Isolation and biochemical characterization of the human Dkk-1 homologue, a novel inhibitor of mammalian Wnt signaling

Dickkopf-1 promotes tumor progression of gefitinib- resistant non-small cell lung cancer through cancer cell-fibroblast interactions

BACKGROUND

Cancer cell-secreted proteins play a critical role in tumor progression and chemoresistance by influencing intercellular interactions within the tumor microenvironment. Investigating the intratumoral functions of these secretory proteins may provide insights into understanding and treating chemoresistant cancers. This study aims to identify potential anticancer target(s) in gefitinib-resistant non-small cell lung cancer (NSCLC), with a focus on secretory proteins and their effects on intercellular interactions.

METHODS

Differentially expressed secretory proteins were identified in gefitinib-resistant human NSCLC cell lines (PC9-GR and HCC827-GR), revealing an elevation in Dickkopf-1 (DKK1) expression and secretion. To elucidate the role of DKK1 in gefitinib-resistant cancer, the anticancer effects of a neutralizing antibody against DKK1 were evaluated in tumors comprising either cancer cells alone or cancer cells co-injected with human lung fibroblasts (MRC-5). Following the confirmation of the importance of cancer cell-fibroblast interactions in the protumorigenic activity of DKK1, the fibroblast traits modulated by DKK1 were further analyzed.

RESULTS

Gefitinib-resistant NSCLC cells exhibited increased DKK1 protein expression. Although elevated DKK1 levels were linked to poor prognosis, DKK1 did not directly affect cancer cell proliferation. However, DKK1 blockade showed significant anticancer effects in gefitinib-resistant tumors containing lung fibroblasts, suggesting that DKK1's pro-tumorigenic roles are mediated through cancer cell-fibroblast interactions. DKK1 altered fibroblast characteristics, enhancing inflammatory fibroblast traits while diminishing myofibroblast traits in tumor microenvironment. These DKK1-induced changes were mediated via activation of the c-JUN pathway in fibroblasts. Moreover, DKK1 was identified as a potential anticancer target across various cancer types beyond gefitinib-resistant lung cancer.

CONCLUSIONS

This study clarifies that DKK1 mediates interactions between cancer cells and fibroblasts in gefitinib-resistant lung cancer, contributing to tumor progression. Therefore, we propose DKK1 as a promising anticancer target for the treatment of gefitinib-resistant NSCLC.

Antisense mediated blockade of Dickkopf 1 attenuates tumor survival, metastases and bone damage in experimental osteosarcoma

Osteosarcoma (OS) is the most common primary bone malignancy. The canonical Wnt inhibitor Dickkopf-1 (Dkk-1) has been implicated in bone destruction, tumor survival and metastases during OS. We examined the role of Dkk-1 in OS disease progression and explored strategies for targeting its activity. Dkk-1 enhances OS survival by amplifying a non-canonical Wnt pathway that upregulates aldehyde dehydrogenase 1A1. Targeting of Dkk-1 transcription with a vivo morpholino (DkkMo) reduced OS survival and enhanced osteogenic activity of OS in vitro. DkkMo as a single agent slowed tumor expansion, increased tumor necrosis, inhibited metastases and preserved bone in a PDX model of OS. DkkMo also reduced the frequency of dividing tumor cells and reinitiated a regenerative osteogenic phenotype in tumors and stroma while reducing infiltration of inflammatory cells. These findings indicate that DkkMo has the potential to safely target osteosarcoma growth, survival, metastases and bone destruction.

DKK1 as a chemoresistant protein modulates oxaliplatin responses in colorectal cancer

Oxaliplatin is effective against colorectal cancer (CRC), but resistance hampers treatment. We found upregulated Dickkopf-1 (DKK1, a secreted protein) in oxaliplatin-resistant (OR) CRC cell lines and DKK1 levels increased by more than 2-fold in approximately 50% of oxaliplatin-resistant CRC tumors. DKK1 activates AKT via cytoskeleton-associated protein 4 (CKAP4, a DKK1 receptor), modulating oxaliplatin responses in vitro and in vivo. The leucine zipper (LZ) domain of CKAP4 and cysteine-rich domain 1 (CRD1) of secreted DKK1 are crucial for their interaction and AKT signaling. By utilizing the LZ protein, we disrupted DKK1 signaling, enhancing oxaliplatin sensitivity in OR CRC cells and xenograft tumors. This suggests that DKK1 as a chemoresistant factor in CRC via AKT activation. Targeting DKK1 with the LZ protein offers a promising therapeutic strategy for oxaliplatin-resistant CRC with high DKK1 levels. This study sheds light on oxaliplatin resistance mechanisms and proposes an innovative intervention for managing this challenge.

Wnt/β-catenin signaling components and mechanisms in bone formation, homeostasis, and disease

Wnts are secreted, lipid-modified proteins that bind to different receptors on the cell surface to activate canonical or non-canonical Wnt signaling pathways, which control various biological processes throughout embryonic development and adult life. Aberrant Wnt signaling pathway underlies a wide range of human disease pathogeneses. In this review, we provide an update of Wnt/β-catenin signaling components and mechanisms in bone formation, homeostasis, and diseases. The Wnt proteins, receptors, activators, inhibitors, and the crosstalk of Wnt signaling pathways with other signaling pathways are summarized and discussed. We mainly review Wnt signaling functions in bone formation, homeostasis, and related diseases, and summarize mouse models carrying genetic modifications of Wnt signaling components. Moreover, the therapeutic strategies for treating bone diseases by targeting Wnt signaling, including the extracellular molecules, cytosol components, and nuclear components of Wnt signaling are reviewed. In summary, this paper reviews our current understanding of the mechanisms by which Wnt signaling regulates bone formation, homeostasis, and the efforts targeting Wnt signaling for treating bone diseases. Finally, the paper evaluates the important questions in Wnt signaling to be further explored based on the progress of new biological analytical technologies.

Detailed survey of an in vitro intestinal epithelium model by single-cell transcriptomics

The co-culture of two adult human colorectal cancer cell lines, Caco-2 and HT29, on Transwell is commonly used as an in vitro gut mimic, yet the translatability of insights from such a system to adult human physiological contexts is not fully characterized. Here, we used single-cell RNA sequencing on the co-culture to obtain a detailed survey of cell type heterogeneity in the system and conducted a holistic comparison with human physiology. We identified the intestinal stem cell-, transit amplifying-, enterocyte-, goblet cell-, and enteroendocrine-like cells in the system. In general, the co-culture was fetal intestine-like, with less variety of gene expression compared to the adult human gut. Transporters for major types of nutrients were found in the majority of the enterocytes-like cells in the system. TLR 4 was not expressed in the sample, indicating that the co-culture model is incapable of mimicking the innate immune aspect of the human epithelium.

Spatial gene expression profile of Wnt-signaling components in the murine enteric nervous system

Introduction

Wnt-signaling is a key regulator of stem cell homeostasis, extensively studied in the intestinal crypt and other metazoan tissues. Yet, there is hardly any data available on the presence of Wnt-signaling components in the adult enteric nervous system (ENS) in vivo.

Methods

Therefore, we employed RNAscope HiPlex-assay, a novel and more sensitive in situ hybridization technology. By amplifying target specific signals, this technique enables the detection of low abundance, tightly regulated RNA content as is the case for Wnt-signaling components. Additionally, we compared our data to previously published physiological single cell RNA and RiboTag-based RNA sequencing analyses of enteric gliosis using data-mining approaches.

