Dickkopf-1 Expression Research Articles

Effect of autonomic nerves on Dickkopf-3 expression in the uterus during early pregnancy of rats

To explore how uterine innervations affect expression of Dickkopf-3 (DKK-3) during peri-implantation, we first examined the consequence of uterine neurectomy on embryo implantation events. We observed that amputation of autonomic nerves innervating the uterus led to the failure of on-time implantation in rats. We then analyzed the effect of neurectomy on expression of DKK-3 further using immunohistochemistry and quantitative real-time reverse transcription polymerase chain reaction. We observed that disconnection of autonomic nerve innervation significantly increased DKK-3 expression in the endometrium before and during invasion of the blastocyst. We also observed high levels of DKK-3 immunoreactivity in the vasculature of the uterus during peri-implantation. Thus, we speculate that DKK-3 may relate to implantation. Besides, our findings provide a new line of evidence that DKK-3 may be regulated by the autonomic nervous system.

Molecular signalling in hepatocellular carcinoma: Role of and crosstalk among WNT/ß-catenin, Sonic Hedgehog, Notch and Dickkopf-1.

Hepatocellular carcinoma is the sixth most common cancer worldwide. In the majority of cases, there is evidence of existing chronic liver disease from a variety of causes including viral hepatitis B and C, alcoholic liver disease and nonalcoholic steatohepatitis. Identification of the signalling pathways used by hepatocellular carcinoma cells to proliferate, invade or metastasize is of paramount importance in the discovery and implementation of successfully targeted therapies. Activation of Wnt/β-catenin, Notch and Hedgehog pathways play a critical role in regulating liver cell proliferation during development and in controlling crucial functions of the adult liver in the initiation and progression of human cancers. β-catenin was identified as a protein interacting with the cell adhesion molecule E-cadherin at the cell-cell junction, and has been shown to be one of the most important mediators of the Wnt signalling pathway in tumourigenesis. Investigations into the role of Dikkopf-1 in hepatocellular carcinoma have demonstrated controversial results, with a decreased expression of Dickkopf-1 and soluble frizzled-related protein in various cancers on one hand, and as a possible negative prognostic indicator of hepatocellular carcinoma on the other. In the present review, the authors focus on the Wnt⁄β-catenin, Notch and Sonic Hedgehog pathways, and their interaction with Dikkopf-1 in hepatocellular carcinoma.

Increased expression of the Wnt signalling inhibitor Dkk-1 in non-lesional skin and peripheral blood mononuclear cells of patients with plaque psoriasis.

Psoriasis is a common inflammatory skin disease characterised by abnormal keratinocyte proliferation, increased dermal angiogenesis and systemic inflammation. The cell signalling cascades provoked by Wnt proteins and their inhibitors, such as Dickkopf-1, play crucial roles to maintain homeostasis of a variety of tissues, including skin, and are also involved in angiogenesis and innate immunity. This study was designed to investigate the distribution of Dickkopf-1, in lesional and non-lesional skin, in serum and in peripheral blood mononuclear cell (PBMCs) of patients with psoriasis compared with healthy controls. Our results showed significantly increased mRNA and protein expression of Dickkopf-1 in non-lesional compared with lesional skin and healthy control skin. No significant differences of Dickkopf-1 serum levels were observed, but Dickkopf-1 protein expression was significantly increased in patients' PBMC. Increased levels of Dickkopf-1 in PBMC, suggest a possible role of Dickkopf-1 in the chronic systemic inflammation of psoriasis. Increased levels of Dickkopf-1 in non-lesional psoriasis skin offers new insights in the local inflammatory processes in psoriasis skin since Wnt signalling regulates angiogenesis. In conclusion, Dickkopf-1 may be a possible target for future treatment options.

