Dickkopf-3 (Dkk3) induces apoptosis in cisplatin-resistant lung adenocarcinoma cells via the Wnt/β-catenin pathway

Study on the role of MYCN in retinoblastoma by inhibiting p53 and activating wnt/βcatenin/Fra-1 signaling pathway by reducing DKK3

Retinoblastoma (RB) is a pediatric malignancy, typically diagnosed at birth or during early childhood. The pathogenesis of RB is marked by the amplification of the Basic Helix-Loop-Helix (BHLH) Transcription Factor MYCN, which serves as a transcriptional regulator capable of binding to Dickkopf 3 (DKK3). However, the precise role of DKK3 in the malignant progression of RB cells caused by MYCN remains elusive. In the present study, the expression of MYCN was either overexpressed or interfered in RB cells. Subsequently, the expression level of DKK3 was assessed through quantitative real-time polymerase chain reaction and western blot analysis. Cell proliferation was evaluated using the Cell Counting Kit-8 assay and 5-ethynyl-2'-deoxyuridine staining, while cell cycle progression and apoptosis were analyzed by flow cytometry and western blot analysis, respectively. Additionally, the expression of proteins involved in the Wnt/β-catenin/Fra-1/p53 signaling pathway was evaluated via western blot analysis. To gain further insights, Wnt agonists and the P53 inhibitor PFT-α were introduced into exploration. The current investigation revealed a negative correlation between the expression levels of MYCN and DKK3 in RB cells. Additionally, DKK3 overexpression inhibited cell proliferation, promoted cell apoptosis, and arrested cell cycle in RB cells with high expression of MYCN. Moreover, enhanced DKK3 expression inhibited proliferation, promoted cell cycle arrest and apoptosis of RB cells by modulating the wnt/βcatenin/Fra-1/p53 signaling pathway. Furthermore, in vivo experiments revealed that overexpression of DKK3 inhibits the growth of RB tumors. Collectively, our findings elucidate that MYCN stimulates the Wnt/β-catenin/Fra-1 pathway by suppressing DKK3 expression, ultimately suppressing p53 activity and contributing to malignant progression of RB.

Role of Wnt/β-catenin pathway in cancer drug resistance: Insights into molecular aspects of major solid tumors

Adaptive resistance to conventional and targeted therapies remains one of the major obstacles in the effective management of cancer. Aberrant activation of key signaling mechanisms plays a pivotal role in modulating resistance to drugs. An evolutionarily conserved Wnt/β-catenin pathway is one of the signaling cascades which regulate resistance to drugs. Elevated Wnt signaling confers resistance to anticancer therapies, either through direct activation of its target genes or via indirect mechanisms and crosstalk over other signaling pathways. Involvement of the Wnt/β-catenin pathway in cancer hallmarks like inhibition of apoptosis, promotion of invasion and metastasis and cancer stem cell maintenance makes this pathway a potential target to exploit for addressing drug resistance. Accumulating evidences suggest a critical role of Wnt/β-catenin pathway in imparting resistance across multiple cancers including PDAC, NSCLC, TNBC, etc. Here we present a comprehensive assessment of how Wnt/β-catenin pathway mediates cancer drug resistance in majority of the solid tumors. We take a deep dive into the Wnt/β-catenin signaling-mediated modulation of cellular and downstream molecular mechanisms and their impact on cancer resistance.

Role of microRNA-363 during tumor progression and invasion

Recent progresses in diagnostic and therapeutic methods have significantly improved prognosis in cancer patients. However, cancer is still considered as one of the main causes of human deaths in the world. Late diagnosis in advanced tumor stages can reduce the effectiveness of treatment methods and increase mortality rate of cancer patients. Therefore, investigating the molecular mechanisms of tumor progression can help to introduce the early diagnostic markers in these patients. MicroRNA (miRNAs) has an important role in regulation of pathophysiological cellular processes. Due to their high stability in body fluids, they are always used as the non-invasive markers in cancer patients. Since, miR-363 deregulation has been reported in a wide range of cancers, we discussed the role of miR-363 during tumor progression and metastasis. It has been reported that miR-363 has mainly a tumor suppressor function through the regulation of transcription factors, apoptosis, cell cycle, and structural proteins. MiR-363 also affected the tumor progression via regulation of various signaling pathways such as WNT, MAPK, TGF-β, NOTCH, and PI3K/AKT. Therefore, miR-363 can be introduced as a probable therapeutic target as well as a non-invasive diagnostic marker in cancer patients.

