Dkk-3 expression in the tumor endothelium: a novel prognostic marker of pancreatic adenocarcinomas

DKK3, Downregulated in Invasive Epithelial Ovarian Cancer, Is Associated with Chemoresistance and Enhanced Paclitaxel Susceptibility via Inhibition of the β-Catenin-P-Glycoprotein Signaling Pathway

Simple Summary

Dickkopf-3 (DKK3) is considered a tumor suppressor as it possesses anti-tumoral properties and is frequently downregulated in various cancers. However, the role of DKK3 in ovarian cancer is not known. In this study, we showed that DKK3 loss occurred in 56.1% of patients with ovarian cancer and that it was significantly associated with poor survival and chemoresistance. Secreted DKK3 possessed anti-tumoral properties and enhanced paclitaxel susceptibility by inhibiting the β-catenin-P-glycoprotein signaling pathway in ovarian cancer. This study revealed promising therapeutic effects of secreted DKK3, which targets paclitaxel-resistant ovarian cancer.

Abstract

Dickkopf-3 (DKK3), a tumor suppressor, is frequently downregulated in various cancers. However, the role of DKK3 in ovarian cancer has not been evaluated. This study aimed to assess aberrant DKK3 expression and its role in epithelial ovarian carcinoma. DKK3 expression was assessed using immunohistochemistry with tissue blocks from 82 patients with invasive carcinoma, and 15 normal, 19 benign, and 10 borderline tumors as controls. Survival data were analyzed using Kaplan–Meier and Cox regression analysis. Paclitaxel-resistant cells were established using TOV-21G and OV-90 cell lines. Protein expression was assessed using Western blotting and immunofluorescence analysis. Cell viability was assessed using the MT assay and 3D-spheroid assay. Cell migration was determined using a migration assay. DKK3 was significantly downregulated in invasive carcinoma compared to that in normal, benign, and borderline tumors. DKK3 loss occurred in 56.1% invasive carcinomas and was significantly associated with disease-free survival and chemoresistance in serous adenocarcinoma. DKK3 was lost in paclitaxel-resistant cells, while β-catenin and P-glycoprotein were upregulated. Exogenous secreted DKK3, incorporated by cells, enhanced anti-tumoral effect and paclitaxel susceptibility in paclitaxel-resistant cells, and reduced the levels of active β-catenin and its downstream P-glycoprotein, suggesting that DKK3 can be used as a therapeutic for targeting paclitaxel-resistant cancer.

Targeting Wnt Signaling in Endometrial Cancer

Simple Summary

Wnt has diverse regulatory roles at multiple cellular levels and numerous targeting points, and aberrant Wnt signaling has crucial roles in carcinogenesis, metastasis, cancer recurrence, and chemotherapy resistance; based on these facts, Wnt represents an appealing therapeutic target for cancer treatment. Although preclinical data supports a role for the Wnt signaling pathway in uterine carcinogenesis, this area remains understudied. In this review, we identify the functions of several oncogenes of the Wnt/β-catenin signaling pathway in tumorigenesis and address the translation approach with potent Wnt inhibitors that have already been established or are being investigated to target key components of the pathway. Further research is likely to expand the potential for both biomarker and cancer drug development. There is a scarcity of treatment choices for advanced and recurrent endometrial cancer; investigating the sophisticated connections of Wnt signaling networks in endometrial cancer could address the unmet need for new therapeutic targets.

Abstract

This review presents new findings on Wnt signaling in endometrial carcinoma and implications for possible future treatments. The Wnt proteins are essential mediators in cell signaling during vertebrate embryo development. Recent biochemical and genetic studies have provided significant insight into Wnt signaling, in particular in cell cycle regulation, inflammation, and cancer. The role of Wnt signaling is well established in gastrointestinal and breast cancers, but its function in gynecologic cancers, especially in endometrial cancers, has not been well elucidated. Development of a subset of endometrial carcinomas has been attributed to activation of the APC/β-catenin signaling pathway (due to β-catenin mutations) and downregulation of Wnt antagonists by epigenetic silencing. The Wnt pathway also appears to be linked to estrogen and progesterone, and new findings implicate it in mTOR and Hedgehog signaling. Therapeutic interference of Wnt signaling remains a significant challenge. Herein, we discuss the Wnt-activating mechanisms in endometrial cancer and review the current advances and challenges in drug discovery.

Serum dickkopf-3 is associated with death and vascular events after ischemic stroke: an observational study from CATIS

BACKGROUND

Dickkopf-3 (Dkk-3) is implicated in the progression of atherosclerosis. This study aimed to investigate the association between serum Dkk-3 and the prognosis of ischemic stroke.

METHODS

We measured serum Dkk-3 levels in 3344 ischemic stroke patients from CATIS (China Antihypertensive Trial in Acute Ischemic Stroke). The primary outcome was a combination of death and vascular events within 3 months after ischemic stroke.

RESULTS

During 3 months of follow-up, the cumulative incidence rates of primary outcome among ischemic stroke patients in five quintiles of serum Dkk-3 (from low to high) were 4.49%, 3.74%, 2.54%, 5.23%, and 6.73%, respectively (log-rank p = 0.004). Multivariable Cox proportional hazards regression analyses showed that compared with the third quintile of serum Dkk-3, the adjusted hazard ratios (95% confidence intervals) associated with the first and fifth quintile were 3.49 (1.46-8.34) and 4.23 (1.86-9.64) for primary outcome, 3.47 (1.06-11.36) and 5.30 (1.81-15.51) for death, and 2.66 (1.01-7.01) and 3.35 (1.33-8.40) for vascular events, respectively. Multivariable-adjusted Cox proportional hazards regression model with restricted cubic splines showed a U-shaped association between serum Dkk-3 and the risk of primary outcome (p for nonlinearity = 0.030). Moreover, adding serum Dkk-3 to conventional risk factors could improve the predictive power for primary outcome (net reclassification improvement 28.44%, p < 0.001; integrated discrimination improvement 0.48%, p = 0.001).

