RESUMEN
Staphylococcus aureus is an important human pathogen, and the prevalence of antibiotic resistance is a major public health concern. The evolution of pathogenicity and resistance in S. aureus often involves acquisition of mobile genetic elements (MGEs). Bacteriophages play an especially important role, since transduction represents the main mechanism for horizontal gene transfer. S. aureus pathogenicity islands (SaPIs), including SaPI1, are MGEs that carry genes encoding virulence factors, and are mobilized at high frequency through interactions with specific "helper" bacteriophages, such as 80α, leading to packaging of the SaPI genomes into virions made from structural proteins supplied by the helper. Among these structural proteins is the portal protein, which forms a ring-like portal at a fivefold vertex of the capsid, through which the DNA is packaged during virion assembly and ejected upon infection of the host. We have used high-resolution cryo-electron microscopy to determine structures of the S. aureus bacteriophage 80α portal itself, produced by overexpression, and in situ in the empty and full SaPI1 virions, and show how the portal interacts with the capsid. These structures provide a basis for understanding portal and capsid assembly and the conformational changes that occur upon DNA packaging and ejection.
Asunto(s)
Islas Genómicas , Fagos de Staphylococcus , Staphylococcus aureus , Humanos , Proteínas de la Cápside/química , Microscopía por Crioelectrón , Staphylococcus aureus/genética , Staphylococcus aureus/patogenicidad , Staphylococcus aureus/virología , Fagos de Staphylococcus/genética , Factores de Virulencia/genética , Transducción Genética , Empaquetamiento del ADN , Conformación de Ácido NucleicoRESUMEN
Staphylococcus aureus is an important human pathogen, and the prevalence of antibiotic resistance is a major public health concern. The evolution of pathogenicity and resistance in S. aureus often involves acquisition of mobile genetic elements (MGEs). Bacteriophages play an especially important role, since transduction represents the main mechanism for horizontal gene transfer. S. aureus pathogenicity islands (SaPIs), including SaPI1, are MGEs that carry genes encoding virulence factors, and are mobilized at high frequency through interactions with specific "helper" bacteriophages, such as 80α, leading to packaging of the SaPI genomes into virions made from structural proteins supplied by the helper. Among these structural proteins is the portal protein, which forms a ring-like portal at a fivefold vertex of the capsid, through which the DNA is packaged during virion assembly and ejected upon infection of the host. We have used high-resolution cryo-electron microscopy to determine structures of the S. aureus bacteriophage 80α portal in solution and in situ in the empty and full SaPI1 virions, and show how the portal interacts with the capsid. These structures provide a basis for understanding portal and capsid assembly and the conformational changes that occur upon DNA packaging and ejection.
RESUMEN
Staphylococcus epidermidis is an opportunistic pathogen of the human skin, often associated with infections of implanted medical devices. Staphylococcal picoviruses are a group of strictly lytic, short-tailed bacteriophages with compact genomes that are attractive candidates for therapeutic use. Here, we report the structure of the complete virion of S. epidermidis-infecting phage Andhra, determined using high-resolution cryo-electron microscopy, allowing atomic modeling of 11 capsid and tail proteins. The capsid is a T = 4 icosahedron containing a unique stabilizing capsid lining protein. The tail includes 12 trimers of a unique receptor binding protein (RBP), a lytic protein that also serves to anchor the RBPs to the tail stem, and a hexameric tail knob that acts as a gatekeeper for DNA ejection. Using structure prediction with AlphaFold, we identified the two proteins that comprise the tail tip heterooctamer. Our findings elucidate critical features for virion assembly, host recognition, and penetration.
