CCN1 coordinately regulates intestinal stem cell proliferation and differentiation through integrins αvβ3/αvβ5

Intestinal stem cells (ISCs) at the crypt base contribute to intestinal homeostasis through a balance between self-renewal and differentiation. However, the molecular mechanisms regulating this homeostatic balance remain elusive. Here we show that the matricellular protein CCN1/CYR61 coordinately regulates ISC proliferation and differentiation through distinct pathways emanating from CCN1 interaction with integrins αvβ3/αvβ5. Mice that delete Ccn1 in Lgr5+ ISCs or express mutant CCN1 unable to bind integrins αvβ3/αvβ5 exhibited exuberant ISC expansion and enhanced differentiation into secretory cells at the expense of absorptive enterocytes in the small intestine, leading to nutrient malabsorption. Analysis of crypt organoids revealed that through integrins αvβ3/αvβ5, CCN1 induces NF-κB-dependent Jag1 expression to regulate Notch activation for differentiation and promotes Src-mediated YAP activation and Dkk1 expression to control Wnt signaling for proliferation. Moreover, CCN1 and YAP amplify the activities of each other in a regulatory loop. These findings establish CCN1 as a novel niche factor in the intestinal crypts, providing new insights into how matrix signaling exerts overarching control of ISC homeostasis.

Canonical Wnt Signaling Inhibition in Renal Cell Carcinoma Bone Metastasis: Immunohistochemical Study of DKK1 and LRP5 Expression

Introduction & Objectives: Canonical Wnt signaling (Wnt/β-catenin signaling) maintains the bone homeostasis by promoting the osteoblastic activities. The inhibitory factor, Dickkopf (DKK)1, enhances the bone resorption, especially in malignancies. The low density lipoprotein related protein (LRP) 5 is a component of membranous co-receptor of Wnt/β-catenin signaling and is also involved in serum low density lipoprotein cholestrol (LDL-C) level regulation. The clear cell renal cell carcinoma bone metastasis (ccRCC-BM) is characterized by osteolytic bone resorption. Whether and how Wnt/β-catenin signaling plays roles in regulating the invasion, metastasis and osteolytic process of ccRCC to bone remain unclear. This study investigated the expression of DKK1, LRP5 proteins in primary and metastatic lesions of RCC-BM. The therapeutic potential of Wnt/β-catenin signaling target medication was also evaluated.Materials & Methods: ccRCC-BM patients with paired samples of primary and metastatic lesions were selected. ccRCC patients without any metastasis (ccRCC-only) were set as control. Slides of paraffin-embedded tissue underwent immunohistochemical staining with monoclonalanti-DKK1 antibody and polyclonal anti-LRP5 antibody. Semi-quantitatively scoring according to staining intensity was performed. The staining results in the renal tissue adjacent to RCC, the primary RCC lesions (with BM or without BM), and the RCC-BM lesions were recorded. The expression difference was analyzed by univariate analysis of variance (ANOVA).Results: The expression of DKK1 was significantly different amid renal tissue adjacent to RCC, primary RCC and RCC-BM tissues (p< 0.001). The expression of DKK1 in primary RCC was significantly lower than that in renal tissue adjacent to RCC (p<0.001). No difference was found between ccRCC-BM group and ccRCC-only group. DKK1 expression in bone metastasis was significantly higher than that in primary tumor (p < 0.001). The expression of LRP5 in the primary tumor of ccRCC-BM group was significantly lower than that of adjacent renal tissue (p<0.01). Tendency of decreasing expression was found between primary lesion of ccRCC-BM group and primary lesion of ccRCC-only group (p=0.073). In bone metastasis, the expression of LRP5 protein was not significantly different from that in adjacent renal tissue and RCC primary lesion.Conclusions: A "rebound" of DKK1 expression was found in bone metastasis lesions. Along with the decreasing LRP5 expression in primary lesions of RCC-BM patients, this suggests that the canonical Wnt signaling (Wnt/β-catenin signaling) is inhibited during the bone metastasis process in ccRCC. The overexpression of DKK1 and the down-regulation of LRP5 receptor are involved.

