Selective depletion of HBV-infected hepatocytes by class A capsid assembly modulators requires high levels of intrahepatic HBV core protein.

Capsid assembly mediated by hepatitis B virus (HBV) core protein (HBc) is an essential part of the HBV replication cycle, which is the target for different classes of capsid assembly modulators (CAMs). While both CAM-A ("aberrant") and CAM-E ("empty") disrupt nucleocapsid assembly and reduce extracellular HBV DNA, CAM-As can also reduce extracellular HBV surface antigen (HBsAg) by triggering apoptosis of HBV-infected cells in preclinical mouse models. However, there have not been substantial HBsAg declines in chronic hepatitis B (CHB) patients treated with CAM-As to date. To investigate this disconnect, we characterized the antiviral activity of tool CAM compounds in HBV-infected primary human hepatocytes (PHHs), as well as in HBV-infected human liver chimeric mice and mice transduced with adeno-associated virus-HBV. Mechanistic studies in HBV-infected PHH revealed that CAM-A, but not CAM-E, induced a dose-dependent aggregation of HBc in the nucleus which is negatively regulated by the ubiquitin-binding protein p62. We confirmed that CAM-A, but not CAM-E, induced HBc-positive cell death in both mouse models via induction of apoptotic and inflammatory pathways and demonstrated that the degree of HBV-positive cell loss was positively correlated with intrahepatic HBc levels. Importantly, we determined that there is a significantly lower level of HBc per hepatocyte in CHB patient liver biopsies than in either of the HBV mouse models. Taken together, these data confirm that CAM-As have a unique secondary mechanism with the potential to kill HBc-positive hepatocytes. However, this secondary mechanism appears to require higher intrahepatic HBc levels than is typically observed in CHB patients, thereby limiting the therapeutic potential.

Mapping the hepatic immune landscape identifies monocytic macrophages as key drivers of steatohepatitis and cholangiopathy progression.

BACKGROUND AND AIMS: The progression of chronic liver diseases towards liver cirrhosis is accompanied by drastic tissue changes. This study combines elaborate transcriptomic and histological methods aiming at spatially resolving the hepatic immune microenvironment in NAFLD (including NASH, primary sclerosing cholangitis, primary biliary cholangitis, and severe alcoholic hepatitis). APPROACH AND RESULTS: Human liver samples were subjected to RNA-sequencing (n=225) and imaging cytometry (n=99) across 3 independent patient cohorts. Liver samples from alcoholic hepatitis and primary biliary cholangitis patients were used for comparison. Myeloid populations were further characterized in corresponding mouse models. Imaging, clinical, and phenotypical data were combined for multidimensional analysis. NAFLD/NASH and primary sclerosing cholangitis disease stages were associated with loss of parenchymal areas, increased ductular cell accumulation, and infiltration of immune cells. NASH patients predominantly exhibited myeloid cell accumulation, whereas primary sclerosing cholangitis patients additionally had pronounced lymphoid cell responses. Correlating to disease stage, both etiologies displayed intense IBA1 + CD16 low CD163 low macrophage aggregation in nonparenchymal areas, with a distinct spatial proximity to ductular cells. Mouse models revealed that disease-associated IBA1 + hepatic macrophages originated from bone marrow-derived monocytes. Using an unbiased, machine learning-based algorithm, IBA1 in combination with hepatocyte and ductular cell immunostaining-predicted advanced cirrhosis in human NASH, primary sclerosing cholangitis, and alcoholic hepatitis. CONCLUSIONS: Loss of hepatocytes and increased ductular reaction are tightly associated with monocyte-derived macrophage accumulation and represent the most prominent common immunological feature revealing the progression of NAFLD, primary sclerosing cholangitis, primary biliary cholangitis, and alcoholic hepatitis, suggesting IBA1 + CD163 low macrophages are key pathogenic drivers of human liver disease progression across diverse etiologies.

Repurposing mebendazole against triple-negative breast cancer CNS metastasis.