Dickkopf1 Up-Regulation Induced by a High Concentration of Dexamethasone Promotes Rat Tendon Stem Cells to Differentiate Into Adipocytes

Background/Aims: Dexamethasone (Dex)-induced spontaneous tendon rupture and decreased self-repair capability is very common in clinical practice. The metaplasia of adipose tissue in the ruptured tendon indicates that Dex may induce tendon stem cells (TSCs) to differentiate into adipocytes, but the mechanism remains unclear. In the present study, we used in vitro methods to investigate the effects of Dex on rat TSC differentiation and the molecular mechanisms underlying this process. Methods: First, we used qPCR and Western blotting to detect the expression of the adipogenic differentiation markers aP2 and C/EBPα after treating the TSCs with Dex. Oil red staining was used to confirm that high concentration Dex promoted adipogenic differentiation of rat TSCs. Next, we used qPCR and Western blotting to detect the effect of a high concentration of dexamethasone on molecules related to the canonical WNT/β-catenin pathway in TSCs. Results: Treating rat TSCs with Dex promoted the synthesis of the inhibitory molecule dickkopf1 (DKK1) at the mRNA and protein levels. Western blotting results further showed that Dex downregulated the cellular signaling molecule phosphorylated glycogen synthase kinase-3β (P-GSK-3 β (ser9)), upregulated P-GSK-3β (tyr216), and downregulated the pivotal signaling molecule β-catenin. Furthermore, DKK1 knockdown attenuated Dex-induced inhibition of the canonical WNT/β-catenin pathway and of the adipogenic differentiation of TSCs. Lithium chloride (LiCl, a GSK-3β inhibitor) reduced Dex-induced inhibition of the classical WNT/β-catenin pathway in TSCs and of the differentiation of TSCs to adipocytes. Conclusion: In conclusion, by upregulating DKK1 expression, reducing the level of P-GSK-3β (ser9), and increasing the level of P-GSK-3β (tyr216), Dex causes the degradation of β-catenin, the central molecule of the classical WNT pathway, thereby inducing rat TSCs to differentiate into adipocytes.

Serum Dickkopf-1 levels as a clinical and prognostic factor in patients with bladder cancer.

Dickkopf-1 (DKK-1) is a secreted protein that inhibits Wnt signaling. However, the clinical significance and prognostic value of serum DKK-1 levels have not been previously investigated in bladder cancer in Chinese patients. Blood samples were taken from 94 consecutive patients diagnosed with bladder cancer and 60 healthy control subjects. Serum DKK-1 expression levels were measured by enzyme-linked immunosorbent assay according to the manufacturer's directions. The Kaplan-Meier method was used to estimate survival, and the log-rank test was used to test differences between the survival curves. Multivariate survival analysis was performed for all parameters deemed significant in the univariate analyses using the Cox regression model. The mean serum DKK-1 level in patients with bladder cancer was 35.91 ± 16.09 ng/mL, which was significantly higher than that in healthy individuals (9.08 ± 5.21 ng/mL, P < 0.001). Furthermore, serum DKK-1 levels were correlated significantly with lymph node metastasis (P = 0.021), distant metastasis (P = 0.013), and TNM stage (P = 0.008). Kaplan-Meier analysis using the log-rank test indicated that high serum DKK-1 levels were linked to poorer survival (33.4 vs 70.1%; P = 0.007). Multivariate analysis revealed that serum DKK-1 levels represented an independent prognostic factor for overall survival (hazard ratio = 2.365, 95% confidence interval = 1.873-8.881, P = 0.029). High serum DKK-1 levels may be associated with tumor progression and poor prognosis in bladder cancer and may be used as a potential biomarker to predict the prognosis of patients with bladder cancer.

Heritability and genetics of serum dickkopf 1 levels in African ancestry families.

