954 resultados para Disease evolution model
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International audience
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This research explores the business model (BM) evolution process of entrepreneurial companies and investigates the relationship between BM evolution and firm performance. Recently, it has been increasingly recognised that the innovative design (and re-design) of BMs is crucial to the performance of entrepreneurial firms, as BM can be associated with superior value creation and competitive advantage. However, there has been limited theoretical and empirical evidence in relation to the micro-mechanisms behind the BM evolution process and the entrepreneurial outcomes of BM evolution. This research seeks to fill this gap by opening up the ‘black box’ of the BM evolution process, exploring the micro-patterns that facilitate the continuous shaping, changing, and renewing of BMs and examining how BM evolutions create and capture value in a dynamic manner. Drawing together the BM and strategic entrepreneurship literature, this research seeks to understand: (1) how and why companies introduce BM innovations and imitations; (2) how BM innovations and imitations interplay as patterns in the BM evolution process; and (3) how BM evolution patterns affect firm performances. This research adopts a longitudinal multiple case study design that focuses on the emerging phenomenon of BM evolution. Twelve entrepreneurial firms in the Chinese Online Group Buying (OGB) industry were selected for their continuous and intensive developments of BMs and their varying success rates in this highly competitive market. Two rounds of data collection were carried out between 2013 and 2014, which generates 31 interviews with founders/co-founders and in total 5,034 pages of data. Following a three-stage research framework, the data analysis begins by mapping the BM evolution process of the twelve companies and classifying the changes in the BMs into innovations and imitations. The second stage focuses down to the BM level, which addresses the BM evolution as a dynamic process by exploring how BM innovations and imitations unfold and interplay over time. The final stage focuses on the firm level, providing theoretical explanations as to the effects of BM evolution patterns on firm performance. This research provides new insights into the nature of BM evolution by elaborating on the missing link between BM dynamics and firm performance. The findings identify four patterns of BM evolution that have different effects on a firm’s short- and long-term performance. This research contributes to the BM literature by presenting what the BM evolution process actually looks like. Moreover, it takes a step towards the process theory of the interplay between BM innovations and imitations, which addresses the role of companies’ actions, and more importantly, reactions to the competitors. Insights are also given into how entrepreneurial companies achieve and sustain value creation and capture by successfully combining the BM evolution patterns. Finally, the findings on BM evolution contributes to the strategic entrepreneurship literature by increasing the understanding of how companies compete in a more dynamic and complex environment. It reveals that, the achievement of superior firm performance is more than a simple question of whether to innovate or imitate, but rather an integration of innovation and imitation strategies over time. This study concludes with a discussion of the findings and their implications for theory and practice.
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The Li-ion rechargeable battery (LIB) is widely used as an energy storage device, but has significant limitations in battery cycle life and safety. During initial charging, decomposition of the ethylene carbonate (EC)-based electrolytes of the LIB leads to the formation of a passivating layer on the anode known as the solid electrolyte interphase (SEI). The formation of an SEI has great impact on the cycle life and safety of LIB, yet mechanistic aspects of SEI formation are not fully understood. In this dissertation, two surface science model systems have been created under ultra-high vacuum (UHV) to probe the very initial stage of SEI formation at the model carbon anode surfaces of LIB. The first model system, Model System I, is an lithium-carbonate electrolyte/graphite C(0001) system. I have developed a temperature programmed desorption/temperature programmed reaction spectroscopy (TPD/TPRS) instrument as part of my dissertation to study Model System I in quantitative detail. The binding strengths and film growth mechanisms of key electrolyte molecules on model carbon anode surfaces with varying extents of lithiation were measured by TPD. TPRS was further used to track the gases evolved from different reduction products in the early-stage SEI formation. The branching ratio of multiple reaction pathways was quantified for the first time and determined to be 70.% organolithium products vs. 30% inorganic lithium product. The obtained branching ratio provides important information on the distribution of lithium salts that form at the very onset of SEI formation. One of the key reduction products formed from EC in early-stage SEI formation is lithium ethylene dicarbonate (LEDC). Despite intensive studies, the LEDC structure in either the bulk or thin-film (SEI) form is unknown. To enable structural study, pure LEDC was synthesized and subject to synchrotron X-ray diffraction measurements (bulk material) and STM measurements (deposited films). To enable studies of LEDC thin films, Model System II, a lithium ethylene dicarbonate (LEDC)-dimethylformamide (DMF)/Ag(111) system was created by a solution microaerosol deposition technique. Produced films were then imaged by ultra-high vacuum scanning tunneling microscopy (UHV-STM). As a control, the dimethylformamide (DMF)-Ag(111) system was first prepared and its complex 2D phase behavior was mapped out as a function of coverage. The evolution of three distinct monolayer phases of DMF was observed with increasing surface pressure — a 2D gas phase, an ordered DMF phase, and an ordered Ag(DMF)2 complex phase. The addition of LEDC to this mixture, seeded the nucleation of the ordered DMF islands at lower surface pressures (DMF coverages), and was interpreted through nucleation theory. A structural model of the nucleation seed was proposed, and the implication of ionic SEI products, such as LEDC, in early-stage SEI formation was discussed.