Asunto(s)
Especificidad del Huésped , Fagos de Staphylococcus , Humanos , Staphylococcus epidermidis , Microscopía por Crioelectrón , Cápside , Proteínas de la CápsideRESUMEN
Rubbers are ubiquitous in engineering applications where they are often subjected to loading leading to high strain rate deformation. The strong rate and temperature dependence of rubbers and their composites motivates research into understanding their mechanical response under a wide range of conditions. However, experimental characterisation of the rate-temperature dependence of soft rubbers is challenging. In this methods paper, an improved methodology is proposed for conducting Dynamic Mechanical Analysis (DMA) experiments on rubbers. The higher quality data produced can be used in time-temperature superposition (TTS) applications to derive a more accurate definition of the rubber's rate-temperature dependence. Overall, the improvements obtained can be summarised as follows:â¢Overall, the proposed methodology can be summarised with the following improvements:â¢Reducing clamping artefacts due to volume expansionâ¢Ensuring high quality temperature stabilityâ¢Improving the contact area between the specimen and the clamps.
RESUMEN
Staphylococcus aureus pathogenicity islands (SaPIs) are molecular parasites that hijack helper phages for their transfer. SaPIbov5, the prototypical member of a family of cos type SaPIs, redirects the assembly of Ï12 helper capsids from prolate to isometric. This size and shape shift is dependent on the SaPIbov5-encoded protein Ccm, a homolog of the Ï12 capsid protein (CP). Using cryo-electron microscopy, we have determined structures of prolate Ï12 procapsids and isometric SaPIbov5 procapsids. Ï12 procapsids have icosahedral end caps with Tend = 4 architecture and a Tmid = 14 cylindrical midsection, whereas SaPIbov5 procapsids have T = 4 icosahedral architecture. We built atomic models for CP and Ccm, and show that Ccm occupies the pentameric capsomers in the isometric SaPIbov5 procapsids, suggesting that preferential incorporation of Ccm pentamers prevents the cylindrical midsection from forming. Our results highlight that pirate elements have evolved diverse mechanisms to suppress phage multiplication, including the acquisition of phage capsid protein homologs.
Asunto(s)
Staphylococcus/virología , Cápside/metabolismo , Proteínas de la Cápside/metabolismo , Islas Genómicas/genéticaRESUMEN
At LFB USA, Inc., the ultimate use for transgenic cloned goats is for the production of recombinant human protein therapeutics in their milk. This retrospective analysis of the Somatic Cell Nuclear Transfer (SCNT) program, spanning from 1998 to 2010, examined parameters potentially affecting the outcomes and efficiencies in this commercial operation. Over 37,000 + ova were utilized in the SCNT protocol producing a total of 203 cloned goats. Fifty one (51) clones were produced from non-transfected (transgenic and non-transgenic animal donor) cell lines and 152 clones were produced from transfected cell lines. Comparisons and summaries of (a) transfected versus non-transfected cell lines, (b) relationship of SCNT parameters to offspring produced, (c) skin versus fetal cells, (d) fresh versus cryopreserved cells, (e) parameters from all cell lines used versus those producing SCNT offspring, (f) variation among cell sources, (g) methods of SCNT parturition management and effects on live offspring, and lastly (h) SCNT variation by program are reported. Findings indicate that (a) non-transfected cell lines were more efficient versus transfected cell lines in generating viable cloned offspring on a per reconstructed embryo transferred basis, (b) transfected fetal fibroblasts had improved efficiency versus transfected skin fibroblasts, (c) the percentage of non-transfected cell lines that produced offspring was statistically higher than transfected cell lines, (d) and induction of parturition improved the percentage of viable offspring. In summary, this retrospective analysis on the SCNT process has identified certain parameters for improved efficiency in producing viable cloned goats in a commercial setting.