Results

Our descriptive analysis shows that several components of the multidi-mensional regulatory network of the Wnt-signaling pathway are present in the murine ENS. The transport and secretion protein for Wnt-ligands Wntless as well as canonical (Wnt3a and Wnt2b) and non-canonical Wnt-ligands (Wnt5a, Wnt7a, Wnt8b and Wnt11) are detectable within submucosal and myenteric plexus. Further, corresponding Frizzled receptors (Fzd1, Fzd3, Fzd6, and Fzd7) and regulatory signaling mediators like R-Spondin/DKK ligands are present in the ENS of the small and large intestine. Further, data mining approaches revealed, that several Wnt-related molecules are expressed by enteric glial cell clusters and are dynamically regulated during the inflammatory manifestation of enteric gliosis.

Discussion

Our results suggest, that canonical and non-canonical Wnt-signaling has a much broader impact on the mature ENS and its cellular homeostasis in health and inflammation, than previously anticipated.

Design, synthesis and anti-osteosarcoma activity study of novel pyrido[2,3-d]pyrimidine derivatives by inhibiting DKK1-Wnt/β-catenin pathway

Osteosarcoma is a common primary malignant bone tumor in adolescents. Wnt/β-catenin has been proved to play a pro-oncogenic role and was overactivated in osteosarcoma. Therefore, this pathway has become an interesting therapeutic target for osteosarcoma. Herein we report the design, synthesis and biological activities of a series of novel pyrido[2,3-d]pyrimidine derivatives based on our previous work. Among these, the representative compound 2-{[1,3-dimethyl-7-(4-methylpiperazin-1-yl)-2,4-dioxo-1,2,3,4-tetrahydropyrido[2,3-d]pyrimidin-5-yl]amino}-N-[4-(trifluoromethoxy)phenyl]acetamide (7m) has exhibited good antiproliferative activity towards 143B and MG63 cells with good selectivity over non-cancerous HSF cells. In the assay of Ca2+ concentration, the compound 7m increased the intracellular Ca2+ concentration in 143B cells. In addition, the expression of DKK1 increased, and that of p-β-catenin decreased by 7m treatment. Finally, the Hoechst 33,342 staining, Annexin-FITC/PI staining and mitochondrial fluorescence staining have clearly demonstrated that compound 7m induced apoptosis in 143B cells.

Inhibition of Dickkopf-1 enhances the anti-tumor efficacy of sorafenib via inhibition of the PI3K/Akt and Wnt/β-catenin pathways in hepatocellular carcinoma

BACKGROUND

Sorafenib improves the overall survival in patients with advanced hepatocellular carcinoma (HCC). Dickkopf-1 (DKK1) is commonly overexpressed in HCC. In this study, we investigated whether the inhibition of DKK1 enhances the anti-tumor efficacy of sorafenib in HCC.

METHODS

HCC cells were treated with sorafenib and WAY-262611, which is an inhibitor of DKK1. Transgenic mouse models were also developed using hydrodynamic tail vein injection. Mice were orally administered with sorafenib (32 mg/kg), WAY-262611 (16 mg/kg), or sorafenib + WAY-262611 for 10 days. Mechanisms of sorafenib and WAY-262611 were explored via western blotting, immunostaining, and RNA sequencing.

RESULTS

DKK1 was significantly overexpressed in patients with HCC than in the healthy controls and patients with liver diseases except HCC (all P < 0.05). Compared with sorafenib alone, sorafenib + WAY-262611 significantly inhibited the cell viability, invasion, migration, and colony formation by promoting apoptosis and altering the cell cycles in HCC cells (all P < 0.05). Moreover, sorafenib + WAY-262611 decreased the p110α, phospho-Akt (all P < 0.05), active β-catenin (all P < 0.05) and phospho-GSK-3β (Ser9) expression levels, while increasing the phospho-GSK-3β (Tyr216) expression levels compared with those in the sorafenib alone in vitro and in vivo. In addition, sorafenib + WAY-262611 inhibited tumor progression by regulating cell proliferation and apoptosis, significantly better than sorafenib alone in mouse models.

CONCLUSIONS

Our results indicate that DKK1 inhibition significantly enhances the anti-tumor efficacy of sorafenib by inhibiting the PI3K/Akt and Wnt/β-catenin pathways via regulation of GSK3β activity, suggesting a novel therapeutic strategy for HCC. Video Abstract.

Molecular Evolution and Protein Structure Variation of Dkk Family

Dkks have inhibitory effects on the Wnt signaling pathway, which is involved in the development of skin and its appendages and the regulation of hair growth. The nucleotide sequences were compared and analyzed to further investigate the relationship between the structure and function of the Dkk gene family and vertebrate epidermal hair. The analysis of the molecular evolution of the Dkk family revealed that the evolution rate of the genes changed significantly after speciation, with the Aves and Reptilia branches showing accelerated evolution. Additionally, positive selection was observed at specific sites. The tertiary structure of the protein was also predicted. The analysis of the functional divergence of the Dkk family revealed that the functional divergence coefficient of each gene was greater than 0, with most of the functional divergence sites were located in the Cys-2 domain and a few in the Cys-1 domain. This suggests that the amino acid and functional divergence sites may play a role in regulating the binding of the Dkk family to LRP5/6, and thus affect the inhibition of Wnt signaling, leading to different functions of Dkk1, Dkk2, and Dkk4 in the development of skin hair follicles. In addition, the Dkk families of Aves and Reptilia may have undergone adaptive evolution and functional divergence.

Dickkopf1 induces enteric neurogenesis and gliogenesis in vitro if apoptosis is evaded

Neurogenesis in the postnatal enteric nervous system (ENS) is controversially discussed. Yet, deciphering the regenerative potential of the ENS is essential for our understanding and therapy of human enteric neuropathies. Dickkopf1 (DKK1) is a Wnt-antagonist and involved in the homeostasis of various tissues. We hypothesize that DKK1 could function as a negative regulator on the proliferation of ENS-progenitors in the postnatal gut of mice and human infants. Here, we provide evidence that DKK1 is expressed in the murine and human ENS. If applied to ENS-progenitors in vitro, DKK1 leads to an increased proliferation, however, followed by extensive apoptosis. Yet, once we block apoptosis, DKK1-stimulation markedly increases enteric neurogenesis in murine and human ENS-progenitors. Thus, DKK1 is a strong, ambivalent regulator of the ENS-progenitor cell pool in mice and humans. These results are fundamental steps to reshaping our understanding of the homeostasis of the ENS in health and disease.

Dickkopf-1 and ROCK2 upregulation and associated protein aggregation in pseudoexfoliation syndrome and glaucoma

AIMS

The etiology of pseudoexfoliation (PEX), a stress-induced fibrillopathy and a leading cause of secondary glaucoma worldwide, remains limited. This study aims to understand the role of the Wnt antagonist Dickkopf-related protein 1 (DKK1) in PEX pathophysiology and assess its candidature as a biomarker for PEX.

MAIN METHODS

Expression levels of DKK1 and Wnt signaling genes were assayed in the anterior ocular tissues of study subjects by qRT-PCR, Western blotting, and immunohistochemistry. Protein aggregation was studied through Proteostat staining. Role of DKK1 in protein aggregation and regulation of target Wnt signaling genes was elucidated through overexpression and knockdown studies in Human Lens Epithelial cells (HLEB3). Levels of DKK1 in circulating fluids were assayed through ELISA.

KEY FINDINGS

DKK1 upregulation was observed in lens capsule and conjunctiva tissues of PEX individuals compared to controls correlating with an upregulation of the Wnt signaling target, ROCK2. Proteostat staining showed increased protein aggregates in lens epithelial cells of PEX patients. HLE B-3 cells overexpressed with DKK1 showed increased protein aggregates along with upregulation of ROCK2, and knockdown of DKK1 in HLE B-3 cells demonstrated downregulation of ROCK2. Further, ROCK2 inhibition by Y-27632 in DKK1 overexpressed cells showed that DKK1 regulated protein aggregation via ROCK2. Also, increased levels of DKK1 were observed in patients' plasma and aqueous humor compared to controls.