PURPOSE: Triple-negative breast cancer (TNBC) often metastasizes to the central nervous system (CNS) and has the highest propensity among breast cancer subtypes to develop leptomeningeal disease (LMD). LMD is a spread of cancer into leptomeningeal space that speeds up the disease progression and severely aggravates the prognosis. LMD has limited treatment options. We sought to test whether the common anti-helminthic drug mebendazole (MBZ) may be effective against murine TNBC LMD. METHODS: A small-molecule screen involving TNBC cell lines identified benzimidazoles as potential therapeutic agents for further study. In vitro migration assays were used to evaluate cell migration capacity and the effect of MBZ. For in vivo testing, CNS metastasis was introduced into BALB/c athymic nude mice through internal carotid artery injections of brain-tropic MDA-MB-231-BR or MCF7-BR cells. Tumor growth and spread was monitored by bioluminescence imaging and immunohistochemistry. MBZ was given orally at 50 and 100 mg/kg doses. MBZ bioavailability was assayed by mass spectrometry. RESULTS: Bioinformatic analysis and migration assays revealed higher migratory capacity of TNBC compared to other breast cancer subtypes. MBZ effectively slowed down migration of TNBC cell line MDA-MB-231 and its brain tropic derivative MDA-MB-231-BR. In animal studies, MBZ reduced leptomeningeal spread, and extended survival in brain metastasis model produced by MDA-MB-231-BR cells. MBZ did not have an effect in the non-migratory MCF7-BR model. CONCLUSIONS: We demonstrated that MBZ is a safe and effective oral agent in an animal model of TNBC CNS metastasis. Our findings are concordant with previous efforts involving MBZ and CNS pathology and support the drug's potential utility to slow down leptomeningeal spread.

Measurement Instruments Assessing Multi-Faceted Stigma Regarding Sexual and Gender Minorities: A Systematic Review of Psychometric Properties.

Stigma against sexual and gender minorities (SGM) populations has serious negative health effects for SGM populations. Despite the growing need for accurate stigma measurement in SGM, there are insufficient valid measurement instruments. Moreover, the lack of consistency in construct usage makes comparisons across studies particularly challenging. A critical review and comparative evaluation of the psychometric properties of the various stigma measures for SGM is necessary to advance our understanding regarding stigma measurement against/among SGMs. Based on the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, a comprehensive search was conducted in 4 bibliographic databases (MEDLINE, PsycINFO, CINAHL, and Web of Science) for empirical articles published from 2010 to 2022 that evaluated the psychometrics properties of measurement instruments assessing stigma against SGMs. The screening, extraction, and scoring of the psychometric properties and methodological quality of selected instruments were performed by following the established standards and COSMIN (Consensus-based Standards for the selection of health Measurement Instruments) checklist, respectively. Of the 2031 studies identified, 19 studies were included that reported psychometric properties of 17 measurement instruments. All instruments, except two, were developed for SGMs (n = 15/17). Most instruments included men who have sex with men (MSM) or gay men (n = 11/15), whereas less than half of the instruments assessed stigma among SGM women (n = 6/15). Internal consistency (Cronbach's alpha) and content validity was reported for all instruments (n = 17); construct and structural validity was also reported for majority of the instruments (n = 15 and 10, respectively). However, test-retest reliability and criterion validity was reported for very few instruments (n = 5 each). Based on the COSMIN checklist, we identified the most psychometrically and methodologically robust instruments for each of the five stigma types: combined stigma, enacted stigma, internalized stigma, intersectional stigma, and perceived stigma. For each stigma type, except anticipated stigma, at least one instrument demonstrated strong promise for use in empirical research; however, the selection of instrument depends on the target population and context of the study. Findings indicated a growing use of instruments assessing multiple stigma types. Future studies need to develop intersectional stigma instruments that account for the multiple and intersecting social identities of SGMs. Additionally, most existing instruments would benefit from further psychometric testing, especially on test-retest reliability, criterion validity, adaptability to different LGBTQIA + populations and cultures.

Stigmatizing clinical setting erodes physician-patient interaction quality for sexual minority men through perceived HIV stigma and HIV infection concerns in Zambia.