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Crianza de Animales Domésticos/métodos , Animales Modificados Genéticamente/genética , Blastocisto/citología , Transferencia de Embrión/veterinaria , Embrión de Mamíferos/citología , Feto/citología , Técnicas de Transferencia Nuclear/estadística & datos numéricos , Animales , Clonación de Organismos , Comercio , Cabras , Estudios RetrospectivosRESUMEN
AIMS: To estimate the rate at which people with diabetes and a low risk of foot ulceration change diabetic foot ulceration risk status over time, and to estimate the rate of ulceration, amputation and death among this population. METHODS: We conducted an observational study of 10 421 people with diabetes attending foot screening in an outpatient setting in NHS Fife, UK, using routinely collected data from a national diabetes register, NHS SCI Diabetes. We estimated the proportion of people who changed risk status and the cumulative incidence of ulceration, amputation and death, respectively, among people with diabetes at low risk of diabetic foot ulceration at 2-year follow-up. RESULTS: At 2-year follow-up, 5.1% (95% CI 4.7, 5.6) of people with diabetes classified as low risk at their first visit had progressed to moderate risk. The cumulative incidence of ulceration, amputation and death was 0.4% (95% CI 0.3, 0.6), 0.1% (95% CI 0.1, 0.2) and 3.4% (95% CI 3.1, 3.8), respectively. CONCLUSIONS: At 2-year follow-up, 5% of people at low risk of diabetic foot ulceration changed clinical risk status and <1% of people experienced foot ulceration or amputation. These findings provide information which will help to inform the current debate regarding optimal foot screening intervals.
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Amputación Quirúrgica/estadística & datos numéricos , Diabetes Mellitus/epidemiología , Pie Diabético/epidemiología , Mortalidad , Anciano , Femenino , Humanos , Masculino , Tamizaje Masivo/métodos , Persona de Mediana Edad , Guías de Práctica Clínica como Asunto , Medición de Riesgo , Reino Unido/epidemiologíaRESUMEN
OBJECTIVES: To evaluate the cost-effectiveness of changing opening times, introducing a donor health report and reducing the minimum inter-donation interval for donors attending static centres. BACKGROUND: Evidence is required about the effect of changes to the blood collection service on costs and the frequency of donation. METHODS/MATERIALS: This study estimated the effect of changes to the blood collection service in England on the annual number of whole-blood donations by current donors. We used donors' responses to a stated preference survey, donor registry data on donation frequency and deferral rates from the INTERVAL trial. Costs measured were those anticipated to differ between strategies. We reported the cost per additional unit of blood collected for each strategy versus current practice. Strategies with a cost per additional unit of whole blood less than £30 (an estimate of the current cost of collection) were judged likely to be cost-effective. RESULTS: In static donor centres, extending opening times to evenings and weekends provided an additional unit of whole blood at a cost of £23 and £29, respectively. Introducing a health report cost £130 per additional unit of blood collected. Although the strategy of reducing the minimum inter-donation interval had the lowest cost per additional unit of blood collected (£10), this increased the rate of deferrals due to low haemoglobin (Hb). CONCLUSION: The introduction of a donor health report is unlikely to provide a sufficient increase in donation frequency to justify the additional costs. A more cost-effective change is to extend opening hours for blood collection at static centres.
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Donantes de Sangre , Selección de Donante/economía , Adolescente , Adulto , Análisis Costo-Beneficio , Inglaterra , Femenino , Humanos , Masculino , Persona de Mediana EdadRESUMEN
The evolution of resistance poses an ongoing threat to crop protection. Fungicide resistance provides a selective advantage under fungicide selection, but resistance-conferring mutations may also result in fitness penalties, resulting in an evolutionary trade-off. These penalties may result from the functional constraints of an evolving target site or from the resource allocation costs of overexpression or active transport. The extent to which such fitness penalties are present has important implications for resistance management strategies, determining whether resistance persists or declines between treatments, and for resistance risk assessments for new modes of action. Experimental results have proven variable, depending on factors such as temperature, nutrient status, osmotic or oxidative stress, and pathogen life-cycle stage. Functional genetics tools allow pathogen genetic background to be controlled, but this in turn raises the question of epistatic interactions. Combining fitness penalties under various conditions into a field-realistic scenario poses an important future challenge.
