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Nerves enable cancer progression, as cancers have been shown to extend along nerves through the process of perineural invasion, which carries a poor prognosis. Furthermore, the innervation of some cancers promotes growth and metastases. It remains unclear, however, how nerves mechanistically contribute to cancer progression. Here, we demonstrated that Schwann cells promote cancer invasion through direct cancer cell contact. Histological evaluation of murine and human cancer specimens with perineural invasion uncovered a subpopulation of Schwann cells that associates with cancer cells. Coculture of cancer cells with dorsal root ganglion extracts revealed that Schwann cells direct cancer cells to migrate toward nerves and promote invasion in a contact-dependent manner. Upon contact, Schwann cells induced the formation of cancer cell protrusions in their direction and intercalated between the cancer cells, leading to cancer cell dispersion. The formation of these processes was dependent on Schwann cell expression of neural cell adhesion molecule 1 (NCAM1) and ultimately promoted perineural invasion. Moreover, NCAM1-deficient mice showed decreased neural invasion and less paralysis. Such Schwann cell behavior reflects normal Schwann cell programs that are typically activated in nerve repair but are instead exploited by cancer cells to promote perineural invasion and cancer progression., Introduction Nerves play an important role in cancer invasion. The innervation of prostate and gastric cancers promotes tumor growth and spread (1, 2), and perineural invasion is an aggressive form [...]

Cellular protrusions generated by the actin cytoskeleton are central to the process of building the body of the embryo. Problems with cellular protrusions underlie human diseases and syndromes, including implantation defects and pregnancy loss, congenital birth defects, and cancer. Cells use protrusive activity together with actin-myosin contractility to create an ordered body shape of the embryo. Here, I review how actin-rich protrusions are used by two major morphological cell types, epithelial and mesenchymal cells, during collective cell migration to sculpt the mouse embryo body. Pre-gastrulation epithelial collective migration of the anterior visceral endoderm is essential for establishing the anterior-posterior body axis. Gastrulation mesenchymal collective migration of the mesoderm wings is crucial for body elongation, and somite and heart formation. Analysis of mouse mutants with disrupted cellular protrusions revealed the key role of protrusions in embryonic morphogenesis and embryo survival. Recent technical approaches have allowed examination of the mechanisms that control cell and tissue movements in vivo in the complex 3D microenvironment of living mouse embryos. Advancing our understanding of protrusion-driven morphogenesis should provide novel insights into human developmental disorders and cancer metastasis. [ABSTRACT FROM AUTHOR]

Abstract Background Germline mutations in LKB1 result in Peutz-Jeghers Syndrome characterized by intestinal hamartomas and increased incidence of epithelial cancers. LKB1 encodes a serine/threonine kinase that plays an important role in regulating energy metabolism through the AMPK/mTOR signaling pathway. In addition, LKB1 is homologous to PAR-4, a polarity protein first described in C. elegans, while activation of LKB1 in mammalian epithelial cells induces the polarized assembly of actin filaments. Results To explore the mechanism by which LKB1 interacts with the actin cytoskeleton, we introduced LKB1 into HeLa cells that lack endogenous LKB1. This results in activation of the small GTPase Rho and the assembly of linear actin filaments associated with focal adhesions. These effects on the actin cytoskeleton are attenuated by siRNA-mediated depletion of the guanine nucleotide exchange factor Dbl. Co-expression of the LKB1 with the adaptor protein STRAD induces actin filament puncta associated with phospho-ezrin. Conclusions This study reveals that LKB1 regulates the actin cytoskeleton through a Dbl/Rho pathway.

Collective epithelial migration is important throughout embryonic development. The underlying mechanisms are poorly understood but likely involve spatially localized activation of Rho GTPases. We previously reported that Rac1 is essential for generating the protrusive activity that drives the collective migration of anterior visceral endoderm (AVE) cells in the early mouse embryo. To identify potential regulators of Rac1, we first performed an RNAi screen of Rho family exchange factors (guanine nucleotide exchange factor [GEF]) in an in vitro collective epithelial migration assay and identified β-Pix. Genetic deletion of β-Pix in mice disrupts collective AVE migration, while high-resolution live imaging revealed that this is associated with randomly directed protrusive activity. We conclude that β-Pix controls the spatial localization of Rac1 activity to drive collective AVE migration at a critical stage in mouse development. [ABSTRACT FROM AUTHOR]