The Multifaceted Role of Human Dickkopf-3 (DKK-3) in Development, Immune Modulation and Cancer

The human Dickkopf (DKK) family includes four main secreted proteins, DKK-1, DKK-2, DKK-3, and DKK-4, as well as the DKK-3 related protein soggy (Sgy-1 or DKKL1). These glycoproteins play crucial roles in various biological processes, and especially modulation of the Wnt signaling pathway. DKK-3 is distinct, with its multifaceted roles in development, stem cell differentiation and tissue homeostasis. Intriguingly, DKK-3 appears to have immunomodulatory functions and a complex role in cancer, acting as either a tumor suppressor or an oncogene, depending on the context. DKK-3 is a promising diagnostic and therapeutic target that can be modulated by epigenetic reactivation, gene therapy and DKK-3-blocking agents. However, further research is needed to optimize DKK-3-based therapies. In this review, we comprehensively describe the known functions of DKK-3 and highlight the importance of context in understanding and exploiting its roles in health and disease.

Apogossypolone Inhibits Cell Proliferation and Epithelial-Mesenchymal Transition in Cervical Cancer via Activating DKK3

Apogossypolone (ApoG2), a novel derivative of gossypol lacking of two aldehyde groups, exhibits anti-tumor effects. However, the mechanisms by which ApoG2 regulates cervical cancer (CC) cells remain unclear. In this study, we treated two CC cell lines (CaSki and HeLa) with an increasing concentration of ApoG2 for 24 h. Cell Counting Kit-8 (CCK-8) assay, colony formation assay, flow cytometry and transwell invasion assay were utilized to detect cell proliferation, apoptosis and invasion in vitro. We first observed that ApoG2 inhibited cell proliferation, invasion and epithelial-to-mesenchymal transition (EMT) process in CC cells, along with upregulation of Dickkopf Wnt signaling pathway inhibitor 3 (DKK3) in a dose-dependent manner. The immunohistochemistry confirmed the downregulation of DKK3 in tumor tissues. Moreover, DKK3 was correlated with FIGO stage and lymph node metastasis. Functionally, DKK3 overexpression significantly suppressed cell viability, colony formation and invasion, but promoted apoptosis in CaSki and HeLa cells. Overexpression of DKK3 upregulated the protein levels of cleaved caspase-3 and E-cadherin, but downregulated the protein levels of Bcl-2, N-cadherin and Vimentin. Furthermore, DKK3 knockdown reversed the suppressive effects of ApoG2 on CaSki cell proliferation, invasion and EMT markers, while DKK3 overexpression enhanced these effects. In addition, ApoG2 treatment inhibited CC xenograft tumor growth and upregulated the protein levels of DKK3, cleaved caspase-3 and E-cadherin. In conclusions, these findings suggested that ApoG2 could effectively inhibit the growth and invasion of CC cells at least partly by activating DKK3.

MiR-363-3p promotes prostate cancer tumor progression by targeting Dickkopf 3

BACKGROUND

Prostate cancer (PCa) is a frequent malignant tumor worldwide with high morbidity along with mortality. MicroRNAs (miRNAs) have been identified as key posttranscriptional modulators in diverse cancers. Herein, we purposed to explore the impacts of miR-363-3p on PCa growth, migration, infiltration along with apoptosis.