This study investigated whether perceived HIV stigma and HIV infection concerns among healthcare providers (HCPs) mediate the association between stigmatizing clinical setting and their interaction quality with sexual minority men (SMM) patients in Zambia. In 2021, a cross-sectional survey was conducted with 91 HCPs offering HIV-related services to SMM in Zambia. Path analysis was conducted to examine the potential mediation effect of "perceived HIV stigma" and "HIV infection concern" among HCPs in the association between "stigmatizing clinical setting" and their "interaction quality with SMM". Mediators i.e., "perceived HIV stigma" and "HIV infection concern" among HCPs, were associated positively with the stigmatizing clinical setting (ß = 0.329, p < .01, ß = 0.917, p < 0.01), and negatively with physician-patient interaction quality (ß = -0.167, p = 0.051; ß = -0.126, p < 0.05). Stigmatizing clinical setting had a significant and negative indirect effect on HCPs interaction quality with SMM through increased perceived HIV stigma (z = -1.966, p < 0.05) and increased HIV infection concern (z = -1.958, p = 0.050). To improve physician-patient interaction quality, stigma reduction interventions among HCPs, who serve SMM in Zambia, should target development of development of inclusive policies and the cultivation of cultural norms that are supportive and respectful to SMM, and protection of HCPs from enacted stigma due to offering care to SMM.

Impact of enacted stigma on mental health, substance use, and HIV-related behaviors among sexual minority men in Zambia.

Sexual minority men (SMM) in Zambia face significant challenges including stigma, discrimination, and mental health issues, which further impact their HIV-related risk behaviors. This study aimed to investigate the associations between enacted stigma, substance abuse, HIV-related behaviors, and mental health (i.e., depression, anxiety, and post-traumatic stress disorder [PTSD] symptoms) among SMM in Zambia. SMM aged 18-35 years who reported having multiple and/or concurrent sexual partners or low and/or inconsistent condom use in the past three months were recruited from four districts in Zambia between February and November 2021. Participants completed an anonymous interviewer-administered survey. Key variables of interest were compared between participants with higher vs. lower levels of enacted stigma. Independent samples t-tests were used for continuous variables, and chi-squared tests were used for categorical variables. A total of 197 eligible SMM participated in the study (mean age = 24.41 years). Participants with a higher level of enacted stigma showed a higher level of anxiety symptoms (χ2 = 12.91, p ≤ .001), PTSD symptoms (χ2 = 7.13, p < .01), tobacco use (χ2 = 10.47, p < .01), cannabis use (χ2 = 5.90, p < .05), and a higher number of sexual partners (t = 1.99, p < .05) in the past three months. Stigma reduction interventions may help mitigate substance abuse, HIV-related behaviors, and adverse mental health outcomes among SMM in Zambia. Health care providers, especially psychiatric-mental health nurses, can incorporate strategies for recognizing and addressing stigma into their practice through training and integrate multiple resources to create an inclusive and non-judgmental environment for SMM to improve their well-being.

Efficient Removal of Uranyl Ions Using PAMAM Dendrimer: Simulation and Experiment.

In this work, using atomistic molecular dynamics (MD) simulations and polymer-assisted ultrafiltration experiments, we explore the adsorption and removal of uranyl ions from aqueous solutions using poly(amidoamine) (PAMAM) dendrimers. The effects of uranyl ion concentration and the pH of the solution were examined for PAMAM dendrimers of generations 3, 4, and 5. Our simulation results show that PAMAM has a high adsorption capacity for the uranyl ions. The adsorption capacity increases with increasing concentration of uranyl ions for all 3 generations of PAMAM in agreement with experimental findings. We find that the number of uranyl ions bound to PAMAM is significantly higher in acidic solutions (pH < 3) as compared to neutral solutions (pH ∼ 7) for all uranyl ion concentrations. Additionally, we find an increase in the number of adsorbed uranyl ions to PAMAM with the increase in the dendrimer generation. This increase is due to the greater number of binding sites present for higher-generation PAMAM dendrimers. Our simulation study shows that nitrate ions form a solvation shell around uranyl ions, which allows them to bind to PAMAM binding sites, including the amide, amine, and carbonyl groups. In polymer-assisted ultrafiltration (PAUF) experiments, the removal percentage of uranyl ions by G3 PAMAM dendrimer increased from 36.3% to 42.6% as the metal ion concentration increased from 2.1 × 10-5 M to 10.5 × 10-5 M at a pH of 2. Our combined experiment and simulation study suggests that PAMAM is an effective adsorbent for removing uranyl ions from aqueous solutions.

Physician-Patient Interaction Quality Mediates the Association Between HIV-Related Stigma and HIV-Prevention Behaviors Among Sexual Minority Men in Zambia.

