Dickkopf-1 is overexpressed in human pancreatic ductal adenocarcinoma cells and is involved in invasive growth

Investigating the influence of taurochenodeoxycholic acid (TCDCA) on pancreatic cancer cell behavior: An RNA sequencing approach

Pancreatic cancer (PC) poses a substantial global health challenge, ranking as the fourth leading cause of cancer-related deaths due to its high mortality rate. Late-stage diagnoses are common due to the absence of specific symptoms. Pancreatic ductal adenocarcinoma (PDAC) accounts for the majority of PC cases. Recent research has suggested a potential link between elevated serum levels of bile acids (BAs) and tumorigenesis of PDAC. This study aims to understand how taurochenodeoxycholic acid (TCDCA), a secondary BA, influences PDAC using RNA sequencing techniques on the Capan-1 cell line. We identified 2,950 differentially expressed genes (DEGs) following TCDCA treatment, with 1,597 upregulated and 1,353 downregulated genes. These DEGs were associated with critical PDAC pathways, including coagulation, angiogenesis, cell migration, and signaling regulation. Furthermore, we reviewed relevant literature highlighting genes like DKK-1, KRT80, UPLA, and SerpinB2, known for their roles in PDAC tumorigenesis and metastasis. Our study sheds light on the complex relationship between BAs and PDAC, offering insights into potential diagnostic markers and therapeutic targets. Further research is needed to unravel these findings' precise mechanisms and clinical implications, potentially improving PDAC diagnosis and treatment.

Dickkopf-1 (DKK1) drives growth and metastases in castration-resistant prostate cancer

Metastatic castration-resistant prostate cancer (mCRPC) is associated with a poor prognosis and remains an incurable fatal disease. Therefore, the identification of molecular markers involved in cancer progression is urgently needed to develop more-effective therapies. The present study investigated the role of the Wnt signaling modulator Dickkopf-1 (DKK1) in the growth and metastatic progression of mCRPC. DKK1 silencing through siRNA and deletion via CRISPR/Cas9 editing were performed in two different metastatic castration-resistant prostate cancer cell lines (PC3 and DU145). A xenograft tumor model was used to assess tumor growth and metastases. In in vitro experiments, both DKK1 silencing and deletion reduced cell growth and migration of both cell lines. DKK1 knockout clones (DKK1-KO) exhibited cell cycle arrest, tubulin reorganization, and modulation of tumor metastasis-associated genes. Furthermore, in DKK1-KO cells, E-cadherin re-expression and its membrane co-localization with β-catenin were observed, contributing to reduced migration; Cadherin-11, known to increase during epithelial-mesenchymal transition, was down-regulated in DKK1-KO cells. In the xenograft mouse model, DKK1 deletion not only reduced tumor growth but also inhibited the formation of lung metastases. In conclusion, our findings support the key role of DKK1 in the growth and metastatic dissemination of mCRPC, both in vitro and in vivo.

Cancer-associated fibroblast-derived Dickkopf-1 suppresses NK cell cytotoxicity in breast cancer

Breast cancer is poorly immunogenic, hence able to evade T cell recognition and respond poorly to immune checkpoint blockade. Breast cancer cells can also evade NK cell-mediated immune surveillance, but the mechanism remains enigmatic. Dickkopf-1 (DKK1) is a Wnt/b-catenin inhibitor, whose levels are increased in breast cancer patients and correlate with reduced overall survival. DKK1 is expressed by cancer-associated fibroblasts (CAFs) in orthotopic breast tumors and patient samples, and at higher levels by bone cells. While bone-derived DKK1 contributes to the systemic elevation of DKK1 in tumor-bearing mice, CAFs represent the primary source of DKK1 at the tumor site. Systemic or bone-specific DKK1 targeting reduces primary tumor growth. Intriguingly, specific deletion of CAF-derived DKK1 also limits breast cancer progression, regardless of its elevated levels in circulation and in the bone. DKK1 does not support tumor proliferation directly but rather suppresses the activation and tumoricidal activity of NK cells. Importantly, increased DKK1 levels and reduced number of cytotoxic NK cells are detected in breast cancer patients with progressive bone metastases compared to those with stable disease. Our findings indicate that DKK1 creates a tumor-supporting environment through the suppression of NK cells in breast cancer.

Investigation of the Antitumor Effects of Tamoxifen and Its Ferrocene-Linked Derivatives on Pancreatic and Breast Cancer Cell Lines

Tamoxifen is a long-known anti-tumor drug, which is the gold standard therapy in estrogen receptor (ER) positive breast cancer patients. According to previous studies, the conjugation of the original tamoxifen molecule with different functional groups can significantly improve its antitumor effect. The purpose of this research was to uncover the molecular mechanisms behind the cytotoxicity of different ferrocene-linked tamoxifen derivates. Tamoxifen and its ferrocene-linked derivatives, T5 and T15 were tested in PANC1, MCF7, and MDA-MB-231 cells, where the incorporation of the ferrocene group improved the cytotoxicity on all cell lines. PANC1, MCF7, and MDA-MB-231 express ERα and GPER1 (G-protein coupled ER 1). However, ERβ is only expressed by MCF7 and MDA-MB-231 cells. Tamoxifen is a known agonist of GPER1, a receptor that can promote tumor progression. Analysis of the protein expression profile showed that while being cytotoxic, tamoxifen elevated the levels of different tumor growth-promoting factors (e.g., Bcl-XL, Survivin, EGFR, Cathepsins, chemokines). On the other hand, the ferrocene-linked derivates were able to lower these proteins. Further analysis showed that the ferrocene-linked derivatives significantly elevated the cellular oxidative stress compared to tamoxifen treatment. In conclusion, we were able to find two molecules possessing better cytotoxicity compared to their unmodified parent molecule while also being able to counter the negative effects of the presence of the GPER1 through the ER-independent mechanism of oxidative stress induction.