The aim of the study was to determine the heritability of serum dickkopf-1 (DKK1) and its association with DKK1 polymorphisms in African ancestry subjects. Serum DKK1 was measured in 422 Afro-Caribbean men and women aged 18+ from 7 large, multi-generational families (mean family size: 60; 3,215 relative pairs). Twenty-four common single nucleotide polymorphisms (SNPs) were genotyped within an 80 kilobase-pair region encompassing the DKK1 gene. Heritability was estimated and SNPs were tested for association with serum DKK1 using variance components analysis. DKK1 mRNA expression was tested in peripheral blood of 16 individuals from each of the rs7069912 genotypes. Mean serum DKK1 was 1724.1 pg/mL and was significantly lower in women than men (P = 0.043). Residual genetic heritability of serum DKK1 was 0.4460 (P < 0.0001). Six SNPs reached nominal significance with DKK1, with rs7069912 being significant after adjustment for multiple comparisons. Two of these six SNPs represented independent association signals (rs7069912 and rs16928725), which accounted for 4.6% of the phenotypic variation in DKK1. Additionally, carriers of the rs7069912 variant had significantly greater DKK1 expression than non-carriers (P = 0.036). Serum DKK1 levels are highly heritable in the African ancestry families. Two SNPs within the DKK1 region accounted for nearly 5% of the variation in serum DKK1.

Induction of DKK1 by ox-LDL negatively regulates intracellular lipid accumulation in macrophages

Dickkopf1 (DKK1), a canonical Wnt/β-catenin pathway antagonist, is closely associated with cardiovascular disease and adipogenesis. We performed an in vitro study to determine whether oxidized low-density lipoprotein (ox-LDL) increased the expression of DKK1 in macrophages and whether β-catenin and liver X receptor α (LXRα) were involved in this regulation. Induction of DKK1 expression by ox-LDL decreased the level of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) via a Wnt/β-catenin pathway and increased ATP-binding cassette transporter A/G1 (ABCA/G1) levels via a signal transducer and activator of transcription 3 (STAT3) pathway. Lower LOX-1 and higher ABCA/G1 levels inhibited cholesterol loading in macrophages. In conclusion, ox-LDL may induce DKK1 expression in macrophages to inhibit the accumulation of lipids through a mechanism that involves downregulation of LOX-1-mediated lipid uptake and upregulation of ABCA/G1-dependent cholesterol efflux.

Protective effect of minocycline on hepatic ischemia-reperfusion injury in rats

To explore the protective eff ect of minocycline on hepatic ischemia-reperfusion injury (IRI) in rats and the underlying mechanisms. A total of 54 male Sprague-Dawley rats were randomly divided into 3 groups: the sham-operated group (control group), the ischemic-reperfusion (IR group), and the minocycline preconditioning group (n=18 per group). The rats in the minocycline preconditioning group were given minocycline (45 mg/kg) by gastric irrigation at 36 h before operation and then were subsequently administered with minocycline (22.5 mg/kg) at every 12 h. Th e rats were sacrifi ced at 2, 6, 24 h after reperfusion. The serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) were measured. HE staining of liver tissues was performed to detect the histological changes, and the degree of liver IRI according to Suzuki score were calculated. The levels of malondialdehyde (MDA) and myeloperoxidase (MPO) were determined by spectrophotometer; the mRNA expression of tumor necrosis factor-α (TNF-α) and interleukin-1 beta (IL-1β) in the liver were measured by real-time PCR; Dickkopf-1 (DKK-1) and beta-catenin (β-catenin) protein expression in the liver were detected by Western blot. After 2, 6, 24 h reperfusion, compared with the IR group, the liver function (ALT, AST and LDH) in the minocycline group was significantly improved (all P<0.05); the Suzuki's scores and the levels of hepatic TNF-α and IL-1β mRNA were significantly decreased (all P<0. 05); the MDA and MPO levels the liver were decreased (both P<0.05); the protein expression of hepatic DKK-1 was decreased (P<0.05), while the protein expression of β-catenin was increased (P<0.05). Minocycline can alleviate the ischemic-reperfusion injury mainly through reducing oxidative stress and inhibiting the release of pro-inflammatory cytokines depends on the activation of the Wnt/β-catenin signaling pathway in the liver.

Morphine protects SH-SY5Y human neuroblastoma cells against Dickkopf1-induced apoptosis.