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International audience
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Tese de Doutoramento, Ciências Biomédicas, Departamento de Ciências Biomédicas e Medicina, Universidade do Algarve, 2016
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Purpose: To evaluate the protective effects of Cuminum cyminum Linn (Apiaceae, CCY) against 1- methyl-4 phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced oxidative stress and behavioral impairments in mouse model of Parkinson’s disease (PD). Methods: MPTP-intoxicated mice model of PD was used for evaluating the effect of CCY extract on behavioral deficits through rota rod, passive avoidance and open field tasks. The effect of CCY extract on oxidative stress levels were assessed by estimating enzyme status, including superoxide dismutase (SOD), catalase (CAT) and lipid peroxidation(LPO) in brain tissues of MPTP-induced mice. Results: MPTP (25 mg/kg, i.p.)-treated mice resulted in a significant (p < 0.001) behavioral deficit in locomotor behavior (from 56.24 ± 1.21 to 27.64 ± 0.94) and cognitive functions (from 298 ± 3.68 s to 207.28 ± 4.12 s) compared with their respective control groups. Administration of CCY extract (100, 200 and 300 mg/kg, p.o.) for three weeks significantly and dose-dependently improved (p < 0.001 at 300 mg/kg) locomotor and cognitive deficits in MPTP-treated mice. CCY treatment also significantly (p < 0.001 at 300 mg/kg) inhibited MPTP-induced decrease in antioxidant enzyme levels (superoxide dismutase and catalase) and lipid peroxides in mice brain tissues. Conclusion: CCY extract exhibits strong protection against MPTP-induced behavioral deficit through enhancement of antioxidant defense mechanisms. Therefore, CCY may be developed as a therapeutic strategy in the treatment of neurodegeneration seen in PD.
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Understanding how virus strains offer protection against closely related emerging strains is vital for creating effective vaccines. For many viruses, including Foot-and-Mouth Disease Virus (FMDV) and the Influenza virus where multiple serotypes often co-circulate, in vitro testing of large numbers of vaccines can be infeasible. Therefore the development of an in silico predictor of cross-protection between strains is important to help optimise vaccine choice. Vaccines will offer cross-protection against closely related strains, but not against those that are antigenically distinct. To be able to predict cross-protection we must understand the antigenic variability within a virus serotype, distinct lineages of a virus, and identify the antigenic residues and evolutionary changes that cause the variability. In this thesis we present a family of sparse hierarchical Bayesian models for detecting relevant antigenic sites in virus evolution (SABRE), as well as an extended version of the method, the extended SABRE (eSABRE) method, which better takes into account the data collection process. The SABRE methods are a family of sparse Bayesian hierarchical models that use spike and slab priors to identify sites in the viral protein which are important for the neutralisation of the virus. In this thesis we demonstrate how the SABRE methods can be used to identify antigenic residues within different serotypes and show how the SABRE method outperforms established methods, mixed-effects models based on forward variable selection or l1 regularisation, on both synthetic and viral datasets. In addition we also test a number of different versions of the SABRE method, compare conjugate and semi-conjugate prior specifications and an alternative to the spike and slab prior; the binary mask model. We also propose novel proposal mechanisms for the Markov chain Monte Carlo (MCMC) simulations, which improve mixing and convergence over that of the established component-wise Gibbs sampler. The SABRE method is then applied to datasets from FMDV and the Influenza virus in order to identify a number of known antigenic residue and to provide hypotheses of other potentially antigenic residues. We also demonstrate how the SABRE methods can be used to create accurate predictions of the important evolutionary changes of the FMDV serotypes. In this thesis we provide an extended version of the SABRE method, the eSABRE method, based on a latent variable model. The eSABRE method takes further into account the structure of the datasets for FMDV and the Influenza virus through the latent variable model and gives an improvement in the modelling of the error. We show how the eSABRE method outperforms the SABRE methods in simulation studies and propose a new information criterion for selecting the random effects factors that should be included in the eSABRE method; block integrated Widely Applicable Information Criterion (biWAIC). We demonstrate how biWAIC performs equally to two other methods for selecting the random effects factors and combine it with the eSABRE method to apply it to two large Influenza datasets. Inference in these large datasets is computationally infeasible with the SABRE methods, but as a result of the improved structure of the likelihood, we are able to show how the eSABRE method offers a computational improvement, leading it to be used on these datasets. The results of the eSABRE method show that we can use the method in a fully automatic manner to identify a large number of antigenic residues on a variety of the antigenic sites of two Influenza serotypes, as well as making predictions of a number of nearby sites that may also be antigenic and are worthy of further experiment investigation.