Dickkopf-1 Inhibition Reactivates Wnt/β-Catenin Signaling in Rhabdomyosarcoma, Induces Myogenic Markers In Vitro and Impairs Tumor Cell Survival In Vivo

The Wnt/β-catenin signaling pathway plays a pivotal role during embryogenesis and its deregulation is a key mechanism in the origin and progression of several tumors. Wnt antagonists have been described as key modulators of Wnt/β-catenin signaling in cancer, with Dickkopf-1 (DKK-1) being the most studied member of the DKK family. Although the therapeutic potential of DKK-1 inhibition has been evaluated in several diseases and malignancies, little is known in pediatric tumors. Only a few works have studied the genetic inhibition and function of DKK-1 in rhabdomyosarcoma. Here, for the first time, we report the analysis of the therapeutic potential of DKK-1 pharmaceutical inhibition in rhabdomyosarcoma, the most common soft tissue sarcoma in children. We performed DKK-1 inhibition via shRNA technology and via the chemical inhibitor WAY-2626211. Its inhibition led to β-catenin activation and the modulation of focal adhesion kinase (FAK), with positive effects on in vitro expression of myogenic markers and a reduction in proliferation and invasion. In addition, WAY-262611 was able to impair survival of tumor cells in vivo. Therefore, DKK-1 could constitute a molecular target, which could lead to novel therapeutic strategies in RMS, especially in those patients with high DKK-1 expression.

Serum Dickkopf-1 in Combined with CA 19-9 as a Biomarker of Intrahepatic Cholangiocarcinoma

Simple Summary

Cholangiocarcinoma (CCC) is a rare cancer, but its incidence and mortality have been increased in the past few decades worldwide, representing a global health problem. CCC is usually asymptomatic in early stages and, therefore, often diagnosed when the disease is already in advanced stages, which highly compromises therapeutic options, resulting in a dismal prognosis. The current diagnosis of CCC by non-invasive approaches such as serum biomarker, carbohydrate antigen 19-9 (CA 19-9), is not accurate enough due to the limitations in its low sensitivity, especially at the early stages of the disease. Therefore, new biomarkers with higher sensitivity and specificity are needed. As the clinical significance of dickkopf-related protein-1 (DKK-1) has been reported in various tumors including intrahepatic CCC (ICC), we aimed to identify the diagnostic and prognostic performance of the DKK-1 and its additive effect combined with CA 19-9 in patients with CCC.

Abstract

Dickkopf-related protein 1 (DKK-1) has a diagnostic and prognostic value in various malignant tumors. We investigated the diagnostic and prognostic performance of DKK-1 in combination with carbohydrate antigen 19-9 (CA 19-9) in cholangiocarcinoma (CCC) patients. Serum DKK-1 levels were measured using enzyme-linked immunosorbent assay. The receiver operating characteristic (ROC) curve, area under ROC (AUROC) analyses, Kaplan–Meier method, and Cox proportional hazard model were used to evaluate the diagnostic and prognostic performance of DKK-1 in combination with CA 19-9. We checked DKK-1 levels in 356 CCC patients and found that DKK-1 was significantly elevated only in 79 intrahepatic CCC (ICC) patients compared to controls (340.5 vs. 249.8 pg/mL, p = 0.002). The optimal cutoff level of DKK-1 used to identify ICC patients was 258.0 pg/mL (AUROC = 0.637, sensitivity = 59.5%, specificity = 56.9%, positive predictive value (PPV) = 40.5%, negative predictive value (NPV) = 74.0%, positive likelihood ratio (LR) = 1.38, and negative LR = 0.71). Using this cutoff, 47 (59.5%) patients were correctly diagnosed with ICC. DKK-1 in combination with CA 19-9 showed a better diagnostic performance (AUROC = 0.793, sensitivity = 74.7%, specificity = 56.3%, PPV = 45.7, NPV = 81.8, positive LR = 1.71, and negative LR = 0.45) than CA 19-9 alone. The low DKK-1 and CA 19-9 expression group had a significantly longer overall survival (OS) than the high expression group (p = 0.006). The higher level of DKK-1 and CA 19-9 was independently associated with shorter OS (hazard ratio = 3.077, 95% confidence interval 1.389–6.819, p = 0.006). The diagnostic and prognostic performance of DKK-1 in combination with CA 19-9 might be better than those of CA 19-9 alone in ICC patients.

Expression and Role of Dickkopf-1 (Dkk1) in Tumors: From the Cells to the Patients

Dickkopf-1 (Dkk1) is a secretory antagonist of the classical Wnt signaling pathway. Many studies have reported that Dkk1 is abnormally expressed in tumor cells, and abnormal expression of Dkk1 can inhibit cell proliferation or induce apoptosis through pro-apoptotic factors, However, due to the differences in tumor environment and the complex regulatory mechanisms in different tumors, Dkk1 has different effects on the progression of different tumors. In many tumors, high expression of Dkk1 may promote tumor metastasis. However, Dkk1, which is highly expressed in other tumors, can inhibit tumor invasion and metastasis. More and more evidence shows that Dkk1 plays a complex and different role in tumor occurrence, development and metastasis in different tumor environments and through a variety of complex regulatory mechanisms. Therefore, Dkk1 may not only be a useful biomarker of metastasis, but also a target for studying the metabolic mechanism of tumor cells and treating tumors in many tumor types. Therefore, this article reviews the research progress on the expression, mechanism and function of Dkk1 in different tumors, and at the same time, based on the public database data, we made a further analysis of the expression of Dkk1 in different tumors.