Hyperleukocytic Acute Leukemia Circulating Exosomes Regulate HSCs and BM-MSCs

Hyperleukocytic acute leukemia (HLAL) circulating exosomes are delivered to hematopoietic stem cells (HSCs) and bone marrow mesenchymal stem cells (BM-MSCs), thereby inhibiting the normal hematopoietic process. In this paper, we have evaluated and explored the effects of miR-125b, which is carried by HLAL-derived exosomes, on the hematopoietic function of HSCs and BM-MSCs. For this purpose, we have isolated exosomes from the peripheral blood of HLAL patients and healthy volunteers. Then, we measured the level of miR-125b in exosomes cocultured exosomes with HSCs and BM-MSCs. Moreover, we have used miR-125b inhibitors/mimic for intervention and then measured miR-125b expression and colony forming unit (CFU). Apart from it, HSC and BM-MSC hematopoietic-related factors α-globulin, γ-globulin, CSF2, CRTX4 and CXCL12, SCF, IGF1, and DKK1 expression were measured. Evaluation of the miR-125b and BAK1 targeting relationship, level of miR-125b, and expression of hematopoietic-related genes was performed after patients are treated with miR-125b mimic and si-BAK1. We have observed that miR-125b was upregulated in HLAL-derived exosomes. After HLAL-exosome acts on HSCs, the level of miR-125b is upregulated, reducing CFU and affecting the expression of α-globulin, γ-globulin, CSF2, and CRCX4. For BM-MSCs, after the action of HLAL-exo, the level of miR-125b is upregulated and affected the expression of CXCL12, SCF, IGF1, and DKK1. Exosomes derived from HLAL carry miR-125b to target and regulate BAK1. Further study confirmed that miR-125b and BAK1mimic reduced the expression of miR-125b and reversed the effect of miR-125b mimic on hematopoietic-related genes. These results demonstrated that HLAL-derived exosomes carrying miR-125b inhibit the hematopoietic differentiation of HSC and hematopoietic support function of BM-MSC through BAK1.

940 Targeting DKK1 to reverse immunosuppressive macrophages and enhance PD-1 blockade therapy in gastric cancer

BackgroundGastric cancer (GC) is a highly heterogeneous and immunosuppressive cancer type with poor prognosis. Current immunotherapies like immune checkpoint blockade (ICB) have very modest therapeutic effect in GC patients, reflecting urgent need for exploring new immunotherapeutic targets.MethodsIHC and mRNA analysis of 384 patients from Drum Tower Hospital Cohort and 1192 patients from other databases were performed to investigate Dickkopf-1 (DKK1) expression and local immune status. The MFC-challenged subcutaneous and abdominal dissemination GC models were established, and the impact of DKK1 blockade on gastric tumor immune microenvironment (TIME) and anti-tumor responses was explored by flow cytometry and RNA sequencing. In vivo immune cell-depletion GC models were constructed to further assess the function of DKK1 on different immune cell types. RAW264.7 and mouse bone marrow derived macrophages (BMDMs) were employed to analyze DKK1 modulation on macrophages in vitro by Cytometric Bead Array, flow cytometry and western bolt.ResultsIn present study, we found high DKK1 expression is associated with poor overall survival and worse immune status in GC patients. DKK1 blockade could improve gastric TIME, including increased accumulation and activation of CD8+ T cells and NK cells, and trigger an effective anti-tumor response both in subcutaneous and abdominal dissemination GC models. DKK1 directly induces macrophages towards an immunosuppressive phenotype, while the TIME improvement and tumor reduction depend on the reversion of immunosuppressive macrophages mediated by DKK1 blockade. Furthermore, combined inhibition of PD-1 and DKK1 could achieve superior anti-tumor effect on GC models.ConclusionsThus, our work identifies a new role of DKK1 to induce immunosuppressive TIME through macrophage modulation, and reveals DKK1 to be a novel and promising immunotherapeutic target for GC.Ethics ApprovalThe collection and analysis of tumor tissue sections were approved by the Ethics Committee of Nanjing University Medical School Affiliated Drum Tower Hospital (2021-324-01). All animal experiments were approved by the Institutional Animal Care and Use Committee of Drum Tower Hospital (approval number: 2020AE01064).