CONCLUSIONS

Both low and high serum Dkk-3 levels are associated with increased risks of death and vascular events within 3 months after ischemic stroke, indicating that serum Dkk-3 may have a special effect on the prognosis of ischemic stroke. We also found that serum Dkk-3 might be a prognostic biomarker for ischemic stroke. Further studies are needed to replicate our findings and to determine the optimal levels of serum Dkk-3.

The clinicopathological and prognostic significances of Dkk3 expression in cancers: A bioinformatics analysis

BACKGROUND

Dkk3 protein attenuates the expression of Wnt3a, Wnt5a and LRP6, and their interaction, and interacts with βTrCP to suppress wnt/β-catenin pathway.

METHODS

We performed a bioinformatics analysis of Dkk3 mRNA expression through Oncomine, TCGA and Kaplan-Meier plotter databases up to July 10, 2017.

RESULTS

Up-regulated Dkk3 expression was higher in gastric, breast, and ovarian cancers than normal tissues (p< 0.05). Bitter's database showed a higher Dkk3 expression in ovarian cytoadenocarcinoma than clear cell adenocarcinoma (p< 0.05). Dkk3 was more expressed in ductal breast cancer in situ than invasive ductal breast cancer (p< 0.05), in mixed lobular and ductal cancer, and lobular cancer than ductal breast cancer (p< 0.05). In TCGA data, Dkk3 expression was lower in gastric cancers with than without Barret's esophagus (p< 0.05), in intestinal-type than diffuse-type cancers (p< 0.05), and in the cancers of elder than younger patients (p< 0.05). Dkk3 expression was higher in squamous cell carcinoma than adenocarcinoma (p< 0.05). Dkk3 expression was higher in ductal than lobular breast cancer, or in younger than elder patients with breast cancer (p< 0.05). According to Kaplan-Meier plotter, Dkk3 expression was negatively correlated with overall, progression-free, relapse-free or distant-metastasis-free survival rate of gastric, breast or ovarian cancer patients, but versa for lung cancer patients (p< 0.05).

CONCLUSION

Dkk3 expression might be employed as a potential marker to indicate carcinogenesis and histogenesis, even prognosis.

Dkk-3 as a potential biomarker for diagnosis and prognosis of colorectal cancer

Background: The Dickkopf 3 (Dkk-3) protein is a member of the Dkk family known as Wnt signaling inhibitor. The level of DKk-3 changes in a wide range of cancers, such as colorectal cancer, lung cancer, prostate cancer, and bladder cancer, is proposed as a biomarker for diagnosis and prognosis of many cancers. The present study was conducted to evaluate the serum level of Dkk-3 as a cancer biomarker and to determine their prognostic value in colorectal cancer (CRC) patients and healthy matched controls.

Methods: A total of 30 colorectal cancer patients at different stages of the disease and healthy matched controls with no history of inflammatory and autoimmune disease or cancer were enrolled in the study. The level of Dkk-3 was assessed serologically using enzymelinked immunosorbent assay (ELISA) method, moreover, relevance of these markers with patients’ clinicopathological features was subsequently assessed. Means comparison and ROC curves analysis were done using SPSS software. P-value ˂0.05 was considered significant in all the tests.

Results: In this study, it was revealed that serum level of Dkk-3 was significantly (p<0.001) lower in patients compared to the healthy controls. Statistical analysis showed that serum level of Dkk-3 has 78% specificity and 77% sensitivity (AUC= 0.782, 95% CI) for diagnosis of colorectal cancer.

Conclusion: Dkk-3 protein can be considered as a potential biomarker for diagnosis and possibly the prognosis of colorectal cancer.

Protective effect of stromal Dickkopf-3 in prostate cancer: opposing roles for TGFBI and ECM-1

Aberrant transforming growth factor-β (TGF-β) signaling is a hallmark of the stromal microenvironment in cancer. Dickkopf-3 (Dkk-3), shown to inhibit TGF-β signaling, is downregulated in prostate cancer and upregulated in the stroma in benign prostatic hyperplasia, but the function of stromal Dkk-3 is unclear. Here we show that DKK3 silencing in WPMY-1 prostate stromal cells increases TGF-β signaling activity and that stromal cell-conditioned media inhibit prostate cancer cell invasion in a Dkk-3-dependent manner. DKK3 silencing increased the level of the cell-adhesion regulator TGF-β-induced protein (TGFBI) in stromal and epithelial cell-conditioned media, and recombinant TGFBI increased prostate cancer cell invasion. Reduced expression of Dkk-3 in patient tumors was associated with increased expression of TGFBI. DKK3 silencing reduced the level of extracellular matrix protein-1 (ECM-1) in prostate stromal cell-conditioned media but increased it in epithelial cell-conditioned media, and recombinant ECM-1 inhibited TGFBI-induced prostate cancer cell invasion. Increased ECM1 and DKK3 mRNA expression in prostate tumors was associated with increased relapse-free survival. These observations are consistent with a model in which the loss of Dkk-3 in prostate cancer leads to increased secretion of TGFBI and ECM-1, which have tumor-promoting and tumor-protective roles, respectively. Determining how the balance between the opposing roles of extracellular factors influences prostate carcinogenesis will be key to developing therapies that target the tumor microenvironment.

Cardiac Remodeling: Endothelial Cells Have More to Say Than Just NO

The heart is a highly structured organ consisting of different cell types, including myocytes, endothelial cells, fibroblasts, stem cells, and inflammatory cells. This pluricellularity provides the opportunity of intercellular communication within the organ, with subsequent optimization of its function. Intercellular cross-talk is indispensable during cardiac development, but also plays a substantial modulatory role in the normal and failing heart of adults. More specifically, factors secreted by cardiac microvascular endothelial cells modulate cardiac performance and either positively or negatively affect cardiac remodeling. The role of endothelium-derived small molecules and peptides—for instance NO or endothelin-1—has been extensively studied and is relatively well defined. However, endothelial cells also secrete numerous larger proteins. Information on the role of these proteins in the heart is scattered throughout the literature. In this review, we will link specific proteins that modulate cardiac contractility or cardiac remodeling to their expression by cardiac microvascular endothelial cells. The following proteins will be discussed: IL-6, periostin, tenascin-C, thrombospondin, follistatin-like 1, frizzled-related protein 3, IGF-1, CTGF, dickkopf-3, BMP-2 and−4, apelin, IL-1β, placental growth factor, LIF, WISP-1, midkine, and adrenomedullin. In the future, it is likely that some of these proteins can serve as markers of cardiac remodeling and that the concept of endothelial function and dysfunction might have to be redefined as we learn more about other factors secreted by ECs besides NO.

