Dickkopf1 - A New Player in Modelling the Wnt Pathway

The Wnt signaling pathway transducing the stabilization of β-catenin is essential for metazoan embryo development and is misregulated in many diseases such as cancers. In recent years models have been proposed for the Wnt signaling pathway during the segmentation process in developing embryos. Many of these include negative feedback loops where Axin2 plays a key role. However, Axin2 null mice show no segmentation phenotype. We therefore propose a new model where the negative feedback involves Dkk1 rather than Axin2. We show that this model can exhibit the same type of oscillations as the previous models with Axin2 and as observed in experiments. We show that a spatial Wnt gradient can consistently convert this temporal periodicity into the spatial periodicity of somites, provided the oscillations in new cells arising in the presomitic mesoderm are synchronized with the oscillations of older cells. We further investigate the hypothesis that a change in the Wnt level in the tail bud during the later stages of somitogenesis can lengthen the time period of the oscillations and hence the size and separation of the later somites

GLUT1 gene is a potential hypoxic marker in colorectal cancer patients

<p>Abstract</p> <p>Background</p> <p>Tumor hypoxia is an important factor related to tumor resistance to radiotherapy and chemotherapy. This study investigated molecules synthesized in colorectal cancer cells during hypoxia to explore the possibility of developing molecular probes capable of detecting cell death and/or the efficiency of radiotherapy and chemotherapy.</p> <p>Methods</p> <p>At first, we incubated two human colorectal adenocarcinoma cell lines SW480 (UICC stage II) and SW620 (UICC stage III) cells in hypoxic (≤2% O₂, 93% N₂, and 5% CO₂) and normoxic conditions (20% O₂, 75% N₂, and 5% CO₂) for 24 h and 48 h. The relative expression ratio of GLUT1 mRNA in hypoxic conditions was analyzed by RT-PCR. Ten cancerous tissues collected from human colorectal cancer patients were examined. HIF-1α and HIF-2α levels were measured to indicate the degree of hypoxia, and gene expression under hypoxic conditions was determined. As a comparison, HIF-1α, HIF-2α, and GLUT1 levels were measured in the peripheral blood of 100 CRC patients.</p> <p>Results</p> <p>Hypoxia-induced lactate was found to be elevated 3.24- to 3.36-fold in SW480 cells, and 3.06- to 3.17-fold in SW620 cells. The increased relative expression ratio of GLUT1 mRNA, under hypoxic conditions was higher in SW620 cells (1.39- to 1.72-fold elevation) than in SW480 cells (1.24- to 1.66-fold elevation). HIF-1α and HIF-2α levels were elevated and GLUT1 genes were significantly overexpressed in CRC tissue specimens. The elevated ratio of GLUT1 was higher in stage III and IV CRC tissue specimens than in the stage I and II (2.97–4.73 versus 1.44–2.11). GLUT1 mRNA was also increased in the peripheral blood of stage II and III CRC patients as compared to stage I patients, suggesting that GLUT1 may serve as a hypoxic indicator in CRC patients.</p> <p>Conclusion</p> <p>In conclusion, this study demonstrated that GLUT1 has the potential to be employed as a molecular marker to indicate the degree of hypoxia experienced by tumors circulating in the blood of cancer patients.</p

Stochastic Modeling of B Lymphocyte Terminal Differentiation and Its Suppression by Dioxin

<p>Abstract</p> <p>Background</p> <p>Upon antigen encounter, naïve B lymphocytes differentiate into antibody-secreting plasma cells. This humoral immune response is suppressed by the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and other dioxin-like compounds, which belong to the family of aryl hydrocarbon receptor (AhR) agonists.</p> <p>Results</p> <p>To achieve a better understanding of the immunotoxicity of AhR agonists and their associated health risks, we have used computer simulations to study the behavior of the gene regulatory network underlying B cell terminal differentiation. The core of this network consists of two coupled double-negative feedback loops involving transcriptional repressors Bcl-6, Blimp-1, and Pax5. Bifurcation analysis indicates that the feedback network can constitute a bistable system with two mutually exclusive transcriptional profiles corresponding to naïve B cells and plasma cells. Although individual B cells switch to the plasma cell state in an all-or-none fashion when stimulated by the polyclonal activator lipopolysaccharide (LPS), stochastic fluctuations in gene expression make the switching event probabilistic, leading to heterogeneous differentiation response among individual B cells. Moreover, stochastic gene expression renders the dose-response behavior of a population of B cells substantially graded, a result that is consistent with experimental observations. The steepness of the dose response curve for the number of plasma cells formed vs. LPS dose, as evaluated by the apparent Hill coefficient, is found to be inversely correlated to the noise level in Blimp-1 gene expression. Simulations illustrate how, through AhR-mediated repression of the AP-1 protein, TCDD reduces the probability of LPS-stimulated B cell differentiation. Interestingly, stochastic simulations predict that TCDD may destabilize the plasma cell state, possibly leading to a reversal to the B cell phenotype.</p> <p>Conclusion</p> <p>Our results suggest that stochasticity in gene expression, which renders a graded response at the cell population level, may have been exploited by the immune system to launch humoral immune response of a magnitude appropriately tuned to the antigen dose. In addition to suppressing the initiation of the humoral immune response, dioxin-like compounds may also disrupt the maintenance of the acquired immunity.</p