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Cysticercosis results from the ingestion Taenia solium eggs directly by faecal-oral route or contaminated food or water. Human tapeworm carriers who have become infected after ingesting pork meat contaminated with cysticerci release these eggs. Cysticercosis occurs after tapeworm eggs are ingested by an intermediate host (pig or human) and then hatch, migrate, and lodge in the host's tissues, where they develop onto larval cysticerci. When they lodged in the central nervous system of humans, results in the disease condition called Neurocysticercosis (NCC), with a heterogeneous manifestations depending of the locations of cysts, number, size and their stage of evolution (1). Consequently the prognostic ranges from asymptomatic to situations leading to death in 2% to 9.8%. of cases (7) In swine’s there are few studies, but recent works have proved that animals, for the same reasons, also have neurological abnormalities, expressed by seizures, stereotypic walk in circles, chewing motions with foamy salivation included tonic muscle contractions followed by a sudden diminution in all muscle tone leading to collapse (2). Conventional domestic wastewater treatment processes may not be totally effective in inactivating parasites eggs from Taenia solium, allowing some contamination of soils and agricultural products (11). In Portugal there are some evidence of aggregation of human cysticercosis cases in specific regions, bases in ecological design studies (6). There are few information about human tapeworm carriers and social and economic factors associated with them. Success in knowledge and consequently in lowering transmission is limited by the complex network of biological and social factors that maintain the spread. Effective control of mostly zoonosis require One Health approach, after a real knowledge and transparency in the information provided by the institutions responsible for both animal and human health, allowing sustained interventions targeted at the transmission cycle's crucial nodes. In general, the model used to control, reflects a rural reality, where pigs are raised freely, poor sanitation conditions and incipient sanitary inspection. In cysticercosis, pigs are obligate intermediate hosts and so considered as first targets for control and used as sentinels to monitor environmental T. solium contamination (3). Usually environmental contamination with Taenia spp. eggs is a key issue in most of studies with landscape factors influencing presence of Taenia spp. antigens in both pigs and humans (5). Soil-related factors as well as socio-economic and behavioural factors are associated with the emergence of significant clustering human cysticercosis (4,5). However scarce studies has been produced in urban environmental and in developed countries with the finality to characterize the spatial pattern. There are still few data available regarding its prevalence and spatial distribution; Transmission patterns are likely to exhibit correlations as housing conditions, water supply, basic sanitation, schooling and birthplace of the individual or relatives, more than pigs rearing free, soil conditions (9). As a matter of fact, tapeworm carriers from endemic zones can auto-infect or transmit infection to other people or arrive already suffering NCC (as a result of travelling to or being a citizen from an endemic cysticercosis country) to a free cysticercosis country. Transmission is fecal-oral; this includes transmission through person-to-person contact, through autoinfection, or through contaminated food This has been happening in different continents as North America (5.4–18% been autochthonous), Europe and Australia (7). Recently, case reports of NCC have also emerged from Muslim countries. (10). Actually, different papers relate an epidemic situation in Spain and Portugal (7, 8). However the kind of study done does not authorize such conclusion. There are no evidence that infections were acquired in Portugal and there are not characterized the mode of transmission. Papers with these kind of information will be allow to have economic consequences resulted from artificial trade barriers with serious consequences for pig producers and pig meat trade. We need transparency in information’s that allow provide the basis to support the development and targeting of future effective control programmes (and prove we need that). So, to have a real picture of the disease, it is necessary integrate data from human, animal and environmental factors surrounding human and pig cases to characterize the pattern of the transmission. The design needs to be able to capture unexpected, and not common outcomes (routine data). We need to think “One Health” to get a genuine image of the situation.
