Solid-State Nanopore/Nanochannel Sensors with Enhanced Selectivity through Pore-in Modification.

Nanopore sensing technology, as an emerging analytical method, has the advantages of simple operation, fast output, and label-free and has been widely used in fields such as protein analysis, gene sequencing, and biomarker detection. Inspired by biological ion channels, scientists have prepared various artificial solid-state nanopores/nanochannels. Biological ion channels have extremely high ion transport selectivity, while solid-state nanopores/nanochannels have poor selectivity. The selectivity of solid-state nanopores and nanochannels can be enhanced by modifying channel charge, varying pore size, incorporating specific chemical functionality, and adjusting operating (or solution) conditions. This Perspective highlights pore-in modification strategies for enhancing the selectivity of solid-state nanopore/nanochannel sensors by summarizing the articles published in the last 10 years. The future development prospects and challenges of pore-in modification in solid-state nanopore and nanochannel sensors are discussed. This Perspective helps readers better understand nanopore sensing technology, especially the importance of detection selectivity. We believe that solid-state nanopore/nanochannel sensors will soon enter our homes after various challenges.

Regulation of transmembrane current through modulation of biomimetic lipid membrane composition.

Ion transport through biological channels is influenced not only by the structural properties of the channels themselves but also by the composition of the phospholipid membrane, which acts as a scaffold for these nanochannels. Drawing inspiration from how lipid membrane composition modulates ion currents, as seen in the activation of the K+ channel in Streptomyces A (KcsA) by anionic lipids, we propose a biomimetic nanochannel system that integrates DNA nanotechnology with two-dimensional graphene oxide (GO) nanosheets. By modifying the length of the multibranched DNA nanowires generated through the hybridization chain reaction (HCR) and varying the concentration of the linker strands that integrate these DNA nanowire structures with the GO membrane, the composition of the membrane can be effectively adjusted, consequently impacting ion transport. This method provides a strategy for developing devices with highly efficient and tunable ion transport, suitable for applications in mass transport, environmental protection, biomimetic channels, and biosensors.

Stochastic Sensing of Dynamic Interactions and Chemical Reactions with Nanopores/Nanochannels.

Nanopore sensing technology is an emerging analysis method with the advantages of simple operation, high sensitivity, fast output and being label free, and it is widely used in protein analysis, gene sequencing, biomarker detection, and other fields. The confined space of the nanopore provides a place for dynamic interactions and chemical reactions between substances. The use of nanopore sensing technology to track these processes in real time is helpful to understand the interaction/reaction mechanism at the single-molecule level. According to nanopore materials, we summarize the development of biological nanopores and solid-state nanopores/nanochannels in the stochastic sensing of dynamic interactions and chemical reactions. The goal of this paper is to stimulate the interest of researchers and promote the development of this field.

Solid-State Nanopore Sensors with Enhanced Sensitivity through Nucleic Acid Amplification.

Solid-state nanopores have wide applications in DNA sequencing, energy conversion and storage, seawater desalination, sensors, and reactors due to their high stability, controllable geometry, and a variety of pore-forming materials. Solid-state nanopore sensors can be used for qualitative and quantitative analyses of ions, small molecules, proteins, and nucleic acids. The combination of nucleic acid amplification and solid-state nanopores to achieve trace detection of analytes is gradually attracting attention. This review outlines nucleic acid amplification strategies for enhancing the sensitivity of solid-state nanopore sensors by summarizing the articles published in the past 10 years. The future development prospects and challenges of nucleic acid amplification in solid-state nanopore sensors are discussed. This review helps readers better understand the field of solid-state nanopore sensors. We believe that solid-state nanopore sensors will break through the bottleneck of traditional detection and become a powerful single-molecule detection platform.

Bioequivalence study of domperidone dry suspension in healthy Chinese subjects under fasted and fed conditions: An open-label, randomized, single-dose, crossover trial.