Diagnosis Accuracy and Prognostic Significance of the Dickkopf-1 Protein in Gastrointestinal Carcinomas: Systematic Review and Network Meta-analysis

Objective: To evaluate the diagnosis accuracy and prognostic significance of bio-marker dickkopf-1(DKK-1) protein in GIC, and also sub-type of hepatocellular carcinoma (HCC), pancreas carcinomas (PC), oesophageal carcinoma (EPC) and Adenocarcinoma of esophago-gastric junction (AEGJ), etc.

Methods: Electronic databases were searched from inception to May 2020. Patients were diagnosed with gastrointestinal carcinomas, and provided data on the correlation between high and low DKK-1 expression and diagnosis or prognosis.

Results: Forty-three publications involving 9318 participants were included in the network meta-analysis, with 31 of them providing data for diagnosis value and 18 records were eligible for providing prognosis value of DKK-1. DKK-1 has a moderate diagnostic value for overall GIC, HCC and PC. In addition, for the combined diagnosis value of DKK-1 +AFP, high diagnostic accuracy value could be determined in HCC and early HCC group, respectively. Whereas, diagnosis efficiency of DKK-1+CA19-9 was also better than that of DKK-1 alone with AUC value is above 0.95. For the prognosis meta-analysis of histopathological stratification, we found that EPC and AEGJ ranked the best for the histopathological stratification of prognosis from network meta-analysis. This systematic review protocol was registered with the PROSPERO registry (No.CRD42020167910).

Conclusion: DKK-1 has good diagnostic accuracy, especially combination of DKK-1+AFP in HCC and DKK-1+CA19-9 in PC, whereas modest prognostic significant in GIC. Future head-to-head researches are warranted for DKK-1 expression in HCC and PC tissue.

The Clinical Diagnostic and Prognostic Value of Dickkopf-1 in Cancer

The Wnt signaling pathway extensively participates in diverse processes such as embryonic development, maintenance of homeostasis and tumor pathogenesis. Dickkopf-1 (DKK1), a Wnt inhibitor, plays a vital role for over the past decades regarding its role in the regulation of several types of cancers. However, studies have shown that DKK1 is expressed differently in cancer and plays a role as a cancer-promoting factor or a tumor suppressor, which is worthy of further exploration. We herein study whether DKK1 is highly expressed in all cancers and plays a crucial role in promoting cancer. Furthermore, we discussed as to which stages of cancer development it plays in. Finally, the present detection methods were introduced and indicated the clinical application of DKK1 in tumor development.

Analyzing the prognostic value of DKK1 expression in human cancers based on bioinformatics

Background

The Dickkopf1 (DKK1) gene encodes a protein that belongs to the Dickkopf family. The protein can inhibit the Wnt signaling pathway which plays a key role in the carcinogenesis and progression of various types of cancers. Based on this, we hypothesized that the differential expression of DKK1 may figure significantly in cancers by regulating Wnt signaling pathway transduction. In this study, we conducted bioinformatics analysis to evaluate the prognostic and therapeutic value of DKK1 expression level in human cancers.

Methods

The expression level was analyzed by using the Oncomine database and Gene Expression Profiling Interactive Analysis tool. The analysis of prognosis was conducted by using the UALCAN, Gene Expression Profiling Interactive Analysis (GEPIA), and DriverDBv3 databases. We also investigated using DKK1 promoter methylation to define cancer types through the UALCAN database. Meanwhile, the related functional networks of DKK1 were analyzed by using the GeneMANIA interactive tool and Cytoscape software. Furthermore, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis was conducted using the Metascape online website, and we used the cBioPotartal database to explored DKK1 expression, aberrant information, and the co-expression genes in the subgroups of lung cancer. Finally, we performed the overall survival (OS) meta-analysis of the DKK1 expression in lung squamous cell carcinoma (LUSC) via the Lung Cancer Explorer (LCE).

Results

DKK1 was differentially expressed in different types of human cancers. DKK1 was overexpressed in human cancers including head and neck squamous cell carcinoma (HNSC), LUSC, and pancreatic adenocarcinoma (PAAD). Overexpression of DKK1 indicated adverse OS in bladder urothelial carcinoma (BLCA), HNSC, and PADD, but no difference in OS was found between the LUSC and healthy groups. The high expression of DKK1 was also associated with shorter disease-free survival (DFS) in HNSC, LUSC, and PAAD. Gene regulation network analysis indicated that DKK1 was mainly involved in Wnt signaling pathways and several other signaling pathways.

Conclusions

Our findings showed that DKK1 is significantly expressed in various cancers and could be a biomarker for targeted therapy and a predictor for prognosis of these specific cancers. The bioinformatics analysis revealed a significant overexpression of DKK1 in HNSC, LUSC, and PAAD, with DKK1 overexpression being associated with adverse outcome in these patients, but how DKK1 expression levels relate to hematological malignancies and prognosis is still unclear. These new insights into the function of DKK1 may provide a basis for new targeted drug therapy and an avenue for further investigation into the mechanisms underlying carcinogenesis of DKK1 in different cancer types.

Human Intestinal Morphogenesis Controlled by Transepithelial Morphogen Gradient and Flow-Dependent Physical Cues in a Microengineered Gut-on-a-Chip

We leveraged a human gut-on-a-chip (Gut Chip) microdevice that enables independent control of fluid flow and mechanical deformations to explore how physical cues and morphogen gradients influence intestinal morphogenesis. Both human intestinal Caco-2 and intestinal organoid-derived primary epithelial cells formed three-dimensional (3D) villi-like microarchitecture when exposed to apical and basal fluid flow; however, 3D morphogenesis did not occur and preformed villi-like structure involuted when basal flow was ceased. When cells were cultured in static Transwells, similar morphogenesis could be induced by removing or diluting the basal medium. Computational simulations and experimental studies revealed that the establishment of a transepithelial gradient of the Wnt antagonist Dickkopf-1 and flow-induced regulation of the Frizzled-9 receptor mediate the histogenesis. Computational simulations also predicted spatial growth patterns of 3D epithelial morphology observed experimentally in the Gut Chip. A microengineered Gut Chip may be useful for studies analyzing stem cell biology and tissue development.