SIGNIFICANCE

This study shows that DKK1 and ROCK2 might play a role in protein aggregation in PEX. Further, elevated levels of DKK1 in aqueous humor serve as a fair classifier of pseudoexfoliation glaucoma.

Single-cell characteristics and malignancy regulation of alpha-fetoprotein-producing gastric cancer

OBJECTIVE

To characterize alpha-fetoprotein (AFP)-producing gastric cancer (AFPGC) at the single-cell level and to identify regulatory factors for AFP expression and malignancy.

METHODS

ScRNA-seq was performed on two tumors collected from patients with AFPGC. InferCNV and sub-clustering were applied to identify typical AFPGC cells, followed by AddModuleScore, pathway enrichment, Pseudo-time, and Scenic analyses. Data from a gastric cancer (GC) cohort were collected for conjoint analysis. The analytical results were verified by cell experiments and immunohistochemistry.

RESULTS

AFPGC cells are similar to hepatocytes in transcriptome and transcriptional regulation, with kinetic malignancy-related pathways, compared to the common malignant epithelium. In addition, compared to common GC cells, malignancy-related pathways, such as epithelial-mesenchymal transition (EMT) and angiogenesis, were upregulated in AFPGC. Mechanistically, Dickkopf-1 (DKK1) was found to be associated with AFP expression and malignant phenotype upon combining our scRNA-seq data with a public database, which was further verified by a series of in vitro experiments and immunohistochemistry.

CONCLUSION

We demonstrated the single-cell characteristics of AFPGC and that DKK1 facilitates AFP expression and malignancy.

CDK9 inhibitors downregulate DKK1 expression to suppress the metastatic potential of HCC cells

BACKGROUND

Elevated expression of Dickkopf-1 (DKK1) is frequently observed in hepatocellular carcinoma (HCC) patients with poor clinical outcomes. Several reports indicating the functional involvement of DKK1 in HCC progression have suggested DKK1 as a promising therapeutic target for HCC.

OBJECTIVE

In this study, to develop an efficient way to target DKK1, we assessed the effect of CDK9 inhibitors on DKK1 expression linked to metastatic movement of HCC.

METHODS

The expression of DKK1 in CDK9 inhibitor-treated HCC cells was measured by western blot, ELISA and quantitative real-time reverse transcription PCR. Wound healing assay, migration assay, invasion assay and western blot were examined to evaluate the functional role of DKK1 in CDK9 inhibitors-treated HCC.

RESULTS

Inactivation of CDK9 either by a catalytic inhibitor being clinically evaluated or by a specific CDK9 protein degrader largely downregulated DKK1 expression at the transcript and protein levels. In addition, CDK9 inhibitors suppressed the migration and invasion of HCC cells. We observed that ectopic high expression of DKK1 at least partially reversed the defects in metastatic movement of HCC cells mediated by CDK9 inhibitors. We further discovered that the DKK1-nuclear β-catenin axis associated with the metastatic potential of HCC cells was impaired by CDK9 inhibitors.

CONCLUSION

Taken together, our findings suggest that CDK9 inhibitors are potent tools to target DKK1, which can suppress the metastatic progression of HCC.

Chromatin modifier developmental pluripotency associated factor 4 (DPPA4) is a candidate gene for alcohol-induced developmental disorders

BACKGROUND

Prenatal alcohol exposure (PAE) affects embryonic development, causing a variable fetal alcohol spectrum disorder (FASD) phenotype with neuronal disorders and birth defects. We hypothesize that early alcohol-induced epigenetic changes disrupt the accurate developmental programming of embryo and consequently cause the complex phenotype of developmental disorders. To explore the etiology of FASD, we collected unique biological samples of 80 severely alcohol-exposed and 100 control newborns at birth.

METHODS

We performed genome-wide DNA methylation (DNAm) and gene expression analyses of placentas by using microarrays (EPIC, Illumina) and mRNA sequencing, respectively. To test the manifestation of observed PAE-associated DNAm changes in embryonic tissues as well as potential biomarkers for PAE, we examined if the changes can be detected also in white blood cells or buccal epithelial cells of the same newborns by EpiTYPER. To explore the early effects of alcohol on extraembryonic placental tissue, we selected 27 newborns whose mothers had consumed alcohol up to gestational week 7 at maximum to the separate analyses. Furthermore, to explore the effects of early alcohol exposure on embryonic cells, human embryonic stem cells (hESCs) as well as hESCs during differentiation into endodermal, mesodermal, and ectodermal cells were exposed to alcohol in vitro.

RESULTS

DPPA4, FOXP2, and TACR3 with significantly decreased DNAm were discovered-particularly the regulatory region of DPPA4 in the early alcohol-exposed placentas. When hESCs were exposed to alcohol in vitro, significantly altered regulation of DPPA2, a closely linked heterodimer of DPPA4, was observed. While the regulatory region of DPPA4 was unmethylated in both control and alcohol-exposed hESCs, alcohol-induced decreased DNAm similar to placenta was seen in in vitro differentiated mesodermal and ectodermal cells. Furthermore, common genes with alcohol-associated DNAm changes in placenta and hESCs were linked exclusively to the neurodevelopmental pathways in the enrichment analysis, which emphasizes the value of placental tissue when analyzing the effects of prenatal environment on human development.

CONCLUSIONS

Our study shows the effects of early alcohol exposure on human embryonic and extraembryonic cells, introduces candidate genes for alcohol-induced developmental disorders, and reveals potential biomarkers for prenatal alcohol exposure.

Effects of HSD11B1 knockout and overexpression on local cortisol production and differentiation of mesenchymal stem cells

Exogenous glucocorticoids increase the risk for osteoporosis, but the role of endogenous glucocorticoids remains elusive. Here, we describe the generation and validation of a loss- and a gain-of-function model of the cortisol producing enzyme 11β-HSD1 (HSD11B1) to modulate the endogenous glucocorticoid conversion in SCP-1 cells — a model for human mesenchymal stem cells capable of adipogenic and osteogenic differentiation. CRISPR-Cas9 was successfully used to generate a cell line carrying a single base duplication and a 5 bp deletion in exon 5, leading to missense amino acid sequences after codon 146. These inactivating genomic alterations were validated by deep sequencing and by cloning with subsequent capillary sequencing. 11β-HSD1 protein levels were reduced by 70% in the knockout cells and cortisol production was not detectable. Targeted chromosomal integration was used to stably overexpress HSD11B1. Compared to wildtype cells, HSD11B1 overexpression resulted in a 7.9-fold increase in HSD11B1 mRNA expression, a 5-fold increase in 11β-HSD1 protein expression and 3.3-fold increase in extracellular cortisol levels under adipogenic differentiation. The generated cells were used to address the effects of 11β-HSD1 expression on adipogenic and osteogenic differentiation. Compared to the wildtype, HSD11B1 overexpression led to a 3.7-fold increase in mRNA expression of lipoprotein lipase (LPL) and 2.5-fold increase in lipid production under adipogenic differentiation. Under osteogenic differentiation, HSD11B1 knockout led to enhanced alkaline phosphatase (ALP) activity and mRNA expression, and HSD11B1 overexpression resulted in a 4.6-fold and 11.7-fold increase in mRNA expression of Dickkopf-related protein 1 (DKK1) and LPL, respectively. Here we describe a HSD11B1 loss- and gain-of-function model in SCP-1 cells at genetic, molecular and functional levels. We used these models to study the effects of endogenous cortisol production on mesenchymal stem cell differentiation and demonstrate an 11β-HSD1 dependent switch from osteogenic to adipogenic differentiation. These results might help to better understand the role of endogenous cortisol production in osteoporosis on a molecular and cellular level.