METHODS

The expressions of miR-363-3p along with Dickkopf 3 (DKK3) were assessed in clinical PCa specimens. We adopted the PCa cell line PC3 and transfected it using miR-363-3p repressors or mimic. The relationship of miR-363-3p with DKK3 was verified by a luciferase enzyme reporter assay. Cell viability along with apoptosis were determined by MTT assay coupled with flow cytometry analysis. Cell migration along infiltration were detected via wound healing, as well as Transwell assays. The contents of DKK3, E-cadherin, vimentin along with N-cadherin were analyzed via Western blotting accompanied with qRT-PCR.

RESULTS

MiR-363-3p was found to be inversely associated with the content of DKK3 in clinical PCa specimens. Further investigations revealed that DKK3 was miR-363-3p's direct target. Besides, overexpression of miR-363-3p decreased the contents of DKK3, promoted cell viability, migration coupled with infiltration, and reduced cell apoptosis, while silencing of miR-363-3p resulted in opposite influence. Upregulation of miR-363-3p diminished E-cadherin contents but increased vimentin along with N-cadherin protein contents in PC3 cells; in contrast, miR-363-3p downregulation produced the opposite result.

CONCLUSION

Our study indicates that miR-363-3p promotes PCa growth, migration coupled with invasion while dampening apoptosis by targeting DKK3.

GSK-3 Inhibition Modulates Metalloproteases in a Model of Lung Inflammation and Fibrosis

Idiopathic pulmonary fibrosis (IPF) is mainly characterized by aberrant extracellular matrix deposition, consequent to epithelial lung injury and myofibroblast activation, and inflammatory response. Glycogen synthase kinase 3 (GSK-3) is a serine-threonine kinase involved in several pathways, and its inhibition has been already suggested as a therapeutic strategy for IPF patients. There is evidence that GSK-3 is able to induce matrix metalloproteinase (MMP) expression and that its inhibition modulates MMP expression in the tissues. The aim of our study was to investigate the role of GSK-3 and its inhibition in the modulation of MMP-9 and -2 in an in vivo mouse model of lung fibrosis and in vitro using different cell lines exposed to pro-inflammatory or pro-fibrotic stimuli. We found that GSK-3 inhibition down-modulates gene expression and protein levels of MMP-9, MMP-2, and their inhibitors TIMP-1 and TIMP-2 in inflammatory cells harvested from bronchoalveolar lavage fluid (BALF) of mice treated with bleomycin as well as in interstitial alveolar macrophages and cuboidalized epithelial alveolar cells. To the same extent, GSK-3 inhibition blunted the increased MMP-9 and MMP-2 activity induced by pro-fibrotic stimuli in a human lung fibroblast cell line. Moreover, the αSMA protein level, a marker of fibroblast-to-myofibroblast transition involved in fibrosis, was decreased in primary fibroblasts treated with TGFβ following GSK-3 inhibition. Our results confirm the implication of GSK-3 in lung inflammation and fibrosis, suggesting that it might play its role by modulating MMP expression and activity but also pushing fibroblasts toward a myofibroblast phenotype and therefore enhancing extracellular matrix deposition. Thus, its inhibition could represent a possible therapeutic strategy.

Emerging strategies for sensitization of therapy resistant tumors toward cancer therapeutics by targeting the Bcl-2 family, TGF-β, Wnt/β-Catenin, RASSF and miRNA regulated signaling pathways

Conventional chemotherapy relies on the cytotoxicity of chemo-drugs to inflict destructive effects on tumor cells. However, as most tumor cells develop resistance to chemo-drugs, small doses of chemo-drugs are unlikely to provide significant clinical benefits in cancer treatment while high doses of chemo-drugs have been shown to impact normal human cells negatively due to the non-specific nature and cytotoxicity associated with chemo-drugs. To overcome this challenge, sensitizations of tumor cells with bioactive molecules that specifically target the pro-survival and pro-apoptosis signaling pathways of the tumor cells are likely to increase the therapeutic impacts and improve the clinical outcomes by reducing the dependency and adverse effects associated with using high doses of chemo-drugs in cancer treatment. This review focuses on emerging strategies to enhance the sensitization of tumor cells toward cancer therapies based on our understanding of tumor cell biology and underlying signaling pathways.

