Yoonmi Lee

Caspase‐2 primes cancer cells for TRAIL‐mediated apoptosis by processing procaspase‐8

Although caspase‐2 is believed to be involved in death receptor‐mediated apoptosis, the exact function, mode of activation, and regulation of caspase‐2 remain unknown. Here we show that protein kinase (PK) CK2 phosphorylates procaspase‐2 directly at serine‐157. When intracellular PKCK2 activity is low or downregulated by specific inhibitors, procaspase‐2 is dephosphorylated, dimerized, and activated in a PIDDosome‐independent manner. The activated caspase‐2 then processes procaspase‐8 monomers between the large and small subunits, thereby priming cancer cells for TNF‐related apoptosis‐inducing ligand (TRAIL)‐mediated apoptosis. The processed procaspase‐8 that is recruited to death‐inducing signaling complex by TRAIL engagement becomes fully activated, and cancer cells undergo apoptosis. PKCK2 activity is low in TRAIL‐sensitive cancer cell lines but high in TRAIL‐resistant cancer cell lines. Thus, downregulating PKCK2 activity is required for TRAIL‐mediated apoptosis to occur in TRAIL‐resistant cancer cells. Our data provide novel insights into the regulation, mode of activation, and function of caspase‐2 in TRAIL‐mediated apoptosis.

Helicobacter pylori CagA promotes Snail-mediated epithelial-mesenchymal transition by reducing GSK-3 activity.

Cytotoxin-associated gene A (CagA) is an oncoprotein and a major virulence factor of H. pylori. CagA is delivered into gastric epithelial cells via a type IV secretion system and causes cellular transformation. The loss of epithelial adhesion that accompanies the epithelial-mesenchymal transition (EMT) is a hallmark of gastric cancer. Although CagA is a causal factor in gastric cancer, the link between CagA and the associated EMT has not been elucidated. Here, we show that CagA induces the EMT by stabilizing Snail, a transcriptional repressor of E-cadherin expression. Mechanistically we show that CagA binds GSK-3 in a manner similar to Axin and causes it to shift to an insoluble fraction, resulting in reduced GSK-3 activity. We also find that the level of Snail protein is increased in H. pylori infected epithelium in clinical samples. These results suggest that H. pylori CagA acts as a pathogenic scaffold protein that induces a Snail-mediated EMT via the depletion of GSK-3.

Snail reprograms glucose metabolism by repressing phosphofructokinase PFKP allowing cancer cell survival under metabolic stress

Dynamic regulation of glucose flux between aerobic glycolysis and the pentose phosphate pathway (PPP) during epithelial–mesenchymal transition (EMT) is not well-understood. Here we show that Snail (SNAI1), a key transcriptional repressor of EMT, regulates glucose flux toward PPP, allowing cancer cell survival under metabolic stress. Mechanistically, Snail regulates glycolytic activity via repression of phosphofructokinase, platelet (PFKP), a major isoform of cancer-specific phosphofructokinase-1 (PFK-1), an enzyme involving the first rate-limiting step of glycolysis. The suppression of PFKP switches the glucose flux towards PPP, generating NADPH with increased metabolites of oxidative PPP. Functionally, dynamic regulation of PFKP significantly potentiates cancer cell survival under metabolic stress and increases metastatic capacities in vivo. Further, knockdown of PFKP rescues metabolic reprogramming and cell death induced by loss of Snail. Thus, the Snail-PFKP axis plays an important role in cancer cell survival via regulation of glucose flux between glycolysis and PPP.

Effects of silver and potassium ions on ion exchange in float glass

The variation of optical and mechanical properties in ion-exchanged glasses was investigated. Ion exchange was carried out in KNO3, NaNO3 melts and their mixed melts with AgNO3. The glasses used were soda-lime-silicate glasses produced by the float process. In order to analyse the effects of ion exchange, colour variation for optical properties, bending strength, surface microhardness and softening point for mechanical properties, and resistivity for electrical properties, were measured. In the optical properties, silver ions play an important role in colouring, ion exchange in the mixed melt of KNO3 and AgNO3, and additional heat treatment in air made it possible to obtain a range of colours from yellow to reddish-brown. Bending strength was increased by five times over the values of the parent glasses, surface microhardness was increased about 50 kg mm−2, and the softening point was increased linearly with the amount of ion exchange resulting from ion exchange in the KNO3 melt, because the potassium ion plays a great role in strengthening in the mechanical properties. On the other hand, in the mixed melt of KNO3 and AgNO3, bending strength and surface microhardness were increased slightly in contrast with the KNO3 melt, and the softening point decreased on increasing the amount of ion exchange.

Niclosamide is a potential therapeutic for familial adenomatosis polyposis by disrupting Axin-GSK3 interaction

The epithelial-mesenchymal transition (EMT) is implicated in tumorigenesis and cancer progression, and canonical Wnt signaling tightly controls Snail, a key transcriptional repressor of EMT. While the suppression of canonical Wnt signaling and EMT comprises an attractive therapeutic strategy, molecular targets for small molecules reverting Wnt and EMT have not been widely studied. Meanwhile, the anti-helminthic niclosamide has been identified as a potent inhibitor of many oncogenic signaling pathways although its molecular targets have not yet been clearly identified. In this study, we show that niclosamide directly targets Axin-GSK3 interaction, at least in part, resulting in suppression of Wnt/Snail-mediated EMT. In vitro and in vivo, disruption of Axin-GSK3 complex by niclosamide induces mesenchymal to epithelial reversion at nM concentrations, accompanied with suppression of the tumorigenic potential of colon cancer. Niclosamide treatment successfully attenuates Snail abundance while increasing E-cadherin abundance in xenograft tumor. Notably, oral administration of niclosamide significantly suppressed adenoma formation in an APC-MIN mice model, indicating that niclosamide is an effective therapeutic for familial adenomatosis polyposis (FAP) patients. In this study, we identified a novel target to control the canonical Wnt pathway and Snail-mediated EMT program, and discovered a repositioned therapeutics for FAP patients.