Morphine is used to relieve pain in patients with cancer in terminal phases. Dickkopf‑1 (DKK1), a secreted protein, is a negative regulator of the Wnt/β‑catenin signaling pathway. Morphine and DKK1 are associated with tumorigenesis. However, to the best of our knowledge, there is no study evaluating the effects of these two factors simultaneously. In the present study, the effects of morphine and DKK1 on neuroblastoma cells invivo and invitro were evaluated. To establish the invitro effects of DKK1 and morphine, human neuroblastoma SH‑SY5Y cells were transfected with a DKK1‑expressing plasmid and cell migration, apoptosis, migration and invasion were evaluated prior to and following morphine treatment. The results indicated that DKK1 induced apoptosis and inhibited the mobility of neuroblastoma cells and that morphine attenuated these DKK1‑induced effects. To evaluate the effects of DKK1 and morphine invivo, a mouse model of neuroblastoma was established, where mice bearing tumors of native SH-SY5Y cells were injected with DKK1. Tumor size, spatial memory and survival rate were investigated in untreated, DKK1‑treated and DKK1+morphine‑treated mice. Water maze and T‑maze tests were performed, which revealed that DKK1‑treated mice exhibited a better memory than DKK1+morphine‑treated mice. The expression of DKK1 in established xenografted tumors was associated with decreased tumor size and an increased survival rate, whereas morphine reversed these effects. Furthermore, it was confirmed that morphine and DKK1 take effect, at least in part, via the Wnt/β‑catenin signaling pathway. The results of the present study indicate that morphine may protect neuroblastoma cells and thus, it may be used in neuroblastoma patients.

CBX7 inhibits breast tumorigenicity through DKK-1-mediated suppression of the Wnt/β-catenin pathway.

Polycomb protein chromobox homolog 7 (CBX7) is involved in several biologic processes including stem cell regulation and cancer development, but its roles in breast cancer remain unknown. Here, we demonstrate that CBX7 negatively regulates breast tumor initiation. CD44(+)/CD24(-)/ESA(+) breast stem-like cells showed diminished CBX7 expression. Furthermore, small hairpin RNA-mediated CBX7 knockdown in breast epithelial and cancer cells increased the CD44(+)/CD24(-)/ESA(+) cell population and reinforced in vitro self-renewal and in vivo tumor-initiating ability. Similarly, CBX7 overexpression repressed these effects. We also found that CBX7 inhibits the Wnt/β-catenin/T cell factor pathway by enhancing the expression of Dickkopf-1 (DKK-1), a Wnt antagonist. In particular, CBX7 increased DKK-1 transcription by cooperating with p300 acetyltransferase and subsequently enhancing the histone acetylation of the DKK-1 promoter. Furthermore, pharmacologic inhibition of DKK-1 in CBX7-overexpressing cells showed recovery of Wnt signaling and consequent rescue of the CD44(+)/CD24(-)/ESA(+) cell population. Taken together, these findings indicate that CBX7-mediated epigenetic induction of DKK-1 is crucial for the inhibition of breast tumorigenicity, suggesting that CBX7 could be a potential tumor suppressor in human breast cancer.

Abstract LB-52: CBX7 inhibits breast cancer stem cell activity and tumorigenicity through DKK-1-mediated suppression of the Wnt/β-catenin pathway

Abstract Chromoprotein homologue 7 (CBX7), a member of the polycomb repressive complex (PRC)-1, has been involved in several biological processes including stem cell regulation and cancer development, but its roles in cancer stem cells (CSCs) and breast tumorigenicity remain unknown. Here, we demonstrated that CBX7 negatively regulates breast CSCs. CD44+/CD24-/ESA+ cells, a population of breast CSCs, showed diminished CBX7 expression compared with non-CSCs. Furthermore, small hairpin RNA (shRNA)-mediated CBX7 knockdown in breast epithelial and cancer cell lines increased breast CSC population and reinforced in vitro self-renewal and in vivo tumor initiating ability. Similarly, CBX7 overexpression showed reduced stemness of breast CSCs. We also found that CBX7 inhibits the Wnt/β-catenin/TCF pathway by enhancing the expression of Dickkopf-1 (DKK-1), a Wnt antagonist, to impede self-renewal of breast CSCs. Particularly, CBX7 increased DKK-1 transcription by cooperating with p300 acetyltransferase and subsequently enhancing the histone acetylation of DKK-1 promoter. Furthermore, pharmacological inhibition of DKK-1 in CBX7 overexpressing cells showed recovery of the Wnt signaling and consequent rescue of breast CSC activity. Taken together, these findings indicated that CBX7-mediated epigenetic induction of DKK-1 is crucial for inhibition of breast CSC activity, suggesting that CBX7 could be a potential tumor suppressor as a novel negative regulator of CSCs in human breast cancer. Citation Format: Hey-Yon Kim, Ji-Hye Park, Hee-Young Won, Jeong-Yeon Lee, Gu Kong. CBX7 inhibits breast cancer stem cell activity and tumorigenicity through DKK-1-mediated suppression of the Wnt/β-catenin pathway. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-52. doi:10.1158/1538-7445.AM2014-LB-52