Integrated Proteomic and Phosphoproteomics Analysis of DKK3 Signaling Reveals Activated Kinase in the Most Aggressive Gallbladder Cancer

DKK3 is a secreted protein, which belongs to a family of Wnt antagonists and acts as a potential tumor suppressor in gallbladder cancer. To further understand its tumor suppressor functions, we overexpressed DKK3 in 3 GBC cell lines. We have employed high-resolution mass spectrometry and tandem mass tag (TMT) multiplexing technology along with immobilized metal affinity chromatography to enrich phosphopeptides to check the downstream regulators. In this study, we reported for the first time the alteration in the phosphorylation of 14 kinases upon DKK3 overexpression. In addition, we observed DKK3 induced hyper phosphorylation of 2 phosphatases: PPP1R12A and PTPRA, which have not been reported previously. Canonical pathway analysis of altered molecules indicated differential enrichment of signaling cascades upon DKK3 overexpression in all the 3 cell lines. Protein kinase A signaling, Sirtuin signaling pathway, and Cell Cycle Control of Chromosomal Replication were observed to be differentially activated in the GBC cell lines. Our study revealed, DKK3 overexpression has differential effect based on the aggressive behavior of the cell lines. This study expands the understanding of DKK3-mediated signaling events and can be used as a primary factor for understanding the complex nature of this molecule.

Screening and Identifying Cisplatin-Related Gene Mutations in Lung Squamous Cell Carcinoma

Introduction

Platinum-based chemotherapy is the cornerstone of treatment for patients with LUSC, but cisplatin resistance greatly restricts its clinical application. Therefore, it is particularly important to screen the predominant LUSC population using biomarkers.

Methods

Data for 15 LUSC cell lines were downloaded from the Genomics of Drug Sensitivity in Cancer (GDSC) Project database to screen for mutations related to cisplatin susceptibility. We conducted whole-exome sequencing (WES) of tumors from 58 LUSC patients from Sichuan Provincial People’s Hospital of University of Electronic Science and Technology. Subsequently, the clinical prognostic value of these mutations was verified by using The Cancer Genome Atlas (TCGA)-LUSC cohort and our cohort (n=58).

Results

Based on the cisplatin sensitivity data of GDSC-LUSC and survival analysis of TCGA-LUSC and Local-LUSC cohorts, we found that only mutation of IGF2R was associated with cisplatin sensitivity, better overall survival [OS; P=0.04, HR (95% CI): 0.42 (0.23–0.78)] and progression-free survival [PFS; P =0.016, HR (95% CI): 0.26 (0.12–0.59)]. However, there were no significant differences in the frequencies of gene mutations between the IGF2R-mutant (IGF2R-MT) and IGF2R-wild-type (IGF2R-WT) groups. Gene set enrichment analysis (GSEA) and single-sample GSEA (ssGSEA) indicated enhanced intracellular detoxification and decreased abnormal signaling activity to reverse cisplatin tolerance in the IGF2R-MT group.

Conclusion

The results suggest that IGF2R mutations are a potential biomarker for screening LUSC patients suitable for cisplatin treatment.

miR-1303 promotes the proliferation, migration and invasion of prostate cancer cells through regulating the Wnt/β-catenin pathway by targeting DKK3