Long non-coding RNA LINC01133 silencing exerts antioncogenic effect in pancreatic cancer through the methylation of DKK1 promoter and the activation of Wnt signaling pathway

Recent studies have acknowledged the critical roles played by long non-coding RNAs (lncRNAs) in the development and progression of pancreatic cancer. Therefore, the present study aimed to elucidate the mechanism underlying on how LINC01133 regulates the Wnt signaling pathway in pancreatic cancer. A microarray-based gene expression analysis was performed to identify the differentially expressed lncRNAs in pancreatic cancer. In addition, ectopic expression assays, knockdown experiments and gene reporter assays were conducted to clarify the role of LINC01133 in pancreatic cancer and to understand the interaction between LINC01133 and the methylation of DKK1 promoter. The expression of LINC01133, DKK1, and other genes related to the Wnt signaling pathway was also measured. EDU staining, scratch test and Transwell assay were employed to measure the proliferation, migration and invasion of pancreatic cancer cells, respectively. GSE32676 and GSE16515 revealed that LINC01133 was upregulated in pancreatic cancer, which was also associated with increased DKK1 methylation and higher expression of genes related to the Wnt signaling pathway, although the expression of DKK1 decreased in pancreatic cancer. In addition, LINC01133 bound to the promoter region of DKK1, resulting in the trimethylation of H3K27 and decreased DKK1 expression, while the expression of Wnt-5a, MMP-7, and β-catenin increased upon LINC01133 binding. Finally, over-expressed LINC01133 enhanced the growth, proliferation, migration, metastasis, and invasion of pancreatic cancer cells. The present study clarified the distinct effect of LINC01133 on pancreatic cancer. In summary, by inducing the methylation of DKK1 promoter, LINC01133 silencing suppresses the development of pancreatic cancer cells through the Wnt signaling pathway.

Identification of potential target genes in pancreatic ductal adenocarcinoma by bioinformatics analysis

Pancreatic ductal adenocarcinoma (PDAC) is one of the most complicated and fatally pathogenic human malignancies. Therefore, there is an urgent need to improve our understanding of the underlying molecular mechanism that drives the initiation, progression, and metastasis of PDAC. The aim of the present study was to identify the key genes and signaling pathways associated with PDAC using bioinformatics analysis. Four transcriptome microarray datasets (GSE15471, GSE55643, GSE62165 and GSE91035) were acquired from Gene Expression Omnibus datasets, which included 226 PDAC samples and 65 normal pancreatic tissue samples. We screened differentially expressed genes (DEGs) with GEO2R and investigated their biological function by Gene Ontology (GO) and Kyoto Encyclopedia of Genes (KEGG) analysis. The overall survival data was obtained from UALCAN, which calculated the data shared with The Cancer Genome Atlas. In addition, a protein-protein interaction (PPI) network of the DEGs was constructed by STRING and Cytoscape software. The four sets of DEGs exhibited an intersection consisting of 205 genes (142 up-regulated and 63 down-regulated), which may be associated with PDAC. GO analysis showed that the 205 DEGs were significantly enriched in the plasma membrane, cell adhesion molecule activity and the Energy pathways, and glycine, serine, threonine metabolism were the most enriched pathways according to KEGG pathway analysis. Kaplan-Meier survival analysis revealed that 22 of 205 common genes were significantly associated with the overall survival of pancreatic cancer patients. In the PPI network and sub-network, DKK1 and HMGA2 were considered as hub genes with high connectivity degrees. DKK1 and HMGA2 are strongly associated with WNT3A and TP53 separately, which indicates that they may play an important role in the Wnt and P53 signaling pathways. Using integrated bioinformatics analysis, we identified DKK1 and HMGA2 as candidate genes in PDAC, which may improve our understanding of the mechanisms of the pathogenesis and integration; the two genes may be therapeutic targets and prognostic markers for PDAC.

Proteomic biomarkers in body fluids associated with pancreatic cancer

Pancreatic cancer (PC) is a highly malignant disease that represents the fourth leading cancer-related death worldwide. There has been very little improvement in survival rates over recent years, and surgical resection remains the only reliable curative approach. Factors that contribute to this dismal prognosis for PC include its rapid progression and invasion, the absence of specific symptoms, and the little impact of available chemotherapy. Importantly, the management of this malignancy is also limited by the lack of highly specific and sensitive biomarkers for its diagnosis and follow-up, and their identification is therefore considered a promising strategy to improve outcomes in these patients. Numerous translational studies have explored the usefulness of body fluids as a non-invasive source of PC-specific biomarkers, and innovations in proteomic methods and technologies have provided a myriad of protein biomarkers for different cancers. The adoption of a proteomic approach has improved understanding of the biology of PC and contributed to the potential identification of protein biomarkers for this disease. This review considers the most recent research efforts to develop novel proteomic biomarkers in body fluids for PC.