BACKGROUND: Domperidone has long been used as a prokinetic agent in the treatment of epigastric distress symptoms. This study aimed to provide adequate evidence for registration approval of a new generic dry suspension formulation of domperidone by comparing the safety and pharmacokinetic profiles between the test and branded reference formulation in the context of fasted and fed condition. MATERIALS AND METHODS: This was designed as a randomized, open-label, single-dose, two-period, two-treatment crossover study. 32 and 28 eligible healthy subjects were enrolled in the fasted and fed study, respectively. Each subject was randomly assigned to receive either the test or reference formulation in the first period, followed by a 1-week washout period and dosing of the alternate formulation in the second period. A series of blood samples were collected at scheduled timepoints within 48 hours after administration during each treatment period. Plasma concentrations of domperidone were determined by validated HPLC-MS/MS. Pharmacokinetic parameters, including Cmax, tmax, AUC0-t, AUC0-∞, and T1/2, were acquired based on the concentration vs. time profiles by non-compartmental analysis using WinNonlin software. Then the geometric mean ratios (GMR) of Cmax, AUC0-t, and AUC0-∞ between the two formulations and corresponding 90% confidence intervals (CIs) were calculated for bioequivalence determination. Safety was assessed as routine. RESULTS: The two formulations showed similar pharmacokinetic profiles. Under fasted condition, the GMR and corresponding 90% CIs of AUC0-t, AUC0-∞, and Cmax were 101.48% (96.79 - 106.38%), 101.17% (96.66 - 105.90%), and 104.61% (96.73 - 113.14%), respectively. Under fed condition, the GMR and corresponding 90% CIs were 105.46% (99.19 - 112.12%), 104.21% (98.19 - 110.61%), and 112.78% (103.64 - 122.73%), respectively, for AUC0-t, AUC0-∞, and Cmax. All values fell within the accepted bioequivalence range of 80 - 125%. Both the test and the reference products were well tolerated without any serious or unexpected adverse reactions. CONCLUSION: Pharmacokinetic bioequivalence was established between the two dry suspension formulations of domperidone in healthy Chinese subjects. Both products were safe and well tolerated.

Inner Wall and Outer Surface Distinguished Solid-State Nanopores for Sensing.

Solid-state nanopores, inspired by biological nanopores, have the advantages of good mechanical properties, stability, and easy modification. They have attracted wide attention in the fields of sequencing, sensing, molecular sieving, nanofluidic devices, nanoelectrochemistry, and energy conversion. Because of the ion/molecule transport characteristic of the pore, the research on solid-state nanopores mainly focuses on the functional modification of its inner wall. In recent years, the outer surface of nanopores has also attracted the attention of researchers, and the functional elements on the outer surface have the functions of anti-interference and ionic signal enhancement. In this perspective, we review research progress of inner wall and outer surface distinguished solid-state nanopores, highlight their processing and advantages, summarize their functions and applications in sensing, and give insight into further research.

Polydopamine-Induced Modification on the Highly Charged Surface of Asymmetric Nanofluidics: A Strategy for Adjustable Ion Current Rectification Properties.

Surface charge effects in nanoconfines is one of the fundamentals in the ion current rectification (ICR) of nanofluidics, which provides entropic driving force by asymmetric surface charges and causes ion enrichment/depletion by the electrostatic interaction of fixed surface charges. However, the surface charge effect causes a significant electrostatic repulsion in nanoconfines, restricting additional like charge or elaborate chemistry on the highly charged confined surface, which limits ICR manipulation. Here, we use polydopamine (PDA), a nearly universal adhesive, that adheres to the highly positive-charged poly(ethyleneimine) (PEI) gel network in a nanochannel array. PDA enhances the ICR effect from a low rectification ratio of 9.5 to 92.6 by increasing the surface charge and hydrophobicity of the PEI gel network and, meanwhile, shrinking its gap spacing. Theoretical and experimental results demonstrate the determinants of the fixed surface charge in the enrichment/depletion region on ICR properties, which is adjustable by PDA-induced change in a nanoconfined environment. Chemically active PDA brings Au nanoparticles by chloroauric reduction for further hydrophobization and the modification of negative-charged DNA complexes in nanochannels, whereby ICR effects can be manipulated in versatile means. The results describe an adjustable and versatile strategy for adjusting the ICR behaviors of nanofluidics by manipulating local surface charge effects using PDA.

Effectiveness and safety of non-vitamin K antagonist oral anticoagulants in patients with hypertrophic cardiomyopathy with non-valvular atrial fibrillation.