High serum levels of Dickkopf-1 are associated with a poor prognosis in prostate cancer patients.

BackgroundThe Wnt inhibitor Dickkopf-1 (DKK-1) has been linked to the progression of malignant bone disease by impairing osteoblast activity. In addition, there is increasing data to suggest direct tumor promoting effects of DKK-1. The prognostic role of DKK-1 expression in prostate cancer remains unclear.MethodsA prostate cancer tissue microarray (n = 400) was stained for DKK-1 and DKK-1 serum levels were measured in 80 patients with prostate cancer. The independent prognostic value of DKK-1 expression was assessed using multivariate analyses.ResultsDKK-1 tissue expression was significantly increased in prostate cancer compared to benign disease, but was not correlated with survival. However, high DKK-1 serum levels at the time of the diagnosis were associated with a significantly shorter overall and disease-specific survival. Multivariate analyses defined high serum levels of DKK-1 as an independent prognostic marker in prostate cancer (HR 3.73; 95%CI 1.44-9.66, p = 0.007).ConclusionHigh DKK-1 serum levels are associated with a poor survival in patients with prostate cancer. In light of current clinical trials evaluating the efficacy of anti-DKK-1 antibody therapies in multiple myeloma and solid malignancies, the measurement of DKK-1 in prostate cancer may gain clinical relevance.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2407-14-649) contains supplementary material, which is available to authorized users.

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

BackgroundThe 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.MethodsBlood 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.ResultsThe 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.ConclusionsSerum DKK-1 level can be used as a noninvasive biomarker for the prognosis of breast cancer.Virtual slidesThe virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_161

Correction: Expression of Dickkopf-1 and Beta-Catenin Related to the Prognosis of Breast Cancer Patients with Triple Negative Phenotype

Correction: Expression of Dickkopf-1 and Beta-Catenin Related to the Prognosis of Breast Cancer Patients with Triple Negative Phenotype

Overexpression of Dickkopf-1 predicts poor prognosis for patients with hepatocellular carcinoma after orthotopic liver transplantation by promoting cancer metastasis and recurrence.

Our previous data had shown that Dickkopf-1 (DKK1) combined with β-catenin was a novel prognostic predictor for hepatocellular carcinoma (HCC) patients. However, the role and mechanism of DKK1 in HCC recurrence or metastasis remain poorly understand. This study was to assess the role of DKK1 in tumor metastasis for patients with hepatocellular carcinoma after orthotopic liver transplantation (OLT). The expression of DKK1 protein was detected in hepatic cell lines, HCC cell lines, and HCC patients after OLT with different potential of metastasis. After DKK1 expression in the HCCLM3 cells was downregulated by siRNA-mediated approach, the role of DKK1 in cell invasion and metastasis was investigated. cDNA genechip was used to analyze the differential expressed genes related with DKK1 in two pairs of HCC cells. The prognostic significance of DKK1 was further assessed by Kaplan-Meier and Cox regression analyses in 148 HCC patients after OLT. The expression of DKK1 protein was higher in the high-invasive HCC cells and HCC patients of the disease recurrence group. With the downregulation of DKK1, HCCLM3 cells showed decreased aggressiveness in vitro and lower metastatic ability in vivo. DKK1 could regulate many genes involved in biological processes and pathways related with tumor progression. Furthermore, DKK1 overexpression correlated with tumor microvessel density in clinical HCC samples. Multivariate analysis revealed that DKK1 was an independent prognostic indicator for overall survival and cumulative recurrence in this cohort of HCC patients post-OLT. Collectively, overexpression of DKK1 was implicated in invasion/metastasis of HCC after OLT and DKK1 overexpression may be potential molecular therapeutic targets for liver cancer.

