the proliferation, differentiation, and apoptosis of osteoblasts

The Dickkopf family of proteins is comprised of four members (Dkk1, Dkk2, Dkk3, Dkk4) that are known to modulate Wnt/β-catenin signaling, which is activated during bone formation. Although the effects of Dkk1 on Wnt/β-catenin signaling have been well studied, little is known about the effects of Dkk4. Therefore, to evaluate the role of Dkk4 in osteoblastogenesis, we used the mouse osteoblastic cell line MC3T3-E1, in which Dkk4 expression was suppressed by small interfering RNA knockdown. Our results showed that the suppression of Dkk4 expression promoted osteoblast proliferation and differentiation and suppressed apoptosis. In colony-forming unit alkaline phosphatase assay, Dkk4 knockdown cells possessed markedly higher alkaline phosphatase activity compared with Dkk1 knockdown cells. Reduced Dkk4 expression also led to the up-regulation of β-catenin levels, β-catenin/T cell factor activity, and Wnt-target genes. In contrast, overexpression of Dkk4 in MC3T3-E1 cells led to inhibition of osteoblast differentiation. Our findings reveal that Dkk4 functions as an inhibitor of osteoblastogenesis through Wnt/β-catenin signaling, providing new insights into the relationship between Wnt/β-catenin signaling and Dkk4 in bone formation.

A complex interaction between Wnt signaling and TNF-α in nucleus pulposus cells

Introduction

Increased expression of the proinflammatory cytokine TNF-α in intervertebral discs (IVDs) leads to inflammation, which results in progressive IVD degeneration. We have previously reported that activation of Wnt-β-catenin (hereafter called Wnt) signaling suppresses the proliferation of nucleus pulposus cells and induces cell senescence, suggesting that Wnt signaling triggers the process of degeneration of the IVD. However, it is not known whether cross talk between TNF-α and Wnt signaling plays a role in the regulation of nucleus pulposus cells. The goal of the present study was to examine the effect of the interaction between Wnt signaling and the proinflammatory cytokine TNF-α in nucleus pulposus cells.

Methods

Cells isolated from rat nucleus pulposus regions of IVDs were cultured in monolayers, and the expression and promoter activity of Wnt signaling and TNF-α were evaluated. We also examined whether the inhibition of Wnt signaling using cotransfection with Dickkopf (DKK) isoforms and Sclerostin (SOST) could block the effects of pathological TNF-α expression in nucleus pulposus cells.

Results

TNF-α stimulated the expression and promoter activity of Wnt signaling in nucleus pulposus cells. In addition, the activation of Wnt signaling by 6-bromoindirubin-3′-oxime (BIO), which is a selective inhibitor of glycogen synthase kinase 3 (GSK-3) activity that activates Wnt signaling, increased TNF-α expression and promoter activity. Conversely, the suppression of TNF-α promoter activity using a β-catenin small interfering RNA was evident. Moreover, transfection with DKK-3, DKK-4, or SOST, which are inhibitors of Wnt signaling, blocked Wnt signaling-mediated TNF-α activation; these effects were not observed for DKK-1 or DKK-2.

Conclusions

Here, we have demonstrated that Wnt signaling regulates TNF-α and that Wnt signaling and TNF-α form a positive-feedback loop in nucleus pulposus cells. The results of the present study provide in vitro evidence that activation of Wnt signaling upregulates the TNF-α expression and might cause the degeneration of nucleus pulposus cells. We speculate that blocking this pathway might protect nucleus pulposus cells against degeneration.

Systemic effects of Wnt signaling

Wnt signaling plays a key role in several physiological and pathological aspects. Even if Wnt signal was first described more than 20 years ago, its role in systemic effects, such as angiogenesis and vascular disorders, bone biology, autoimmune diseases, neurological diseases, and neoplastic disorders, was only recently emerged through the use of animal and in vitro models. Moreover, Wnt signaling inhibitors, such as DKK-1, may be advantageously considered targets for the treatment of several diseases, including osteoporosis, vascular diseases, inflammatory diseases, neurological diseases, and cancer. Nevertheless, further studies are required to provide a complete understanding of this complex signaling pathway, and especially of its role in human diseases, considering the possible advantageous effects of Wnt signaling inhibitors on the progression of disease conditions.

Psychiatric patient stratification using biosignatures based on cerebrospinal fluid protein expression clusters

Psychiatric disorders are caused by perturbed molecular pathways that affect brain circuitries. The identification of specific biosignatures that are the result of altered pathway activities in major depression, bipolar disorder and schizophrenia can contribute to a better understanding of disease etiology and aid in the implementation of diagnostic assays. In the present study we identified disease-specific protein biosignatures in cerebrospinal fluid of depressed (n: 36), bipolar (n: 27) and schizophrenic (n: 35) patients using the Reverse Phase Protein Microarray technology. These biosignatures were able to stratify patient groups in an objective manner according to cerebrospinal fluid protein expression patterns. Correct classification rates were over 90%. At the same time several protein sets that play a role in neuronal growth, proliferation and differentiation (NEGR1, NPDC1), neurotransmission (SEZ6) and protection from oxidative damage (GPX3) were able to distinguish diseased from healthy individuals (n: 35) indicating a molecular signature overlap for the different psychiatric phenotypes. Our study is a first step toward implementing a psychiatric patient stratification system based on molecular biosignatures. Protein signatures may eventually be of use as specific and sensitive biomarkers in clinical trials not only for patient diagnostic and subgroup stratification but also to follow treatment response.

Association study of DKK2 polymorphisms with alcohol dependence and alcohol-related harm

BACKGROUND

Alcohol dependence (AD) is a common disorder with both environmental and genetic factors. Previous studies have shown that the genomic region from chromosome 4q22-q32 is closely associated with AD. Furthermore, a study with Irish subjects revealed that the polymorphisms of Dickkopf WNT signaling pathway inhibitor (DKK2), located at 4q25, showed a significant association with AD.

METHODS

We conducted a replication study of the association between DKK2 polymorphisms and AD with 459 alcoholics and 444 normal controls, all of Korean descendent. To rank the AD of the subjects, Alcohol Use Disorders Identification Test (AUDIT) was utilized. Using the TaqMan assay, 21 single-nucleotide polymorphisms (SNPs) of DKK2 were genotyped.

RESULTS

Our analysis showed that rs17037102 (Q146R) was significantly associated with overall AUDIT score (p = 0.003, p(corr)  = 0.05 in dominant model). Further analysis showed that the SNP was significantly associated with alcohol-related harm (p = 0.001, p(corr)  = 0.02 in co-dominant model). Several other SNPs, including the 3 SNPs which were associated with AD in European population, showed marginal associations that were erased when corrections for multiple testing was applied. Furthermore, rs17037102 was in linkage disequilibrium with the nonexonic DKK2 SNPs which showed associations with AD in the previous study with Irish population, which suggests that rs17037102 may be the causal SNP.

CONCLUSIONS

We found 1 DKK2 SNP to be significantly associated with alcohol-related harm in alcoholic subjects. The SNP might be the causal SNP which led its linked SNPs to show associations in previous studies.