Drug Discovery of DKK1 Inhibitors

Dickkopf-1 (DKK1) is a well-characterized Wnt inhibitor and component of the Wnt/β-catenin signaling pathway, whose dysregulation is associated with multiple abnormal pathologies including osteoporosis, Alzheimer's disease, diabetes, and various cancers. The Wnt signaling pathway has fundamental roles in cell fate determination, cell proliferation, and survival; thus, its mis-regulation can lead to disease. Although DKK1 is involved in other signaling pathways, including the β-catenin-independent Wnt pathway and the DKK1/CKAP4 pathway, the inhibition of DKK1 to propagate Wnt/β-catenin signals has been validated as an effective way to treat related diseases. In fact, strategies for developing DKK1 inhibitors have produced encouraging clinical results in different pathological models, and many publications provide detailed information about these inhibitors, which include small molecules, antibodies, and nucleic acids, and may function at the protein or mRNA level. However, no systematic review has yet provided an overview of the various aspects of their development and prospects. Therefore, we review the DKK1 inhibitors currently available or under study and provide an outlook on future studies involving DKK1 and drug discovery.

Roles of Therapeutic Bioactive Compounds in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is due to poor prognosis and lack of availability of effective treatment. Novel therapeutic strategies will be the fine tuning of intracellular ROS signaling to effectively deprive cells of ROS-induced tumor-promoting events. This review discusses the generation of ROS, the major signaling their modulation in therapeutics. We explore some of the major pathways involved in HCC, which include the VEGF, MAPK/ERK, mTOR, FGF, and Ser/Thr kinase pathways. In this review, we study cornerstone on natural bioactive compounds with their effect on hepatocarcinomas. Furthermore, we focus on oxidative stress and FDA-approved signaling pathway inhibitors, along with chemotherapy and radiotherapy enhancers which with early evidence of success. While more in vivo testing is required to confirm the findings presented here, our findings will aid future nonclinical, preclinical, and clinical studies with these compounds, as well as inspire medicinal chemistry scientists to conduct appropriate research on this promising natural compound and their derivatives.

Elevated serum Dickkopf-1 is a biomarker for bone erosion in patients with psoriatic arthritis

Background:

Psoriatic arthritis (PsA) is an inflammatory arthropathy characterized by psoriasis and bone erosion on radiology. Dickkopf-1 (Dkk-1) is considered to be the main inhibitor of the Wnt signaling pathway and results in reduced osteoblast proliferation. The aim of this study was to investigate the serum level of Dkk-1 and its association with bone erosion in PsA patients.

Methods:

Serum Dkk-1 levels were measured by enzyme-linked immunosorbent assay (ELISA) in 69 patients with PsA and 60 controls, including 39 rheumatoid arthritis (RA) patients, and 21 healthy controls (HCs). Rheumatoid factor and anti-cyclic citrullinated peptide levels were also determined by ELISA. The association of Dkk-1 level with clinical and laboratory features of PsA was analyzed. Logistic regression analysis was used to analyze the risk factors for bone erosion in PsA.

Results:

Dkk-1 was elevated in 68.1% (47/69) of the patients with PsA, 46.2% (18/39) of RA patients, and 9.5% (2/21) of HCs. Serum Dkk-1 concentration was significantly higher in PsA patients compared with that in HCs. The level of serum Dkk-1 was correlated with a swollen joint count, and levels of complement components 3 and 4. Elevated Dkk-1 level (odds ratio = 4.440, 95% confidence interval: 1.246–15.817, P = 0.021) was identified as the risk factor for bone erosion in PsA.

Conclusions:

The serum level of Dkk-1 is abnormally elevated in PsA patients. The elevation of Dkk-1 might be involved in the mechanism of bone erosion in patients with PsA.

Dehydrated human amniotic membrane modulates canonical Wnt signaling in multiple cell types in vitro

Canonical Wnt signaling is a major pathway known to regulate diverse physiological processes in multicellular organisms. Signaling is tightly regulated by feedback mechanisms; however, persistent dysregulation of this pathway is implicated in the progression of multiple disease states. In this study, proteomic analysis identified endogenous Wnt antagonists in micronized dehydrated human amnion/chorion membrane (μdHACM); thereby, prompting a study to further characterize the intrinsic properties of μdHACM as it relates to Wnt activity, in vitro. A TCF/LEF reporter cell line demonstrated the general ability of μdHACM to inhibit β-catenin induced transcription activity. Furthermore, in vitro systems, modeling elevated Wnt signaling, were developed in relevant cell types including tenocytes, synoviocytes, and human dermal fibroblasts (HDFs). Stimulation of these cells with Wnt3A resulted in translocation of β-catenin to the nucleus and increased expression of Wnt related genes. The subsequent addition of μdHACM, in the continued presence of Wnt-stimulus, mitigated the downstream effects of Wnt3A in tenocytes, synoviocytes, and HDFs. Nuclear localization of β-catenin was abated with corresponding reduction of Wnt related gene expression. These data demonstrate the in vitro regulation of canonical Wnt signaling as an inherent property of μdHACM and a novel mechanism of action.

Dickkopf-1: A Promising Target for Cancer Immunotherapy

Clinical studies in a range of cancers have detected elevated levels of the Wnt antagonist Dickkopf-1 (DKK1) in the serum or tumors of patients, and this was frequently associated with a poor prognosis. Our analysis of DKK1 gene profile using data from TCGA also proves the high expression of DKK1 in 14 types of cancers. Numerous preclinical studies have demonstrated the cancer-promoting effects of DKK1 in both in vitro cell models and in vivo animal models. Furthermore, DKK1 showed the ability to modulate immune cell activities as well as the immunosuppressive cancer microenvironment. Expression level of DKK1 is positively correlated with infiltrating levels of myeloid-derived suppressor cells (MDSCs) in 20 types of cancers, while negatively associated with CD8⁺ T cells in 4 of these 20 cancer types. Emerging experimental evidence indicates that DKK1 has been involved in T cell differentiation and induction of cancer evasion of immune surveillance by accumulating MDSCs. Consequently, DKK1 has become a promising target for cancer immunotherapy, and the mechanisms of DKK1 affecting cancers and immune cells have received great attention. This review introduces the rapidly growing body of literature revealing the cancer-promoting and immune regulatory activities of DKK1. In addition, this review also predicts that by understanding the interaction between different domains of DKK1 through computational modeling and functional studies, the underlying functional mechanism of DKK1 could be further elucidated, thus facilitating the development of anti-DKK1 drugs with more promising efficacy in cancer immunotherapy.

β-catenin in adrenal zonation and disease

The Wnt signaling pathway is a critical mediator of the development and maintenance of several tissues. The adrenal cortex is highly dependent upon Wnt/β-catenin signaling for proper zonation and endocrine function. Adrenocortical cells emerge in the peripheral capsule and subcapsular cortex of the gland as progenitor cells that centripetally differentiate into steroid hormone-producing cells of three functionally distinct concentric zones that respond robustly to various endocrine stimuli. Wnt/β-catenin signaling mediates adrenocortical progenitor cell fate and tissue renewal to maintain the gland throughout life. Aberrant Wnt/β-catenin signaling contributes to various adrenal disorders of steroid production and growth that range from hypofunction and hypoplasia to hyperfunction, hyperplasia, benign adrenocortical adenomas, and malignant adrenocortical carcinomas. Great strides have been made in defining the molecular underpinnings of adrenocortical homeostasis and disease, including the interplay between the capsule and cortex, critical components involved in maintaining the adrenocortical Wnt/β-catenin signaling gradient, and new targets in adrenal cancer. This review seeks to examine these and other recent advancements in understanding adrenocortical Wnt/β-catenin signaling and how this knowledge can inform therapeutic options for adrenal disease.