Hypertrophic cardiomyopathy (HCM) patients with nonvalvular atrial fibrillation (AF) have an increased risk of suffering thromboembolic events. Vitamin K antagonists (VKA) are recommended as therapy but there is still limited data regarding the efficacy of prescribing non-vitamin K antagonist oral anticoagulants (NOACs). This retrospective study investigates the effectiveness and safety of NOAC administration in patients with HCM and AF. A total of 124 patients with HCM and AF on an oral anticoagulant therapy were recruited between January 2015 and December 2019; these patients were followed up until March 31, 2020. Kaplan-Meier analysis was used to compare the clinical outcomes in patients treated with NOACs versus warfarin. The Cox model was used to estimate the risk of clinically relevant bleeding. Our study included 124 patients, of which 48 (38.7%) received warfarin and 76 (61.3%) received NOACs. Survival analysis showed the patients undergoing NOACs had a lower risk of clinically relevant bleeding (log-rank P = 0.039) over a period of 53.6 months. The median time in therapeutic range (TTR) score was 50% (interquartile range: 40.43 to 57.08%). A total of nine patients (18.75%) had a good TTR with a median score of 66.35% (interquartile range: 64.58 to 77.75%). The incidence of death by all causes, cardiovascular death and thromboembolism were similar between NOAC and warfarin-treated patients (log-rank P = 0.239, log-rank P = 0.386, and log-rank P = 0.257, respectively). Patients treated with NOACs showed a significant reduction in the risk of clinical (P = 0.011) and gastrointestinal bleeding (P = 0.032). Cox multiple regression analysis showed age (HR 1.13, 95% CI 1.03-1.24; P = 0.013) and warfarin therapy (HR 7.37, 95% CI 1.63-33.36; P = 0.010) were independent predictors of clinically relevant bleeding. Compared to warfarin, NOACs were associated with a lower incidence of clinically relevant bleeding in HCM patients with AF, as demonstrated by the similar incidence of death by all causes, cardiovascular death and thromboembolic events.

The effect of strategy game types on inhibition.

Past studies have shown evidence of transfer of learning in action video games, less so in other types, e.g. strategy games. Further, the transfer of learning from games to inhibitory control has yet to be examined from the perspectives of time constraint and logic contradiction. We examined the effect of strategy games (puzzle, turn-based strategy 'TBS', and real-time strategy 'RTS') on inhibition (response inhibition and distractor inhibition) and cerebral hemispheric activation over 4 weeks. We predicted that compared to RTS, puzzle and TBS games would (1) improve response and distractor inhibition, and (2) increase cerebral hemispheric activation demonstrating increased inhibitory control. A total of 67 non-habitual video game players (Mage = 21.63 years old, SD = 2.12) played one of three games: puzzle (n = 19), TBS (n = 24) or RTS (n = 24) for 4 weeks on their smartphones. Participants completed three inhibition tasks, working memory (WM), and had their tympanic membrane temperature (TMT) taken from each ear before and after playing the games. Results showed that only the puzzle game group showed an improved response inhibition while controlling for WM. There were no significant changes in the distractor inhibition tasks. We also found that there was an increase in left TMT while playing RTS, suggesting the presence of increased impulsivity in RTS. Our findings suggest that puzzle games involving logical contradiction could improve response inhibition, showing potential as a tool for inhibition training.

Pharmacokinetics, Safety, and Tolerability of Ravidasvir, with and without Danoprevir/Ritonavir, in Healthy Subjects.

Ravidasvir (RDV) is a novel oral hepatitis C virus NS5A inhibitor. This study aimed to evaluate the pharmacokinetics and safety of RDV and the drug-drug interactions between RDV and ritonavir-boosted danoprevir (DNVr) in healthy adults. In the 1st study, healthy volunteers were administered single oral doses of 100, 200, and 300 mg of RDV and 200 mg once daily for 7 days. The 2nd study was a randomized, double-blinded, and placebo-controlled sequential design (day 1 for 200 mg of RDV alone, day 7 for 100 mg/100 mg of DNVr, day 13 for 200 mg of RDV plus 100 mg/100 mg DNVr, followed by 200 mg of RDV once daily with 100 mg/100 mg of DNVr twice daily for 10 days). The results showed that RDV exposure increased in a dose-proportional manner following a single dose with no evidence of accumulation with multiple doses. Coadministration with DNVr (100 mg/100 mg, twice daily) resulted in a 2.92-fold and 1.99-fold increase in minimum plasma concentration at steady state (Cmin,ss) and area under the concentration-time curve at steady state (AUCτ) of RDV, respectively. With coadministration of RDV, maximum plasma concentration (Cmax) and area under the concentration-time curve from 0 to 12 h (AUC0-12) of DNV increased 1.71-fold and 2.33-fold, respectively. We did not observe any significant changes in ritonavir exposure. Both single and multiple doses of RDV with or without DNVr were well tolerated. The favorable pharmacokinetic and safety results support ravidasvir's continued clinical development and treatment. (The studies described in this paper have been registered at ClinicalTrials.gov under identifiers NCT03430830 and NCT03288636.).