Mammalian Hedgehog (Hh) signal transduction requires a primary cilium, a microtubule-based organelle, and the Gli-Sufu complexes that mediate Hh signalling, which are enriched at cilia tips. Kif7, a kinesin-4 family protein, is a conserved regulator of the Hh signalling pathway and a human ciliopathy protein. Here we show that Kif7 localizes to the cilium tip, the site of microtubule plus ends, where it limits cilium length and controls cilium structure. Purified recombinant Kif7 binds the plus ends of growing microtubules in vitro, where it reduces the rate of microtubule growth and increases the frequency of microtubule catastrophe. Kif7 is not required for normal intraflagellar transport or for trafficking of Hh pathway proteins into cilia. Instead, a central function of Kif7 in the mammalian Hh pathway is to control cilium architecture and to create a single cilium tip compartment, where Gli-Sufu activity can be correctly regulated. [ABSTRACT FROM AUTHOR]

Collective cell migration is a key process during epithelial morphogenesis, tissue regeneration and tumor dissemination. During collective epithelial migration, anterior-posterior polarity, apical-basal polarity and cell-cell junctions must be dynamically coordinated, but the underlying molecular mechanisms controlling this complex behavior are unclear. Rho GTPases regulate the actin cytoskeleton, in particular protrusive and contractile activities at cell-cell contacts. Recently a number of regulators--nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs)--have been identified and suggested to provide spatio-temporal control of Rho GTPases at cell-cell contacts. One of these is myosin IXA, a member of class IX, single-headed actin motors having a conserved RhoGAP domain. Using its actin-binding and motor activities, myosin IX interacts with actin filaments and moves toward filament plus ends. At the plasma membrane, myosin IX's RhoGAP activity negatively regulates Rho to facilitate localized reorganization of the actin cytoskeleton. Here, I discuss how myosin IXA regulates Rho and the actin cytoskeleton during the assembly of nascent cell-cell contacts and how this might contribute to collective epithelial migration. [ABSTRACT FROM AUTHOR]

Summary: Background: Epithelial tissues undergo extensive collective movements during morphogenesis, repair, and renewal. Collective epithelial cell migration requires the intercellular coordination of cell-cell adhesions and the establishment of anterior-posterior polarity, while maintaining apical-basal polarity, but how this is achieved at the molecular level is not well understood. Results: Using an RNA interference-based screen to identify Rho family GTPase regulators required for the collective migration of human bronchial epithelial cells, we identified myosin-IXA (gene name: Myo9a). Depletion of myosin-IXA, a RhoGAP and actin motor protein, in collectively migrating cells led to altered organization of the actin cytoskeleton and tension-dependent disruption of cell-cell adhesions, followed by an inability to form new adhesions resulting in cell scattering. Closer examination revealed that myosin-IXA is required during the formation of junction-associated actin bundles soon after cell-cell contact. Structure-function analysis of myosin-IXA revealed that the motor domain is necessary and sufficient for binding to actin filaments, whereas expression of the RhoGAP domain partially rescued the cell scattering phenotype induced by myosin-IXA depletion. Finally, a fluorescence resonance energy transfer biosensor revealed a significant increase in Rho activity at nascent cell-cell contacts in myosin-IXA depleted cells compared to controls. Conclusion: We propose that myosin-IXA locally regulates Rho and the assembly of thin actin bundles associated with nascent cell-cell adhesions and that this is required to sustain the collective migration of epithelial cells. [Copyright &y& Elsevier]

Cell migration and cell rearrangements are critical for establishment of the body plan of vertebrate embryos. The first step in organization of the body plan of the mouse embryo, specification of the anterior-posterior body axis, depends on migration of the anterior visceral endoderm from the distal tip of the embryo to a more proximal region overlying the future head. The anterior visceral endoderm (AVE) is a cluster of extra-embryonic cells that secretes inhibitors of the Wnt and Nodal pathways to inhibit posterior development. Because Rac proteins are crucial regulators of cell migration and mouse Rac1 mutants die early in development, we tested whether Rac1 plays a role in AVE migration. Here we show that Rac1 mutant embryos fail to specify an anterior-posterior axis and, instead, express posterior markers in a ring around the embryonic circumference. Cells that express the molecular markers of the AVE are properly specified in Rac1 mutants but remain at the distal tip of the embryo at the time when migration should take place. Using tissue specific deletions, we show that Rac1 acts autonomously within the visceral endoderm to promote cell migration. High-resolution imaging shows that the leading wild-type AVE cells extend long lamellar protrusions that span several cell diameters and are polarized in the direction of cell movement. These projections are tipped by filopodia-like structures that appear to sample the environment. Wild-type AVE cells display hallmarks of collective cell migration: they retain tight and adherens junctions as they migrate and exchange neighbors within the plane of the visceral endoderm epithelium. Analysis of mutant embryos shows that Rac1 is not required for intercellular signaling, survival, proliferation, or adhesion in the visceral endoderm but is necessary for the ability of visceral endoderm cells to extend projections, change shape, and exchange neighbors. The data show that Rac1- mediated epithelial migration of the AVE is a crucial step in the establishment of the mammalian body plan and suggest that Rac1 is essential for collective migration in mammalian tissues. [ABSTRACT FROM AUTHOR]