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Evolución Biológica , Farmacorresistencia Fúngica/genética , Fungicidas Industriales/farmacología , Aptitud Genética , Enfermedades de las Plantas/prevención & controlRESUMEN
Production of transgenic founder goats involves introducing and stably integrating an engineered piece of DNA into the genome of the animal. At LFB USA, the ultimate use of these transgenic goats is for the production of recombinant human protein therapeutics in the milk of these dairy animals. The transgene or construct typically links a milk protein specific promoter sequence, the coding sequence for the gene of interest, and the necessary downstream regulatory sequences thereby directing expression of the recombinant protein in the milk during the lactation period. Over the time period indicated (1995-2012), pronuclear microinjection was used in a number of programs to insert transgenes into 18,120, 1- or 2- cell stage fertilized embryos. These embryos were transferred into 4180 synchronized recipient females with 1934 (47%) recipients becoming pregnant, 2594 offspring generated, and a 109 (4.2%) of those offspring determined to be transgenic. Even with new and improving genome editing tools now available, pronuclear microinjection is still the predominant and proven technology used in this commercial setting supporting regulatory filings and market authorizations when producing founder transgenic animals with large transgenes (> 10 kb) such as those necessary for directing monoclonal antibody production in milk.
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Animales Modificados Genéticamente , Ingeniería Genética/estadística & datos numéricos , Cabras/genética , Animales , Técnicas de Cultivo de Embriones , Femenino , Ingeniería Genética/métodos , Cabras/embriología , Masculino , Microinyecciones , Embarazo , Índice de Embarazo , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Estudios RetrospectivosRESUMEN
The ability to design and implement silk feedstock formulations for tailored spinning has so far eluded the bioengineers. Recently, the high throughput screening technique of differential scanning fluorimetry (DSF) demonstrated the link between the instability transition temperature (Ti) and the processability of the silk feedstock. Using DSF we screened a large set of chemicals known to affect solvent quality. A multivariate analysis of the results shows that, regardless of the diversity of chemicals, three groupings are significantly distinguishable: G1 = similar to native silk; G2 = largely dominated by electrostatic interactions; and G3 = dominated by chelating interactions. We propose a thermodynamic analysis based on a pre- and post-transition fit to estimate the van't Hoff enthalpies (ΔHv) and the instability temperature (Ti). Our analysis shows that the ΔTi and ΔHv values were distinct: G1 (ΔTi = 0.23 ± 0.2; ΔHv = -159.1 ± 5.6 kcal mol(-1)), G2 (ΔTi = -7.3 ± 0.7; ΔHv = -191.4 ± 5.5 kcal mol(-1)), and G3 (ΔTi = -19.9 ± 3.3; ΔHv = -68.8 ± 6.0 kcal mol(-1)). Our analysis further combined the ΔTi value and the ΔHv value using stability ΔΔG to find that G1 only marginally stabilizes native silks (ΔΔG = -0.15 ± 0.04 kcal mol(-1)), whereas G2 and G3 destabilize native silk (ΔΔG = 3.8 ± 0.11 and ΔΔG = 3.8 ± 0.3 kcal mol(-1), respectively). Here our analysis shows that native silk has a complex multistep transition that is possibly non-cooperative. However, all three groupings also show a direct and cooperative transition with varied stabilization effects. This analysis suggests that native silks are able to sample multiple substates prior to undergoing (or to delay) the final transition. We conclude by hypothesizing that the observed energetic plasticity may be mediated by a fragile packaging of the silk tertiary structure that is readily lost when the solvent quality changes.