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.

Methylation Assessment of Two DKK2 and DKK4 Genes in Oral Squamous Cell Carcinoma Patients

Background:

Oral squamous cell carcinoma (OSCC) is one of the most important types of oral malignancies. DKK gene family members as well as DKK2/4 have critical roles in regulation of Wnt signaling as one of the main determining pathway in oral carcinogenesis. This study aimed to identify promoter methylation status of DKK2/4 genes to provide possible biomarkers for early detection and treatment of OSCC patients.

Methods:

A case control study was performed on 31 fresh tissues obtained from oral cavity of patients affected by OSCC and 31 fresh corresponding tissues from normal healthy controls in Tehran and, between the years of 2016–2018. Purified DNA from tissue samples was subjected to bisulfite treatment and then methylation specific polymerase chain reaction (MSP-PCR) was carried out on treated DNA samples.

Results:

DKK4 promoter was methylated in none of OSCC samples while it was methylated in 16.1% of healthy controls. 16.1% of OSCC samples were detected to be semimethylated and 22.6% of healthy normal samples were methylated for DKK2 promoter gene. Meaningful difference was found in DKK4 promoter methylation among OSCC patients and healthy controls. Significant correlation was found between DKK4 promoter methylation and tumor grade. The age of all enrolled samples was demonstrated to have strong effect on promoter methylation of studied genes.

Conclusion:

Hypomethylation of DKK2 and DKK4 genes in higher grades of OSCC samples may indicate the pivotal role of their expression in tumor cells invasion and progression through modulation of Wnt signaling pathway. Further study required to determine simultaneous expression of those genes and Wnt signaling elements at mRNA and protein levels.

Canonical Wnts Mediate CD8+ T Cell Noncytolytic Anti-HIV-1 Activity and Correlate with HIV-1 Clinical Status

CD8⁺ T cells do not rely solely on cytotoxic functions for significant HIV control. Moreover, the noncytotoxic CD8⁺ T cell antiviral response is a primary mediator of natural HIV control such as that seen in HIV elite controllers and long-term nonprogressors that does not require combined antiretroviral therapy. In this study, we investigated the biological factors contributing to the noncytotoxic control of HIV replication mediated by primary human CD8⁺ T cells. We report that canonical Wnt signaling inhibits HIV transcription in an MHC-independent, noncytotoxic manner and that mediators of this pathway correlate with HIV controller clinical status. We show that CD8⁺ T cells express all 19 Wnts and CD8⁺ T cell-conditioned medium (CM) induced canonical Wnt signaling in infected recipient cells while simultaneously inhibiting HIV transcription. Antagonizing canonical Wnt activity in CD8⁺ T cell CM resulted in increased HIV transcription in infected cells. Further, Wnt2b expression was upregulated in HIV controllers versus viremic patients, and in vitro depletion of Wnt2b and/or Wnt9b from CD8⁺ CM reversed HIV inhibitory activity. Finally, plasma concentration of Dkk-1, an antagonist of canonical Wnt signaling, was higher in viremic patients with lower CD4 counts. This study demonstrates that canonical Wnt signaling inhibits HIV and significantly correlates with HIV controller status.

Novel biomarkers for the management of chronic hepatitis B

Hepatitis B virus (HBV) cannot be eliminated completely from infected hepatocytes because of the presence of intrahepatic covalently closed circular DNA (cccDNA). As chronic hepatitis B (CHB) can progress to cirrhosis and hepatocellular carcinoma (HCC), it is important to manage CHB to prevent HCC development in high-risk patients with high viral replicative activity or advanced fibrosis. Serum biomarkers are noninvasive and valuable for the management of CHB. Hepatitis B core-related antigen (HBcrAg) correlates with serum HBV DNA and intrahepatic cccDNA. In CHB patients with undetectable serum HBV DNA or loss of HBsAg, HBcrAg still can be detected and the decrease in HBcrAg levels is significantly associated with hopeful outcomes. Therefore, HBcrAg can predict HCC occurrence or recurrence. Measurement of the Mac-2 binding protein glycosylation isomer (M2BPGi) has been introduced for the evaluation of liver fibrosis. Because elevated M2BPGi in CHB is related to liver fibrosis and the prediction of HCC development, monitoring its progression is essential. Because alpha fetoprotein (AFP) has insufficient sensitivity and specificity for early-stage HCC, a combination of AFP plus protein induced by vitamin K absence factor II, or AFP plus Lens culinaris agglutinin-reactive fraction of alpha-fetoprotein might improve the diagnosis of HCC development. Additionally, Dickkopf-1 and circulating immunoglobulin G antibodies are the novel markers to diagnose HCC or assess HCC prognosis. This review provides an overview of novel HBV biomarkers used for the management of intrahepatic viral replicative activity, liver fibrosis, and HCC development.

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.

Rac1-dependent phagocytosis of apoptotic cells by oral squamous cell carcinoma cells: A possible driving force for tumor progression

Apoptotic cell death frequently occurs in human cancer tissues including oral squamous cell carcinoma (SCC), wherein apoptotic tumor cells are phagocytosed not only by macrophages but also by neighboring tumor cells. We previously reported that the engulfment of apoptotic SCC cells by neighboring SCC cells frequently occurs at the invading front. Therefore, we hypothesized that the phagocytosis of these apoptotic cells by tumor cells contributes to disease progression. Herein, using cultured oral SCC cells, we aimed to confirm whether tumor cells actually phagocytose apoptotic cells and to examine whether cellular activities are regulated by the phagocytosis of apoptotic cells. Co-culture experiments showed that living cells could ingest apoptotic cells into phagolysosomes. NSC23766, an inhibitor of Rac1, which is a key regulator of phagocytic cup formation in professional phagocytes, dramatically suppressed the phagocytosis of apoptotic cells by living cells. Additionally, cell migration and the secretion of DKK1, a tumor-promoting protein, were enhanced by co-culture with apoptotic cells, whereas NSC23766 inhibited these effects. These results show that tumor cells can actively phagocytose apoptotic neighbors in a Rac1-dependent manner and that such activity increases their migration. The regulation of apoptotic cell phagocytosis thus represents new directions for therapeutic intervention for oral cancer.

Src and Fyn define a new signaling cascade activated by canonical and non-canonical Wnt ligands and required for gene transcription and cell invasion

Wnt ligands signal through canonical or non-canonical signaling pathways. Although both routes share common elements, such as the Fz2 receptor, they differ in the co-receptor and in many of the final responses; for instance, whereas canonical Wnts increase β-catenin stability, non-canonical ligands downregulate it. However, both types of ligands stimulate tumor cell invasion. We show here that both the canonical Wnt3a and the non-canonical Wnt5a stimulate Fz2 tyrosine phosphorylation, Fyn binding to Fz2, Fyn activation and Fyn-dependent Stat3 phosphorylation. Wnt3a and Wnt5a require Src for Fz2 tyrosine phosphorylation; Src binds to canonical and non-canonical co-receptors (LRP5/6 and Ror2, respectively) and is activated by Wnt3a and Wnt5a. This Fz2/Fyn/Stat3 branch is incompatible with the classical Fz2/Dvl2 pathway as shown by experiments of over-expression or depletion. Fyn is necessary for transcription of genes associated with invasiveness, such as Snail1, and for activation of cell invasion by both Wnt ligands. Our results extend the knowledge about canonical Wnt pathways, demonstrating additional roles for Fyn in this pathway and describing how this protein kinase is activated by both canonical and non-canonical Wnts.