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Fabry disease (FD) is an X‐linked inherited, lysosomal storage disorder characterized by a deficient activity of the enzyme α-Galactosidase A (α-Gal A). This deficiency causes an accumulation of globotriaosylceramide 3 (Gb3), in nearly all organs. Gastrointestinal (GI) symptoms are among the earliest and most frequent symptoms of FD. It has been hypothesized that Gb3 accumulation is the leading cause of these, but their pathophysiology is complex and still poorly understood. Here, we aim at understanding the molecular mechanisms underpinning the GI symptoms of FD. For this purpose, we used the α‐Gal A (-/0) male mouse, a murine model of FD, to characterize morphological and molecular features of the colon tract. Our results show that α‐Gal A (-/0) mice display a thickening of the muscular layer due to a hypertrophic state of myenteric plexus ganglia, caused by an accumulation of Gb3 in neurons. Also, α-Gal A (-/0) mice present a decreased density of mucosal nerve fibres. Furthermore, α-Gal A (-/0) mice presented visceral hyperalgesia, by showing greater visceromotor response (VMR) values and obtaining higher abdominal withdrawal reflex (AWR) scores, following colorectal distension (CRD). Subsequently, the immunoreactivity of the pain-related ion channels TRPV1, TRPV4, TRPA1 and TRPM8 was detected at level of myenteric and submucosal plexus ganglia of both the genotypes. Further studies are required to assess differences of expression between α-Gal A (-/0) and control mice. Finally, we optimized the protocols to obtain three types of primary cultures from mouse intestine to be tested electrophysiologically: a mixed culture containing neurons and glia, an enriched culture of neurons, and one of glia. In summary, we revealed alterations that are likely to be part of the pathophysiological causes of FD GI symptoms. Therefore, together with further studies, this work could help identify new therapeutic targets for the treatment of visceral pain in FD.
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Alzheimer's disease (AD) is the most common neurodegenerative disease in elderly. Donepezil is the first-line drug used for AD. In section one, the experimental activity was oriented to evaluate and characterize molecular and cellular mechanisms that contribute to neurodegeneration induced by the Aβ1-42 oligomers (Aβ1-42O) and potential neuroprotective effects of the hybrids feruloyl-donepezil compound called PQM130. The effects of PQM130 were compared to donepezil in a murine AD model, obtained by intracerebroventricular (i.c.v.) injection of Aβ1-42O. The intraperitoneal administration of PQM130 (0.5-1 mg/kg) after i.c.v. Aβ1-42O injection improved learning and memory, protecting mice against spatial cognition decline. Moreover, it reduced oxidative stress, neuroinflammation and neuronal apoptosis, induced cell survival and protein synthesis in mice hippocampus. PQM130 modulated different pathways than donepezil, and it is more effective in counteracting Aβ1-42O damage. The section two of the experimental activity was focused on studying a loss of function variants of ABCA7. GWA studies identified mutations in the ABCA7 gene as a risk factor for AD. The mechanism through which ABCA7 contributes to AD is not clear. ABCA7 regulates lipid metabolism and critically controls phagocytic function. To investigate ABCA7 functions, CRISPR/Cas9 technology was used to engineer human iPSCs and to carry the genetic variant Y622*, which results in a premature stop codon, causing ABCA7 loss-of-function. From iPSCs, astrocytes were generated. This study revealed the effects of ABCA7 loss in astrocytes. ABCA7 Y622* mutation induced dysfunctional endocytic trafficking, impairing Aβ clearance, lipid dysregulation and cell homeostasis disruption, alterations that could contribute to AD. Though further studies are needed to confirm the PQM130 neuroprotective role and ABCA7 function in AD, the provided results showed a better understanding of AD pathophysiology, a new therapeutic approach to treat AD, and illustrated an innovative methodology for studying the disease.