Microvessel Density in Patients with Cutaneous Melanoma: An Up-to-Date Systematic Review and Meta-Analysis

Background

We conducted a meta-analysis, in order to appraise the effect of microvessel density (MVD) on the survival of patients with cutaneous melanoma.

Methods

This study was conducted according to the PRISMA guidelines and the Cochrane Handbook for Systematic Reviews of Interventions. A systematic literature search in electronic databases (MEDLINE, Web of Science, and Cochrane Central Register of Controlled Clinical Trials) was performed. Fixed Effects or Random Effects model was used, based on the Cochran Q test.

Results

In total 9 studies (903 patients) were included. Pooled HR for overall survival (OS) and disease-free survival (DFS) were 2.62 (95% CI: 0.71–9.60, p = 0.15) and 2.64 (95% CI: 0.82–8.47, p = 0.10), respectively. Odds ratios of overall survival between high and low MVD groups, at 12 (1.45, 95% CI: 0.16–13.24), 36 (2.93, 95% CI: 0.63–13.59), and 60 (4.09, 95% CI: 0.85–19.77) months did not reach statistical significance. Significant superiority of low MVD group, in terms of DFS, at all time intervals (OR: 4.69, p < 0.0001; OR: 2.18, p = 0.004; OR: 7.46, p = 0.01, resp.) was documented.

Discussion

MVD does not affect the HR of OS and DFS. A strong correlation with DFS rates at 12, 36, and 60 months was recorded.

A Cytokine-Like Protein Dickkopf-Related Protein 3 Is Atheroprotective

Supplemental Digital Content is available in the text.

Background:

Dickkopf-related protein 3 (DKK3) is a secreted protein that is involved in the regulation of cardiac remodeling and vascular smooth muscle cell differentiation, but little is known about its role in atherosclerosis.

Methods:

We tested the hypothesis that DKK3 is atheroprotective using both epidemiological and experimental approaches. Blood DKK3 levels were measured in the Bruneck Study in 2000 (n=684) and then in 2005 (n=574). DKK3-deficient mice were crossed with apolipoprotein E^-/- mice to evaluate atherosclerosis development and vessel injury-induced neointimal formation. Endothelial cell migration and the underlying mechanisms were studied using in vitro cell culture models.

Results:

In the prospective population-based Bruneck Study, the level of plasma DKK3 was inversely related to carotid artery intima-media thickness and 5-year progression of carotid atherosclerosis independently from standard risk factors for atherosclerosis. Experimentally, we analyzed the area of atherosclerotic lesions, femoral artery injury-induced reendothelialization, and neointima formation in both DKK3^-/-/apolipoprotein E^-/- and DKK3^+/+/apolipoprotein E^-/- mice. It was demonstrated that DKK3 deficiency accelerated atherosclerosis and delayed reendothelialization with consequently exacerbated neointima formation. To explore the underlying mechanisms, we performed transwell and scratch migration assays using cultured human endothelial cells, which exhibited a significant induction in cell migration in response to DKK3 stimulation. This DKK3-induced migration activated ROR2 and DVL1, activated Rac1 GTPases, and upregulated JNK and c-jun phosphorylation in endothelial cells. Knockdown of the ROR2 receptor using specific siRNA or transfection of a dominant-negative form of Rac1 in endothelial cells markedly inhibited cell migration and downstream JNK and c-jun phosphorylation.

Conclusions:

This study provides the evidence for a role of DKK3 in the protection against atherosclerosis involving endothelial migration and repair, with great therapeutic potential implications against atherosclerosis.

Dickkopf 3 attenuates xanthine dehydrogenase expression to prevent oxidative stress-induced apoptosis

Dickkopf (DKK) 3 is a DKK glycoprotein family member that controls cell fate during embryogenesis and exerts opposing effects on survival in a cell type-dependent manner; however, the mechanisms governing its pro-apoptosis versus pro-survival functions remain unclear. Here, we investigated DKK3 function in Li21 hepatoma cells and tPH5CH immortalized hepatocytes. DKK3 knockdown by siRNA resulted in reactive oxygen species accumulation and subsequent apoptosis, which were abrogated by administration of the antioxidant N-acetyl-cysteine. Moreover, forced DKK3 over-expression induced resistance to hydrogen peroxide (H₂ O₂ )-induced apoptosis. Expression analysis by cDNA microarray showed that xanthine dehydrogenase (XDH) expression was significantly lower in Li21 and tPH5CHDKK3-over-expressing cells in response to H₂ O₂ treatment when compared to that in their respective mock-transfected controls, whereas a marked increase was observed in H₂ O₂ -treated DKK3 knockdown cells. Thus, these data suggest that DKK3 promotes cell survival during oxidative stress by suppressing the expression of the superoxide-producing enzyme XDH.