Dickkopf-1 expression is associated with tumorigenity and lymphatic metastasis in human hilar cholangiocarcinoma

Dickkopf-1 (DKK1) is involved in tumorigenesis and the invasion of several tumors. However, its biological function in human hilar cholangiocarcinoma (HCCA) has not yet been documented. This study was designed to investigate the clinical significance and biological function of DKK1 in HCCA. The expression of DKK1 was investigated in thirty-seven human HCCA biopsy samples by immunohistochemistry. To further explore the biological effects of DKK1 in HCCA, transient and stable knockdown of DKK1 in two human HCCA cells (QBC939 and FRH0201) were established using small interfering or short hairpin RNA expression vector. In the present study, immunohistochemistry revealed that DKK1 was up-regulated in human HCCA tissues (24/37, 64.9%). High levels of DKK1 in human HCCA correlated with metastasis to the hilar lymph nodes (P=0.038). Genetic depletion of DKK1 in HCCA cells resulted in significantly inhibited proliferation, colony formation and migration compared with controls. Most importantly, DKK1 down-regulation impaired tumor formation capacity of HCCA cells in vivo. Subsequent investigations revealed that β-catenin is an important target of DKK1 and DKK1 exerts its pro-invasion function at least in part through the β-catenin/ matrix metalloproteinase-7 (MMP-7) signaling pathway. Consistently, in human HCCA tissues, DKK1 level was positively correlated with β-catenin and MMP-7 expression, as well as tumor hilar lymphatic metastasis. Taken together, our findings indicate that DKK1 may be a crucial regulator in the tumorigenicity and invasion of human HCCA, DKK1 exerts its pro-invasion function at least in part through the β-catenin/ MMP-7 signaling pathway, suggesting DKK1 as a potential therapeutic target for HCCA.

Rationale for targeting the Wnt signalling modulator Dickkopf-1 for oncology

Wnt signalling is a fundamental pathway involved in embryonic development and adult tissue homeostasis. Mutations in the pathway frequently lead to developmental defects and cancer. As such, therapeutic intervention of this pathway has generated tremendous interest. Dickkopf-1 (DKK1) is a secreted inhibitor of β-catenin-dependent Wnt signalling and was originally characterized as a tumour suppressor based on the prevailing view that Wnt signalling promotes cancer pathogenesis. However, DKK1 appears to increase tumour growth and metastasis in preclinical models and its elevated expression correlates with a poor prognosis in a range of cancers, indicating that DKK1 has more complex cellular and biological functions than originally appreciated. Here, we review current evidence for the cancer-promoting activity of DKK1 and recent insights into the effects of DKK1 on signalling pathways in both cancer and immune cells. We discuss the rationale and promise of targeting DKK1 for oncology.

LINKED ARTICLES

This article is part of a themed section on WNT Signalling: Mechanisms and Therapeutic Opportunities. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.24/issuetoc.

Role of Dickkopf-1 in gastrointestinal tumors

As an endogenous inhibitor of the Wnt signaling pathway, Dickkopf-1 (DKK1) plays an important role in the occurrence and development of tumors. However, the role of DKK1 in different tumor types is different, as it is lowly expressed in some tumor types, but over-expressed in others. In recent years, there have been many studies on the role of DKK1 in gastrointestinal tumors. In this paper, we review the latest progress in the understanding of the role of DKK1 in gastrointestinal tumors.

The role of Dickkopf-1 as a potential prognostic marker in pancreatic ductal adenocarcinoma

Dickkopf-1(DKK-1), the downstream target of β-catenin/T-cell factor, participates in a negative feedback loop in the Wnt signaling and reported as an important biomarker in many tumors. In this study, we analyzed the expression of DKK-1 in pancreatic ductal adenocarcinoma (PDAC) patients at both mRNA and protein levels. We used real-time PCR to detect the expression of DKK-1 in 32 PDAC and paired adjacent non-tumor tissues, results suggested that the expression of DKK-1 was increased in PDAC tissues. We found the similar results in the analysis of 3 independent microarray data sets. Immunohistochemical staining of 311 pairs of PDAC tissues suggested that DKK-1 expression was significantly associated with T classification (P = 0.039) and lymph node metastasis (P = 0.035). Furthermore, Kaplan-Meier analysis for DKK-1 expression demonstrated that patients with higher DKK-1 level had shorter overall survival (OS) and relapse-free survival (RFS) time in Ren Ji cohort and online PDAC database at both mRNA and protein levels. Univariable and multivariable Cox regression analysis confirmed that DKK-1 as well as lymph node metastasis and histology were independent predictors of OS in patients with PDAC. This study demonstrated that DKK-1 may be a predictor for prognosis in PDAC patients.

The Dickkopf1-cytoskeleton-associated protein 4 axis creates a novel signalling pathway and may represent a molecular target for cancer therapy

Dickkopf 1 (DKK1) is a secreted protein and antagonizes oncogenic Wnt signalling by binding to the Wnt co-receptor, low-density lipoprotein receptor-related protein 6. DKK1 has also been suggested to regulate its own signalling, associated with tumour aggressiveness. However, the underlying mechanism by which DKK1 promotes cancer cell proliferation has remained to be clarified for a long time. The cytoskeleton-associated protein 4 (CKAP4), originally identified as an endoplasmic reticulum membrane protein, was recently found to act as a novel DKK1 receptor. DKK1 stimulates cancer cell proliferation when CKAP4 is expressed on the cell surface membrane. Although there are no tyrosine residues in the intracellular region of CKAP4, CKAP4 forms a complex with PI3K upon the binding of DKK1, leading to the activation of Akt. Both DKK1 and CKAP4 are frequently expressed in pancreatic and lung tumours, and their simultaneous expression is negatively correlated with prognosis. Knockdown of CKAP4 in cancer cells and treatment of mice with the anti-CKAP4 antibody inhibit Akt activity in cancer cells and suppress xenograft tumour formation, suggesting that CKAP4 may represent a therapeutic target for cancers expressing both DKK1 and CKAP4. This review will provide details of the novel DKK1-CKAP4 signalling axis that promotes cancer proliferation and discuss the possibility of targeting this pathway in future cancer drug development.