Prolyl 4-hydroxylase subunit alpha 1 (P4HA1) is a biomarker of poor prognosis in primary melanomas, and its depletion inhibits melanoma cell invasion and disrupts tumor blood vessel walls

Melanoma is an unpredictable, highly metastatic malignancy, and treatment of advanced melanoma remains challenging. Novel molecular markers based on the alterations in gene expression and the molecular pathways activated or deactivated during melanoma progression are needed for predicting the course of the disease already in primary tumors and for providing new targets for therapy. Here, we sought to identify genes whose expression in primary melanomas correlate with patient disease‐specific survival using global gene expression profiling. Many of the identified potential markers of poor prognosis were associated with the epithelial–mesenchymal transition, extracellular matrix formation, and angiogenesis. We studied further the significance of one of the genes, prolyl 4‐hydroxylase subunit alpha 1 (P4HA1), in melanoma progression. P4HA1 depletion in melanoma cells reduced cell adhesion, invasion, and viability in vitro. In melanoma xenograft assays, we found that P4HA1 knockdown reduced melanoma tumor invasion as well as the deposition of collagens, particularly type IV collagen, in the interstitial extracellular matrix and in the basement membranes of tumor blood vessels, leading to vessel wall rupture and hemorrhages. Further, P4HA1 knockdown reduced the secretion of collagen triple helix repeat containing 1 (CTHRC1), an important mediator of melanoma cell migration and invasion, in vitro and its deposition around tumor blood vessels in vivo. Taken together, P4HA1 is an interesting potential prognostic marker and therapeutic target in primary melanomas, influencing many aspects of melanoma tumor progression.

Generating cell-derived matrices from human trabecular meshwork cell cultures for mechanistic studies

Ocular hypertension has been attributed to increased resistance to aqueous outflow often as a result of changes in trabecular meshwork (TM) extracellular matrix (ECM) using in vivo animal models (for example, by genetic manipulation) and ex vivo anterior segment perfusion organ cultures. These are, however, complex and difficult in dissecting molecular mechanisms and interactions. In vitro approaches to mimic the underlying substrate exist by manipulating either ECM topography, mechanics, or chemistry. These models best investigate the role of individual ECM protein(s) and/or substrate property, and thus do not recapitulate the multifactorial extracellular microenvironment; hence, mitigating its physiological relevance for mechanistic studies. Cell-derived matrices (CDMs), however, are capable of presenting a 3D-microenvironment rich in topography, chemistry, and whose mechanics can be tuned to better represent the network of native ECM constituents in vivo. Critically, the composition of CDMs may also be fine-tuned by addition of small molecules or relevant bioactive factors to mimic homeostasis or pathology. Here, we first provide a streamlined protocol for generating CDMs from TM cell cultures from normal or glaucomatous donor tissues. Second, we document how TM cells can be pharmacologically manipulated to obtain glucocorticoid-induced CDMs and how generated pristine CDMs can be manipulated with reagents like genipin. Finally, we summarize how CDMs may be used in mechanistic studies and discuss their probable application in future TM regenerative studies.

Transcriptional profiling of intramembranous and endochondral ossification after fracture in mice

Bone fracture repair represents an important clinical challenge with nearly 1 million non-union fractures occurring annually in the U.S. Gene expression differs between non-union and healthy repair, suggesting there is a pattern of gene expression that is indicative of optimal repair. Despite this, the gene expression profile of fracture repair remains incompletely understood. In this work, we used RNA-seq of two well-established murine fracture models to describe gene expression of intramembranous and endochondral bone formation. We used top differentially expressed genes, enriched gene ontology terms and pathways, callus cellular phenotyping, and histology to describe and contrast these bone formation processes across time. Intramembranous repair, as modeled by ulnar stress fracture, and endochondral repair, as modeled by femur full fracture, exhibited vastly different transcriptional profiles throughout repair. Stress fracture healing had enriched differentially expressed genes associated with bone repair and osteoblasts, highlighting the strong osteogenic repair process of this model. Interestingly, the PI3K-Akt signaling pathway was one of only a few pathways uniquely enriched in stress fracture repair. Full fracture repair involved a higher level of inflammatory and immune cell related genes than did stress fracture repair. Full fracture repair also differed from stress fracture in a robust downregulation of ion channel genes following injury, the role of which in fracture repair is unclear. This study offers a broad description of gene expression in intramembranous and endochondral ossification across several time points throughout repair and suggests several potentially intriguing genes, pathways, and cells whose role in fracture repair requires further study.

HTRA1 synergizes with oxidized phospholipids in promoting inflammation and macrophage infiltration essential for ocular VEGF expression

Understanding oxidative stress and HTRA1 locus in abnormal angiogenesis resulting in wet AMD pathology is an important step in developing a novel therapeutic approach. Using subretinal injection of oxLDL into C57BL/6 mice, we observed a lesion resembling the features of choroidal neovascularization (CNV), including macrophage infiltration, increased VEGF expression, and neovascularization. However, incubating ARPE-19 cells with oxLDL–a carrier of oxidized phospholipids–resulted in increased expression of inflammatory cytokines and chemoattractant proteins that recruited monocytes, but no substantial increase in expression of VEGF. Furthermore, incubation of ARPE-19 with oxLDL induced higher expression of HTRA1, which we showed to synergize with oxLDL in elevating the expression of inflammatory cytokines and chemoattractant factors. To investigate the role of macrophage infiltration on these expression changes, we treated cultured J774 macrophages with oxLDL and applied the conditioned medium onto ARPE-19 cells. This treatment was found to greatly enhance the expression of VEGF in ARPE-19, indicating the necessity of macrophage secretory products to induce increased expression of VEGF in retinal pigment epithelium. Gene expression analysis revealed that oxLDL induced the expression of Wnt3A in macrophages, a key activator of canonical Wnt signaling pathways. In addition, western blot analysis showed that the macrophage conditioned media further enhanced the reduction of phosphorylated β-catenin induced by oxLDL. Lastly, we investigated HTRA1 as a potential target for AMD therapeutics. We demonstrated the ability of anti-HTRA1 antibody in vitro to neutralize the protease activity of HTRA1 and reduce the inflammatory and angiogenic response to oxidative stress. Finally, we validated the neutralizing effect of anti-HTRA1 antibody in vivo by evaluating lesion size and protein expression in a laser-photocoagulation murine model of CNV. We found that the combination of oxLDL and HTRA1 enhanced CNV size, which was reversed by the addition of anti-HTRA1 antibody. This study not only provides preliminary evidence that HTRA1 may be a viable target for AMD therapeutics but also elucidates the biochemical mechanisms by which this therapeutic effect may be mediated.

R-spondin 2-LGR4 system regulates growth, migration and invasion, epithelial-mesenchymal transition and stem-like properties of tongue squamous cell carcinoma via Wnt/β-catenin signaling

Background

R-spondins (Rspo) and leucine-rich repeat-containing G-protein-coupled receptors (LGR) play important roles in development, stem cells survival, and tumorigenicity by activating Wnt signaling pathway. Whether R-spondins-LGR signaling affects the progression of squamous cell carcinoma (SCC) remain unknown. This study aims to uncover the role of R-spodin2/LGR4 in tongue SCC (TSCC).