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Seda/química , Temperatura de Transición , Quelantes/química , Fluorometría , Conformación Proteica , Estabilidad Proteica , Electricidad Estática , Industria Textil/normasRESUMEN
OBJECTIVE: Implantable cardioverter defibrillators (ICD), cardiac resynchronisation therapy pacemakers (CRT-P) and the combination therapy (CRT-D) have been shown to reduce all-cause mortality compared with medical therapy alone in patients with heart failure and reduced EF. Our aim was to synthesise data from major randomised controlled trials to estimate the comparative mortality effects of these devices and how these vary according to patients' characteristics. METHODS: Data from 13 randomised trials (12â 638 patients) were provided by medical technology companies. Individual patient data were synthesised using network meta-analysis. RESULTS: Unadjusted analyses found CRT-D to be the most effective treatment (reduction in rate of death vs medical therapy: 42% (95% credible interval: 32-50%), followed by ICD (29% (20-37%)) and CRT-P (28% (15-40%)). CRT-D reduced mortality compared with CRT-P (19% (1-33%)) and ICD (18% (7-28%)). QRS duration, left bundle branch block (LBBB) morphology, age and gender were included as predictors of benefit in the final adjusted model. In this model, CRT-D reduced mortality in all subgroups (range: 53% (34-66%) to 28% (-1% to 49%)). Patients with QRS duration ≥150â ms, LBBB morphology and female gender benefited more from CRT-P and CRT-D. Men and those <60 years benefited more from ICD. CONCLUSIONS: These data provide estimates for the mortality benefits of device therapy conditional upon multiple patient characteristics. They can be used to estimate an individual patient's expected relative benefit and thus inform shared decision making. Clinical guidelines should discuss age and gender as predictors of device benefits.
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Desfibriladores Implantables , Insuficiencia Cardíaca/mortalidad , Terapia de Resincronización Cardíaca/mortalidad , Dispositivos de Terapia de Resincronización Cardíaca , Terapia Combinada/mortalidad , Femenino , Insuficiencia Cardíaca/terapia , Humanos , Masculino , Ensayos Clínicos Controlados Aleatorios como Asunto , Volumen Sistólico/fisiologíaRESUMEN
OBJECTIVE: To analyse the falls in coronary heart disease (CHD) mortality in England between 2000 and 2007 and quantify the relative contributions from preventive medications and population-wide changes in blood pressure (BP) and cholesterol levels, particularly by exploring socioeconomic inequalities. DESIGN: A modelling study. SETTING: Sources of data included controlled trials and meta-analyses, national surveys and official statistics. PARTICIPANTS: English population aged 25+ in 2000-2007. MAIN OUTCOME MEASURES: Number of deaths prevented or postponed (DPPs) in 2007 by socioeconomic status. We used the IMPACTSEC model which applies the relative risk reduction quantified in previous randomised controlled trials and meta-analyses to partition the mortality reduction among specific treatments and risk factor changes. RESULTS: Between 2000 and 2007, approximately 20â 400 DPPs were attributable to reductions in BP and cholesterol in the English population. The substantial decline in BP was responsible for approximately 13â 000 DPPs. Approximately 1800 DPPs came from medications and some 11â 200 DPPs from population-wide changes. Reduction in population BP prevented almost twofold more deaths in the most deprived quintile compared with the most affluent. Reduction in cholesterol resulted in approximately 7400 DPPs; approximately 5300 DPPs were attributable to statin use and approximately 2100 DPPs to population-wide changes. Statins prevented almost 50% more deaths in the most affluent quintile compared with the most deprived. Conversely, population-wide changes in cholesterol prevented threefold more deaths in the most deprived quintile compared with the most affluent. CONCLUSIONS: Population-wide secular changes in systolic blood pressure (SBP) and cholesterol levels helped to substantially reduce CHD mortality and the associated socioeconomic disparities. Mortality reductions were, in absolute terms, greatest in the most deprived quintiles, mainly reflecting their bigger initial burden of disease. Statins for high-risk individuals also made an important contribution but maintained socioeconomic inequalities. Our results strengthen the case for greater emphasis on preventive approaches, particularly population-based policies to reduce SBP and cholesterol.