HIV-related stigma is a major challenge to HIV prevention for sexual minority men (SMM) in Zambia, but little is known about the underlying mechanisms. This study aimed to investigate whether physician-patient interaction quality mediates the relationship between HIV-related stigma and HIV-prevention behaviors among SMM. Data were collected using a cross-sectional survey from 194 SMM (aged: mean = 24.08, SD = 4.27) across four districts in Zambia between February and November 2021. Participants were asked about their demographic characteristics, HIV-related stigma, SMM-related stigma, physician-patient interaction quality, HIV-testing intention, and use of pre-exposure prophylaxis (PrEP). Path analysis was used to test the mediation effect of physician-patient interaction quality in the associations of HIV-related stigma/SMM-related stigma with HIV-testing intention and current PrEP use. Higher self-reported physician-patient interaction quality was negatively associated with HIV-related stigma (ß = - 0.444, z = - 2.223, p < 0.05), and positively associated with HIV-testing intention (ß = 0.039, z = 5.121, p < 0.001) and current PrEP use (ß = 0.008, z = 2.723, p < 0.01). HIV-related stigma among SMM had a significant and negative indirect effect on HIV-testing intention (ß = - 0.017, z = - 2.006, p < 0.05), and current PrEP use (ß = - 0.004, z = - 2.009, p < 0.05) through physician-patient interaction quality. Contrary to our expectations, SMM-related stigma did not have a significant and negative indirect effect on HIV prevention behaviors through physician-patient interaction quality. Health interventions need to improve physician-patient interaction quality by offering healthcare provider training, targeting HIV-related stigma in healthcare settings, and devising inclusive healthcare policies to promote HIV prevention efforts.

Artificial Intelligence-Based Chatbots for Promoting Health Behavioral Changes: Systematic Review.

BACKGROUND: Artificial intelligence (AI)-based chatbots can offer personalized, engaging, and on-demand health promotion interventions. OBJECTIVE: The aim of this systematic review was to evaluate the feasibility, efficacy, and intervention characteristics of AI chatbots for promoting health behavior change. METHODS: A comprehensive search was conducted in 7 bibliographic databases (PubMed, IEEE Xplore, ACM Digital Library, PsycINFO, Web of Science, Embase, and JMIR publications) for empirical articles published from 1980 to 2022 that evaluated the feasibility or efficacy of AI chatbots for behavior change. The screening, extraction, and analysis of the identified articles were performed by following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. RESULTS: Of the 15 included studies, several demonstrated the high efficacy of AI chatbots in promoting healthy lifestyles (n=6, 40%), smoking cessation (n=4, 27%), treatment or medication adherence (n=2, 13%), and reduction in substance misuse (n=1, 7%). However, there were mixed results regarding feasibility, acceptability, and usability. Selected behavior change theories and expert consultation were used to develop the behavior change strategies of AI chatbots, including goal setting, monitoring, real-time reinforcement or feedback, and on-demand support. Real-time user-chatbot interaction data, such as user preferences and behavioral performance, were collected on the chatbot platform to identify ways of providing personalized services. The AI chatbots demonstrated potential for scalability by deployment through accessible devices and platforms (eg, smartphones and Facebook Messenger). The participants also reported that AI chatbots offered a nonjudgmental space for communicating sensitive information. However, the reported results need to be interpreted with caution because of the moderate to high risk of internal validity, insufficient description of AI techniques, and limitation for generalizability. CONCLUSIONS: AI chatbots have demonstrated the efficacy of health behavior change interventions among large and diverse populations; however, future studies need to adopt robust randomized control trials to establish definitive conclusions.

Multi-parametric analysis of human livers reveals variation in intrahepatic inflammation across phases of chronic hepatitis B infection.