MicroRNA-1303 (miR-1303) is involved in the tumorigenesis and progression of several cancers, and yet the role of miR-1303 in prostate cancer (PCa) and its underlying mechanism are unknown. To explore this issue, the present study aimed to use PCa tissues, cell lines and a PCa-engrafted mouse model to determine the expression and roles of miR-1303 in PCa. Furthermore, a series of experiments were conducted to explore the underlying mechanisms of action of miR-1303 in PCa cells. miR-1303 was demonstrated to be highly expressed in PCa tissues and cell lines. The level of miR-1303 expression was closely associated with higher Gleason scores and a more developed tumor stage in patients with PCa, and patients with higher levels of miR-1303 displayed a reduced overall survival rate. miR-1303 overexpression promoted the proliferation, migration and invasion of PCa cells. In vivo experiments showed that miR-1303 inhibition suppressed the growth of PCa tumors in mice. Additionally, dickkopf Wnt signaling pathway inhibitor 3 (DKK3) was identified as a target of miR-1303. Knockdown of miR-1303 suppressed the proliferation, migration and invasion of PCa cells, increased DKK3 expression, and inhibited the activity of the Wnt/β-catenin pathway. In conclusion, miR-1303 may promote proliferation, migration and invasion of PCa cells through activating the Wnt/β-catenin pathway by regulating DKK3 expression. These results indicated that miR-1303 may be considered as a potential biomarker for PCa treatment.

Negative regulators of Wnt signaling in non-small cell lung cancer: Theoretical basis and therapeutic potency

Significant advances in the treatment of non-small cell lung cancer (NSCLC) have been made over the past decade, and they predominantly involve molecular targets such as epidermal growth factor receptor (EGFR) mutations and anaplastic lymphoma kinase (ALK) rearrangements. However, despite the initial good response, drug resistance eventually develops. The Wnt signaling pathway has recently been considered important in embryonic development and tumorigenesis in many cancers, particularly NSCLC. Moreover, the aberrant Wnt pathway plays a significant role in NSCLC and is associated with cancer cell proliferation, metastasis, invasion and drug resistance, and the suppression of canonical or noncanonical Wnt signaling through various biological or pharmacological negative regulators has been proven to produce specific anticancer effects. Thus, blocking the Wnt pathway via its negative regulators may overcome the resistance of current treatment methods and lead to new treatment strategies for NSCLC. Therefore, in this review, we summarize recent studies on the role of negative regulators in Wnt signaling in NSCLC and the therapeutic potency of these molecules as agents and targets for NSCLC treatments.

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.

Hypertonic saline attenuates the cytokine-induced pro-inflammatory signature in primary human lung epithelia

Trauma/hemorrhagic shock is a complex physiological phenomenon that leads to dysregulation of many molecular pathways. For over a decade, hypertonic saline (HTS) has been used as an alternative resuscitation fluid in the setting of trauma/hemorrhagic shock. In addition to restoring circulating volume within the vascular space, studies have shown a positive immunomodulatory effect of HTS. Targeted studies have shown that HTS affects the transcription of several pro-inflammatory cytokines by inhibiting the NF-κB-IκB pathway in model cell lines and rats. However, few studies have been undertaken to assess the unbiased effects of HTS on the whole transcriptome. This study was designed to interrogate the global transcriptional responses induced by HTS and provides insight into the underlying molecular mechanisms and pathways affected by HTS. In this study, RNA sequencing was employed to explore early changes in transcriptional response, identify key mediators, signaling pathways, and transcriptional modules that are affected by HTS in the presence of a strong inflammatory stimulus. Our results suggest that primary human small airway lung epithelial cells (SAECS) exposed to HTS in the presence and absence of a strong pro-inflammatory stimulus exhibit very distinct effects on cellular response, where HTS is highly effective in attenuating cytokine-induced pro-inflammatory responses via mechanisms that involve transcriptional regulation of inflammation which is cell type and stimulus specific. HTS is a highly effective anti-inflammatory agent that inhibits the chemotaxis of leucocytes towards a pro-inflammatory gradient and may attenuate the progression of both the innate and adaptive immune response.

Curcumin reduces mitomycin C resistance in breast cancer stem cells by regulating Bcl-2 family-mediated apoptosis

Background

Curcumin, a natural compound derived from the turmeric rhizome Curcuma longa Linn, has anticancer and chemoresistance reduction biological activities. We evaluated the efficacy of curcumin in sensitizing chemotherapy drugs through regulation of Bcl-2-mediated apoptosis in breast cancer stem-like cells (BCSCs).