Oridonin inhibits the proliferation of human osteosarcoma cells by suppressing Wnt/β-catenin signaling.

It has been reported that oridonin (ORI) can inhibit proliferation and induce apoptosis in various types of cancer cell lines. However, the exact mechanism for this function remains unclear. In this study, we investigated the proliferation inhibitory effect of ORI on human osteosarcoma (OS) 143B cells and dissected the possible molecular mechanism(s) underlying this effect. We demonstrated that ORI can inhibit proliferation, induce apoptosis and arrest the cell cycle in 143B cells. Using luciferase reporter assay, we found that the Wnt/β-catenin signaling was inhibited in 143B cells by ORI. Accordingly, the total protein levels and nuclear translocation of β-catenin were reduced by ORI treatment. ORI increased glycogen synthase kinase 3β (GSK3β) activity and upregulated Dickkopf-1 (Dkk-1) expression. We found that Dkk-1 overexpression or β-catenin knockdown can potentiate the proliferation inhibitory effect of ORI in 143B cells, while β-catenin overexpression attenuated this effect. Using the xenograft tumor model of human OS, we demonstrated that ORI effectively inhibited the growth of tumors. Histological examination showed that ORI inhibited cancer cell proliferation, decreased the expression of PNCA and β-catenin. Our findings suggest that ORI can inhibit 143B OS cell proliferation by downregulating Wnt/β-catenin signal transduction, which may be mediated by upregulating the Dkk-1 expression and/or enhancing the function of GSK3β. Therefore, ORI can be potentially used as an effective adjuvant agent for the clinical management of OS.

Dickkopf-1 is a novel prognostic biomarker for laryngeal squamous cell carcinoma

Conclusions: Dickkopf-1 (DKK1) is a novel prognostic biomarker for laryngeal squamous cell carcinoma (LSCC). DKK1 may be a promising strategy for the future treatment of LSCC metastasis and recurrence. Objectives: DKK1 is reportedly involved in the metastasis and invasion of several tumor types. This study aimed to investigate the prognostic value of DKK1 in LSCC. Methods: DKK1 expression was measured in Hep-2 cell lines, as well as in tumor and peritumoral tissues, using quantitative real-time PCR and western blot analyses. The role of DKK1 in LSCC was investigated by depleting DKK1 using small interfering RNAs. Tissue microarrays of 102 LSCC patient samples were employed to immunohistochemically detect expression of DKK1, vascular endothelial growth factor C (VEGF-C), and β-catenin. Prognostic significance was assessed using Kaplan–Meier survival estimates. Results: DKK1 expression was elevated in the Hep-2 cell line and tumor samples. DKK1 depletion decreased cell proliferation, migration, and invasiveness. High DKK1 expression was significantly associated with T and clinical stage, lymph node metastasis, and tumor size (p < 0.05). Increased DKK1 levels in LSCC tissues correlated with elevated VEGF-C and β-catenin. Multivariate analyses revealed that DKK1 was an unfavorable predictor of overall survival.

Osteocytic cell necrosis is caused by a combination of glucocorticoid-induced Dickkopf-1 and hypoxia.