Enzyme and Redox Dual-Triggered Intracellular Release from Actively Targeted Polymeric Micelles

Highly effective delivery of therapeutic agents into target cells using nanocarriers and subsequently rapid intracellular release are of great importance in cancer treatment. Here, we developed an enzyme and redox dual-responsive polymeric micelle with active targeting abilities to achieve rapid intracellular drug release. To overcome both its poor solubility in water and instability in the blood circulation, camptothecin (CPT) was chemically conjugated to monomethyl poly(ethylene glycol) (mPEG) via a redox-responsive linker to form polymeric prodrugs. The enzyme-responsive function is achieved by connecting hydrophobic polycaprolactone segments and hydrophilic PEG segments with azo bonds. Additionally, the end of the PEG segment was decorated with phenylboronic acid (PBA), endowing the nanocarriers with active targeting abilities. The dual-responsive targeting polymeric micelles can be generated by self-assembly of a mixture of the polymeric prodrug and enzyme-responsive copolymer. The in vitro drug release profile revealed that CPT was rapidly released from the micelles under a simulated condition similar to the tumor cell microenvironment. In vivo and ex vivo fluorescence imaging indicated that these micelles possess excellent specificity to target hepatoma carcinoma cells. The antitumor effect in mice liver cancer cells (H22) in tumor-bearing Kunming (KM) mice demonstrated that this nanocarrier exhibits high therapeutic efficiency in artificial solid tumors and low toxicity to normal tissues, with a survival rate of approximately 100% after 160 days of treatment.

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.

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.

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.

Dickkopf-related protein 3 promotes pathogenic stromal remodeling in benign prostatic hyperplasia and prostate cancer

BACKGROUND

Compartment-specific epithelial and stromal expression of the secreted glycoprotein Dickkopf-related protein (Dkk)-3 is altered in age-related proliferative disorders of the human prostate. This study aimed to determine the effect of Dkk-3 on prostate stromal remodeling that is stromal proliferation, fibroblast-to-myofibroblast differentiation and expression of angiogenic factors in vitro.

METHODS

Lentiviral-delivered overexpression and shRNA-mediated knockdown of DKK3 were applied to primary human prostatic stromal cells (PrSCs). Cellular proliferation was analyzed by BrdU incorporation ELISA. Expression of Dkk-3, apoptosis-related genes, cyclin-dependent kinase inhibitors and angiogenic factors were analyzed by qPCR, Western blot analysis or ELISA. Fibroblast-to-myofibroblast differentiation was monitored by smooth muscle cell actin and insulin-like growth factor binding protein 3 mRNA and protein levels. The relevance of Wnt/β-catenin and PI3K/AKT signaling pathways was assessed by cytoplasmic/nuclear β-catenin levels and phosphorylation of AKT.

RESULTS

Knockdown of DKK3 significantly attenuated PrSC proliferation as well as fibroblast-to-myofibroblast differentiation and increased the expression of the vessel stabilizing factor angiopoietin-1. DKK3 knockdown did not affect subcellular localization or levels of β-catenin but attenuated AKT phosphorylation in PrSCs. Consistently the PI3K/AKT inhibitor LY294002 mimicked the effects of DKK3 knockdown.

CONCLUSIONS

Dkk-3 promotes fibroblast proliferation and myofibroblast differentiation and regulates expression of angiopoietin-1 in prostatic stroma potentially via enhancing PI3K/AKT signaling. Thus, elevated Dkk-3 in the stroma of the diseased prostate presumably regulates stromal remodeling by enhancing proliferation and differentiation of stromal cells and contributing to the angiogenic switch observed in BPH and PCa. Therefore, Dkk-3 represents a potential therapeutic target for stromal remodeling in BPH and PCa.

Upregulated microRNA-92b regulates the differentiation and proliferation of EpCAM-positive fetal liver cells by targeting C/EBPß

microRNAs (miRNAs) are short noncoding RNAs that negatively regulate gene expression. Although recent evidences have been indicated that their aberrant expression may play an important role in cancer stem cells, the mechanism of their deregulation in neoplastic transformation of liver cancer stem cells (LCSCs) has not been explored. In our study, the HCC model was established in F344 rats by DEN induction. The EpCAM⁺ cells were sorted out from unfractionated fetal liver cells and liver cancer cells using the FACS analysis and miRNA expression profiles of two groups were screened through microarray platform. Gain-of-function studies were performed in vitro and in vivo to determine the role of miR-92b on proliferation and differentiation of the hepatic progenitors. In addition, luciferase reporter system and gene function analysis were used to predict miR-92b target. we found that miR-92b was highly downregulated in EpCAM⁺ fetal liver cells in expression profiling studies. RT-PCR analysis demonstrated reverse correlation between miR-92b expression and differentiation degree in human HCC samples. Overexpression of miR-92b in EpCAM⁺ fetal liver cells significantly increased proliferation and inhibited differentiation as well as in vitro and in vivo studies. Moreover, we verified that C/EBPß is a direct target of miR-92b and contributes to its effects on proliferation and differentiation. We conclude that aberrant expression of miR-92b can result in proliferation increase and differentiation arrest of hepatic progenitors by targeting C/EBPß.

DKK3 is a potential tumor suppressor gene in papillary thyroid carcinoma

The expression of the Dickkopf homolog 3 (DKK3) gene is downregulated in some human cancers, suggesting a possible tumor suppressor role of this gene. The role and regulation of DKK3 in thyroid cancer have not been examined. In this study, we explored the relationship of promoter methylation with the inactivation of DKK3 and tumor behaviors in papillary thyroid carcinoma (PTC). We used methylation-specific PCR and RT-PCR to examine the promoter methylation and expression of DKK3 and tumor characteristics. We found mRNA expression of DKK3 in 44.9% of the PTC tissue samples vs 100% of the matched normal thyroid tissue samples (P<0.01). In contrast, an opposite distribution pattern of DKK3 gene methylation was observed; specifically, 38.8% of the PTC tissue samples vs 0% of the matched normal thyroid tissue samples harbored DKK3 methylation. An inverse correlation between the promoter methylation and mRNA expression of DKK3 in PTC tissue samples was also observed. Moreover, we also found an inverse correlation between DKK3 expression and some aggressive pathological characteristics of PTC, including high TNM stages and lymph node metastasis, but a positive correlation between DKK3 promoter hypermethylation and pathological aggressiveness of the tumor. Treatment of the PTC cell line TPC-1 with the demethylating agent 5-azaC reduced DKK3 promoter methylation and enhanced its expression, establishing functionally the impact of DKK3 methylation on its expression. Our data thus for the first time demonstrate that the DKK3 gene is a potential tumor suppressor gene in thyroid cancer and that aberrant promoter methylation is an important mechanism for its downregulation, which may play a role in the tumorigenesis and aggressiveness of PTC.

