The evolution of metazoan shelterin.

The mammalian telomeric shelterin complex-comprised of TRF1, TRF2, Rap1, TIN2, TPP1, and POT1-blocks the DNA damage response at chromosome ends and interacts with telomerase and the CST complex to regulate telomere length. The evolutionary origins of shelterin are unclear, partly because unicellular organisms have distinct telomeric proteins. Here, we describe the evolution of metazoan shelterin, showing that TRF1 emerged in vertebrates upon duplication of a TRF2-like ancestor. TRF1 and TRF2 diverged rapidly during vertebrate evolution through the acquisition of new domains and interacting factors. Vertebrate shelterin is also distinguished by the presence of an HJRL domain in the split C-terminal OB fold of POT1, whereas invertebrate POT1s carry inserts of variable nature. Importantly, the data reveal that, apart from the primate and rodent POT1 orthologs, all metazoan POT1s are predicted to have a fourth OB fold at their N termini. Therefore, we propose that POT1 arose from a four-OB-fold ancestor, most likely an RPA70-like protein. This analysis provides insights into the biology of shelterin and its evolution from ancestral telomeric DNA-binding proteins.

FANCJ DNA helicase is recruited to the replisome by AND-1 to ensure genome stability.

FANCJ, a DNA helicase linked to Fanconi anemia and frequently mutated in cancers, counteracts replication stress by dismantling unconventional DNA secondary structures (such as G-quadruplexes) that occur at the DNA replication fork in certain sequence contexts. However, how FANCJ is recruited to the replisome is unknown. Here, we report that FANCJ directly binds to AND-1 (the vertebrate ortholog of budding yeast Ctf4), a homo-trimeric protein adaptor that connects the CDC45/MCM2-7/GINS replicative DNA helicase with DNA polymerase α and several other factors at DNA replication forks. The interaction between FANCJ and AND-1 requires the integrity of an evolutionarily conserved Ctf4-interacting protein (CIP) box located between the FANCJ helicase motifs IV and V. Disruption of the CIP box significantly reduces FANCJ association with the replisome, causing enhanced DNA damage, decreased replication fork recovery and fork asymmetry in cells unchallenged or treated with Pyridostatin, a G-quadruplex-binder, or Mitomycin C, a DNA inter-strand cross-linking agent. Cancer-relevant FANCJ CIP box variants display reduced AND-1-binding and enhanced DNA damage, a finding that suggests their potential role in cancer predisposition.

TDP-43 mediated blood-brain barrier permeability and leukocyte infiltration promote neurodegeneration in a low-grade systemic inflammation mouse model.

BACKGROUND: Neuronal cytoplasmic inclusions containing TAR DNA-binding protein 43 (TDP-43) are a neuropathological feature of several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and Alzheimer's Disease (AD). Emerging evidence also indicates that systemic inflammation may be a contributor to the pathology progression of these neurodegenerative diseases. METHODS: To investigate the role of systemic inflammation in the progression of neuronal TDP-43 pathology, AAV9 particles driven by the UCHL1 promoter were delivered to the frontal cortex of wild-type aged mice via intracranial injections to overexpress TDP-43 or green fluorescent protein (GFP) in corticospinal motor neurons. Animals were then subjected to a low-dose (500 µg/kg) intraperitoneal E. coli lipopolysaccharide (LPS) administration challenge for 2 weeks to mimic a chronically altered low-grade systemic inflammatory state. Mice were then subjected to neurobehavioral studies, followed by biochemical and immunohistochemical analyses of the brain tissue. RESULTS: In the present study, we report that elevated neuronal TDP-43 levels induced microglial and astrocytic activation in the cortex of injected mice followed by increased RANTES signaling. Moreover, overexpression of TDP-43 exerted abundant mouse immunoglobulin G (IgG), CD3, and CD4+ T cell infiltration as well as endothelial and pericyte activation suggesting increased blood-brain barrier permeability. The BBB permeability in TDP-43 overexpressing brains yielded the frontal cortex vulnerable to the systemic inflammatory response following LPS treatment, leading to marked neutrophil infiltration, neuronal loss, reduced synaptosome-associated protein 25 (SNAP-25) levels, and behavioral impairments in the radial arm water maze (RAWM) task. CONCLUSIONS: These results reveal a novel role for TDP-43 in BBB permeability and leukocyte recruitment, indicating complex intermolecular interactions between an altered systemic inflammatory state and pathologically prone TDP-43 protein to promote disease progression.