LINKED ARTICLES

This article is part of a themed section on WNT Signalling: Mechanisms and Therapeutic Opportunities. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.24/issuetoc.

Transcriptomic changes associated with DKK4 overexpression in pancreatic cancer cells detected by RNA-Seq

The promotion of tumor development by Dickkopf 4 (DKK4) is receiving increased attention. However, the association between DKK4 and pancreatic cancer remains unclear. DKK4 expression was measured in pancreatic ductal adenocarcinoma tissues using qRT-PCR and immunohistochemistry. A DKK4-overexpressing pancreatic cancer cell line was established, and the differentially expressed genes (DEGs) that were induced by DKK4 were identified using transcriptome sequencing. The association between the identified DEGs and pancreatic cancer was assessed using gene ontology (GO), pathway analysis, pathway interaction networks, differentially expressed gene interaction network analysis, and co-expression gene networks. Finally, the accuracy of the analyses was validated using serial paraffin and frozen sections of clinical samples. DKK4 is highly expressed in pancreatic cancer tissues. DEGs of overexpression DKK4 of PANC-1 are mostly upregulated. GO and pathway analysis showed that DKK4 are associated with tumor and organ development and immune inflammation. The mitogen-activated protein kinase (MAPK) signaling pathway was the main signal transduction pathway that showed significant enrichment in overexpression DKK4 of PANC-1. The results of GO, pathway analyses, and differentially expressed gene interaction network identified genes that are closely associated with tumor development, including MAPK3, PIK3R3, VAV3, JAG1, and Notch3. The immunohistochemistry and immunofluorescence results suggested that DKK4 is co-expressed with MAPK3 and VAV3 in pancreatic cancer tissues. The results presented here show for the first time that DKK4 is highly expressed in pancreatic cancer tissues. Bioinformatics analysis of a DKK4-overexpressing of PANC-1 identified several oncogenes that are closely associated with tumors, and the MAPK signaling pathway is the core signal transduction pathway. DKK4 can be co-expressed with MAPK3 and VAV3 in pancreatic ductal adenocarcinoma tissues. Thus, DKK4 may have function on the development and progression of pancreatic cancer.

DKK3 blocked translocation of β-catenin/EMT induced by hypoxia and improved gemcitabine therapeutic effect in pancreatic cancer Bxpc-3 cell

The Wnt/β-catenin signalling pathway is activated in pancreatic cancer initiation and progression. Dickkopf-related protein 3 (DKK3) is a member of the human Dickkopf family and an antagonist of Wnt ligand activity. However, the function of DKK3 in this pathway in pancreatic cancer is rarely known. We examined the expression of DKK3 in six human pancreatic cancer cell lines, 75 pancreatic cancer and 75 adjacent non-cancerous tissues. Dickkopf-related protein 3 was frequently silenced and methylation in pancreatic cancer cell lines (3/6). The expression of DKK3 was significantly lower in pancreatic cancer tissues than in adjacent normal pancreas tissues. Further, ectopic expression of DKK3 inhibits nuclear translocation of β-catenin induced by hypoxia in pancreatic cancer Bxpc-3 cell. The forced expression of DKK3 markedly suppressed migration and the stem cell-like phenotype of pancreatic cancer Bxpc-3 cell in hypoxic conditions through reversing epithelial-mesenchymal transition (EMT). The stable expression of DKK3 sensitizes pancreatic cancer Bxpc-3 cell to gemcitabine, delays tumour growth and augments gemcitabine therapeutic effect in pancreatic cancer xenotransplantation model. Thus, we conclude from our finding that DKK3 is a tumour suppressor and improved gemcitabine therapeutic effect through inducing apoptosis and regulating β-catenin/EMT signalling in pancreatic cancer Bxpc-3 cell.

Perspectives in the treatment of pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is an incurable lethal disease whose incidence rate is growing. There is no effective screening for detection of early stage tumors and, in most cases, PDAC is diagnosed at advanced disease stages, when radical pancreatic resection is not possible. The aggressive nature of pancreatic tumor cells lies in the complex genetic mechanisms behind their uncontrolled capability to grow and metastasize, which involve essential adaptive changes in cellular metabolism, signaling, adhesion and immunoediting. In addition, PDAC cells promote a dense functional stroma that facilitates tumor resistance to chemotherapy and radiation. During the last two decades, gemcitabine has been the reference for the systemic treatment of PDAC. However, recently, a regimen combining fluorouracil, irinotecan, oxaliplatin, and leucovorin (FOLFIRINOX) and another combining albumin-bound paclitaxel with gemcitabine have shown clear therapeutic advantage in advanced PDAC, with survival outcomes of 11.3 and 8.5 mo on phase III trials, respectively, over single-agent gemcitabine. With the pending issue of their higher toxicities, these regimens set the reference for ongoing and future clinical studies in advanced PDAC. In addition, the efficacy of oral fluoropyrimidine (S-1) has been well documented in Asiatic PDAC patients. The development of therapeutic approaches other than cytotoxic drugs has proven difficult in the past, with only one drug (erlotinib) approved to date. Besides, a number of agents targeting signaling pathways in tumor or stroma cells are being investigated. Likewise, immunotherapies that target PDAC in various ways are the subject of a number of clinical trials. The search for reliable biomarkers with diagnostic and prognostic value using genomics and mass spectrometry methods may facilitate monitoring and refinement of therapies. This review focuses on current understanding of the pathogenesis of PDAC and the latest developments in the treatment of advanced PDAC.