Methods

Cell survival was measured using MTT assay. Apoptosis-related proteins were observed using western blot analysis. Apoptosis was detected with flow cytometric analysis and by Hoechst 33258 staining. The mitochondrial membrane potential was observed with flow cytometric analysis.

Results

The ability of BCSCs to propagate decreased gradually along the passages and was completely lost at the fifth passage [0.1 μmol/L mitomycin C (MMC) with 5 μmol/L curcumin in MCF-7 and 0.5 μmol/L MMC with 5 μmol/L curcumin in MDA-MB-231 cells]. Curcumin combined with MMC treatment significantly decreased the levels of antiapoptotic Bcl-2 and Bcl-w expression, increased the levels of proapoptotic Bax, Bak, Bad, Bik, and Bim expression, and activated caspase-3 and caspase-9 in MCF-7 BCSCs. In the presence of Bcl-2 siRNA, the apoptosis rate increased by 15% in cells treated with curcumin and MMC. The mitochondrial membrane potential decreased by approximately 20% in MCF-7 BCSCs undergoing the combination treatment of curcumin and MMC. The combination-induced decrease in Bcl-2 was regulated by the presence of the Wnt-specific inhibitor PFK115-584 and PI3k inhibitor LY294002.

Conclusions

Our study indicates that curcumin might represent a novel therapeutic agent for treating breast cancer chemoresistance induced by MMC.

Suppression of miR-708 inhibits the Wnt/β-catenin signaling pathway by activating DKK3 in adult B-all

Inactivation of Dickkopf-3 (DKK3) is closely associated with a poor prognosis in various solid tumor and hematologic malignancies. Promoter hypermethylation is one potential cause of DKK3 inactivation. However, whether other mechanisms lead to DKK3 inactivation and the subsequent effects of these inactivations on cell proliferation and the Wnt signaling pathway in adult B acute lymphoblastic leukemia (B-ALL) remain unclear. In the present study, we found that low DKK3 expression levels were associated with high miR-708 expression and promoter hypermethylation in adult B-ALL. miR-708 was confirmed to directly decrease DKK3 expression in Nalm-6 and BALL-1 cells. Additionally, a miR-708 inhibitor decreased cell proliferation mainly through apoptosis and cell cycle arrest at the G1 phase, and these effects were eliminated by DKK3 siRNA treatment. Moreover, the demethylating agent 5-aza-2'-deoxycytidine (5-aza) decreased the methylation state of the DKK3 promoter based on methylation-specific PCR (MSP) and bisulfite genomic sequencing PCR (BSP), although this demethylation effect was not enhanced by the miR-708 inhibitor. The miR-708 inhibitor or 5-aza significantly increased DKK3 expression and decreased p-GSK3β, cyclin D1 and nuclear and cytoplasmic β-catenin protein expression, indicating that the Wnt/β-catenin signaling pathway was inhibited. These effects became more pronounced when the miR-708 inhibitor and 5-aza were used simultaneously. These findings provide greater insights into the mechanisms that increase DKK3 expression and suggest that a miR-708 inhibitor and 5-aza might be useful as targeted therapies for adult B-ALL.

Differentially expressed genes and gene networks involved in pig ovarian follicular atresia

Ovarian folliculogenesis corresponds to the development of follicles leading to either ovulation or degeneration, this latter process being called atresia. Even if atresia involves apoptosis, its mechanism is not well understood. The objective of this study was to analyze global gene expression in pig granulosa cells of ovarian follicles during atresia. The transcriptome analysis was performed on a 9,216 cDNA microarray to identify gene networks and candidate genes involved in pig ovarian follicular atresia. We found 1,684 significantly regulated genes to be differentially regulated between small healthy follicles and small atretic follicles. Among them, 287 genes had a fold-change higher than two between the two follicle groups. Eleven genes ( DKK3, GADD45A, CAMTA2, CCDC80, DAPK2, ECSIT, MSMB, NUPR1, RUNX2, SAMD4A, and ZNF628) having a fold-change higher than five between groups could likely serve as markers of follicular atresia. Moreover, automatic confrontation of deregulated genes with literature data highlighted 93 genes as regulatory candidates of pig granulosa cell atresia. Among these genes known to be inhibitors of apoptosis, stimulators of apoptosis, or tumor suppressors INHBB, HNF4, CLU, different interleukins ( IL5, IL24), TNF-associated receptor ( TNFR1), and cytochrome-c oxidase ( COX) were suggested as playing an important role in porcine atresia. The present study also enlists key upstream regulators in follicle atresia based on our results and on a literature review. The novel gene candidates and gene networks identified in the current study lead to a better understanding of the molecular regulation of ovarian follicular atresia.