Resonant Inelastic X-Ray Scattering Reveals Hidden Local Transitions of the Aqueous OH Radical.

Resonant inelastic x-ray scattering (RIXS) provides remarkable opportunities to interrogate ultrafast dynamics in liquids. Here we use RIXS to study the fundamentally and practically important hydroxyl radical in liquid water, OH(aq). Impulsive ionization of pure liquid water produced a short-lived population of OH(aq), which was probed using femtosecond x-rays from an x-ray free-electron laser. We find that RIXS reveals localized electronic transitions that are masked in the ultraviolet absorption spectrum by strong charge-transfer transitions-thus providing a means to investigate the evolving electronic structure and reactivity of the hydroxyl radical in aqueous and heterogeneous environments. First-principles calculations provide interpretation of the main spectral features.

Differential escape mechanisms in cetuximab-resistant head and neck cancer cells.

Acquired cetuximab resistance is a challenge for oncologists treating advanced head and neck carcinoma (HNC). While intrinsic cetuximab resistance mechanism in colorectal cancer is known, resistance in HNC is unclear. We established two different cetuximab resistant HNC cell lines by culturing epidermal growth factor (EGFR) expressing UM-SCC-1 and UM-SCC-6 cell lines in the presence of 5 µg/ml cetuximab. We then explored potential mechanisms of resistance. We found that the 2 cell lines developed resistance by different mechanisms. Specifically, we found that UM-SCC-1 resistant cells (UM-SCC-1R) showed enhanced EGF-induced downstream signals while UM-SCC-6 resistant cells (UM-SCC-6R) demonstrated EGF-independent signaling. Global kinase activity (kinomic) profiling revealed unique signaling differences in the two resistant cell lines. However, both of the resistant lines demonstrated increased phospho-serine 727 and total STAT3 expression compared to the parental lines. STAT3 knockdown promoted increased cytotoxicity both in the presence and absence of cetuximab in the resistant lines suggesting that STAT3 may be a common target in cetuximab resistance.

NO2 gas sensing performance enhancement based on reduced graphene oxide decorated V2O5 thin films.

Here, we demonstrate improved NO2 gas sensing properties based on reduced graphene oxide (rGO) decorated V2O5 thin film. Excluding the DC sputtering grown V2O5 thin film, rGO was spread over V2O5 thin film by the drop cast method. The formation of several p-n heterojunctions was greatly affected by the current-voltage relation of the rGO-decorated V2O5 thin film due to the p-type and n-type nature of rGO and V2O5, respectively. Initially with rGO decoration on V2O5 thin film, current decreased in comparison to the pristine V2O5 thin film, whereas depositing rGO film on a glass substrate drastically increased current. Among all sensors, only the rGO-decorated V2O5 sensor revealed a maximum NO2 gas sensing response for 100 ppm at 150 °C, and it achieved an approximately 61% higher response than the V2O5 sensor. The elaborate mechanism for an extremely high sensing response is attributed to the formation and modulation of p-n heterojunctions at the interface of rGO and V2O5. In addition, the presence of active sites like oxygenous functional groups on the rGO surface enhanced the sensing response. On that account, sensors based on rGO-decorated V2O5 thin film are highly suitable for the purpose of NO2 gas sensing. They enable the timely detection of the gas, further protecting the ecosystem from its harmful effects.

Drug interactions between rifamycin antibiotics and hormonal contraception: a systematic review.