Dickkopf-1 is a Prognostic Biomarker and Correlated With Immune Infiltrates in Head and Neck Squamous Cell Carcinoma

Background: Head and neck squamous cell carcinoma(HNSCC) has a high level of immune infiltration, and immunotherapy generates new hope to patients with head and neck tumors. It is currently one of the most promising treatments for HNSCC. Previous studies have shown that Dickkopf-1 (DKK1), an inhibitor of Wnt signaling, is related to the prognosis of a variety of tumors. DKK1 is a key mediator of immune activation and is highly associated with tumor progress and tumor microenvironment. However, the association between DKK1 expression and the prognosis of HNSCC and tumor infiltrating lymphocytes is still unknown.Objective: We aim to test the relationship between DKK1 and HNSCC prognosis and tumor infiltrating lymphocytes.Methods:We explored the DKK1 expression differences in multiple tumor tissues and normal tissues via examing TIMER, Oncomine, and UALCAN databases. Then, we searched the Kaplan-Meier database to assess the correlation between DKK1 mRNA levels and clinical outcomes. Subsequently, the TIMER platform and TISIDB website were selected to evaluate the correlation between DKK1 and the level of tumor immune cell infiltration. We used cBioPortal and UCSC Xena database to further explore the reasons for the aberrant expression of DKK1 in tumorigenesis.Results: We found that DKK1 level was significantly elevated in HNSCC tissues compared with normal tissues. The expression of DKK1 is related to the tumor stage, tumor grade, histology, lymph node metastasis and worse clinical prognosis of HNSCC. In addition, DKK1 is negatively correlated with different tumor-infiltrating immune cells in HNSCC. Moreover, DKK1 is closely related to the genetic markers of a variety of immune cells. Also, the prognosis of HNSCC is worse based on the high DKK1 expression of immune cells. Copy number variation (CNV) and DNA methylation may be the cause of abnormal up-regulation of DKK1 in HNSCC.Conclusion: DKK1 can be used as a biomarker for predicting the prognosis and immune infiltration of HNSCC. These results provide us with important clues to better understand the role of DKK1 in the immunotherapy of head and neck tumors from the perspective of bioinformatics.This study provides a theoretical basis for clinical research on the treatment of head and neck squamous cell carcinoma with the DKK1 gene as a target. It may play a major role in advancing the immunotherapy of head and neck squamous cell carcinoma and enhance the therapeutic effect.

The Dickkopf1 and FOXM1 positive feedback loop promotes tumor growth in pancreatic and esophageal cancers

Dickkopf1 (DKK1) is overexpressed in various cancers and promotes cancer cell proliferation by binding to cytoskeleton-associated protein 4 (CKAP4). However, the mechanisms underlying DKK1 expression are poorly understood. RNA sequence analysis revealed that expression of the transcription factor forkhead box M1 (FOXM1) and its target genes concordantly fluctuated with expression of DKK1 in pancreatic ductal adenocarcinoma (PDAC) cells. DKK1 knockdown decreased FOXM1 expression and vice versa in PDAC and esophageal squamous cell carcinoma (ESCC) cells. Inhibition of either the DKK1-CKAP4-AKT pathway or the ERK pathway suppressed FOXM1 expression, and simultaneous inhibition of both pathways showed synergistic effects. A FOXM1 binding site was identified in the 5ʹ-untranslated region of the DKK1 gene, and its depletion decreased DKK1 expression and cancer cell proliferation. Clinicopathological and database analysis revealed that PDAC and ESCC patients who simultaneously express DKK1 and FOXM1 have a poorer prognosis. Multivariate analysis demonstrated that expression of both DKK1 and FOXM1 is the independent prognostic factor in ESCC patients. Although it has been reported that FOXM1 enhances Wnt signaling, FOXM1 induced DKK1 expression independently of Wnt signaling in PDAC and ESCC cells. These results suggest that DKK1 and FOXM1 create a positive feedback loop to promote cancer cell proliferation.