Reduced expression of DKK3 is associated with adverse clinical outcomes of uterine cervical squamous cell carcinoma

OBJECTIVE

The aim of this study was to assess the expression of DKK3 protein and its target, beta-catenin, in uterine cervical squamous cell carcinoma and to determine potential clinical correlations.

MATERIALS AND METHODS

Six carcinoma in-situ (CIS) tissues and 88 invasive cervical cancer tissues were included in the study. Twenty-two normal cervical tissues and one gastric cancer tissue were used as controls. The expression of DKK3 and beta-catenin proteins was evaluated by immunohistochemical analysis. Clinical and pathological parameters were obtained from medical records. Survival data were estimated using Kaplan-Meier estimates and compared with a log-rank test. Multivariate analysis was performed using the Cox regression method.

RESULTS

DKK3 was predominantly present in the cytoplasm. Beta-catenin was observed only on the cellular membrane of both normal and cancer cells in contrast to earlier reports, in which beta-catenin was localized to the cytoplasm and nucleus of cancer cells. The expressions of beta-catenin and DKK3 were not correlated. Three of 6 CIS (50%) and 57 of 88 invasive cancer specimens (64.8%) had lower DKK3 expression than normal controls. DKK3 expression was decreased in a stage-dependent manner (P = 0.021). The patients with low expression of DKK3 were older than those with high expression of DKK3 (P < 0.01). Moreover, the patients with low DKK3 expression had a significantly lower 5-year disease-free survival rate than those with high DKK3 expression (P = 0.026). A multivariate analysis showed that International Federation of Gynecology and Obstetrics clinical stage and parametrial involvement were independent prognostic factors.

CONCLUSION

Decreased DKK3 expression was associated with advanced International Federation of Gynecology and Obstetrics clinical stages and was predictive of lower disease-free survival in patients with cervical squamous cell carcinoma. DKK3 may be implicated in cervical carcinogenesis through a beta-catenin-independent mechanism.

Smooth muscle cells differentiated from reprogrammed embryonic lung fibroblasts through DKK3 signaling are potent for tissue engineering of vascular grafts

RATIONALE

Smooth muscle cells (SMCs) are a key component of tissue-engineered vessels. However, the sources by which they can be isolated are limited.

OBJECTIVE

We hypothesized that a large number of SMCs could be obtained by direct reprogramming of fibroblasts, that is, direct differentiation of specific cell lineages before the cells reaching the pluripotent state.

METHODS AND RESULTS

We designed a combined protocol of reprogramming and differentiation of human neonatal lung fibroblasts. Four reprogramming factors (OCT4, SOX2, KLF4, and cMYC) were overexpressed in fibroblasts under reprogramming conditions for 4 days with cells defined as partially-induced pluripotent stem (PiPS) cells. PiPS cells did not form tumors in vivo after subcutaneous transplantation in severe combined immunodeficiency mice and differentiated into SMCs when seeded on collagen IV and maintained in differentiation media. PiPS-SMCs expressed a panel of SMC markers at mRNA and protein levels. Furthermore, the gene dickkopf 3 was found to be involved in the mechanism of PiPS-SMC differentiation. It was revealed that dickkopf 3 transcriptionally regulated SM22 by potentiation of Wnt signaling and interaction with Kremen1. Finally, PiPS-SMCs repopulated decellularized vessel grafts and ultimately gave rise to functional tissue-engineered vessels when combined with previously established PiPS-endothelial cells, leading to increased survival of severe combined immunodeficiency mice after transplantation of the vessel as a vascular graft.

CONCLUSIONS

We developed a protocol to generate SMCs from PiPS cells through a dickkopf 3 signaling pathway, useful for generating tissue-engineered vessels. These findings provide a new insight into the mechanisms of SMC differentiation with vast therapeutic potential.

Role of canonical Wnt signaling in endometrial carcinogenesis

While the role of Wnt signaling is well established in colorectal carcinogenesis, its function in gynecologic cancers has not been elucidated. Here, we describe the current state of knowledge of canonical Wnt signaling in endometrial cancer (EC), and its implications for future therapeutic targets. Deregulation of the Wnt/β-catenin signaling pathway in EC occurs by inactivating β-catenin mutations in approximately 10-45% of ECs, and via downregulation of Wnt antagonists by epigenetic silencing. The Wnt pathway is intimately involved with estrogen and progesterone, and emerging data implicate it in other important signaling pathways, such as mTOR and Hedgehog. While no therapeutic agents targeting the Wnt signaling pathway are currently in clinical trials, the preclinical data presented suggest a role for Wnt signaling in uterine carcinogenesis, with further research warranted to elucidate the mechanism of action and to proceed towards targeted cancer drug development.

Expression of the Wnt antagonist Dickkopf-3 is associated with prognostic clinicopathologic characteristics and impairs proliferation and invasion in endometrial cancer

OBJECTIVE

Emerging evidence implicates the Wnt antagonist Dickkopf-3 (Dkk3) as a tumor suppressor and potential biomarker in solid tumors. We investigated whether Dkk3 plays an important role in the carcinogenesis of endometrial cancer (EC).

METHODS

We analyzed Dkk3 mRNA expression via real-time RT-PCR in twenty-seven human primary EC tissues, and six matched normal endometrial controls. Dkk3 levels were correlated with various clinicopathologic characteristics. Additionally, enforced Dkk3 expression was examined in proliferation and tumorigenesis in vitro and in vivo, using MTT, soft agar assay, invasion assay, a xenograft mouse model, and a β-catenin-responsive SuperTopFlash luciferase assay.