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Fabry disease (FD), X-linked metabolic disorder caused by a deficiency in α-galactosidase A activity, leads to the accumulation of glycosphingolipids, mainly Gb3 and lyso-Gb3, in several organs. Gastrointestinal (GI) symptoms are among the earliest and most common, strongly impacting patients’ quality of life. However, the origin of these symptoms and the exact mechanisms of pathogenesis are still poorly understood, thus the pressing need to improve their knowledge. Here we aimed to evaluate whether a FD murine model (α-galactosidase A Knock-Out) captures the functional GI issues experienced by patients. In particular, the potential mechanisms involved in the development and maintenance of GI symptoms were explored by looking at the microbiota-gut-brain axis involvement. Moreover, we sought to examine the effects of lyso-Gb3 on colonic contractility and the intestinal epithelium and the enteric nervous system, which together play important roles in regulating intestinal ion transport and fluid and electrolyte homeostasis. Fabry mice revealed visceral hypersensitivity and a diarrhea-like phenotype accompanied by anxious-like behavior and reduced locomotor activity. They reported also an imbalance of SCFAs and an early compositional and functional dysbiosis of the gut microbiota, which partly persisted with advancing age. Moreover, overexpression of TRPV1 was found in affected mice, and partial alteration of TRPV4 and TRPA1 as well, identifying them as possible therapeutic targets. The Ussing chamber results after treatment with lyso-Gb3 showed an increase in Isc (likely mediated by HCO3- ions movement) which affects neuron-mediated secretion, especially capsaicin- and partly veratridine-mediated. This first characterization of gut-brain axis dysfunction in FD mouse provides functional validation of the model, suggesting new targets and possible therapeutic approaches. Furthermore, lyso-Gb3 is confirmed to be not only a marker for the diagnosis and follow-up of FD but also a possible player in the alteration of the FD colonic ion transport process.
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In this work, integro-differential reaction-diffusion models are presented for the description of the temporal and spatial evolution of the concentrations of Abeta and tau proteins involved in Alzheimer's disease. Initially, a local model is analysed: this is obtained by coupling with an interaction term two heterodimer models, modified by adding diffusion and Holling functional terms of the second type. We then move on to the presentation of three nonlocal models, which differ according to the type of the growth (exponential, logistic or Gompertzian) considered for healthy proteins. In these models integral terms are introduced to consider the interaction between proteins that are located at different spatial points possibly far apart. For each of the models introduced, the determination of equilibrium points with their stability and a study of the clearance inequalities are carried out. In addition, since the integrals introduced imply a spatial nonlocality in the models exhibited, some general features of nonlocal models are presented. Afterwards, with the aim of developing simulations, it is decided to transfer the nonlocal models to a brain graph called connectome. Therefore, after setting out the construction of such a graph, we move on to the description of Laplacian and convolution operations on a graph. Taking advantage of all these elements, we finally move on to the translation of the continuous models described above into discrete models on the connectome. To conclude, the results of some simulations concerning the discrete models just derived are presented.