BACKGROUND & AIMS: Chronic HBV is clinically categorized into 4 phases by a combination of serum HBV DNA levels, HBeAg status and alanine aminotransferase (ALT): immunotolerant (IT), immune-active (IA), inactive carrier (IC) and HBeAg-negative hepatitis (ENEG). Immune and virological measurements in the blood have proven useful but are insufficient to explain the interrelation between the immune system and the virus since immune dynamics differ in the blood and liver. Furthermore, the inflammatory response in the liver and parenchymal cells cannot be fully captured in blood. METHODS: Immunological composition and transcriptional profiles of core needle liver-biopsies in chronic HBV phases were compared to those of healthy controls by multiplex immunofluorescence and RNA-sequencing (n = 37 and 78, respectively) analyses. RESULTS: Irrespective of the phase-specific serological profiles, increased immune-gene expression and frequency was observed in chronic HBV compared to healthy livers. Greater transcriptomic deregulation was seen in IA and ENEG (172 vs. 243 DEGs) than in IT and IC (13 vs. 35 DEGs) livers. Interferon-stimulated genes, immune-activation and exhaustion genes (ICOS, CTLA4, PDCD1) together with chemokine genes (CXCL10, CXCL9) were significantly induced in IA and ENEG livers. Moreover, distinct immune profiles associated with ALT elevation and a more accentuated immune-exhaustion profile (CTLA4, TOX, SLAMF6, FOXP3) were observed in ENEG, which set it apart from the IA phase (LGALS9, PDCD1). Interestingly, all HBV phases showed downregulation of metabolic pathways vs. healthy livers (fatty and bile acid metabolism). Finally, increased leukocyte infiltrate correlated with serum ALT, but not with HBV DNA or viral proteins. CONCLUSION: Our comprehensive multi-parametric analysis of human livers revealed distinct inflammatory profiles and pronounced differences in intrahepatic gene profiles across all chronic HBV phases in comparison to healthy liver. LAY SUMMARY: Immunological studies on chronic HBV remain largely restricted to assessment of peripheral responses due to the limited access to the site of infection, the liver. In this study, we comprehensively analyzed livers from a well-defined cohort of patients with chronic HBV and uninfected controls with state-of-the-art techniques, and evaluated the differences in gene expression profiles and inflammation characteristics across distinct disease phases in patients with chronic HBV.

Quantum Circuit Rules for Molecular Electronic Systems: Where Are We Headed Based on the Current Understanding of Quantum Interference, Thermoelectric, and Molecular Spintronics Phenomena?

In this minireview, we discuss important aspects of the various quantum phenomena (such as quantum interference, spin-dependent charge transport, and thermoelectric effects) relevant in single-molecule charge transport and list some of the basic circuit rules devised for different molecular systems. These quantum phenomena, in conjunction with the existing empirical circuit rules, can help in predicting some of the structure-property relationships in molecular circuits. However, a universal circuit law that predicts the charge transport properties of a molecular circuit has not been derived yet. Having such law(s) will help to design and build a complex molecular device leading to exciting unique applications that are not possible with the traditional silicon-based technologies. Based on the existing knowledge in the literature, here we open the discussion on the possible future research directions for deriving unified circuit law(s) to predict the charge transport in complex single-molecule circuits.

Predicting the DNA Conductance Using a Deep Feedforward Neural Network Model.

Double-stranded DNA (dsDNA) has been established as an efficient medium for charge migration, bringing it to the forefront of the field of molecular electronics and biological research. The charge migration rate is controlled by the electronic couplings between the two nucleobases of DNA/RNA. These electronic couplings strongly depend on the intermolecular geometry and orientation. Estimating these electronic couplings for all the possible relative geometries of molecules using the computationally demanding first-principles calculations requires a lot of time and computational resources. In this article, we present a machine learning (ML)-based model to calculate the electronic coupling between any two bases of dsDNA/dsRNA and bypass the computationally expensive first-principles calculations. Using the Coulomb matrix representation which encodes the atomic identities and coordinates of the DNA base pairs to prepare the input dataset, we train a feedforward neural network model. Our neural network (NN) model can predict the electronic couplings between dsDNA base pairs with any structural orientation with a mean absolute error (MAE) of less than 0.014 eV. We further use the NN-predicted electronic coupling values to compute the dsDNA/dsRNA conductance.

Mechanistic insights into the effects of key mutations on SARS-CoV-2 RBD-ACE2 binding.

Some recent SARS-CoV-2 variants appear to have increased transmissibility compared to the original strain. An underlying mechanism could be the improved ability of the variants to bind receptors on the target cells and infect them. In this study, we provide atomic-level insights into the binding of the receptor binding domain (RBD) of the wild-type SARS-CoV-2 spike protein and its single (N501Y), double (E484Q, L452R) and triple (N501Y, E484Q, L452R) mutated variants to the human ACE2 receptor. Using extensive all-atom molecular dynamics simulations and advanced free energy calculations, we estimate the associated binding affinities and binding hotspots. We observe significant secondary structural changes in the RBD of the mutants, which lead to different binding affinities. We find higher binding affinities for the double (E484Q, L452R) and triple (N501Y, E484Q, L452R) mutated variants than for the wild type and the N501Y variant, which could contribute to the higher transmissibility of recent variants containing these mutations.