Methods

The expression of Rspo2 in TSCC specimens and its correlation with TSCC clinical outcome were evaluated. Levels of Rspo2 or LGR4 were altered by pharmacological and genetic approaches, and the effects on TSCC progression were assessed.

Findings

Aberrantly high levels of Rspo2 were detected in TSCC specimens. Its levels were closely related with lymph node metastasis, clinical stage and survival rate in patients with tongue SCC. Exogenous Rspo2 or overexpression of Rspo2 promoted growth, migration and invasion, epithelial-mesenchymal transition (EMT) and stem-like properties in SCC both in vivo and in vitro. Silence of Rspo2 abolished these phenotypes. LGR4 was functionally upregulated by Rspo2 in TSCC. Overexpression of Rspo2 increased, whereas Rspo2 silencing decreased the expression of LGR4, leading to subsequent phosphorylation of LRP6 and nuclear translocation of β-catenin in TSCC cell lines. This nuclear translocation of β-catenin was associated with a significant alteration in TCF-1, a downstream nuclear transcription factor of β-catenin, as well as its target genes: CD44, CyclinD1 and c-Myc.

Interpretation

Rspo2-LGR4 system regulates growth, migration and invasion, EMT and stem-like properties of TSCC via Wnt/β-catenin signaling pathway.

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Rspo2 and LGR4 are aberrantly expressed in TSCC.

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Rspo2-LGR4 up-regulates growth, migration and invasion, EMT and stem-like properties of TSCC.

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Rspo2-LGR4 regulates TSCC progression via Wnt/β-catenin pathway.

Human gut derived-organoids provide model to study gluten response and effects of microbiota-derived molecules in celiac disease

Celiac disease (CD) is an immune-mediated disorder triggered by gluten exposure. The contribution of the adaptive immune response to CD pathogenesis has been extensively studied, but the absence of valid experimental models has hampered our understanding of the early steps leading to loss of gluten tolerance. Using intestinal organoids developed from duodenal biopsies from both non-celiac (NC) and celiac (CD) patients, we explored the contribution of gut epithelium to CD pathogenesis and the role of microbiota-derived molecules in modulating the epithelium’s response to gluten. When compared to NC, RNA sequencing of CD organoids revealed significantly altered expression of genes associated with gut barrier, innate immune response, and stem cell functions. Monolayers derived from CD organoids exposed to gliadin showed increased intestinal permeability and enhanced secretion of pro-inflammatory cytokines compared to NC controls. Microbiota-derived bioproducts butyrate, lactate, and polysaccharide A improved barrier function and reduced gliadin-induced cytokine secretion. We concluded that: (1) patient-derived organoids faithfully express established and newly identified molecular signatures characteristic of CD. (2) microbiota-derived bioproducts can be used to modulate the epithelial response to gluten. Finally, we validated the use of patient-derived organoids monolayers as a novel tool for the study of CD.

The role of DKK1 in Alzheimer's disease: A potential intervention point of brain damage prevention?

Dickkopf-1 (DKK1), a secretory glycoprotein discovered for 'inducing generation of head', is an endogenous inhibitor of the canonical Wnt/β-catenin signaling pathway. It was found to be involved in many pathophysiological processes in vivo. Abnormal expression of DKK1 will alter expressions of related proteins and genes not only in canonical Wnt/β-catenin signaling pathway but also in other signaling pathways. Previous studies of DKK1 focused on its function in tumors. In recent years, a large number of studies have shown that it plays an important role in embryonic development, neural regeneration, synaptogenesis and so on. Therefore, its role in neuropsychiatric disorders, such as neurodysplasia, cognitive impairment and emotional disorder, has attracted increasing attention. At present, the role of DKK1 in Alzheimer's disease (AD) is one of the research hot topics. This article reviewed the research progress of its role in AD in order to provide new ideas and directions for further studies on the pathogenesis and treatment of AD.

GLI3 repressor but not GLI3 activator is essential for mouse eye patterning and morphogenesis

Since 1967, it is known that the loss of GLI3 causes very severe defects in murine eye development. GLI3 is able to act as a transcriptional activator (GLI3-A) or as a transcriptional repressor (GLI3-R). Soon after the discovery of these GLI3 isoforms, the question arose which of the different isoforms is involved in eye formation - GLI3-A, GLI3-R or even both. For several years, this question remained elusive. By analysing the eye morphogenesis of Gli3^XtJ/XtJ mouse embryos that lack GLI3-A and GLI3-R and of Gli3^Δ699/Δ699 mouse embryos in which only GLI3-A is missing, we revealed that GLI3-A is dispensable in vertebrate eye formation. Remarkably, our study shows that GLI3-R is sufficient for the creation of morphologically normal eyes although the molecular setup deviates substantially from normality. In depth-investigations elucidated that GLI3-R controls numerous key players in eye development and governs lens and retina development at least partially via regulating WNT/β-CATENIN signalling.

Dkk1 involvement and its potential as a biomarker in pancreatic ductal adenocarcinoma

Dickkopf-1 (Dkk1)'s dysregulation has been implicated in the pathogenesis of a variety of cancers. It is part of the Dkk family of proteins that includes Dkk2, Dkk3 and Dkk4. This family of secreted proteins shares similar conserved cysteine domains and inhibits the Wnt/b-catenin pathway by causing proteasomal B-catenin degradation, inducing apoptosis, and preventing cell proliferation. Pancreatic ductal adenocarcinoma (PDAC) is the 4th leading cause of cancer mortality in the United States due to the late stage of diagnosis and the limited effectiveness of current therapy. Dkk1 is found increased in PADC patients' specimens and serum. Dkk1 can be a promising biomarker specific to PDAC, which has the potential to increase PDAC survival rates through improving early stage detection and monitoring progression compared to current biomarker gold standards. In addition, recent studies suggest that Dkk1 could be an excellent target for cancer immunotherapy. Interestingly, Dkk1-CKAP4-PI3K/AKT signal pathway also plays role in pancreatic cancer cell proliferation. In this review, we present the multiple mechanisms of Dkk1 in PDAC studied thus far and explore its function, regulation, and clinical applications in gynecological cancers including pancreatic ductal adenocarcinoma (PDAC), breast, ovarian, cervical, and endometrial cancer. Further research into Dkk1's mechanism and use as a diagnostic tool, alone or in combination with other biomarkers, could prove clinically useful for better understanding the pathology of PDAC and improving its early detection and treatment.

Identification of DKK-1 as a novel mediator of statin effects in human endothelial cells

This study shows that DKK-1, a member of the Dickkopf family and a regulator of the Wnt pathways, represents a novel target of statins which, through the inhibition of HMG-CoA reductase and of non-steroidal isoprenoid intermediates, exert extra-beneficial effect in preventing atherosclerosis beyond their effect on the lipid profile. We found that atorvastatin downregulates DKK-1 protein (−88.3 ± 4.1%) and mRNA expression (−90 ± 4.2%) through the inhibition of Cdc42, Rho and Rac geranylgeranylated proteins. Further, a combined approach based on the integration of label-free quantitative mass spectrometry based-proteomics and gene silencing allowed us to demonstrate that DKK-1 itself mediates, at least in part, statin effects on human endothelial cells. Indeed, DKK-1 is responsible for the regulation of the 21% of the statin-modulated proteins, which include, among others, clusterin/apoJ, plasminogen activator inhibitor type 1 (PAI-1), myristoylated alanine-rich C-kinase substrate (MARCKS), and pentraxin 3 (PTX3). The Gene Ontology enrichment annotation revealed that DKK-1 is also a potential mediator of the extracellular matrix organization, platelet activation and response to wounding processes induced by statin. Finally, we found that plasma level of DKK-1 from cholesterol-fed rabbits treated with atorvastatin (2.5 mg/kg/day for 8 weeks) was lower (−42 ± 23%) than that of control animals. Thus, DKK-1 is not only a target of statin but it directly regulates the expression of molecules involved in a plethora of biological functions, thus expanding its role, which has been so far restricted mainly to cancer.