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This study aimed at evaluating whether human papillomavirus (HPV) groups and E6/E7 mRNA of HPV 16, 18, 31, 33, and 45 are prognostic of cervical intraepithelial neoplasia (CIN) 2 outcome in women with a cervical smear showing a low-grade squamous intraepithelial lesion (LSIL). This cohort study included women with biopsy-confirmed CIN 2 who were followed up for 12 months, with cervical smear and colposcopy performed every three months. Women with a negative or low-risk HPV status showed 100% CIN 2 regression. The CIN 2 regression rates at the 12-month follow-up were 69.4% for women with alpha-9 HPV versus 91.7% for other HPV species or HPV-negative status (P < 0.05). For women with HPV 16, the CIN 2 regression rate at the 12-month follow-up was 61.4% versus 89.5% for other HPV types or HPV-negative status (P < 0.05). The CIN 2 regression rate was 68.3% for women who tested positive for HPV E6/E7 mRNA versus 82.0% for the negative results, but this difference was not statistically significant. The expectant management for women with biopsy-confirmed CIN 2 and previous cytological tests showing LSIL exhibited a very high rate of spontaneous regression. HPV 16 is associated with a higher CIN 2 progression rate than other HPV infections. HPV E6/E7 mRNA is not a prognostic marker of the CIN 2 clinical outcome, although this analysis cannot be considered conclusive. Given the small sample size, this study could be considered a pilot for future larger studies on the role of predictive markers of CIN 2 evolution.
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Congenital diaphragmatic hernia (CDH) is associated with pulmonary hypertension which is often difficult to manage, and a significant cause of morbidity and mortality. In this study, we have used a rabbit model of CDH to evaluate the effects of BAY 60-2770 on the in vitro reactivity of left pulmonary artery. CDH was performed in New Zealand rabbit fetuses (n = 10 per group) and compared to controls. Measurements of body, total and left lung weights (BW, TLW, LLW) were done. Pulmonary artery rings were pre-contracted with phenylephrine (10 μM), after which cumulative concentration-response curves to glyceryl trinitrate (GTN; NO donor), tadalafil (PDE5 inhibitor) and BAY 60-2770 (sGC activator) were obtained as well as the levels of NO (NO3/NO2). LLW, TLW and LBR were decreased in CDH (p < 0.05). In left pulmonary artery, the potency (pEC50) for GTN was markedly lower in CDH (8.25 ± 0.02 versus 9.27 ± 0.03; p < 0.01). In contrast, the potency for BAY 60-2770 was markedly greater in CDH (11.7 ± 0.03 versus 10.5 ± 0.06; p < 0.01). The NO2/NO3 levels were 62 % higher in CDH (p < 0.05). BAY 60-2770 exhibits a greater potency to relax the pulmonary artery in CDH, indicating a potential use for pulmonary hypertension in this disease.
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We assessed associations between steroid receptors including: estrogen-alpha, estrogen-beta, androgen receptor, progesterone receptor, the HER2 status and triple-negative epithelial ovarian cancer (ERα-/PR-/HER2-; TNEOC) status and survival in women with epithelial ovarian cancer. The study included 152 women with primary epithelial ovarian cancer. The status of steroid receptor and HER2 was determined by immunohistochemistry. Disease-free and overall survival were calculated and compared with steroid receptor and HER2 status as well as clinicopathological features using the Cox Proportional Hazards model. A mean follow-up period of 43.6 months (interquartile range=41.4 months) was achieved where 44% of patients had serous tumor, followed by mucinous (23%), endometrioid (9%), mixed (9%), undifferentiated (8.5%) and clear cell tumors (5.3%). ER-alpha staining was associated with grade II-III tumors. Progesterone receptor staining was positively associated with a Body Mass Index≥25. Androgen receptor positivity was higher in serous tumors. In stand-alone analysis of receptor contribution to survival, estrogen-alpha positivity was associated with greater disease-free survival. However, there was no significant association between steroid receptor expression, HER2 status, or TNEOC status, and overall survival. Although estrogen-alpha, androgen receptor, progesterone receptor and the HER2 status were associated with key clinical features of the women and pathological characteristics of the tumors, these associations were not implicated in survival. Interestingly, women with TNEOC seem to fare the same way as their counterparts with non-TNEOC.