Dickkopf-3 is upregulated in osteoarthritis and has a chondroprotective role

OBJECTIVE

Dickkopf-3 (Dkk3) is a non-canonical member of the Dkk family of Wnt antagonists and its upregulation has been reported in microarray analysis of cartilage from mouse models of osteoarthritis (OA). In this study we assessed Dkk3 expression in human OA cartilage to ascertain its potential role in chondrocyte signaling and cartilage maintenance.

METHODS

Dkk3 expression was analysed in human adult OA cartilage and synovial tissues and during chondrogenesis of ATDC5 and human mesenchymal stem cells. The role of Dkk3 in cartilage maintenance was analysed by incubation of bovine and human cartilage explants with interleukin-1β (IL1β) and oncostatin-M (OSM). Dkk3 gene expression was measured in cartilage following murine hip avulsion. Whether Dkk3 influenced Wnt, TGFβ and activin cell signaling was assessed in primary human chondrocytes and SW1353 chondrosarcoma cells using qRT-PCR and luminescence assays.

RESULTS

Increased gene and protein levels of Dkk3 were detected in human OA cartilage, synovial tissue and synovial fluid. DKK3 gene expression was decreased during chondrogenesis of both ATDC5 cells and humans MSCs. Dkk3 inhibited IL1β and OSM-mediated proteoglycan loss from human and bovine cartilage explants and collagen loss from bovine cartilage explants. Cartilage DKK3 expression was decreased following hip avulsion injury. TGFβ signaling was enhanced by Dkk3 whilst Wnt3a and activin signaling were inhibited.

CONCLUSIONS

We provide evidence that Dkk3 is upregulated in OA and may have a protective effect on cartilage integrity by preventing proteoglycan loss and helping to restore OA-relevant signaling pathway activity. Targeting Dkk3 may be a novel approach in the treatment of OA.

Wnt activation protects against neomycin-induced hair cell damage in the mouse cochlea

Recent studies have reported the role of Wnt/β-catenin signaling in hair cell (HC) development, regeneration, and differentiation in the mouse cochlea; however, the role of Wnt/β-catenin signaling in HC protection remains unknown. In this study, we took advantage of transgenic mice to specifically knockout or overactivate the canonical Wnt signaling mediator β-catenin in HCs, which allowed us to investigate the role of Wnt/β-catenin signaling in protecting HCs against neomycin-induced damage. We first showed that loss of β-catenin in HCs made them more vulnerable to neomycin-induced injury, while constitutive activation of β-catenin in HCs reduced HC loss both in vivo and in vitro. We then showed that loss of β-catenin in HCs increased caspase-mediated apoptosis induced by neomycin injury, while β-catenin overexpression inhibited caspase-mediated apoptosis. Finally, we demonstrated that loss of β-catenin in HCs led to increased expression of forkhead box O3 transcription factor (Foxo3) and Bim along with decreased expression of antioxidant enzymes; thus, there were increased levels of reactive oxygen species (ROS) after neomycin treatment that might be responsible for the increased aminoglycoside sensitivity of HCs. In contrast, β-catenin overexpression reduced Foxo3 and Bim expression and ROS levels, suggesting that β-catenin is protective against neomycin-induced HC loss. Our findings demonstrate that Wnt/β-catenin signaling has an important role in protecting HCs against neomycin-induced HC loss and thus might be a new therapeutic target for the prevention of HC death.