RESULTS

Compared with matched normal endometrial cases, Dkk3 was down-regulated in EC (p<0.0001). Among cancer cases, Dkk3 expression was significantly reduced in patients with higher stage (p=0.002), positive pelvic lymph nodes (p=0.0004), non-endometrioid histology (p=0.02), and cytology-positive ECs (p=0.02). Enforced expression of Dkk3 in EC cell lines showed reduced proliferation (p<0.0001), anchorage-independent growth (p=0.005), invasion (p=0.02), and reduced TCF activity (p=0.04), confirming Dkk3 as a negative regulator of the β-catenin/Wnt signaling pathway. Tumor growth in Dkk3-injected mice was not statistically different, though did plateau towards the end, and was associated with increased lymphoid infiltration and tumor necrosis.

CONCLUSION

Dkk3 gene expression is frequently downregulated in endometrial cancer, and is associated with poor prognostic clinicopathologic markers. The results also identify a role for Dkk3 as a tumor suppressor in EC, affecting both proliferation and invasiveness. These findings may prove to be important in the design of novel biomarkers and treatment modalities for advanced EC.

Secreted proteins as a fundamental source for biomarker discovery

The proteins secreted by various cells (the secretomes) are a potential rich source of biomarkers as they reflect various states of the cells at real time and at given conditions. To have accessible, sufficient and reliable protein markers is desirable as they mark various stages of disease development and their presence/absence can be used for diagnosis, prognosis, risk stratification and therapeutic monitoring. As direct analysis of blood/plasma, a common and noninvasive patient screening method, can be difficult for candidate protein biomarker identification, the alternative/complementary approaches are required, one of them is the analysis of secretomes in cell conditioned media in vitro. As the proteins secreted by cells as a response to various stimuli are most likely secreted into blood/plasma, the identification and pre-selection of candidate protein biomarkers from cell secretomes with subsequent validation of their presence at higher levels in serum/plasma is a promising approach. In this review, we discuss the proteins secreted by three progenitor cell types (smooth muscle, endothelial and cardiac progenitor cells) and two adult cell types (neonatal rat ventrical myocytes and smooth muscle cells) which can be relevant to cardiovascular research and which have been recently published in the literature. We found, at least for secretome studies included in this review, that secretomes of progenitor and adult cells overlap by 48% but the secretomes are very distinct among progenitor cell themselves as well as between adult cells. In addition, we compared secreted proteins to protein identifications listed in the Human Plasma PeptideAtlas and in two reports with cardiovascular-related proteins and we performed the extensive literature search to find if any of these secreted proteins were identified in a biomarker study. As expected, many proteins have been identified as biomarkers in cancer but 18 proteins (out of 62) have been tested as biomarkers in cardiovascular diseases as well.

Targeting the Wnt pathway in cancer: the emerging role of Dickkopf-3

Aberrant activation of the Wnt signaling pathway is a major trait of many human cancers. Due to its vast implications in tumorigenesis and progression, the Wnt pathway has attracted considerable attention at several molecular levels, also with respect to developing novel cancer therapeutics. Indeed, research in Wnt biology has recently provided numerous clues, and evidence is accumulating that the secreted Wnt antagonist Dickkopf-related protein 3 (Dkk-3) and its regulators may constitute interesting therapeutic targets in the most important human cancers. Based on the currently available literature, we here review the knowledge on the biological role of Dkk-3 as an antagonist of the Wnt signaling pathway, the involvement of Dkk-3 in several stages of tumor development, the genetic and epigenetic mechanisms disrupting DKK3 gene function in cancerous cells, and the potential clinical value of Dkk-3 expression/DKK3 promoter methylation as a biomarker and molecular target in cancer diseases. In conclusion, Dkk-3 rapidly emerges as a key player in human cancer with auspicious tumor suppressive capacities, most of all affecting apoptosis and proliferation. Its gene expression is frequently downregulated by promoter methylation in almost any solid and hematological tumor entity. Clinically, evidence is accumulating of Dkk-3 being both a potential tumor biomarker and effective anti-cancer agent. Although further research is needed, re-establishing Dkk-3 expression in cancer cells holds promise as novel targeted molecular tumor therapy.

Looking to the future: biomarkers in the management of pancreatic adenocarcinoma

The incidence and mortality of pancreas cancer converge. There has been little advancement in the treatment of pancreas cancer since the acceptance of gemcitabine as the standard therapy. Unfortunately, the efficacy of gemcitabine is dismal. While there is much discussion for the development of biomarkers to help direct therapy in this area, there is little action to move them into clinical practice. Herein, we review potential pancreatic cancer biomarkers and discuss the limitations in their implementation.

Dickkopf3 overexpression inhibits pancreatic cancer cell growth in vitro

AIM: To elucidate the role of dickkopf3 (Dkk3) in human pancreatic cancer cell growth.

METHODS: Dkk3 mRNA and protein expression in human pancreatic cancer cell lines were detected by real-time reverse transcription polymerase chain reaction (real-time RT-PCR), Western blotting and immunofluorescence. Methylation of the Dkk3 promoter sequence was examined by methylation-specific polymerase chain reaction (MSP) and Dkk3 mRNA expression was determined by real-time RT-PCR after 5-aza-2’-deoxycytidine (5-aza-dC) treatment. The effects of Dkk3 on cancer cell proliferation and in vitro sensitivity to gemcitabine were investigated by CellTiter 96^® AQueous One Solution Cell Proliferation Assay (MTS) after transfecting the Dkk3 expression plasmid into human pancreatic cancer cells. The expression of β-catenin, phosphorylated extracellular signal-regulated protein kinases (pERK) and extracellular signal-regulated protein kinases (ERK) was also examined by real-time RT-PCR and Western blotting after upregulating Dkk3 expression in human pancreatic cancer cells.