Molecular changes in pre-metastatic lymph nodes of esophageal cancer patients

Lymph node metastasis indicates poor prognosis in esophageal cancer. To understand the underlying mechanisms, most studies so far focused on investigating the tumors themselves and/or invaded lymph nodes. However they neglected the potential events within the metastatic niche, which precede invasion. Here we report the first description of these regulations in patients on transcription level. We determined transcriptomic profiles of still metastasis-free regional lymph nodes for two patient groups: patients classified as pN1 (n = 9, metastatic nodes exist) or pN0 (n = 5, no metastatic nodes exist). All investigated lymph nodes, also those from pN1 patients, were still metastasis-free. The results show that regional lymph nodes of pN1 patients differ decisively from those of pN0 patients – even before metastasis has taken place. In the pN0 group distinct immune response patterns were observed. In contrast, lymph nodes of the pN1 group exhibited a clear profile of reduced immune response and reduced proliferation, but increased apoptosis, enhanced hypoplasia and morphological conversion processes. DKK1 was the most significant gene associated with the molecular mechanisms taking place in lymph nodes of patients suffering from metastasis (pN1). We assume that the two molecular profiles observed constitute different stages of a progressive disease. Finally we suggest that DKK1 might play an important role within the mechanisms leading to lymph node metastasis.

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.

Dickkopf-1 is oncogenic and involved in invasive growth in non small cell lung cancer

Dickkopf-1 (DKK1) is an inhibitor of the Wnt/β-catenin signaling pathway. However, the role of DKK1 in the progression of non small cell lung cancer (NSCLC) is not fully understood. In this study, RT-PCR and Western blot were used to examine the expression of DKK1 in a panel of ten human NSCLC cell lines and NSCLC tissues. DKK1 expression was highly transactivated in the great majority of these cancer lines. The expression of DKK1 was upregulated on both mRNA and protein levels in NSCLC tissues compared with the adjacent normal lung tissues. Immunohistochemistry and immunofluoresence revealed that DKK1 was mainly distributed in the cytoplasm in both carcinoma tissues and cell lines. DKK1 protein expression was also evaluated in paraffin sections from 102 patients with NSCLC by immunohistochemistry, and 65(63.73%)tumors were DKK1 positive. Relative analysis showed a significant relationship between DKK1 positive expression and lymph node metastasis(P<0.05). Patients with DKK1-positive tumors had poorer DFS than those with negative ESCC (5-year DFS; 15.4% versus 27%, P = 0.007). To further explore the biological effects of DKK1 in NSCLC cells, we over-expressed DKK1 in NSCLC 95C cell using eukaryotic expression vector pCMV-Tab-2b and performed a knockdown of DKK1 in LTEP-a-2 cell using a short hairpin RNA expression vector pSilencer 5.1. DKK1 did not have any effect on proliferation, but seemed to play a role in migration and invasion capability. Overexpression of DKK1 promotes migratory and invasive activity of 95C, while DKK1 knockdown resulted in the suppression of migration and invasion potentials of LTEP-a-2 cell. Taken together, these results indicate that DKK1 may be a crucial regulator in the progression of NSCLC. DKK1 might be a potential therapeutic target in NSCLC.

Molecular markers associated with outcome and metastasis in human pancreatic cancer

Background

Pancreatic ductal adenocarcinoma (PDAC) is a heterogeneous cancer in which differences in survival rates might be related to a variety in gene expression profiles. Although the molecular biology of PDAC begins to be revealed, genes or pathways that specifically drive tumour progression or metastasis are not well understood.

Methods

We performed microarray analyses on whole-tumour samples of 2 human PDAC subpopulations with similar clinicopathological features, but extremely distinct survival rates after potentially curative surgery, i.e. good outcome (OS and DFS > 50 months, n = 7) versus bad outcome (OS < 19 months and DFS < 7 months, n = 10). Additionally, liver- and peritoneal metastases were analysed and compared to primary cancer tissue (n = 11).

Results

The integrin and ephrin receptor families were upregulated in all PDAC samples, irrespective of outcome, supporting an important role of the interaction between pancreatic cancer cells and the surrounding desmoplastic reaction in tumorigenesis and cancer progression. Moreover, some components such as ITGB1 and EPHA2 were upregulated in PDAC samples with a poor outcome, Additionally, overexpression of the non-canonical Wnt/β-catenin pathway and EMT genes in PDAC samples with bad versus good outcome suggests their contribution to the invasiveness of pancreatic cancer, with β-catenin being also highly upregulated in metastatic tissue.

Conclusions

Components of the integrin and ephrin pathways and EMT related genes, might serve as molecular markers in pancreatic cancer as their expression seems to be related with prognosis.

Multispecies model of cell lineages and feedback control in solid tumors

We develop a multispecies continuum model to simulate the spatiotemporal dynamics of cell lineages in solid tumors. The model accounts for protein signaling factors produced by cells in lineages, and nutrients supplied by the microenvironment. Together, these regulate the rates of proliferation, self-renewal and differentiation of cells within the lineages, and control cell population sizes and distributions. Terminally differentiated cells release proteins (e.g., from the TGFβ superfamily) that feedback upon less differentiated cells in the lineage both to promote differentiation and decrease rates of proliferation (and self-renewal). Stem cells release a short-range factor that promotes self-renewal (e.g., representative of Wnt signaling factors), as well as a long-range inhibitor of this factor (e.g., representative of Wnt inhibitors such as Dkk and SFRPs). We find that the progression of the tumors and their response to treatment is controlled by the spatiotemporal dynamics of the signaling processes. The model predicts the development of spatiotemporal heterogeneous distributions of the feedback factors (Wnt, Dkk and TGFβ) and tumor cell populations with clusters of stem cells appearing at the tumor boundary, consistent with recent experiments. The nonlinear coupling between the heterogeneous expressions of growth factors and the heterogeneous distributions of cell populations at different lineage stages tends to create asymmetry in tumor shape that may sufficiently alter otherwise homeostatic feedback so as to favor escape from growth control. This occurs in a setting of invasive fingering, and enhanced aggressiveness after standard therapeutic interventions. We find, however, that combination therapy involving differentiation promoters and radiotherapy is very effective in eradicating such a tumor.