BACKGROUND: Rifamycin antibiotics are commonly used for treatment of tuberculosis, but may reduce the effectiveness of hormonal contraception (HC). OBJECTIVES: To determine whether interactions between rifamycins and HC result in decreased effectiveness or increased toxicity of either therapy. SEARCH STRATEGY: We searched MEDLINE, Embase, Cochrane and clinicaltrials.gov through May 2017. SELECTION CRITERIA: We included trials, cohort, and case-control studies addressing pregnancy rates, pharmacodynamics or pharmacokinetic (PK) outcomes when HC and rifamycins were administered together versus apart. Of 7291 original records identified, 11 met inclusion criteria after independent review by two authors. DATA COLLECTION AND ANALYSIS: Two authors independently abstracted study details and assessed study quality using the United States Preventive Services Task Force grading system. Findings are reported descriptively. MAIN RESULTS: Studies only addressed combined oral contraceptives (COCs) and none reported pregnancy rates. Quality ranged from good to poor. Rifampin increased the frequency of ovulation in two of four studies, and reduced estrogen and/or progestin exposure in five studies. Rifabutin led to smaller PK changes than rifampin in two studies. In one study each, rifaximin and rifalazil did not alter hormone PK. CONCLUSIONS: No studies evaluated pregnancy risk or non-oral HCs. PK and ovulation outcomes support a clinically concerning drug interaction between COCs and rifampin, and to a lesser extent rifabutin. Data are limited for other rifamycins. TWEETABLE ABSTRACT: Rifampin and rifabutin reduce systemic exposure of oral contraceptives, but no studies have evaluated pregnancy risk.

Low dietary iron intake restrains the intestinal inflammatory response and pathology of enteric infection by food-borne bacterial pathogens.

Orally administrated iron is suspected to increase susceptibility to enteric infections among children in infection endemic regions. Here we investigated the effect of dietary iron on the pathology and local immune responses in intestinal infection models. Mice were held on iron-deficient, normal iron, or high iron diets and after 2 weeks they were orally challenged with the pathogen Citrobacter rodentium. Microbiome analysis by pyrosequencing revealed profound iron- and infection-induced shifts in microbiota composition. Fecal levels of the innate defensive molecules and markers of inflammation lipocalin-2 and calprotectin were not influenced by dietary iron intervention alone, but were markedly lower in mice on the iron-deficient diet after infection. Next, mice on the iron-deficient diet tended to gain more weight and to have a lower grade of colon pathology. Furthermore, survival of the nematode Caenorhabditis elegans infected with Salmonella enterica serovar Typhimurium was prolonged after iron deprivation. Together, these data show that iron limitation restricts disease pathology upon bacterial infection. However, our data also showed decreased intestinal inflammatory responses of mice fed on high iron diets. Thus additionally, our study indicates that the effects of iron on processes at the intestinal host-pathogen interface may highly depend on host iron status, immune status, and gut microbiota composition.

A novel multi-task machine learning classifier for rare disease patterning using cardiac strain imaging data.

To provide accurate predictions, current machine learning-based solutions require large, manually labeled training datasets. We implement persistent homology (PH), a topological tool for studying the pattern of data, to analyze echocardiography-based strain data and differentiate between rare diseases like constrictive pericarditis (CP) and restrictive cardiomyopathy (RCM). Patient population (retrospectively registered) included those presenting with heart failure due to CP (n = 51), RCM (n = 47), and patients without heart failure symptoms (n = 53). Longitudinal, radial, and circumferential strains/strain rates for left ventricular segments were processed into topological feature vectors using Machine learning PH workflow. In differentiating CP and RCM, the PH workflow model had a ROC AUC of 0.94 (Sensitivity = 92%, Specificity = 81%), compared with the GLS model AUC of 0.69 (Sensitivity = 65%, Specificity = 66%). In differentiating between all three conditions, the PH workflow model had an AUC of 0.83 (Sensitivity = 68%, Specificity = 84%), compared with the GLS model AUC of 0.68 (Sensitivity = 52% and Specificity = 76%). By employing persistent homology to differentiate the "pattern" of cardiac deformations, our machine-learning approach provides reasonable accuracy when evaluating small datasets and aids in understanding and visualizing patterns of cardiac imaging data in clinically challenging disease states.