Effect of a Cholesterol Rich Diet, Recurrent Infection and Possible Treatment Modalities on the Pulmonary Vascular System: An Experimental Study

Objective: Infection may lead to inflammation, atherosclerosis and thrombotic vascular events. The atherosclerotic effect of hypercholesterolaemia on the vascular system is well-known. However, limited studies were done on the therapeutic and preventative agents. The aim of this study was to investigate the effects of infection and cholesterol rich diet combined with an antibiotic, anti-inflammatory agent and red wine on the pulmonary vascular system. Methods: Fifty-nine rats were evaluated. Six groups were created: Control-Group I (n = 10); infection – Group II (n = 9), infection-cholesterol rich diet – Group III (n = 12), infection-cholesterol rich diet-cefepime – Group IV (n = 11); infection-cholesterol rich diet-diclofenac potassium – Group V (n = 9); infection-cholesterol rich diet and red wine – Group VI (n = 8). Blood samples of rats were collected for cholesterol analysis every month. Sections of central pulmonary arteries were examined for thickness of the intima and medial wall by computerised image analysis. Results: There was a statistically significant difference in serum cholesterol levels and in thickness of the intima between the groups (p = 0.000). The rest of the groups had more intimal thickening than Group I (p = 0.000). Group III had thicker intima than Groups IV and V (p = 0.009, p = 0.011 respectively). There was no significant difference between the groups in thickness of media (p = 0.432). Conclusion: Infection and cholesterol rich diet have a synergistic effect on atherosclerosis in pulmonary arteries. However, antibiotics and anti-inflammatory agents could be useful in prevention. Key Words: Atherosclerosis, cefepime, diclofenac potassium, pulmonary artery, red wine "Efecto de la dieta Rica en Colesterol, la Infección Recurrente, y las Posibles Modalidades de Tratamiento Sobre el Sistema Vascular Pulmonar: un Estudio Experimental" RESUMEN Objetivo: La infección puede conducir a inflamación, ateroesclerosis y eventos vasculares trombóticos. El efecto aterosclerótico de la hipercolesterolemia en el sistema vascular es bien conocido. Sin embargo, se hicieron estudios limitados sobre los agentes preventivos y terapéuticos. El objetivo de este estudio fue investigar los efectos de la infección y la dieta rica en colesterol, combinados con agentes antibióticos, anti-inflamatorios, y vino tinto, sobre el sistema vascular pulmonar. Métodos: Cincuenta y nueve ratas fueron evaluadas. Se hicieron seis grupos: grupo-control I (n = 10), grupo-infección II (n = 9), grupo infección-dieta rica en colesterol III (n = 12), grupo-infección-dieta rica en colesterol-cefepima IV (n = 11), grupo-infección-dieta rica en colesterol-diclofenaco potásico V (n = 9), grupo-infección-dieta rica en –vino tinto VI (n = 8). Se tomaron muestras de sangre de ratas para analizar el colesterol cada mes. Se examinaron secciones de las arterias pulmonares centrales para determinar el grosor de la pared íntima y media mediante análisis computarizado de imágenes. Resultados: Hubo una diferencia estadísticamente significativa en los niveles de colesterol en suero y el grosor de la íntima entre los grupos (p = 0.000). El resto de los grupos tenía más engrosamiento de la íntima que el grupo I (p = 0.000). El grupo III tenía una íntima más gruesa que los grupos IV y V (p = 0,009, p = 0.011 respectivamente). No hubo ninguna diferencia significativa entre los grupos en cuanto al espesor de la media (p = 0.432). Conclusión: La infección y la dieta rica en colesterol tienen un efecto sinérgico sobre la aterosclerosis en las arterias pulmonares. Sin embargo, los antibióticos y los agentes antiinflamatorios podrían ser útiles para la prevención. Palabras claves: Aterosclerosis, cefepima, diclofenaco potásico, arteria pulmonar, vino tinto

Increased microvascular proliferation is negatively correlated to tumour blood flow and is associated with unfavourable outcome in endometrial carcinomas

Background: We aimed to study the angiogenic profile based on histomorphological markers in endometrial carcinomas in relation to imaging parameters obtained from preoperative dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion-weighted imaging (DWI) and to explore the potential value of these markers to identify patients with poor outcome. Methods: In fifty-four surgically staged endometrial carcinoma patients, immunohistochemical staining with factor VIII and Ki67 allowed assessment of microvessel density (MVD) and microvascular proliferation reflecting tumour angiogenesis. In the same patients, preoperative pelvic DCE-MRI and DWI allowed the calculation of parameters describing tumour microvasculature and microstructure in vivo. Results: Microvascular proliferation was negatively correlated to tumour blood flow (Fb) (r=−0.36, P=0.008), capillary permeability surface area product (PS) (r=−0.39, P=0.004) and transfer from the blood to extravascular extracellular space (EES) (Ktrans) (r=−0.40, P=0.003), and was positively correlated to tumour volume (r=0.34; P=0.004). High-tumour microvascular proliferation, low Fb and low Ktrans were all significantly associated with reduced progression/recurrence-free survival (P<0.05). Conclusion: Disorganised angiogenesis with coexisting microvascular proliferation and low tumour blood flow is a poor prognostic factor supporting that hypoxia is associated with progression and metastatic spread in endometrial carcinomas