Joo Kyung Ryu

A Wnt–Axin2–GSK3β cascade regulates Snail1 activity in breast cancer cells

Accumulating evidence indicates that hyperactive Wnt signalling occurs in association with the development and progression of human breast cancer. As a consequence of engaging the canonical Wnt pathway, a β-catenin–T-cell factor (TCF) transcriptional complex is generated, which has been postulated to trigger the epithelial–mesenchymal transition (EMT) that characterizes the tissue-invasive phenotype. However, the molecular mechanisms by which the β-catenin–TCF complex induces EMT-like programmes remain undefined. Here, we demonstrate that canonical Wnt signalling engages tumour cell dedifferentiation and tissue-invasive activity through an Axin2-dependent pathway that stabilizes the Snail1 zinc-transcription factor, a key regulator of normal and neoplastic EMT programmes. Axin2 regulates EMT by acting as a nucleocytoplasmic chaperone for GSK3β, the dominant kinase responsible for controlling Snail1 protein turnover and activity. As dysregulated Wnt signalling marks a diverse array of cancerous tissue types, the identification of a β-catenin–TCF-regulated Axin2–GSK3β–Snail1 axis provides new mechanistic insights into cancer-associated EMT programmes.

p53 and microRNA-34 are suppressors of canonical Wnt signaling.

The tumor suppressor p53 activates miRNA-34 to inhibit Wnt signaling and colorectal cancer cell invasiveness. p53 Activates MicroRNA-34 to Inhibit Wnt Signaling The tumor suppressor p53 is missing or nonfunctional in many cancers, whereas the canonical Wnt signaling pathway is frequently activated. Here, Kim et al. show that p53 restrained Wnt signaling during Xenopus development, whereas loss of p53 function led to aberrant activation of the canonical Wnt signaling pathway, with microRNA-34 (miR-34) providing the connection between the two. They found that p53 stimulated production of miR-34, which, in turn, targeted key genes in the Wnt signaling pathway. Analyses of gene expression data sets indicated that loss of p53 or miR-34 function was associated with activation of Wnt signaling in human cancers; moreover, loss of p53 function increased Wnt signaling in colon cancer cells in vitro. In p53-mutant colon cancer cells, miR-34 attenuated Wnt signaling and decreased the invasiveness of these cells in vitro. Thus, the p53–miR-34–Wnt pathway appears to be crucial not only during development but also for p53’s tumor suppressor function. Although loss of p53 function and activation of canonical Wnt signaling cascades are frequently coupled in cancer, the links between these two pathways remain unclear. We report that p53 transactivated microRNA-34 (miR-34), which consequently suppressed the transcriptional activity of β-catenin–T cell factor and lymphoid enhancer factor (TCF/LEF) complexes by targeting the untranslated regions (UTRs) of a set of conserved targets in a network of genes encoding elements of the Wnt pathway. Loss of p53 function increased canonical Wnt signaling by alleviating miR-34–specific interactions with target UTRs, and miR-34 depletion relieved p53-mediated Wnt repression. Gene expression signatures reflecting the status of β-catenin–TCF/LEF transcriptional activity in breast cancer and pediatric neuroblastoma patients were correlated with p53 and miR-34 functional status. Loss of p53 or miR-34 contributed to neoplastic progression by triggering the Wnt-dependent, tissue-invasive activity of colorectal cancer cells. Further, during development, miR-34 interactions with the β-catenin UTR affected Xenopus body axis polarity and the expression of Wnt-dependent patterning genes. These data provide insight into the mechanisms by which a p53–miR-34 network restrains canonical Wnt signaling cascades in developing organisms and human cancer.

p53 regulates nuclear GSK-3 levels through miR-34-mediated Axin2 suppression in colorectal cancer cells

p53 is a bona fide tumor suppressor gene whose loss of function marks the most common genetic alteration in human malignancy. Although the causal link between loss of p53 function and tumorigenesis has been clearly demonstrated, the mechanistic links by which loss of p53 potentiates oncogenic signaling are not fully understood. Recent evidence indicates that the microRNA-34 (miR-34) family, a transcriptional target of the p53, directly suppresses a set of canonical Wnt genes and Snail, resulting in p53-mediated suppression of Wnt signaling and the EMT process. In this study, we report that p53 regulates GSK-3β nuclear localization via miR-34-mediated suppression of Axin2 in colorectal cancer. Exogenous miR-34a decreases Axin2 UTR-reporter activity through multiple binding sites within the 5′ and 3′ UTR of Axin2. Suppression of Axin2 by p53 or miR-34 increases nuclear GSK-3β abundance and leads to decreased Snail expression in colorectal cancer cells. Conversely, expression of the non-coding UTR of Axin2 causes depletion of endogenous miR-34 via the miR-sponge effect together with increased Axin2 function, supporting that the RNA-RNA interactions with Axin2 transcripts act as an endogenous decoy for miR-34. Further, RNA transcripts of miR-34 target were correlated with Axin2 in clinical data set of colorectal cancer patients. Although the biological relevance of nuclear GSK-3 level has not been fully studied, our results demonstrate that the tumor suppressor p53/miR-34 axis plays a role in regulating nuclear GSK-3 levels and Wnt signaling through the non-coding UTR of Axin2 in colorectal cancer.

Anchored proteinase-targetable optomagnetic nanoprobes for molecular imaging of invasive cancer cells.

Herein, we describe the development of a bimodalimaging probe enabling precise recognition of the expressionof MT1-MMP anchored on invasive cancer cells and itsprotease activity simultaneously. MT1-MMP may be atargetable biomarker for a specific delivery and possessesproteolytic activity for certain substrates.

Real‐Time Quantitative Monitoring of Specific Peptide Cleavage by a Proteinase for Cancer Diagnosis

.…(MMPs;greenmissilesinthepicture)expressedonacancercellsurfacecanbesensedby a resonant cantilever device (satellite arm in the picture), as J. Yang, D. S. Yoon, T.Kwon et al. report in their Communication on page 5837 ff. Active MMPs attack thepeptide sequence that is immobilized on the cantilever surface. The peptide cleavageleads to an increase in the resonant frequency of the cantilever, owing to a decrease inthe mass of immobilized peptide.

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.

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.