Real-time motion-enabling positron emission tomography of the brain of upright ambulatory humans.

BACKGROUND: Mobile upright PET devices have the potential to enable previously impossible neuroimaging studies. Currently available options are imagers with deep brain coverage that severely limit head/body movements or imagers with upright/motion enabling properties that are limited to only covering the brain surface. METHODS: In this study, we test the feasibility of an upright, motion-compatible brain imager, our Ambulatory Motion-enabling Positron Emission Tomography (AMPET) helmet prototype, for use as a neuroscience tool by replicating a variant of a published PET/fMRI study of the neurocorrelates of human walking. We validate our AMPET prototype by conducting a walking movement paradigm to determine motion tolerance and assess for appropriate task related activity in motor-related brain regions. Human participants (n = 11 patients) performed a walking-in-place task with simultaneous AMPET imaging, receiving a bolus delivery of F18-Fluorodeoxyglucose. RESULTS: Here we validate three pre-determined measure criteria, including brain alignment motion artifact of less than <2 mm and functional neuroimaging outcomes consistent with existing walking movement literature. CONCLUSIONS: The study extends the potential and utility for use of mobile, upright, and motion-tolerant neuroimaging devices in real-world, ecologically-valid paradigms. Our approach accounts for the real-world logistics of an actual human participant study and can be used to inform experimental physicists, engineers and imaging instrumentation developers undertaking similar future studies. The technical advances described herein help set new priorities for facilitating future neuroimaging devices and research of the human brain in health and disease.

Brain imaging plays an important role in understanding how the human brain functions in both health and disease. However, traditional brain scanners often require people to remain still, limiting the study of the brain in motion, and excluding people who cannot remain still. To overcome this, our team developed an imager that moves with a person's head, which uses a suspended ring of lightweight detectors that fit to the head. Using our imager, we were able to obtain clear brain images of people walking in place that showed the expected brain activity patterns during walking. Further development of our imager could enable it to be used to better understand real-world brain function and behavior, enabling enhanced knowledge and treatment of neurological conditions.

RTF2 controls replication repriming and ribonucleotide excision at the replisome.

DNA replication through a challenging genomic landscape is coordinated by the replisome, which must adjust to local conditions to provide appropriate replication speed and respond to lesions that hinder its progression. We have previously shown that proteasome shuttle proteins, DNA Damage Inducible 1 and 2 (DDI1/2), regulate Replication Termination Factor 2 (RTF2) levels at stalled replisomes, allowing fork stabilization and restart. Here, we show that during unperturbed replication, RTF2 regulates replisome localization of RNase H2, a heterotrimeric enzyme that removes RNA from RNA-DNA heteroduplexes. RTF2, like RNase H2, is essential for mammalian development and maintains normal replication speed. However, persistent RTF2 and RNase H2 at stalled replication forks prevent efficient replication restart, which is dependent on PRIM1, the primase component of DNA polymerase α-primase. Our data show a fundamental need for RTF2-dependent regulation of replication-coupled ribonucleotide removal and reveal the existence of PRIM1-mediated direct replication restart in mammalian cells.

Mechanism for the compressive strain induced oscillations in the conductance of carbon nanotubes.

We report on the monotonic increase and the oscillation of electrical conductance in multiwalled carbon nanotubes with compressive strain. Combined experimental and theoretical analyses confirm that the conductance variation with strain is because of the transition from sp^{2} to sp^{3} configurations that are promoted by the interaction of walls in the nanotubes. The intrawall interaction is the reason for the monotonic increase in the conduction, while the oscillations are attributable to interwall interactions. This explains the observed electromechanical oscillation in multiwalled nanotubes and its absence in single-walled nanotubes, thereby resolving a long-standing debate on the interpretation of these results. Moreover, the current carrying capability of nanotubes can be enhanced significantly by controlling applied strains.