Machine Learning Prediction of Electronic Coupling between the Guanine Bases of DNA.

Charge transport in deoxyribonucleic acid (DNA) is of immense interest in biology and molecular electronics. Electronic coupling between the DNA bases is an important parameter describing the efficiency of charge transport in DNA. A reasonable estimation of this electronic coupling requires many expensive first principle calculations. In this article, we present a machine learning (ML) based model to calculate the electronic coupling between the guanine bases of the DNA (in the same strand) of any length, thus avoiding expensive first-principle calculations. The electronic coupling between the bases are evaluated using density functional theory (DFT) calculations with the morphologies derived from fully atomistic molecular dynamics (MD) simulations. A new and simple protocol based on the coarse-grained model of the DNA has been used to extract the feature vectors for the DNA bases. A deep neural network (NN) is trained with the feature vector as input and the DFT-calculated electronic coupling as output. Once well trained, the NN can predict the DFT-calculated electronic coupling of new structures with a mean absolute error (MAE) of 0.02 eV.

Expression profiling of colorectal cancer cells reveals inhibition of DNA replication licensing by extracellular calcium.

Colorectal cancer is one of the most common cancers in industrialised societies. Epidemiological studies, animal experiments, and randomized clinical trials have shown that dietary factors can influence all stages of colorectal carcinogenesis, from initiation through promotion to progression. Calcium is one of the factors with a chemoprophylactic effect in colorectal cancer. The aim of this study was to understand the molecular mechanisms of the anti-tumorigenic effects of extracellular calcium ([Ca2+]o) in colon cancer cells. Gene expression microarray analysis of colon cancer cells treated for 1, 4, and 24h with 2mM [Ca2+]o identified significant changes in expression of 1571 probe sets (ANOVA, p<10-5). The main biological processes affected by [Ca2+]o were DNA replication, cell division, and regulation of transcription. All factors involved in DNA replication-licensing were significantly downregulated by [Ca2+]o. Furthermore, we show that the calcium-sensing receptor (CaSR), a G protein-coupled receptor is a mediator involved in this process. To test whether these results were physiologically relevant, we fed mice with a standard diet containing low (0.04%), intermediate (0.1%), or high (0.9%) levels of dietary calcium. The main molecules regulating replication licensing were inhibited also in vivo, in the colon of mice fed high calcium diet. We show that among the mechanisms behind the chemopreventive effect of [Ca2+]o is inhibition of replication licensing, a process often deregulated in neoplastic transformation. Our data suggest that dietary calcium is effective in preventing replicative stress, one of the main drivers of cancer and this process is mediated by the calcium-sensing receptor.

Remarkable similarity of force induced dsRNA conformational changes to stretched dsDNA and their detection using electrical measurements.

In spite of the striking difference between twist-stretch coupling of dsRNA and dsDNA under external force, dsRNA shows similar structural polymorphism to dsDNA under different pulling protocols. Our atomistic MD simulations show that overstretching dsRNA along the 3' direction of the opposite strands (OS3) leads to the emergence of S-RNA whereas overstretching along the 5' directions of the opposite strands (OS5) leads to melting of dsRNA at lower forces. Using the dsRNA morphology from pulling MD simulations, we use a multiscale method involving ab initio calculations and Kinetic Monte Carlo (KMC) simulations to estimate the conductance of dsRNA and find that the conformational changes drastically affect its conductance. The current through dsRNA chains drastically drops after a critical stretching length and critically depends on the pulling protocol. The critical stretching length for the OS3 pulling case is around 65% higher than that of the OS5 case.

The calcium-sensing receptor and the hallmarks of cancer.