Developing slow-off dickkopf-1 aptamers for early-diagnosis of hepatocellular carcinoma

In this work, we obtained fast-off and slow-off aptamer recognizing dickkopf-1(DKK1), a promising biomarker for detection of early-stage hepatocellular carcinoma (HCC), with high affinity in a single SELEX procedure. The two types of aptamer possessed distinct characteristics confirmed via different validation methods. In comparison to fast-off aptamers, slow-off aptamers were proven more suitable for aptamer-based ELISA assay. Using slow dissociation SELEX, slow-off aptamers were selectively retained. Meanwhile, a mutant (34del) of slow-off D10 was estimated with picomolar affinity (371.9 pM). The mutant was further truncated into 39nt before pairing with an antibody in the aptamer-based ELISA. The aptamer-target-antibody construction showed similar performance as conventional ELISA with a detection limit of 62.5 pg/ml. Quantification in 60 sera samples with the construction was also correlated with conventional ELISA. The results demonstrated novel DKK1 aptamer could replace capture antibody for potential early HCC diagnosis.

Structural and functional analysis of Dickkopf 4 (Dkk4): New insights into Dkk evolution and regulation of Wnt signaling by Dkk and Kremen proteins

Dickkopf (Dkk) family proteins are important regulators of Wnt signaling pathways, which play key roles in many essential biological processes. Here, we report the first detailed structural and dynamics study of a full-length mature Dkk protein (Dkk4, residues 19–224), including determination of the first atomic-resolution structure for the N-terminal cysteine-rich domain (CRD1) conserved among Dkk proteins. We discovered that CRD1 has significant structural homology to the Dkk C-terminal cysteine-rich domain (CRD2), pointing to multiple gene duplication events during Dkk family evolution. We also show that Dkk4 consists of two independent folded domains (CRD1 and CRD2) joined by a highly flexible, nonstructured linker. Similarly, the N-terminal region preceding CRD1 and containing a highly conserved NXI(R/K) sequence motif was shown to be dynamic and highly flexible. We demonstrate that Dkk4 CRD2 mediates high-affinity binding to both the E1E2 region of low-density lipoprotein receptor–related protein 6 (LRP6 E1E2) and the Kremen1 (Krm1) extracellular domain. In contrast, the N-terminal region alone bound with only moderate affinity to LRP6 E1E2, consistent with binding via the conserved NXI(R/K) motif, but did not interact with Krm proteins. We also confirmed that Dkk and Krm family proteins function synergistically to inhibit Wnt signaling. Insights provided by our integrated structural, dynamics, interaction, and functional studies have allowed us to refine the model of synergistic regulation of Wnt signaling by Dkk proteins. Our results indicate the potential for the formation of a diverse range of ternary complexes comprising Dkk, Krm, and LRP5/6 proteins, allowing fine-tuning of Wnt-dependent signaling.

The Changing Landscape in the Genetic Etiology of Human Tooth Agenesis

Despite much progress in understanding the genetics of syndromic tooth agenesis (TA), the causes of the most common, isolated TA remain elusive. Recent studies have identified novel genes and variants contributing to the etiology of TA, and revealed new pathways in which tooth development genes belong. Further, the use of new research approaches including next-generation sequencing has provided increased evidence supporting an oligogenic inheritance model for TA, and may explain the phenotypic variability of the condition. In this review, we present current knowledge about the genetic mechanisms underlying syndromic and isolated TA in humans, and highlight the value of incorporating next-generation sequencing approaches to identify causative and/or modifier genes that contribute to the etiology of TA.

Systems for localized release to mimic paracrine cell communication in vitro

Paracrine cell communication plays a pivotal role for signal exchange between proximal cells in vivo. However, this localized, gradient type release of mediators at very low concentrations (pg/ml), relevant during physiological and pathological processes, is rarely reflected within in vitro approaches. This review gives an overview on state-of-the-art approaches, which transfer the paracrine cell-to-cell communication into in vitro cell culture model setups. The traditional methods like trans-well assays and more advanced microfluidic approaches are included. The review focusses on systems for localized release, mostly based on microparticles, which tightly mimic the paracrine interaction between single cells in 3D microenvironments. Approaches based on single microparticles, with the main focus on affinity-controlled storage and release of cytokines, are reviewed and their importance for understanding paracrine communication is highlighted. Various methods to study the cytokine release and their advantages and disadvantages are discussed. Basic principles of the release characteristics, like diffusion mechanisms, are quantitatively described, including the formation of resulting gradients around the local sources. In vitro cell experiments using such localized microparticle release systems in approaches to increase understanding of stem cell behavior within their niches and regulation of wound healing are highlighted as examples of successful localized release systems for mimicking paracrine cell communication.

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.

Shanghai Score: A Prognostic and Adjuvant Treatment-evaluating System Constructed for Chinese Patients with Hepatocellular Carcinoma after Curative Resection

BACKGROUND

For Chinese patients with hepatocellular carcinoma (HCC), surgical resection is the most important treatment to achieve long-term survival for patients with an early-stage tumor, and yet the prognosis after surgery is diverse. We aimed to construct a scoring system (Shanghai Score) for individualized prognosis estimation and adjuvant treatment evaluation.

METHODS

A multivariate Cox proportional hazards model was constructed based on 4166 HCC patients undergoing resection during 2001-2008 at Zhongshan Hospital. Age, hepatitis B surface antigen, hepatitis B e antigen, partial thromboplastin time, total bilirubin, alkaline phosphatase, γ-glutamyltransferase, α-fetoprotein, tumor size, cirrhosis, vascular invasion, differentiation, encapsulation, and tumor number were finally retained by a backward step-down selection process with the Akaike information criterion. The Harrell's concordance index (C-index) was used to measure model performance. Shanghai Score is calculated by summing the products of the 14 variable values times each variable's corresponding regression coefficient. Totally 1978 patients from Zhongshan Hospital undergoing resection during 2009-2012, 808 patients from Eastern Hepatobiliary Surgery Hospital during 2008-2010, and 244 patients from Tianjin Medical University Cancer Hospital during 2010-2011 were enrolled as external validation cohorts. Shanghai Score was also implied in evaluating adjuvant treatment choices based on propensity score matching analysis.

RESULTS

Shanghai Score showed good calibration and discrimination in postsurgical HCC patients. The bootstrap-corrected C-index (confidence interval [CI]) was 0.74 for overall survival (OS) and 0.68 for recurrence-free survival (RFS) in derivation cohort (4166 patients), and in the three independent validation cohorts, the CI s for OS ranged 0.70-0.72 and that for RFS ranged 0.63-0.68. Furthermore, Shanghai Score provided evaluation for adjuvant treatment choices (transcatheter arterial chemoembolization or interferon-α). The identified subset of patients at low risk could be ideal candidates for curative surgery, and subsets of patients at moderate or high risk could be recommended with possible adjuvant therapies after surgery. Finally, a web server with individualized outcome prediction and treatment recommendation was constructed.

CONCLUSIONS

Based on the largest cohort up to date, we established Shanghai Score - an individualized outcome prediction system specifically designed for Chinese HCC patients after surgery. The Shanghai Score web server provides an easily accessible tool to stratify the prognosis of patients undergoing liver resection for HCC.