Impact of a financial incentive scheme on purchase of fruits and vegetables from unorganised retailers in rural India: a cluster-randomised controlled trial.

Background: Inadequate intake of fruits and vegetables is prevalent in rural areas of India, where around 65% of the population reside. Financial incentives have been shown to increase the purchase of fruits and vegetables in urban supermarkets, but their feasibility and effectiveness with unorganised retailers in rural India is unclear. Methods: A cluster-randomised controlled trial of a financial incentive scheme involving ∼20% cashback on purchase of fruits and vegetables from local retailers was conducted in six villages (3535 households). All households in three intervention villages were invited to participate in the scheme which ran for three months (February-April 2021), while no intervention was offered in control villages. Self-reported (pre-intervention and post-intervention) data on purchase of fruits and vegetables were collected from a random sub-sample of households in control and intervention villages. Findings: A total of 1109 households (88% of those invited) provided data. After the intervention, the weekly quantity of self-reported fruits and vegetables purchased were (i) 18.6 kg (intervention) and 14.2 kg (control), baseline-adjusted mean difference 4 kg (95% CI: -6.4 to 14.4) from any retailer (primary outcome); and (ii) 13.1 kg (intervention) and 7.1 kg (control), baseline-adjusted mean difference 7.4 kg (95% CI: 3.8-10.9) from local retailers participating in the scheme (secondary outcome). There was no evidence of differential effects of the intervention by household food security or by socioeconomic position, and no unintended adverse consequences were noted. Interpretation: Financial incentive schemes are feasible in unorganised food retail environments. Effectiveness in improving diet quality of the household likely hinges on the percentage of retailers willing to participate in such a scheme. Funding: This research has been funded by the Drivers of Food Choice (DFC) Competitive Grants Program, which is funded by the UK Government's Department for International Development and the Bill & Melinda Gates Foundation, and managed by the University of South Carolina, Arnold School of Public Health, USA; however, the views expressed do not necessarily reflect the UK Government's official policies.

RTF2 controls replication repriming and ribonucleotide excision at the replisome.

Genetic information is duplicated via the highly regulated process of DNA replication. The machinery coordinating this process, the replisome, encounters many challenges, including replication fork-stalling lesions that threaten the accurate and timely transmission of genetic information. Cells have multiple mechanisms to repair or bypass lesions that would otherwise compromise DNA replication1,2. We have previously shown that proteasome shuttle proteins, DNA Damage Inducible 1 and 2 (DDI1/2) function to regulate Replication Termination Factor 2 (RTF2) at the stalled replisome, allowing for replication fork stabilization and restart3. Here we show that RTF2 regulates replisome localization of RNase H2, a heterotrimeric enzyme responsible for removing RNA in the context of RNA-DNA heteroduplexes4-6. We show that during unperturbed DNA replication, RTF2, like RNase H2, is required to maintain normal replication fork speeds. However, persistent RTF2 and RNase H2 at stalled replication forks compromises the replication stress response, preventing efficient replication restart. Such restart is dependent on PRIM1, the primase component of DNA polymerase α-primase. Our data show a fundamental need for regulation of replication-coupled ribonucleotide incorporation during normal replication and the replication stress response that is achieved through RTF2. We also provide evidence for PRIM1 function in direct replication restart following replication stress in mammalian cells.

Haploinsufficiency of NFKBIA reshapes the epigenome antipodal to the IDH mutation and imparts disease fate in diffuse gliomas.