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Enfermedad Coronaria/mortalidad , Prevención Primaria/métodos , Adulto , Anciano , Antihipertensivos/uso terapéutico , Presión Sanguínea/fisiología , Colesterol/sangre , Enfermedad Coronaria/fisiopatología , Enfermedad Coronaria/prevención & control , Inglaterra/epidemiología , Femenino , Humanos , Inhibidores de Hidroximetilglutaril-CoA Reductasas/uso terapéutico , Hipertensión/tratamiento farmacológico , Masculino , Persona de Mediana Edad , Modelos Estadísticos , Factores de Riesgo , Factores Sexuales , Factores SocioeconómicosRESUMEN
We compared the efficacy of ponatinib and second-generation tyrosine kinase inhibitors (2G-TKIs: bosutinib, dasatinib, and nilotinib) in chronic phase CML resistant/intolerant to ≥1 prior 2G-TKI. Estimated probabilities of CCyR with 2G-TKI ranged from 22% to 26%, compared with 60% (95% CrI 52-68%) with ponatinib. The estimated probability of ponatinib providing higher response rate than all other included treatments was 99% (CCyR) and 97% (MCyR). Use of further 2G-TKI may provide limited benefit in CP-CML patients resistant/intolerant to prior 2G-TKI treatment. Compared with 2G-TKIs, ponatinib is estimated to provide substantially higher probability of achieving CCyR and MCyR; safety was not compared.
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Leucemia Mielógena Crónica BCR-ABL Positiva/tratamiento farmacológico , Inhibidores de Proteínas Quinasas/uso terapéutico , Supervivencia sin Enfermedad , Humanos , Leucemia Mielógena Crónica BCR-ABL Positiva/mortalidad , Inhibidores de Proteínas Quinasas/efectos adversos , Tasa de SupervivenciaRESUMEN
PURPOSE: Wnt signalling has been implicated in breast cancer, and in particular aberrant ß-catenin-independent Wnt signalling has been associated with breast cancer metastasis and Tamoxifen resistance. Despite Wnt pathway involvement in many human cancers, attempts to target the pathway therapeutically have been disappointing. The recent discovery that the receptor tyrosine kinase-like orphan receptor 2 (ROR2) is a novel Wnt receptor provides a potential new therapeutic and diagnostic target. METHODS: To clarify the role of ROR2 in breast cancer, we investigated its expression via ROR2 immunohistochemistry in a clinical cohort of breast cancer patients, and via in vitro studies incorporating both overexpression and knock-down of ROR2. RESULTS: ROR2 was expressed in the majority of breast cancer patients (87%), including those classed as triple negative. Breast cancer patients expressing ROR2 had a significantly shorter overall survival than those lacking ROR2 expression (P < 0.05). Overexpression of ROR2 in the mammary epithelial cell line, MCF10A, increased both ß-catenin-dependent and ß-catenin-independent targets and decreased cell adhesion. Knock-down of ROR2 in the breast cancer cell lines, MDA-MB-453 and HCC1143, decreased both ß-catenin-dependent and ß-catenin-independent targets and increased cell adhesion. Treatment of ROR2-expressing breast cancer cells with the novel berberine derivative, NAX53, significantly inhibited cell proliferation and migration. CONCLUSIONS: This is the first study to report the expression of ROR2 in breast cancer. Breast cancer patients expressing ROR2 had a significantly worse prognosis than those lacking ROR2. ROR2 may regulate both ß-catenin-dependent and ß-catenin-independent Wnt signalling pathways, and represents a potential diagnostic and therapeutic target.
