THE ROLE OF THE EPITHELIAL-TO-MESENCHYMAL TRANSITION (EMT) IN LUNG CANCER PROGRESSION

Lung cancer is the leading cause of cancer-related deaths due to conventional therapy resistance and metastatic disease, therefore understanding the mechanisms governing these biological functions is vital for improving patient survival. Approximately 30% of patients with the adenocarcinoma histologic subset of lung cancer possess an activating KRAS mutation, characterized by a lack of response to chemotherapies with a poor overall 5-year survival rate. Despite the mutational frequency, KRAS remains a challenge to pharmacologically inhibit and current drugs undergoing clinical trials that target specific downstream effector proteins of KRAS, such as MEK inhibitors, have failed to produce significant clinical benefits. Previous studies by our group on the metastatic process revealed that malignant lung cancer cells undergo an epithelial-to-mesenchymal transition (EMT) that is regulated by a double-negative feedback loop between the transcription factor Zeb1 and the microRNA-200 family (miR-200). Furthermore, these studies demonstrated that mesenchymal lung cancer cell invasion and metastasis are dependent on interaction with the extracellular matrix (ECM). In addition to metastasis, EMT has been implicated in resistance to radiation and chemotherapies as well as resistance to certain targeted drug treatments. Thus, the comprehensive objective of this study was to: (1) elucidate the detailed mechanisms of metastasis by investigating the collaborative effect of EMT and ECM on KRAS mutant lung cancer metastasis, and (2) delineate the mechanism of EMT in promoting MEK inhibitor resistance in KRAS mutant lung cancers. Our findings reveal increased collagen deposition in mesenchymal tumor tissues due to amplification of collagen gene expression in Zeb1-driven mesenchymal lung cancer cells. Additionally, collagen fibers in the metastatic tumor tissues exhibit greater linearity and organization, correlating with direct Zeb1-upregulation of the collagen crosslinking enzyme LOXL2. Coordinated expression of LOXL2 with collagen increases insoluble collagen crosslinking and deposition in the tumor microenvironment, resulting in activated Fak/Src signaling to promote metastasis. Using functional in vivo shRNA screens coupled with proteomic profiling, we identified Zeb1-driven epithelial-to-mesenchymal transition (EMT) as a regulator of MAPK-dependent signaling activity and tumor maintenance in lung cancer cells. Mechanistic studies in novel cell line and animal models further demonstrated that the Ras-Raf-Mek-Erk MAPK signaling cascade in epithelial cells is activated through upregulation of the scaffold protein Il17rd, which is directly repressed by Zeb1 during EMT. Translationally, we observe that poorly-differentiated, mesenchymal lung cancer cells within the heterogeneous lung tumor tissue of in vivo models are resistant to MEK inhibitors and identified Zeb1 and Il17rd as potential biomarkers from large patient datasets. Reversion of functional EMT by genetic expression of miR-200 or treatment with the class I HDAC inhibitor mocetinostat sensitized resistant cancer cells to MEK inhibition and significantly reduced tumor growth. This study establishes the mechanisms of metastasis and MEK inhibitor resistance in KRAS mutant lung cancers, identifies multiple potential prognostic markers of metastasis and resistance, and provides pre-clinical evidence for a promising combinatorial therapy against lung cancer progression

Interaction of CK1δ with γTuSC ensures proper microtubule assembly and spindle positioning.

Casein kinase 1δ (CK1δ) family members associate with microtubule-organizing centers (MTOCs) from yeast to humans, but their mitotic roles and targets have yet to be identified. We show here that budding yeast CK1δ, Hrr25, is a γ-tubulin small complex (γTuSC) binding factor. Moreover, Hrr25's association with γTuSC depends on its kinase activity and its noncatalytic central domain. Loss of Hrr25 kinase activity resulted in assembly of unusually long cytoplasmic microtubules and defects in spindle positioning, consistent with roles in regulation of γTuSC-mediated microtubule nucleation and the Kar9 spindle-positioning pathway, respectively. Hrr25 directly phosphorylated γTuSC proteins in vivo and in vitro, and this phosphorylation promoted γTuSC integrity and activity. Because CK1δ and γTuSC are highly conserved and present at MTOCs in diverse eukaryotes, similar regulatory mechanisms are expected to apply generally in eukaryotes

Uptake of iron and its effect on grain refinement of pure magnesium by zirconium

The uptake of iron by molten magnesium from uncoated new mild steel crucibles at temperatures 680°C, 730°C, and 780°C has been investigated. It was shown that the uptake of iron was sluggish at 680°C and the use of 0.05% zirconium addition could effectively suppress the increase in iron content within the first 2 h of holding at temperature. Rapid and severe uptake of iron was observed at 780°C. As a consequence, it was found that the grain refinement of pure magnesium achieved by 1% zirconium addition nearly vanished after 60 min hold at 780°C due to the depletion of soluble zirconium. The uptake of iron at 730°C was conspicuous but it was still controllable by use of 0.05% zirconium addition within the first 60 min of holding at temperature. The work conducted using an aluminium titanite crucible and a boron nitride coated mild steel crucible at 730°C further confirmed the highly detrimental influence of the uptake of iron on the grain refinement of pure magnesium by zirconium. The characteristic zirconium rich coring structures developed from circular to rosette like when the melt was held at 730°C in an uncoated mild steel crucible, while no such evolution was observed when held in an aluminium titanite crucible at the same temperature. Recommendations to minimise the consumption of zirconium by the uptake of iron were made based on the results obtained from this investigation. The mechanism of grain refinement of magnesium by a low concentration of zirconium is discussed