Genetic alterations help predict the clinical behavior of diffuse gliomas, but some variability remains uncorrelated. Here, we demonstrate that haploinsufficient deletions of chromatin-bound tumor suppressor NFKB inhibitor alpha (NFKBIA) display distinct patterns of occurrence in relation to other genetic markers and are disproportionately present at recurrence. NFKBIA haploinsufficiency is associated with unfavorable patient outcomes, independent of genetic and clinicopathologic predictors. NFKBIA deletions reshape the DNA and histone methylome antipodal to the IDH mutation and induce a transcriptome landscape partly reminiscent of H3K27M mutant pediatric gliomas. In IDH mutant gliomas, NFKBIA deletions are common in tumors with a clinical course similar to that of IDH wild-type tumors. An externally validated nomogram model for estimating individual patient survival in IDH mutant gliomas confirms that NFKBIA deletions predict comparatively brief survival. Thus, NFKBIA haploinsufficiency aligns with distinct epigenome changes, portends a poor prognosis, and should be incorporated into models predicting the disease fate of diffuse gliomas.

The role of mast cells on angiogenesis in oral squamous cell carcinoma.

OBJECTIVE: Angiogenesis or neovascularization has long been known to aid in progression and metastasis of malignant tumors. Tumor angiogenesis is a complex event mediated by angiogenic factors released from cancer cells and or by host immune cells. Mast cells may induce tumor progression and potentiate metastasis by stimulating angiogenesis. The purpose of the present study was to validate topographic distribution of micro vessel density (MVD) and mast cell density (MCD) and help to elucidate the possible role of mast cells in tumor angiogenesis and correlating this with advanced disease parameters. . STUDY DESIGN: MVD and MCD were investigated in tumor specimens from 30 patients diagnosed with different histologic grades of oral squamous cell carcinoma (OSCC). Intratumor vessels were stained with collagen Type IV antibody and mast cells with Toluidine blue before being measured by light microscopy. RESULTS: There was a significant correlation between MVD and disease progression and number of blood vessels increased from well to poorly differentiated OSCC where as MCD decreased. CONCLUSIONS: These findings suggest that angiogenesis indeed occur in OSCC and might be used as an index to inflect the aggression of the disease however mast cells make up only a part of complex process of angiogenesis along with other factors secreted by tumor.

Ultrasonic Texture Features for Assessing Cardiac Remodeling and Dysfunction.

BACKGROUND: Changes in cardiac size, myocardial mass, cardiomyocyte appearance, and, ultimately, the function of the entire organ are interrelated features of cardiac remodeling that profoundly affect patient outcomes. OBJECTIVES: This study proposes that the application of radiomics for extracting cardiac ultrasonic textural features (ultrasomics) can aid rapid, automated assessment of left ventricular (LV) structure and function without requiring manual measurements. METHODS: This study developed machine-learning models using cardiac ultrasound images from 1,915 subjects in 3 clinical cohorts: 1) an expert-annotated cardiac point-of-care-ultrasound (POCUS) registry (n = 943, 80% training/testing and 20% internal validation); 2) a prospective POCUS cohort for external validation (n = 275); and 3) a prospective external validation on high-end ultrasound systems (n = 484). In a type 2 diabetes murine model, echocardiography of wild-type (n = 10) and Leptr-/- (n = 8) mice were assessed longitudinally at 3 and 25 weeks, and ultrasomics features were correlated with histopathological features of hypertrophy. RESULTS: The ultrasomics model predicted LV remodeling in the POCUS and high-end ultrasound external validation studies (area under the curve: 0.78 [95% CI: 0.68-0.88] and 0.79 [95% CI: 0.73-0.86], respectively). Similarly, the ultrasomics model predicted LV remodeling was significantly associated with major adverse cardiovascular events in both cohorts (P < 0.0001 and P = 0.0008, respectively). Moreover, on multivariate analysis, the ultrasomics probability score was an independent echocardiographic predictor of major adverse cardiovascular events in the high-end ultrasound cohort (HR: 8.53; 95% CI: 4.75-32.1; P = 0.0003). In the murine model, cardiomyocyte hypertrophy positively correlated with 2 ultrasomics biomarkers (R2 = 0.57 and 0.52, Q < 0.05). CONCLUSIONS: Cardiac ultrasomics-based biomarkers may aid development of machine-learning models that provide an expert-level assessment of LV structure and function.