Dishevelled has a YAP nuclear export function in a tumor suppressor context-dependent manner

Phosphorylation-dependent YAP translocation is a well-known intracellular mechanism of the Hippo pathway; however, the molecular effectors governing YAP cytoplasmic translocation remains undefined. Recent findings indicate that oncogenic YAP paradoxically suppresses Wnt activity. Here, we show that Wnt scaffolding protein Dishevelled (DVL) is responsible for cytosolic translocation of phosphorylated YAP. Mutational inactivation of the nuclear export signal embedded in DVL leads to nuclear YAP retention, with an increase in TEAD transcriptional activity. DVL is also required for YAP subcellular localization induced by E-cadherin, α-catenin, or AMPK activation. Importantly, the nuclear-cytoplasmic trafficking is dependent on the p53-Lats2 or LKB1-AMPK tumor suppressor axes, which determine YAP phosphorylation status. In vivo and clinical data support that the loss of p53 or LKB1 relieves DVL-linked reciprocal inhibition between the Wnt and nuclear YAP activity. Our observations provide mechanistic insights into controlled proliferation coupled with epithelial polarity during development and human cancer.Hippo and Wnt pathways are important for cancer development, and they can cross talk; however, the mechanisms behind this connection are unknown. Here the authors show that DVL (a scaffold protein in the Wnt pathway) regulates the shuttling of YAP (a key component of the Hippo pathway) between cytoplasm and nucleus in specific tumor suppressor contexts.

Anti-helminthic niclosamide inhibits Ras-driven oncogenic transformation via activation of GSK-3

Despite the importance of Ras oncogenes as a therapeutic target in human cancer, their ‘undruggable’ tertiary structures limit the effectiveness of anti-Ras drugs. Canonical Wnt signaling contributes to Ras activity by glycogen synthase kinase 3 (GSK-3)-dependent phosphorylation at the C-terminus and subsequent degradation. In the accompanying report, we show that the anti-helminthic niclosamide directly binds to GSK-3 and inhibits Axin functions in colon cancer cells, with reversion of Snail-mediated epithelial-mesenchymal transition. In this study, we report that niclosamide effectively suppresses Ras and nuclear NFAT activities regardless of the mutational status of Ras at nM levels. Mechanistically, niclosamide increased endogenous GSK-3 activity, shortening the half-life of mutant Ras. Further, niclosamide activates Raf-1 kinase inhibitory protein, a downstream target of Snail repressor. Niclosamide treatment attenuates Ras-induced oncogenic potential in vitro and in vivo. These findings provide a clinically available repositioned Ras inhibitor as well as a novel strategy for inhibiting the Ras via GSK-3.

Effect of the initial grain size and orientation on the formation of deformation twins in Ti-15Mo alloy

This study was conducted to evaluate the effect of the grain size and orientation on the formation of deformation twins in Ti-15Mo alloy. For this material, cold rolling was carried out to achieve a 90% thickness reduction on the samples. In order to recrystallize the severely deformed alloy and to obtain two types of grain sizes, the alloys were then annealed at 900xa0°C for 1 and 30xa0min, respectively. After this work, electron backscattered diffraction was introduced to analyze grain boundary character distributions. As a result, the coarsened grains (average size ~154xa0μm) formed denser deformation twins relative to that of the finer grains (average size ~25xa0μm), which was attributed to the grain boundary constraint and orientation. These effects led to an enhancement of the strain-hardening constant of the alloy, which in turn resulted in a notable increase in the elongation without any significant decrease in the tensile strength. In this study, we systematically discussed the formation of twins in terms of grain size and Schmid factor.

A platform technique for growth factor delivery with novel mode of action.

Though growth factors allow tissue regeneration, the trade-off between their effectiveness and adverse effects limits clinical application. The key issues in current growth factor therapy largely derive from initial burst pharmacokinetics, rapid clearance, and proteolytic cleavage resulting in clinical ineffectiveness and diverse complications. While a number of studies have focused on the development of carriers, issues arising from soluble growth factor remain. In this study, we report a prodrug of growth factors constituting a novel mode of action (MoA). To mimic endogenous protein processing in cells, we developed a recombinant BMP-2 polypeptide based on a protein transduction domain (PTD) to transduce the protein into cells followed by furin-mediated protein cleavage and secretion of active growth factor. As proof of concept, a few micrograms scale of PTD-BMP-2 polypeptide sufficed to induce bone regeneration in vivo. As a simple platform, our technique can easily be extended to delivery of BMP-7 and DKK-1 as therapeutics for TGF-β and canonical Wnt signaling, respectively, to suppress the epithelial-mesenchymal transition (EMT), which constitutes a fundamental biological mechanism of many diseases. This technique largely overcomes the limitations of current soluble growth factors and opens the door to next generation growth factor therapeutics.