Photoresponsive Electrochemical DNA Biosensors Achieving Various Dynamic Ranges by Using Only-One Capture Probe.

The rational design of DNA capture probes for modulating the binding affinity to tune the dynamic range of electrochemical DNA (E-DNA) biosensors is valuable and effective. Most of current strategies, however, require designing several DNA capture probes to achieve the tunable dynamic range, which is cumbersome and costly. Herein, we develop the photoresponsive E-DNA biosensors with tunable dynamic ranges by using only one photocleavable capture probe (PC-CP). The photoresponsive PC-CP is a stem-loop DNA structure containing a photocleavable linker (PC-linker) in the loop. The PC-linker can be cleaved by UV irradiation to switch the structure of PC-CP, through which the binding affinity to the target could be tuned. In this way, the dynamic range, the sensitivity, and the specificity of photoresponsive E-DNA biosensors can be tuned. Furthermore, the developed photoresponsive E-DNA biosensors enable sensitive and selective detection of target DNA in complex samples with a tunable dynamic range, which offers the possibility of clinical applications.

DNA Framework-Mediated Electrochemical Biosensing Platform for Amplification-Free MicroRNA Analysis.

MicroRNAs (miRNAs) have been explored as biomarkers for early diagnosis of diseases like cancers. However, it remains challenging to detect low-level miRNAs in the total RNA from real samples in a facile approach. In this work, we report a two-phase miRNA biosensing strategy based on a modular framework nucleic acid (FNA) platform, which combines the high efficiency of homogeneous reaction and the convenience of heterogeneous biosensing. In the first phase, free DNA probes bind target miRNAs in a homogeneous solution, forming a DNA-RNA complex with high base stacking energy. Then, at the second phase, the universal FNA interface on the electrode selectively mediated the transition of the complex from the solution onto the interface for electrochemical signal generating and transduction. By applying this method, we detected as few as 1 aM of miR-141, a cancer marker miRNA, without the need for nucleic acid amplification. The dynamic range spans 10 orders of magnitude. We demonstrate multiplex miRNA detection and discrimination of highly homologous miRNAs with mismatches as few as a single base. We also show that this system can detect miR-141 in only 50 ng of total RNA samples from real cells, which allows discrimination of prostate cancer cells with normal cells. We envision this platform may satisfy the need for facile and high-throughput screening of early cancer markers.

Improving Ion Selectivity of 1,4,7-Triazacyclononane-Based Receptor by Zinc Coordination: "Turn-On" Chemosensor for Br- and Fe3+ Ions.

Ion-responsive probes have gathered significant attention because of health and environmental factors, but there are few reports on the "turn-on" mechanism of Fe3+ and sensitive detection of Br- by fluorescence measurement. Herein, a green luminescence material, N-5-acetyl-2-hydroxy-benzamide-1,4,7-triazacyclononane (btacn), was successfully synthesized for the first time and comprehensively characterized. As expected, btacn exhibits high sensitive, but nonspecific, extensive interaction with Cu2+, Co2+, Zn2+, Mn2+, and Fe3+ ions. Therefore, to improve the specificity of the probe, we tried to synthesize transition metal complexes of btacn, but all failed except Zn(btacn)Cl2. In addition, the preformed complex, Zn(btacn)Cl2, was used as a special "turn-on" chemosensor for detecting trace amounts of Br- and Fe3+. The electrostatic interaction with Fe3+ and the hydrogen bond of PhO-H···Br- leads to obvious changes in the electronic cloud of Zn(btacn)Cl2, which are reflected in different spectral responses.

Potential Cytotoxicity, Pharmacokinetics, and Excretion Properties of Sapindoside B from the Seeds of Nigella sativa var. hispidula.