Osteonecrosis is a major glucocorticoid-induced complication in the orthopedics field. Despite the extensive researches, mechanisms underlining the glucocorticoid-induced osteonecrosis are largely unknown. Here, we first provide the evidence that a combined treatment of cultured osteocytic cells with glucocorticoid and hypoxia caused necrotic cell death, which is assumed to occur in the acute bone injuries induced by glucocorticoids. We cultured MLO-Y4 murine osteocytic cells under hypoxia in the presence or absence of Dexamethasone (Dex) and examined the rates of apoptotic and necrotic cell death. Dex or hypoxia alone increased apoptotic cells, but not necrotic cells. The combination of Dex and hypoxia dramatically increased osteocytic cell death, notably necrotic cell death. The expression of Dickkopf-1 (Dkk-1), an inhibitor of Wnt/β-catenin signal, was scarcely expressed in the control and hypoxic cells, but a dramatic increase of the Dkk-1 expression was detected in Dex-treated cells. siRNA-mediated knockdown of Dkk-1 in Dex and hypoxia-treated osteocytic cells showed the significant decreases in both apoptotic and necrotic cells. The results indicated that the combination of Dkk-1 overexpression by Dex and hypoxia causes the necrotic osteocytic cell death. The results also indicated that blocking of Dkk-1 can protect bone cells from glucocorticoid and hypoxia-induced cell injury.

Histochemical Localization of Dickkopf-1 in Induced Rat Periapical Lesions

IntroductionThe purpose of this study was to evaluate the expression of Dickkopf-1 (DKK-1), a secreted antagonist of the Wnt (wingless)/beta-catenin signaling pathway, during the development of periapical lesions in rats. MethodsPeriapical lesions were induced in Wistar rats by occlusal exposure of the pulp of their mandibular first molars. The animals were sacrificed randomly at 0, 7, 14, 21, and 28 day after pulpal exposure. Jaws containing the first molar were obtained and routinely prepared for histologic, immunohistochemical, and enzyme histochemical double immunofluorescence analyses. Data were analyzed using 1-way analysis of variance and Pearson correlation test. ResultsThe expansion of the area of periapical lesions was visible from days 7–21 and slowed down thereafter. A few DKK-1- and receptor activator of nuclear factor kappa B ligand (RANKL)-positive cells and osteoclasts were observed on day 7. All positive samples peaked in number on day 14. The expression levels of DKK-1 and RANKL and the number of osteoclasts decreased on days 21 and 28. DKK-1 expression was positively correlated with RANKL expression and osteoclast number from days 7–28. ConclusionsDKK-1 expression was up-regulated during periapical lesion development. DKK-1 may be associated with the inflammatory response and bone resorption in periapical lesions.

The expression of Wnt-inhibitor DKK1 (Dickkopf 1) is determined by intercellular crosstalk and hypoxia in human malignant gliomas.

Wnt signalling pathways regulate proliferation, motility and survival in a variety of human cell types. Dickkopf 1 (DKK1) gene codes for a secreted Wnt inhibitory factor. It functions as tumour suppressor gene in breast cancer and as a pro-apoptotic factor in glioma cells. In this study, we aimed to demonstrate whether the different expression of DKK1 in human glioma-derived cells is dependent on microenvironmental factors like hypoxia and regulated by the intercellular crosstalk with bone-marrow-derived mesenchymal stem cells (bmMSCs). Glioma cell line U87-MG, three cell lines from human glioblastoma grade IV (glioma-derived mesenchymal stem cells) and three bmMSCs were selected for the experiment. The expression of DKK1 in cell lines under normoxic/hypoxic environment or co-culture condition was measured using real-time PCR and enzyme-linked immunoadsorbent assay. The effect of DKK1 on cell migration and proliferation was evaluated by in vitro wound healing assays and sulphorhodamine assays, respectively. Glioma-derived cells U87-MG displayed lower DKK1 expression compared with bmMSCs. Hypoxia led to an overexpression of DKK1 in bmMSCs and U87-MG when compared to normoxic environment, whereas co-culture of U87-MG with bmMSCs induced the expression of DKK1 in both cell lines. Exogenous recombinant DKK1 inhibited cell migration on all cell lines, but did not have a significant effect on cell proliferation of bmMSCs and glioma cell lines. In this study, we showed for the first time that the expression of DKK1 was hypoxia dependent in human malignant glioma cell lines. The induction of DKK1 by intracellular crosstalk or hypoxia stimuli sheds light on the intense adaption of glial tumour cells to environmental alterations.