Striatal Synapse Degeneration and Dysfunction Are Reversed by Reactivation of Wnt Signaling

Synapse degeneration in the striatum has been associated with the early stages of Parkinson’s and Huntington’s diseases (PD and HD). However, the molecular mechanisms that trigger synaptic dysfunction and loss are not fully understood. Increasing evidence suggests that deficiency in Wnt signaling triggers synapse degeneration in the adult brain and that this pathway is affected in neurodegenerative diseases. Here, we demonstrate that endogenous Wnt signaling is essential for the integrity of a subset of inhibitory synapses on striatal medium spiny neurons (MSNs). We found that inducible expression of the specific Wnt antagonist Dickkopf-1 (Dkk1) in the adult striatum leads to the loss of inhibitory synapses on MSNs and affects the synaptic transmission of D2-MSNs. We also discovered that re-activation of the Wnt pathway by turning off Dkk1 expression after substantial loss of synapses resulted in the complete recovery of GABAergic and dopamine synapse number. Our results also show that re-activation of the Wnt pathway leads to a recovery of amphetamine response and motor function. Our studies identify the Wnt signaling pathway as a potential therapeutic target for restoring neuronal circuits after synapse degeneration.

Prognostic value of dickkopf-1 and ß-catenin expression according to the antitumor immunity of CD8-positive tumor-infiltrating lymphocytes in biliary tract cancer.

e16172 Background: Despite recent advancements in the understanding of the molecular biology of biliary tract cancer (BTC), target therapy and immunotherapy have demonstrated only limited efficacy, with cytotoxic systemic therapy still being the most effective treatment in BTC, except for surgery. Thus, this study aimed to analyze the role of DKK1 or β-catenin as a prognostic factor in BTC and determine the clinical association of ß-catenin and DKK1 with CD8+ tumor-infiltrating lymphocyte (TIL). Methods: We used data in The Cancer Genome Atlas (TCGA) Research Network and the clinicopathological data of 145 patients with BTC who had undergone primary radical resection between 2006 and 2016. Immunohistochemistry was performed on formalin-fixed, paraffin-embedded tissue sections, and whole tissue sections of representative tumor samples were used for antigen retrieval. Results: CD8+TIL expression was a significant predictor of favorable overall survival (OS) and recurrence-free survival (RFS) (median OS, 34.9months in TIL-high, 16.7months in TIL-low, P < 0.0001 respectively; median RFS, 27.1months in TIL-high, 10months in TIL-low, P < 0.0001 respectively). Positive ß-catenin expression and high DKK1 expression was also associated with a shorter OS (median OS, 23.95months in positive ß-catenin, 26.1months in negative ß-catenin, P = 0.1009 respectively; median OS, 19.4months in high DKK1, 31.65months in Low DKK1, P = 0.0093 respectively), but not RFS (p = 0.1466, at ß-catenin respectively; p = 0.2924, in DKK1 respectively). In the CD8+TIL-high BTC group, the tumor expression of β-catenin and DKK1 had a significant negative impact on either OS or RFS (p = 0.0146 and p = 0.0112, at ß-catenin respectively; p = 0.0950 and p = 0.3904, in DKK1 respectively). However, in the TIL-low BTC group, there were no differences in OS or RFS according to ß-catenin and DKK1 expression (p = 0.5108 and p = 0.8431, at ß-catenin respectively; p = 0.1127 and p = 0.1095, in DKK1 respectively). Cox regression multivariate analysis demonstrated that CD8+ TIL (hazard ratio [HR], 0.490; 95% confidence interval (CI), 0.303-0.791; p = 0.004) and β-catenin (HR, 1.652; 95% CI, 1.035-2.639; p = 0.036) retained significant association with OS after adjustment for all variables. Conclusions: Among patients with resected BTC, β-catenin and DKK1 protein levels are associated with poor clinical outcomes, whereas high CD8+ TIL levels are associated with good clinical outcomes. This confirms the differential clinical role of Wnt/β-catenin and DKK1 proteins according to TIL expression in BTC.

