Neuropathological hallmarks of Alzheimer's disease are neurofibrillary tangles composed of tau and neuritic plaques comprising amyloid-beta peptides (Abeta) derived from amyloid precursor protein (APP), but their exact relationship remains elusive. Phosphorylation of tau and APP on certain serine or threonine residues preceding proline affects tangle formation and Abeta production in vitro. Phosphorylated Ser/Thr-Pro motifs in peptides can exist in cis or trans conformations, the conversion of which is catalysed by the Pin1 prolyl isomerase. Pin1 has been proposed to regulate protein function by accelerating conformational changes, but such activity has never been visualized and the biological and pathological significance of Pin1 substrate conformations is unknown. Notably, Pin1 is downregulated and/or inhibited by oxidation in Alzheimer's disease neurons, Pin1 knockout causes tauopathy and neurodegeneration, and Pin1 promoter polymorphisms appear to associate with reduced Pin1 levels and increased risk for late-onset Alzheimer's disease. However, the role of Pin1 in APP processing and Abeta production is unknown. Here we show that Pin1 has profound effects on APP processing and Abeta production. We find that Pin1 binds to the phosphorylated Thr 668-Pro motif in APP and accelerates its isomerization by over 1,000-fold, regulating the APP intracellular domain between two conformations, as visualized by NMR. Whereas Pin1 overexpression reduces Abeta secretion from cell cultures, knockout of Pin1 increases its secretion. Pin1 knockout alone or in combination with overexpression of mutant APP in mice increases amyloidogenic APP processing and selectively elevates insoluble Abeta42 (a major toxic species) in brains in an age-dependent manner, with Abeta42 being prominently localized to multivesicular bodies of neurons, as shown in Alzheimer's disease before plaque pathology. Thus, Pin1-catalysed prolyl isomerization is a novel mechanism to regulate APP processing and Abeta production, and its deregulation may link both tangle and plaque pathologies. These findings provide new insight into the pathogenesis and treatment of Alzheimer's disease.

Epithelial-mesenchymal transition (EMT) is a crucial, evolutionarily conserved process that occurs during development and is essential for shaping embryos. Also implicated in cancer, this morphological transition is executed through multiple mechanisms in different contexts, and studies suggest that the molecular programs governing EMT, albeit still enigmatic, are embedded within developmental programs that regulate specification and differentiation. As we review here, knowledge garnered from studies of EMT during gastrulation, neural crest delamination and heart formation have furthered our understanding of tumor progression and metastasis.Key words: Epithelial-mesenchymal transition, Gastrulation, Neural crest, Heart morphogenesis Introduction Epithelial-mesenchymal transition (EMT) is an evolutionarily conserved developmental process that contributes to the formation of the body plan, histogenesis and organogenesis. In the late 19th century, mesenchymal and epithelial cells were recognized as having distinct phenotypes (Duval, 1879) and, although EMT was apparent to embryologists (Platt, 1894), it only became interesting to developmental biologists in the 1960s. Following pioneering work from Elizabeth Hay (Greenburg and Hay, 1982; Hay, 2005), we now know that epithelial cells lose apicobasal polarity and intercellular junctions during EMT. These changes in cell polarity and adhesion disrupt the epithelial basement membrane and allow cellular penetration into an extracellular matrix (ECM)-rich compartment: a process referred to as delamination (see Glossary, Box 1). These newly formed mesenchymal cells transiently express distinct mesenchymal markers, acquire a front-rear polarity and become invasive, favoring cell-ECM rather than cell-cell adhesions.Interestingly, EMT is not irreversible: cells frequently cycle between epithelial and mesenchymal states via EMT and the reverse process, mesenchymal-epithelial transition (MET). Importantly, EMT has been implicated in pathological conditions, such as organ fibrosis, and in cancer, where it contributes to tumor progression and metastasis (Kalluri and Weinberg, 2009;Thiery et al., 2009). As such, much effort has been devoted to understanding the molecular regulation of EMT during development as an insight into the role and regulation of EMT in pathology.EMT is context dependent, occurring within the framework of other signaling mechanisms, such as cell fate induction, commitment and differentiation. However, the precise events that drive EMT are not fully understood. Genetic studies in Drosophila originally identified the transcription factors Twist and Snail as potential drivers of EMT during gastrulation (Leptin and Grunewald, 1990). Soon after, a Snail ortholog, Slug (Snai2), was shown to be involved in EMT in chicken embryo gastrulation (Nieto et al., 1994). Since then, several genes encoding transcription factors, cell polarity proteins and effector proteins have been shown to govern EMT in normal and transformed epithelial cells (see Table 1), suggesting tha...

Although biologic characteristics remain important predictors of survival for patients with resected pancreatic cancer, the most powerful determinant is postoperative adjuvant chemoradiation therapy. An interesting finding that warrants further investigation is the effect of socioeconomic status on both the likelihood of receiving adjuvant treatment and subsequent survival, indicating a possible relationship between the quality of care delivered and outcomes.