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Regulación Neoplásica de la Expresión Génica , Receptores Huérfanos Similares al Receptor Tirosina Quinasa/metabolismo , Transducción de Señal , Neoplasias de la Mama Triple Negativas/metabolismo , Proteínas Wnt/metabolismo , beta Catenina/metabolismo , Apoptosis , Western Blotting , Mama/citología , Mama/metabolismo , Adhesión Celular , Movimiento Celular , Proliferación Celular , Células Cultivadas , Estudios de Cohortes , Femenino , Estudios de Seguimiento , Humanos , Técnicas para Inmunoenzimas , Invasividad Neoplásica , Estadificación de Neoplasias , Pronóstico , ARN Mensajero/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Receptores Huérfanos Similares al Receptor Tirosina Quinasa/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Tasa de Supervivencia , Análisis de Matrices Tisulares , Neoplasias de la Mama Triple Negativas/mortalidad , Neoplasias de la Mama Triple Negativas/patología , Proteínas Wnt/genética , beta Catenina/genéticaRESUMEN
The aim of this study was to develop a user-friendly checklist for critical appraisal of indirect comparisons of drugs, considering clinical, methodological/statistical and quality aspects, mainly to be applied in drug evaluation in the decision-making context. After conducting a review of the literature, we used group consensus to establish the key points of the checklist, focusing mainly on indirect comparisons, but including topics related to network meta-analysis or multiple treatment comparisons. The coordinating group elaborated the first draft, which was reviewed by external experts, re-evaluated by the coordinating group and finally assessed by 23 drug evaluation experts trained in indirect comparisons, who applied the checklist to one study. The Kappa index of agreement was calculated and the final checklist was developed by group consensus including the external experts. The checklist has two parts. The first consists of three eliminatory key questions while the second includes 17 items: 5 regarding quality, 5 regarding clinical issues and 7 dealing with methodology/statistics. The median kappa values of the 23 evaluations were 0.83 (range 0.67-0.93), 0.61 (0.54-0.91) and 0.36 (0.22-1) with regard to quality, clinical aspects and methodology/statistics, respectively. A structured checklist was developed to facilitate critical appraisal of key issues in indirect comparisons, including comments for assessing the consequences of its application to drug evaluation in the decision-making context. Agreement between reviewers in clinical and quality items was good, but weaker in methodology/statistics ones.
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Benchmarking , Lista de Verificación , Técnicas de Apoyo para la Decisión , Medicina Basada en la Evidencia/métodos , Medicina Basada en la Evidencia/normas , HumanosRESUMEN
BACKGROUND: RAD21 is a component of the cohesion complex and is integral to chromosome segregation and error-free DNA repair. RAD21 is functionally important in tumour progression but its role in colorectal carcinoma (CRC) is unclear. We therefore assessed its clinicopathological and prognostic significance in CRC, as well as its effect on chemosensitivity. METHODS: A retrospective observation study examined RAD21 expression in 652 CRCs using a tissue microarray approach. Correlation with clinicopathological factors including gender, tumour grade, mucinous subtype, TNM stage, disease-specific survival (DSS), BRAF and KRAS mutation status, tumour p53 immunostaining, tumour microsatellite instability and tumour CpG island methylator phenotype was performed. Colorectal cancer cell clones with stable RAD21 knockdown were generated and tested for cellular sensitivity to conventional chemotherapeutic drugs. RESULTS: RAD21 expression was significantly correlated with male gender (56.7% vs 43.3%, P=0.02), well-differentiated histology (14.4% vs 4.0%, P=0.0001), higher T-stage (36.1% vs 27.0%, P=0.01), presence of metastasis (18.8% vs 12.6%, P=0.03), and shorter DSS (hazard ratio (HR) 1.4, 95% CI 1.1 to 1.9, P=0.01) in both univariate and multivariate analysis. RAD21 expression was associated with shorter DSS in patients with KRAS mutant tumours (HR:2.6, 95% CI:1.4-4.3, P=0.001) and in patients receiving adjuvant chemoradiotherapy (HR:1.9, 95% CI:1.2-3.0, P=0.008). Colorectal cancer cells with RAD21 knockdown exhibited enhanced sensitivity to 5-fluorouracil, either alone or in combination with oxaliplatin. CONCLUSIONS: RAD21 expression in CRC is associated with aggressive disease especially in KRAS mutant tumours and resistance to chemoradiotherapy. RAD21 may be an important novel therapeutic target.