Dickkopf-1 is involved in invasive growth of esophageal cancer cells

Dickkopf-1 (DKK1) is an inhibitor of Wnt/β-catenin signaling pathway. High levels of DKK1 protein were found in a series of cancers. However, the role of DKK1 in the progression of esophageal carcinoma is not fully understood. In the present study, RT-PCR and Western blot were used to detect the expression of DKK1 in esophageal carcinoma tissues, matched adjacent normal esophageal tissues, and esophageal carcinoma cell lines. Our results showed that the expression of DKK1 was upregulated on both mRNA and protein levels in esophageal carcinoma tissues compared with the adjacent normal esophageal tissues, meanwhile, in four esophageal carcinoma cell lines analyzed, expression of DKK1 was detected with different levels. Immunohistochemistry and immunofluoresence revealed that the distribution of DKK1 was mainly in the cytoplasm in both carcinoma tissues and cell lines. To further explore the biological effects of DKK1 on proliferation, cell cycle and invasion capability, we constructed the eukaryotic expression vector pCMV-Tab-2b-DKK1 which can effectively overexpress DKK1. Subsequently, we observed that exogenous expression of DKK1 in EC9706 cell line resulted in an increased rate of proliferation, and S stage and G2/M stage ratio whereas G0/G1 ratio was decreased. In order to evaluate the invasion capability Boyden chamber was analyzed which implied that overexpression of DKK1 resulted in an increase in the invasion ability in EC9706 cell line. Taken together, the study indicates that DKK1 might be a key regulator in the progression of esophageal carcinoma and a potential therapeutic target in esophageal carcinoma.

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.

GATA6 activates Wnt signaling in pancreatic cancer by negatively regulating the Wnt antagonist Dickkopf-1

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal disease characterized by late diagnosis and treatment resistance. Recurrent genetic alterations in defined genes in association with perturbations of developmental cell signaling pathways have been associated with PDAC development and progression. Here, we show that GATA6 contributes to pancreatic carcinogenesis during the temporal progression of pancreatic intraepithelial neoplasia by virtue of Wnt pathway activation. GATA6 is recurrently amplified by both quantitative-PCR and fluorescent in-situ hybridization in human pancreatic intraepithelial neoplasia and in PDAC tissues, and GATA6 copy number is significantly correlated with overall patient survival. Forced overexpression of GATA6 in cancer cell lines enhanced cell proliferation and colony formation in soft agar in vitro and growth in vivo, as well as increased Wnt signaling. By contrast siRNA mediated knockdown of GATA6 led to corresponding decreases in these same parameters. The effects of GATA6 were found to be due to its ability to bind DNA, as forced overexpression of a DNA-binding mutant of GATA6 had no effects on cell growth in vitro or in vivo, nor did they affect Wnt signaling levels in these same cells. A microarray analysis revealed the Wnt antagonist Dickopf-1 (DKK1) as a dysregulated gene in association with GATA6 knockdown, and direct binding of GATA6 to the DKK1 promoter was confirmed by chromatin immunoprecipitation and electrophoretic mobility shift assays. Transient transfection of GATA6, but not mutant GATA6, into cancer cell lines led to decreased DKK1 mRNA expression and secretion of DKK1 protein into culture media. Forced overexpression of DKK1 antagonized the effects of GATA6 on Wnt signaling in pancreatic cancer cells. These findings illustrate that one mechanism by which GATA6 promotes pancreatic carcinogenesis is by virtue of its activation of canonical Wnt signaling via regulation of DKK1.

KRAS, Hedgehog, Wnt and the twisted developmental biology of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is characterized by near-universal mutations in KRAS and frequent deregulation of crucial embryonic signalling pathways, including the Hedgehog (Hh) and Wnt-β-catenin cascades. The creation of mouse models that closely resemble the human disease has provided a platform to better understand when and in which cell types these pathways are misregulated during PDAC development. Here we examine the central part that KRAS plays in the biology of PDAC, and how the timing and location of Hh and Wnt-β-catenin signalling dictate the specification and oncogenic properties of PDAC.

Inhibition of canonical Wnt signaling increases microvascular hemorrhaging and venular remodeling in adult rats

OBJECTIVE

The canonical Wnt signaling pathway, heavily studied in development and cancer, has recently been implicated in microvascular growth with the use of developmental and in vitro models. To date, however, no study exists showing the effects of perturbing the canonical Wnt pathway in a complete microvascular network undergoing physiological remodeling in vivo. Our objective was to investigate the effects of canonical Wnt inhibition on the microvascular remodeling of adult rats.

METHODS

Canonical Wnt inhibitor DKK-1, Wnt inhibitor sFRP-1, BSA or saline was superfused onto the exteriorized mesenteric windows of 300 g adult female Sprague-Dawley rats for 20 minutes. Three days following surgery, mesenteric windows were imaged intravitally and harvested for immunofluorescence staining with smooth muscle alpha-actin and BRDU.

RESULTS

We observed prominent differences in the response of the mesenteric microvasculature amongst the various treatment groups. Significant increases in hemorrhage area, vascular density, and draining vessel diameter were observed in windows treated with Wnt inhibitors as compared to control-treated windows. Additionally, confocal imaging analysis showed significant increases in proliferating cells as well as evidence of proliferating smooth muscle cells along venules.

CONCLUSIONS

Together, our results suggest that canonical Wnt inhibition plays an important role in microvascular remodeling, specifically venular remodeling.