Tissue Doppler imaging following paediatric cardiac surgery : early patterns of change and relationship to outcome

In this study, tissue Doppler imaging (TDI) was used to assess changes in ventricular function following repair of congenital heart defects. The relationship between TDI indices, myocardial injury and clinical outcome was explored. Forty-five children were studied; 35 withcardiac lesions and 10 controls. TDI was performed preoperatively, on admission to paediatric intensive care unit (PICU) and day 1. Regional myocardial Doppler signals were acquired from the right ventricle (RV), left ventricle (LV) and septum. TDI indices included: peak systolicvelocities, isovolumetric velocities (IVV) and isovolumetric acceleration (IVA). Preoperatively, bi-ventricular TDI velocities in the study groupwere reduced compared with normal controls. Postoperatively, RV velocities were significantly reduced and this persisted to day-1 (PreOp vs. PICU and day-1: 7.7+2.2 vs. 3.4+1.0, P < 0.0001 and 3.55+1.29, P < 0.0001). LV velocities initially declined but recovered towards baseline by day-1 (PreOp vs. PICU: 5.31+1.50 vs. 3.51+1.23, P < 0.0001). Isovolumetric parameters in all regions were reduced throughout the postoperative period. Troponin-I release correlated with longer X-clamp times (r=0.82, P < 0.0001) and reduced RV velocities (r=0.42, P=0.028). Reduced pre- and postoperative LV velocities correlated with longer ventilation (PreOp: r=0.54, P=0.002; PostOp: r=0.42, P=0.026). This study identified reduced postoperative RV velocities correlated with myocardial injury while reduced LV TDI correlated with longer postoperative ventilation

Energy-resolved Photoconductivity Mapping in a Monolayer-bilayer WSe2 Lateral Heterostructure

Vertical and lateral heterostructures of van der Waals materials provide tremendous flexibility for band structure engineering. Since electronic bands are sensitively affected by defects, strain, and interlayer coupling, the edge and heterojunction of these two-dimensional (2D) systems may exhibit novel physical properties, which can be fully revealed only by spatially resolved probes. Here, we report the spatial mapping of photoconductivity in a monolayer-bilayer WSe2 lateral heterostructure under multiple excitation lasers. As the photon energy increases, the light-induced conductivity detected by microwave impedance microscopy first appears along the hetero-interface and bilayer edge, then along the monolayer edge, inside the bilayer area, and finally in the interior of the monolayer region. The sequential emergence of mobile carriers in different sections of the sample is consistent with the theoretical calculation of local energy gaps. Quantitative analysis of the microscopy and transport data also reveals the linear dependence of photoconductivity on the laser intensity and the influence of interlayer coupling on carrier recombination. Combining theoretical modeling, atomic scale imaging, mesoscale impedance microscopy, and device-level characterization, our work suggests an exciting perspective to control the intrinsic band-gap variation in 2D heterostructures down to the few-nanometer regime.Comment: 18 pages, 5 figures; Nano Lett., Just Accepted Manuscrip

The environmental dependence of the stellar mass-size relation in STAGES galaxies

We present the stellar mass-size relations for elliptical, lenticular, and spiral galaxies in the field and cluster environments using HST/ACS imaging and data from the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). We use a large sample of ~1200 field and cluster galaxies, and a sub-sample of cluster core galaxies, and quantify the significance of any putative environmental dependence on the stellar mass-size relation. For elliptical, lenticular, and high-mass (log M*/M_sun > 10) spiral galaxies we find no evidence to suggest any such environmental dependence, implying that internal drivers are governing their size evolution. For intermediate/low-mass spirals (log M*/M_sun < 10) we find evidence, significant at the 2-sigma level, for a possible environmental dependence on galaxy sizes: the mean effective radius a_e for lower-mass spirals is ~15-20 per cent larger in the field than in the cluster. This is due to a population of low-mass large-a_e field spirals that are largely absent from the cluster environments. These large-a_e field spirals contain extended stellar discs not present in their cluster counterparts. This suggests the fragile extended stellar discs of these spiral galaxies may not survive the environmental conditions in the cluster. Our results suggest that internal physical processes are the main drivers governing the size evolution of galaxies, with the environment possibly playing a role affecting only the discs of intermediate/low-mass spirals.Comment: 16 pages, 10 figures, accepted to MNRA

A Study of Variable Stiffness Alginate Printing for Medical Applications

Technologies for multi-material 3D-printing of anatomical shapes are useful both for fabrication of heterogeneous cell-seeded implants as well as for fabrication of synthetic models for surgical planning and training. For both these applications, it would be desirable to print directly with biological materials to best emulate the target’s properties. Using a novel material platform, we describe a series of experiments attempting to print variable-stiffness hydrogels. We vary compliances by alternating 2% alginate hydrogel and a Dextran-infused calcium chloride post-crosslinker. Stiffness throughout the construct ranged from 4 kPa to 20 kPa as a function of post-crosslinker concentration, which was spatially specified by the user.Mechanical Engineerin