Background: Germline mutations in LKB1 result in Peutz-Jeghers Syndrome characterized by intestinal hamartomas and increased incidence of epithelial cancers. LKB1 encodes a serine/threonine kinase that plays an important role in regulating energy metabolism through the AMPK/mTOR signaling pathway. In addition, LKB1 is homologous to PAR-4, a polarity protein first described in C. elegans, while activation of LKB1 in mammalian epithelial cells induces the polarized assembly of actin filaments. Results: To explore the mechanism by which LKB1 interacts with the actin cytoskeleton, we introduced LKB1 into HeLa cells that lack endogenous LKB1. This results in activation of the small GTPase Rho and the assembly of linear actin filaments associated with focal adhesions. These effects on the actin cytoskeleton are attenuated by siRNAmediated depletion of the guanine nucleotide exchange factor Dbl. Co-expression of the LKB1 with the adaptor protein STRAD induces actin filament puncta associated with phospho-ezrin. Conclusions: This study reveals that LKB1 regulates the actin cytoskeleton through a Dbl/Rho pathway. [ABSTRACT FROM AUTHOR]

Lung squamous cell carcinoma (LSCC) remains a leading cause of cancer death with few therapeutic options. We characterized the proteogenomic landscape of LSCC, providing a deeper exposition of LSCC biology with potential therapeutic implications. We identify NSD3 as an alternative driver in FGFR1-amplified tumors and low-p63 tumors overexpressing the therapeutic target survivin. SOX2 is considered undruggable, but our analyses provide rationale for exploring chromatin modifiers such as LSD1 and EZH2 to target SOX2-overexpressing tumors. Our data support complex regulation of metabolic pathways by crosstalk between post-translational modifications including ubiquitylation. Numerous immune-related proteogenomic observations suggest directions for further investigation. Proteogenomic dissection of CDKN2A mutations argue for more nuanced assessment of RB1 protein expression and phosphorylation before declaring CDK4/6 inhibition unsuccessful. Finally, triangulation between LSCC, LUAD, and HNSCC identified both unique and common therapeutic vulnerabilities. These observations and proteogenomics data resources may guide research into the biology and treatment of LSCC. [Display omitted] • Unsupervised clustering revealed subtype with EMT and phosphoprotein signatures • Potential therapeutic vulnerabilities included survivin, NSD3, LSD1, and EZH2 • Rb phosphorylation nominated as a biomarker for trials with CDK4/6 inhibitors • Detailed immune landscape analysis highlighted targetable points of immuneregulation Comprehensive proteogenomic characterization of lung squamous cell carcinomas and paired normal adjacent tissues identifies taxonomic subclasses, alternative driver events, and insights into immune modulation, as well as putative biomarkers and potential therapeutic targets. [ABSTRACT FROM AUTHOR]

We report a comprehensive proteogenomics analysis, including whole-genome sequencing, RNA sequencing, and proteomics and phosphoproteomics profiling, of 218 tumors across 7 histological types of childhood brain cancer: low-grade glioma (n = 93), ependymoma (32), high-grade glioma (25), medulloblastoma (22), ganglioglioma (18), craniopharyngioma (16), and atypical teratoid rhabdoid tumor (12). Proteomics data identify common biological themes that span histological boundaries, suggesting that treatments used for one histological type may be applied effectively to other tumors sharing similar proteomics features. Immune landscape characterization reveals diverse tumor microenvironments across and within diagnoses. Proteomics data further reveal functional effects of somatic mutations and copy number variations (CNVs) not evident in transcriptomics data. Kinase-substrate association and co-expression network analysis identify important biological mechanisms of tumorigenesis. This is the first large-scale proteogenomics analysis across traditional histological boundaries to uncover foundational pediatric brain tumor biology and inform rational treatment selection. • Proteogenomics characterization of 218 pediatric brain tumor samples of 7 histologies • Proteomic clusters reveal actionable biological features spanning histological boundaries • Proteomics reveal downstream effects of DNA alterations not evident in transcriptomics • Kinase activity analyses provide insights into pathway activities and druggable targets Integrative proteogenomics analysis of pediatric tumors identifies common underlying biological processes and potential treatments as well as the functional effects of somatic mutations and CNVs driving tumorigenesis. [ABSTRACT FROM AUTHOR]