RESULTS: The results show that the expression levels of both Dkk3 mRNA and protein were low in all pancreatic cancer cell lines tested. The Dkk3 promoter sequence was methylated in the MIA PaCa-2 and AsPC-1 cell lines, which showed reduced Dkk3 expression. These two cell lines, which initially had a methylated Dkk3 promoter, showed increased Dkk3 mRNA expression that was dependent upon the dosage and timing of the DNA demethylating agent, 5-aza-dC, treatment (P < 0.05 or P < 0.01). When Dkk3 expression was upregulated following the transfection of a Dkk3 expression plasmid into MIA PaCa-2 cells, the ability of cells to proliferate decreased (P < 0.01), and the expression of β-catenin and pERK was downregulated (P < 0.01). Sensitivity to gemcitabine was enhanced in Dkk3 expression plasmid-transfected cells.

CONCLUSION: Our findings, for the first time, implicate Dkk3 as a tumor suppressor in human pancreatic cancer, through the downregulation of β-catenin expression via the ERK-mediated pathway.

Systematic review of immunohistochemical biomarkers to identify prognostic subgroups of patients with pancreatic cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) carries a dismal prognosis. There is a need to identify prognostic subtypes of PDAC to predict clinical and therapeutic outcomes accurately, and define novel therapeutic targets. The purpose of this review was to provide a systematic summary and review of available data on immunohistochemical (IHC) prognostic and predictive markers in patients with PDAC.

METHODS

Relevant articles in English published between January 1990 and June 2010 were obtained from PubMed searches. Other articles identified from cross-checking references and additional sources were reviewed. The inclusion was limited to studies evaluating IHC markers in a multivariable setting.

RESULTS

Database searches identified 76 independent prognostic and predictive molecular markers implicated in pancreatic tumour growth, apoptosis, angiogenesis, invasion and resistance to chemotherapy. Of these, 11 markers (Ki-67, p27, p53, transforming growth factor β1, Bcl-2, survivin, vascular endothelial growth factor, cyclo-oxygenase 2, CD34, S100A4 and human equilibrative nucleoside transporter 1) provided independent prognostic or predictive information in two or more separate studies.

CONCLUSION

None of the molecular markers described can be recommended for routine clinical use as they were identified in small cohorts and there were inconsistencies between studies. Their prognostic and predictive values need to be validated further in prospective multicentre studies in larger patient populations. A panel of molecular markers may become useful in predicting individual patient outcome and directing novel types of intervention.

MYCN-regulated miRNA-92 inhibits secretion of the tumor suppressor DICKKOPF-3 (DKK3) in neuroblastoma

The MYCN oncogene is frequently amplified in neuroblastoma. It is one of the most consistent markers of bad prognosis for this disease. Dickkopf-3 (DKK3) is a secreted protein of the DKK family of Wnt regulators. It functions as a tumor suppressor in a range of cancers, including neuroblastoma. MYCN was recently found to downregulate DKK3 mRNA. In this study, we show that MYCN knockdown in MYCN-amplified (MNA) neuroblastoma cell lines increases secretion of endogenous DKK3 to the culture media. MicroRNAs (miRNAs) are ∼20 nt long single-stranded RNA molecules that downregulate messenger RNAs by targeting the 3' untranslated region (3'UTR). Many miRNAs regulate genes involved in the pathogenesis of cancer and are extensively deregulated in different tumors. Using miRNA target prediction software, we found several MYCN-regulated miRNAs that could target the 3'UTR sequence of DKK3, including mir-92a, mir-92b and let-7e. Luciferase expression from a reporter vector containing the DKK3-3'UTR was decreased when this construct was cotransfected with mir-92a, mir-92b or let-7e in HEK293 cells. Mutation of the mir-92 seed sequence in the 3'UTR completely rescued the observed decrease in reporter expression when cotransfected with mir-92a and mir-92b. Antagomir and miRNA-mimic transfections in neuroblastoma cell lines confirmed that DKK3 secretion to the culture media is regulated by mir-92. Consistent with reports from other cancers, we found DKK3 to be expressed in the endothelium of primary neuroblastoma samples and to be absent in tumors with MYCN amplification. Our data demonstrate that MYCN-regulated miRNAs are able to modulate the expression of the tumor suppressor DKK3 in neuroblastoma.

Tissue biomarkers for prognosis in pancreatic ductal adenocarcinoma: a systematic review and meta-analysis

PURPOSE

The management of pancreatic ductal adenocarcinoma (PDAC) continues to present a great challenge particularly with regard to prediction of outcome following pancreaticoduodenectomy. Molecular markers have been extensively investigated by numerous groups with the aim of enhancing prognostication; however, despite hundreds of studies that have sought to assess the potential prognostic value of molecular markers in predicting the clinical course following resection of PDAC, at this time, no molecular marker assay forms part of recommended clinical practice.

EXPERIMENTAL DESIGN

We conducted a systematic review and meta-analysis of the published literature for immunohistochemistry-based biomarkers of PDAC outcome. A dual search strategy was applied to the PubMed database on January 6, 2010, to identify cohort studies that reported associations between immunohistochemical biomarker expression and survival outcomes in PDAC, and conformed to the REMARK (REporting recommendations for tumor MARKer prognostic studies) criteria.

RESULTS

A total of 103 distinct proteins met all inclusion criteria. Promising markers that emerged for the prediction of overall survival included BAX (HR = 0.31, 95% CI: 0.71-0.56), Bcl-2 (HR = 0.41, 95% CI: 0.27-0.63), survivin (HR = 0.46, 95% CI: 0.29-0.73), Ki-67: (HR = 2.42, 95% CI: 1.87-3.14), COX-2 (HR = 1.39, 95% CI: 1.13-1.71), E-cadherin (HR = 1.80, 95% CI: 1.33-2.42), and S100 calcium-binding proteins, in particular S100A2 (HR = 3.23, 95% CI: 1.58-6.62).

CONCLUSIONS

We noted that that there was incomplete adherence to the REMARK guidelines with inadequate methodology reporting as well as failure to perform multivariate analysis. Addressing the persistent incomplete adoption of these criteria may eventually result in the incorporation of molecular marker assessment within PDAC management algorithms.