The calcium-sensing receptor (CaSR) plays a pivotal role in systemic calcium metabolism by regulating parathyroid hormone secretion and urinary calcium excretion. The CaSR is ubiquitously expressed, implying a wide range of functions regulated by this receptor. Abnormal CaSR function affects the development of both calciotropic disorders such as hyperparathyroidism, and non-calciotropic disorders such as cardiovascular disease and cancer, which are the leading causes of mortality worldwide. The CaSR is able to bind a plethora of ligands; it interacts with multiple G protein subtypes, and regulates highly divergent downstream signalling pathways, depending on the cellular context. The CaSR is a key regulator for such diverse processes as hormone secretion, gene expression, inflammation, proliferation, differentiation, and apoptosis. Due to this pleiotropy, the CaSR is able to regulate cell fate and is implicated in the development of many types of benign or malignant tumours of the breast, prostate, parathyroid, and colon. In cancer, the CaSR appears to have paradoxical roles, and depending on the tissue involved, it is able to prevent or promote tumour growth. In tissues like the parathyroid or colon, the CaSR inhibits proliferation and induces terminal differentiation of the cells. Therefore, loss of the receptor, as seen in colorectal or parathyroid tumours, confers malignant potential, suggestive of a tumour suppressor role. In contrast, in prostate and breast tumours the expression of the CaSR is increased and it seems that it favours metastasis to the bone, acting as an oncogene. Deciphering the molecular mechanism driving the CaSR in the different tissues could lead to development of new allosteric drug compounds that selectively target the CaSR and have therapeutic potential for cancer. This article is part of a Special Issue entitled: Calcium and Cell Fate. Guest Editors: Jacques Haiech, Claus Heizmann, Joachim Krebs, Thierry Capiod and Olivier Mignen.

The calcium-sensing receptor: A promising target for prevention of colorectal cancer.

The inverse correlation between dietary calcium intake and the risk of colorectal cancer (CRC) is well known, but poorly understood. Expression of the calcium-sensing receptor (CaSR), a calcium-binding G protein-coupled receptor is downregulated in CRC leading us to hypothesize that the CaSR has tumor suppressive roles in the colon. The aim of this study was to understand whether restoration of CaSR expression could reduce the malignant phenotype in CRC. In human colorectal tumors, expression of the CaSR negatively correlated with proliferation markers whereas loss of CaSR correlated with poor tumor differentiation and reduced apoptotic potential. In vivo, dearth of CaSR significantly increased expression of proliferation markers and decreased levels of differentiation and apoptotic markers in the colons of CaSR/PTH double knock-out mice confirming the tumor suppressive functions of CaSR. In vitro CRC cells stably overexpressing wild-type CaSR showed significant reduction in proliferation, as well as increased differentiation and apoptotic potential. The positive allosteric modulator of CaSR, NPS R-568 further enhanced these effects, whereas treatment with the negative allosteric modulator, NPS 2143 inhibited these functions. Interestingly, the dominant-negative mutant (R185Q) was able to abrogate these effects. Our results demonstrate a critical tumor suppressive role of CaSR in the colon. Restoration of CaSR expression and function is linked to regulation of the balance between proliferation, differentiation, and apoptosis and provides a rationale for novel strategies in CRC therapy.

miR-135b- and miR-146b-dependent silencing of calcium-sensing receptor expression in colorectal tumors.

Studies have shown that the calcium-sensing receptor (CaSR) mediates the antitumorigenic effects of calcium against colorectal cancer (CRC). Expression of the CaSR in colorectal tumors is often reduced. We have reported previously that silencing of CaSR in CRC is caused in part by methylation of CaSR promoter 2 and loss of histone acetylation. We investigated the impact of aberrant microRNA expression on loss of CaSR expression. A microarray study in two Caco-2 subclones (Caco2/AQ and Caco2/15) that have similar genetic background, but different CaSR expression levels (Caco2/AQ expressing more CaSR than Caco2/15), identified 22 differentially expressed microRNAs that potentially target the CaSR. We validated these results by performing gain- and loss-of-function studies with the top candidates: miR-9, miR-27a, miR-135b, and miR-146b. Modulation of miR-135b or miR-146b expression by mimicking or inhibiting their expression regulated CaSR protein levels in two different colon cancer cell lines: Caco2/AQ (moderate endogenous CaSR expression) and HT29 (low endogenous CaSR levels). Inhibition of miR-135b and miR-146b expression led to high CaSR levels and significantly reduced proliferation. In samples of colorectal tumors we observed overexpression of miR-135b and miR-146b, and this correlated inversely with CaSR expression (miR-135b: r = -0.684, p < 0.001 and miR-146b: r = -0.448, p < 0.001), supporting our in vitro findings. We demonstrate that miR-135b and miR-146b target the CaSR and reduce its expression in colorectal tumors, reducing the antiproliferative and prodifferentiating actions of calcium. This provides a new approach for finding means to prevent CaSR loss, developing better treatment strategies for CRC.