Drosophila Sprouty (dSpry) was genetically identi®ed as a novel antagonist of ®broblast growth factor receptor (FGFR), epidermal growth factor receptor (EGFR) and Sevenless signalling, ostensibly by eliciting its response on the Ras/MAPK pathway. Four mammalian sprouty genes have been cloned, which appear to play an inhibitory role mainly in FGFmediated lung and limb morphogenesis. Evidence is presented herein that describes the functional implications of the direct association between human Sprouty2 (hSpry2) and c-Cbl, and its impact on the cellular localization and signalling capacity of EGFR. Contrary to the consensus view that Spry2 is a general inhibitor of receptor tyrosine kinase signalling, hSpry2 was shown to abrogate EGFR ubiquitylation and endocytosis, and sustain EGF-induced ERK signalling that culminates in differentiation of PC12 cells. Correlative evidence showed the failure of hSpry2DN11 and mSpry4, both de®cient in c-Cbl binding, to instigate these effects. hSpry2 interacts speci®cally with the c-Cbl RING ®nger domain and displaces UbcH7 from its binding site on the E3 ligase. We conclude that hSpry2 potentiates EGFR signalling by speci®cally intercepting c-Cbl-mediated effects on receptor down-regulation.

We propose a model to infer from live cell images of actin filament (F-actin) flow intracellular force variations during protrusion-retraction cycles of epithelial cells in a wound healing response. To establish mechanistic relations between force development and cytoskeleton dynamics, force fluctuations were correlated with fluctuations in F-actin turnover, flow, and F-actin-vinculin coupling. Our analyses suggest that force transmission at focal adhesions (FA) requires binding of vinculin to F-actin and integrin (indirectly), which is modulated at the vinculin-integrin but not the vinculin-F-actin interface. Force transmission at FAs is co-localized in space and synchronized in time with transient increases of the boundary force at the cell edge. Surprisingly, the maxima in adhesion and boundary forces lag maximal edge advancement by ∼40 s. Maximal F-actin assembly is observed ∼20 s after maximal edge advancement. Based on these findings, we propose that protrusion events are limited by membrane tension and that the characteristic duration of a protrusion cycle is determined by the efficiency in reinforcing F-actin assembly and adhesion formation as tension increases.

Several genetic studies in Drosophila have shown that the dSprouty (dSpry) protein inhibits the Ras/mitogenactivated protein (MAP) kinase pathway induced by various activated receptor tyrosine kinase receptors, most notably those of the epidermal growth factor receptor (EGFR) and fibroblast growth factor receptor (FGFR). Currently, the mode of action of dSpry is unknown, and the point of inhibition remains controversial. There are at least four mammalian Spry isoforms that have been shown to co-express preferentially with FGFRs as compared with EGFRs. In this study, we investigated the effects of the various mammalian Spry isoforms on the Ras/MAP kinase pathway in cells overexpressing constitutively active FGFR1. hSpry2 was significantly more potent than mSpry1 or mSpry4 in inhibiting the Ras/MAP kinase pathway. Additional experiments indicated that full-length hSpry2 was required for its full potency. hSpry2 had no inhibitory effect on either the JNK or the p38 pathway and displayed no inhibition of FRS2 phosphorylation, Akt activation, and Ras activation. Constitutively active mutants of Ras, Raf, and Mek were employed to locate the prospective point of inhibition of hSpry2 downstream of activated Ras. Results from this study indicated that hSpry2 exerted its inhibitory effect at the level of Raf, which was verified in a Raf activation assay in an FGF signaling context.

SUMMARY Dynamic actin cytoskeletal reorganization is integral to cell motility. Profilins are well-characterized regulators of actin polymerization; however, functional differences among co-expressed profilin isoforms are not well defined. Here, we demonstrate that profilin-1 and profilin-2 differentially regulate membrane protrusion, motility, and invasion; these processes are promoted by profilin-1 and suppressed by profilin-2. Compared to profilin-1, profilin-2 preferentially drives actin polymerization by the Ena/VASP protein, EVL. Profilin-2 and EVL suppress protrusive activity and cell motility by an actomyosin contractility-dependent mechanism. Importantly, EVL or profilin-2 downregulation enhances invasion in vitro and in vivo. In human breast cancer, lower EVL expression correlates with high invasiveness and poor patient outcome. We propose that profilin-2/EVL-mediated actin polymerization enhances actin bundling and suppresses breast cancer cell invasion.

Introduction:Chromosomal rearrangements involving neurotrophic tyrosine kinase 1 (NTRK1) occur in a subset of non-small cell lung cancers (NSCLCs) and other solid tumor malignancies, leading to expression of an oncogenic TrkA fusion protein. Entrectinib (RXDX-101) is an orally available tyrosine kinase inhibitor, including TrkA. We sought to determine the frequency of NTRK1 rearrangements in NSCLC and to assess the clinical activity of entrectinib.Methods:We screened 1378 cases of NSCLC using anchored multiplex polymerase chain reaction (AMP). A patient with an NTRK1 gene rearrangement was enrolled onto a Phase 1 dose escalation study of entrectinib in adult patients with locally advanced or metastatic tumors (NCT02097810). We assessed safety and response to treatment.Results:We identified NTRK1 gene rearrangements at a frequency of 0.1% in this cohort. A patient with stage IV lung adenocrcinoma with an SQSTM1-NTRK1 fusion transcript expression was treated with entrectinib. Entrectinib was well tolerated, with no grade 3–4 adverse events. Within three weeks of starting on treatment, the patient reported resolution of prior dyspnea and pain. Restaging CT scans demonstrated a RECIST partial response (PR) and complete resolution of all brain metastases. This patient has continued on treatment for over 6 months with an ongoing PR.Conclusions:Entrectinib demonstrated significant anti-tumor activity in a patient with NSCLC harboring an SQSTM1-NTRK1 gene rearrangement, indicating that entrectinib may be an effective therapy for tumors with NTRK gene rearrangements, including those with central nervous system metastases.