The seeds of Nigella sativa var. hispidula are widely used in food preparation by the Uighur people in western China. Recently, series of oleanane triterpenoid saponins were extracted from the seeds of Nigella sativa var. hispidula, especially α-hederin as representative that exhibited strong antitumor activity. Compared to α-hederin, sapindoside B has just 1 more terminal xylopyranose in the 3-O position and displays similar effects against various human cancer cell lines with cisplatin. Considering this potential cytotoxic activity, a reliable LC-MS/MS method was developed to quantify sapindoside B in rat plasma, urine, and feces. Chromatographic separation was conducted on an Agilent Zorbax SB-Aq (3.0 × 150 mm, 3.5 µm) column via an isocratic elution procedure with acetonitrile and water containing 0.1% formic acid. Mass spectrometric detection was coupled with an electrospray ionization source in the MRM mode. The linear range of calibration curves was 15 ~ 3000 ng/mL in plasma/urine and 30 ~ 3000 ng/g in feces. The intra-day and inter-day precision was less than 11.1%, and accuracy ranged from 92.2% to 108.7%. The proposed method was validated and shown to be reliable, precise, and accurate and was successfully applied to its pharmacokinetics and excretion studies. Sapindoside B exhibited dosage-dependent pharmacokinetics in the range of 2.5 mg/kg to 12.5 mg/kg, and only about 2% of intravenous dose of sapindoside B was excreted by the feces and urine in its unchanged form over 48 h. These results provide further data support for evaluating the druggability of sapindoside B.

DNA Framework-Programmed Cell Capture via Topology-Engineered Receptor-Ligand Interactions.

Receptor-ligand interactions (RLIs) that play pivotal roles in living organisms are often depicted with the classic keys-and-locks model. Nevertheless, RLIs on the cell surface are generally highly complex and nonlinear, partially due to the noncontinuous and dynamic distribution of receptors on extracellular membranes. Here, we develop a tetrahedral DNA framework (TDF)-programmed approach to topologically engineer RLIs on the cell membrane, which enables active recruitment-binding of clustered receptors for high-affinity capture of circulating tumor cells (CTCs). The four vertices of a TDF afford orthogonal anchoring of ligands with spatial organization, based on which we synthesized n-simplexes harboring 1-3 aptamers targeting epithelial cell adhesion molecule (EpCAM) that are overexpressed on the membrane of tumor cells. The 2-simplex with three aptamers not only shows increased binding affinity (∼19-fold) but prevents endocytosis by cells. By using 2-simplex as the capture probe, we demonstrate the high-efficiency CTC capture, which is challenged in real clinical breast cancer patient samples. This TDF-programmed platform thus provides a powerful means for studying RLIs in physiological settings and for cancer diagnosis.

Photoactivated Nanoflares for mRNA Detection in Single Living Cells.

Gold nanoparticles (AuNPs) have shown great promise as a universal platform for biosensing and are often functionalized with a densely packed DNA for intracellular detection. While DNA-AuNP conjugates, such as nanoflares, have been used for single and multiple mRNA molecules detection in living cells, the target recognition reaction is triggered once they enter into cells, making it impossible to control the initial reaction at the desired time. To solve this problem, we have designed photoactivated (PA) nanoflares for intracellular mRNA analysis with high spatiotemporal control. PA nanoflares consist of AuNP and photoresponsive DNA hairpin probes. Without UV irradiation, the DNA hairpin could be kept unawakened and show no reactivity to target the probe. Upon UV activation, the hairpin structures are destroyed and expose the sticky domains, which act as toeholds to mediate strand displacement reactions, making flares release from the gold surface and causing an increase of fluorescence. By tuning light irradiation, PA nanoflares for mRNA detection in living cells can be temporally controlled. With the benefit from two-photon laser illumination, PA nanoflares can detect mRNA in selective cells at a desired time point at the single-cell level. Compared to the traditional nanoflares, the novel PA nanoflares have increased the detection sensitivity and achieved intracellular biomarkers detection at the single-cell level with high spatiotemporal control.

Photoactivated Specific mRNA Detection in Single Living Cells by Coupling "Signal-on" Fluorescence and "Signal-off" Electrochemical Signals.

The spatiotemporal detection of a target mRNA in a single living cell is a major challenge in nanoscience and nanomedicine. We introduce a versatile method to detect mRNA at a single living cell level that uses photocleavable hairpin probes as functional units for the optical (fluorescent) and electrochemical (voltammetric) detection of MnSOD mRNA in single MCF-7 cancer cells. The fluorescent probe is composed of an ortho-nitrophenylphosphate ester functionalized hairpin that includes the FAM fluorophore in a caged configuration quenched by Dabcyl. The fluorescent probe is further modified with the AS1411 aptamer to facilitate the targeting and internalization of the probe into the MCF-7 cells. Under UV irradiation, the hairpin is cleaved, leading to the intracellular mRNA toehold-stimulated displacement of the FAM-functionalized strand resulting in a switched-on fluorescence signal upon the detection of the mRNA in a single cell. In addition, a nanoelectrode functionalized with a methylene blue (MB) redox-active photocleavable hairpin is inserted into the cytoplasm of a single MCF-7 cell. Photocleavage of the hairpin leads to the mRNA-mediated toehold displacement of the redox-active strand associated with the probe, leading to the depletion of the voltammetric response of the probe. The parallel optical and electrochemical detection of the mRNA at a single cell level is demonstrated.