FOXC1 Negatively Regulates DKK1 Expression to Promote Gastric Cancer Cell Proliferation Through Activation of Wnt Signaling Pathway

Gastric cancer (GC), characterized by uncontrolled growth, is a common malignant tumor of the digestive system. The Wnt signaling pathway plays an important role in the tumorigenesis and proliferation of GC. Many studies on this signaling pathway have focused on its intracellular regulatory mechanism, whereas little attention has been given to extracellular regulatory factors. Dickkopf-1 (Dkk1) is a secretory glycoprotein, and it can bind inhibit activation of the Wnt pathway. However, the regulation and mechanism of DKK1 in the proliferation of GC remain unclear. FOXC1 plays an important role in organ development and tumor growth, but its role in GC tumor growth remains unknown. In this study, we found that the FOXC1 is highly expressed in patients with GC and high expression of FOXC1 correlates to poor prognosis. In addition, we found that the Wnt signaling pathway in GC cells with high FOXC1 expression was strongly activated. FOXC1 negatively regulates DKK1 expression by binding to its promoter region, thereby promoting the activation of Wnt pathway. FOXC1 can also form a complex with unphosphorylated β-catenin protein in the cytoplasm and then dissociates from β-catenin in the nucleus, thereby promoting the entry of β-catenin into the nucleus and regulating expression of c-MYC, which promotes the proliferation of GC cells. Our study not only reveals the function and mechanism of FOXC1 in GC, but also provides a potential target for clinic GC treatment.

Dickkopf 1 impairs the tumor response to PD-1 blockade by inactivating CD8+ T cells in deficient mismatch repair colorectal cancer

BackgroundDickkopf 1 (DKK1) is associated with tumor progression. However, whether DKK1 influences the tumor response to programmed cell death protein 1 (PD-1) blockade in colorectal cancers (CRCs) with deficient mismatch repair (dMMR) or microsatellite instability (MSI) has never been clarified.MethodsTumor tissues from 80 patients with dMMR CRC were evaluated for DKK1 expression and immune status via immunohistochemistry. Serum DKK1 was measured in another set of 43 patients who received PD-1 blockade therapy. CT26 cells and dMMR CRC organoids were cocultured with T cells, and CT26-grafted BALB/c mice were also constructed. T-cell cytotoxicity was assessed by apoptosis assays and flow cytometry. The pathway through which DKK1 regulates CD8+ T cells was investigated using RNA sequencing, and chromatin immunoprecipitation and luciferase reporter assays were conducted to determine the downstream transcription factors of DKK1.ResultsElevated DKK1 expression was associated with recurrence and decreased CD8+ T-cell infiltration in dMMR CRCs, and patients with high-serum DKK1 had a poor response to PD-1 blockade. RNA interference or neutralization of DKK1 in CRC cells enhanced CD8+ T-cell cytotoxicity, while DKK1 decreased T-bet expression and activated GSK3β in CD8+ T cells. In addition, E2F1, a downstream transcription factor of GSK3β, directly upregulated T-bet expression. In organoid models, the proportion of apoptotic cells was elevated after individual neutralization of PD-1 or DKK1 and was further increased on combined neutralization of PD-1 and DKK1.ConclusionsDKK1 suppressed the antitumor immune reaction through the GSK3β/E2F1/T-bet axis in CD8+ T cells. Elevated serum DKK1 predicted poor tumor response to PD-1 blockade in dMMR/MSI CRCs, and DKK1 neutralization may restore sensitivity to PD-1 blockade.