HuR keeps an angiogenic switch on by stabilising mRNA of VEGF and COX-2 in tumour endothelium

Background:

Tumour stromal cells differ from its normal counterpart. We have shown that tumour endothelial cells (TECs) isolated from tumour tissues are also abnormal. Furthermore, we found that mRNAs of vascular endothelial growth factor-A (VEGF-A) and cyclooxygenase-2 (COX-2) were upregulated in TECs. Vascular endothelial growth factor-A and COX-2 are angiogenic factors and their mRNAs contain an AU-rich element (ARE). AU-rich element-containing mRNAs are reportedly stabilised by Hu antigen R (HuR), which is exported to the cytoplasm.

Methods:

Normal endothelial cell (NEC) and two types of TECs were isolated. We evaluated the correlation of HuR and accumulation of VEGF-A and COX-2 mRNAs in TECs and effects of HuR on biological phenotypes of TECs.

Results:

The HuR protein was accumulated in the cytoplasm of TECs, but not in NECs. Vascular endothelial growth factor-A and COX-2 mRNA levels decreased due to HuR knockdown and it was shown that these ARE-mRNA were bound to HuR in TECs. Furthermore, HuR knockdown inhibited cell survival, random motility, tube formation, and Akt phosphorylation in TECs.

Conclusion:

Hu antigen R is associated with the upregulation of VEGF-A and COX-2 mRNA in TECs, and has an important role in keeping an angiogenic switch on, through activating angiogenic phenotype in tumour endothelium.

Adenoviral-mediated RNA interference targeting URG11 inhibits growth of human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the second most common malignancy in Asia, with a 5-year survival rate of less than 5% due to high recurrence after surgery and resistance to chemotherapy. A variety of therapeutic interventions to treat HCC, particularly gene therapy, have recently been investigated in tumor model systems to provide a more complete understanding of hepatocarcinogenesis and effectively design therapeutic strategies to treat this disease. In our study, we constructed an adenoviral vector expressing small interfering RNA (siRNA) targeting a newly discovered gene named upregulated gene 11 (URG11). We introduced this vector into HCC cells to investigate the role of URG11 in HCC carcinogenesis. We observed that upon URG11 knockdown, HCC cell proliferation was inhibited through downregulation of several G1-S phase related molecules including cyclin D1 and apoptosis was induced as a result of Bcl-2 downregulation. Besides decreased expression of cyclin D1, CDK4, pRb and Bcl-2, URG11 also suppressed several other proteins including CAPN9, which was identified by cDNA microarray and 2D gel electrophoresis. Moreover, Ad-URG11-siRNA significantly suppressed HCC tumor growth in nude mice. In conclusion, Ad-URG11-siRNA can significantly suppress HCC tumor growth in vitro and in vivo by silencing the URG11 gene, and the use of this vector for gene therapy may represent a novel strategy to treat human HCC.

The Wnt antagonist Dickkopf-1 increases endothelial progenitor cell angiogenic potential

OBJECTIVE

To determine the role of Wnt antagonist Dickkopf (DKK) 1 in human endothelial colony-forming cells (ECFCs) in view of the emerging importance of Wnt pathways in vascular biology.

METHODS AND RESULTS

Endothelial progenitor cells have been proposed to be crucial in tumor neovascularization. Recombinant DKK1 has been tested in ECFC angiogenic properties in vitro. DKK1 enhanced ECFC proliferation and the capacity of ECFCs to form pseudotubes in Matrigel. These effects have been attributed to enhancement of vascular endothelial growth factor receptor 2, SDF-1, and CXCR4. DKK1 gene silencing has been realized on ECFCs and mesenchymal stem cells, and we found that DKK1 silencing in the 2 cell types decreased their angiogenic potential. We then examined the possible role of DKK1 in tumor neovasculogenesis and found that blood vessels of breast cancer tissues expressed DKK1 far more strongly in human breast tumors than in normal breast tissues. By studying 62 human breast tumors, we found a significant positive correlation between DKK1 expression and von Willebrand factor. In vivo, DKK1 strongly enhanced the vascularization of Matrigel plugs and increased tumor size in a xenograft model of human breast carcinoma in nude mice.

CONCLUSIONS

DKK1 enhances angiogenic properties of ECFCs in vitro and is required for ECFC and mesenchymal stem cell angiogenic phenotypes in vivo. DKK1 also increases tumoral angiogenesis. Thus, we demonstrated a major role of DKK1 in angiogenic processes.

Expression of the Wnt antagonist DKK3 is frequently suppressed in sporadic epithelial ovarian cancer

PURPOSE

The Wnt pathway plays an important role in embryonic development, and defects in this pathway have been implicated in the tumorigenesis. The Dickkopf 3 (DKK3) is a putative Wnt signaling inhibitor that is frequently inactivated in human cancers. However, the expression of DKK3 in ovarian cancer remains unknown.

METHODS

We investigated the expression of DKK3 in silico using the Digital Differential Display. DKK3 mRNA expression was also analyzed by real-time RT-PCR in ovarian carcinomas and normal ovarian tissues. DKK3 protein expression was determined by immunohistochemistry in the same ovarian carcinomas and normal ovarian tissues.

RESULTS

A significantly reduced expression of DKK3 (P < 0.05) was found after comparison of normal ovary- and tumor-derived libraries in the Cancer Genome Anatomy Project (CGAP). DKK3 mRNA expression was reduced in 63% (35 of 56) of tumors compared with normal ovarian samples (P < 0.02). Analysis of 13 matched pairs of ovarian carcinomas and adjacent normal tissues showed significant transcriptional downregulation of DKK3 (>twofold) in 9 paired carcinomas (69%). Loss or weak membranous expression of DKK3 protein was observed in 66% of ovarian cancers (37 of 56) including all tumors with low transcriptional level of DKK3 gene analyzed by real-time PCR.

CONCLUSIONS

To our best knowledge, this is the first time to demonstrate altered expression of DKK3 in ovarian cancer. The latter could be a relevant mechanism for the activation of the Wnt pathway in the carcinogenesis of ovarian cancer but additional studies are required to elucidate the function of DKK3 silencing in ovarian carcinogenesis.