Simultaneous pharmacokinetics and stability studies of physalins in rat plasma and intestinal bacteria culture media using liquid chromatography with mass spectrometry.

Physalins are the major steroidal constituent of Physalis plants and display a range of biological activities. For this study, a rapid and sensitive high-performance liquid chromatography with triple quadrupole mass spectrometry method was developed for the simultaneous quantification of six physalins. Specifically, it was for the quantification of physalin A, physalin B, physalin D, physalin G, 4,7-didehydroneophysalin B, and isophysalin B in rat plasma and rat intestinal bacteria. After a solid-phase extraction, analytes and internal standards (prednisolone) were separated on a Shield reverse-phase C18 column (measuring 3 mm × 150 mm with an internal diameter of 3.5 µm) and determined using multiple reactions in a monitoring mode with a positive-ion electrospray ionization source. The mobile phase was a mixture of 0.1% formic acid in water (A) and acetonitrile (B) and was used at a flow rate of 0.6 mL/min. The intra- and interday precisions were within 15% with accuracies ranging from 86.2 to 114%. The method was validated and successfully applied to pharmacokinetics and stability studies of six physalins in rat plasma and rat intestinal bacteria, respectively. The results showed that physalin B and isophysalin B could not be absorbed by rats, and rat intestinal bacteria could quickly transform physalins.

Identification and quantitative analysis of physalin D and its metabolites in rat urine and feces by liquid chromatography with triple quadrupole time-of-flight mass spectrometry.

Physalin D is known to show extensive bioactivities. However, no excretion study has elucidated the excretion of physalin D and its metabolites. This study investigates the excretion of physalin D and its metabolites in rats. Metabolites in rat urine and feces were separated and identified by liquid chromatography with triple quadrupole time-of-flight mass spectrometry. Furthermore, a validated high-performance liquid chromatography with tandem mass spectrometry method was developed to quantify physalin D, physalin D glucuronide, and physalin D sulfate in rat feces and urine after the intragastric administration of physalin D. The analyte showed good linearity over a wide concentration range (r > 0.995), and the lower limit of quantification was 0.0532 µg/mL and 0.226 µg/g for urine and feces, respectively. Nine metabolites, including five phase I and four phase II metabolites, were identified and clarified after dosing in vivo. Only 4.0% of the gavaged dose, including physalin D and its phase II metabolites, was excreted in urine, whereas 10.8% was found in feces in the unchanged form. The results indicate that the extensive and rapid metabolism may be the main factors leading to the short half-life of physalin D. These results can provide a basis for further studies on the structural modification and pharmacology of physalin D.

Chronic restraint stress attenuates p53 function and promotes tumorigenesis.

Epidemiological studies strongly suggest that chronic psychological stress promotes tumorigenesis. However, its direct link in vivo and the underlying mechanisms that cause this remain unclear. This study provides direct evidence that chronic stress promotes tumorigenesis in vivo; chronic restraint, a well-established mouse model to induce chronic stress, greatly promotes ionizing radiation (IR)-induced tumorigenesis in p53(+/-) mice. The tumor suppressor protein p53 plays a central role in tumor prevention. Loss or attenuation of p53 function contriubutes greatly to tumorigenesis. We found that chronic restraint decreases the levels and function of p53 in mice, and furthermore, promotes the growth of human xenograft tumors in a largely p53-dependent manner. Our results show that glucocorticoids elevated during chronic restraint mediate the effect of chronic restraint on p53 through the induction of serum- and glucocorticoid-induced protein kinase (SGK1), which in turn increases MDM2 activity and decreases p53 function. Taken together, this study demonstrates that chronic stress promotes tumorigenesis in mice, and the attenuation of p53 function is an important part of the underlying mechanism, which can be mediated by glucocortcoids elevated during chronic restraint.