Transcatheter Closure of Complex Left Circumflex to Coronary Sinus Fistula.

Coronary artery fistulae connecting the left circumflex to the coronary sinus are rare. Surgical closure of coronary sinus connections is technically challenging because of the location, especially in high-risk surgical patients. We used multimodality imaging to delineate the drainage site and successfully closed a left circumflex to coronary sinus fistula using a transcatheter closure technique. (Level of Difficulty: Advanced.).

Chemical Biology Screening Identifies a Vulnerability to Checkpoint Kinase Inhibitors in TSC2-Deficient Renal Angiomyolipomas.

The tuberous sclerosis complex (TSC) is a rare genetic syndrome and multisystem disease resulting in tumor formation in major organs. A molecular hallmark of TSC is a dysregulation of the mammalian target of rapamycin (mTOR) through loss-of-function mutations in either tumor suppressor TSC1 or TSC2. Here, we sought to identify drug vulnerabilities conferred by TSC2 tumor-suppressor loss through cell-based chemical biology screening. Our small-molecule chemical screens reveal a sensitivity to inhibitors of checkpoint kinase 1/2 (CHK1/2), regulators of cell cycle, and DNA damage response, in both in vitro and in vivo models of TSC2-deficient renal angiomyolipoma (RA) tumors. Further, we performed transcriptional profiling on TSC2-deficient RA cell models and discovered that these recapitulate some of the features from TSC patient kidney tumors compared to normal kidneys. Taken together, our study provides a connection between mTOR-dependent tumor growth and CHK1/2, highlighting the importance of CHK1/2 inhibition as a potential antitumor strategy in TSC2-deficient tumors.

Dickkopf-1 (DKK-1) stimulated prostate cancer growth and metastasis and inhibited bone formation in osteoblastic bone metastases.

BACKGROUND: Osteoblastic bone metastasis is the predominant phenotype observed in prostate cancer patients and is associated with high patient mortality and morbidity. However, the mechanisms determining the development of this phenotype are not well understood. Prostate cancer cells secrete several osteogenic factors including Wnt proteins, which are not only osteoinductive but also oncogenic. Therefore, the purpose of the study was to investigate the contribution of the Wnt signaling pathway in prostate cancer growth, incidence of bone metastases, and osteoblastic phenotype of bone metastases. The strategy involved overexpressing the Wnt antagonist, DKK-1, in the mixed osteoblastic and osteolytic Ace-1 prostate cancer cells. METHODS: Ace-1 prostate cancer cells stably expressing human DKK-1 or empty vector were established and transduced with lentiviral yellow fluorescent protein (YFP)-luciferase (Luc). The Ace-1/vector(YFP-LUC) and Ace-1/DKK-1(YFP-LUC) cells were injected subcutaneously, intratibially, or in the left cardiac ventricle in athymic mice. RESULTS: Unexpectedly, DKK-1 significantly increased Ace-1 subcutaneous tumor mass and the incidence of bone metastases after intracardiac injection of Ace-1 cells. DKK-1 increased Ace-1 tumor growth associated with increased phospho46 c-Jun amino-terminal kinase by the Wnt noncanonical pathway. As expected, DKK-1 decreased the Ace-1 osteoblastic phenotype of bone metastases, as confirmed by radiographic, histopathologic, and microcomputed tomographic analysis. DKK-1 decreased osteoblastic activity via the Wnt canonical pathway evidenced by an inhibition of T-cell factor activity in murine osteoblast precursor ST2 cells. CONCLUSION: The present study showed that DKK-1 is a potent inhibitor of bone growth in prostate cancer-induced osteoblastic metastases.