Focal adhesions lie at the convergence of integrin adhesion, signaling and the actin cytoskeleton. Cells modify focal adhesions in response to changes in the molecular composition, two-dimensional (2D) vs. three-dimensional (3D) structure, and physical forces present in their extracellular matrix environment. We consider here how cells use focal adhesions to regulate signaling complexes and integrin function. Furthermore, we examine how this regulation controls complex cellular behaviors in response to matrices of diverse physical and biochemical properties. One event regulated by the physical structure of the ECM is phosphorylation of focal adhesion kinase (FAK) at Y397, which couples FAK to several signaling pathways that regulate cell proliferation, survival, migration, and invasion.

Purpose: Small-cell lung cancer (SCLC) has been treated clinically as a homogeneous disease, but recent discoveries suggest that SCLC is heterogeneous. Whether metabolic differences exist among SCLC subtypes is largely unexplored. In this study, we aimed to determine whether metabolic vulnerabilities exist between SCLC subtypes that can be therapeutically exploited.Experimental Design: We performed steady state metabolomics on tumors isolated from distinct genetically engineered mouse models (GEMM) representing the MYC-and MYCLdriven subtypes of SCLC. Using genetic and pharmacologic approaches, we validated our findings in chemo-na€ ve and -resistant human SCLC cell lines, multiple GEMMs, four human cell line xenografts, and four newly derived PDX models.Results: We discover that SCLC subtypes driven by different MYC family members have distinct metabolic pro-files. MYC-driven SCLC preferentially depends on arginineregulated pathways including polyamine biosynthesis and mTOR pathway activation. Chemo-resistant SCLC cells exhibit increased MYC expression and similar metabolic liabilities as chemo-na€ ve MYC-driven cells. Arginine depletion with pegylated arginine deiminase (ADI-PEG 20) dramatically suppresses tumor growth and promotes survival of mice specifically with MYC-driven tumors, including in GEMMs, human cell line xenografts, and a patient-derived xenograft from a relapsed patient. Finally, ADI-PEG 20 is significantly more effective than the standard-of-care chemotherapy.Conclusions: These data identify metabolic heterogeneity within SCLC and suggest arginine deprivation as a subtype-specific therapeutic vulnerability for MYC-driven SCLC. DiscussionDespite numerous clinical trials and years of research, therapeutic options for SCLC remain limited. However, recent studies suggest that molecular subtypes of SCLC exist with distinct

We previously showed that activation of the small GTPase Cdc42 promotes breast cell migration on a collagen matrix. Here we further define the signaling pathways that drive this response and show that Cdc42-mediated migration relies on the adaptor molecule p130Cas . Activated Cdc42 enhanced p130Cas phosphorylation and its binding to Crk. Cdc42-driven migration and p130 Cas phosphorylation were dependent on the Cdc42 effector Ack1 (activated Cdc42-associated kinase). Ack1 formed a signaling complex that also included Cdc42, p130Cas , and Crk, formation of which was regulated by collagen stimulation. The interaction between Ack1 and p130Cas occurred through their respective SH3 domains, while the substrate domain of p130 Cas was the major site of Ack1-dependent phosphorylation. Signaling through this complex is functionally relevant, because treatment with either p130Cas or Ack1 siRNA blocked Cdc42-induced migration. These results suggest that Cdc42 exerts its effects on cell migration in part through its effector Ack1, which regulates p130Cas signaling.Integrin-mediated cell interactions with components of the extracellular matrix regulate several aspects of both epithelial polarization and migration. Integrins are involved in signaling pathways that include activation of small GTPases, scaffolding molecules, and protein kinases (1-3). These signaling pathways regulate various aspects of cell migration on integrin ligands, such as collagen.Members of the Rho family of GTPases, Rho, Rac, and Cdc42, are important regulators of the actin cytoskeleton and have been shown to mediate cell migration (4 -10, for review see Refs. 3 and 11). Although much work has focused on understanding the mechanism by which Rho GTPases regulate the actin cytoskeleton, relatively less is known about the effects they have on integrin signaling pathways.Ack1 and Ack2 are homologous tyrosine kinases that bind exclusively to activated Cdc42-GTP, but not Rac or Rho (12, 13). The structure of Ack includes a kinase domain, an SH3 2 domain, a Cdc42/Rac-interactive binding (CRIB) domain, and a proline-rich C terminus, which is the key determinant between Ack1, a 120-kDa protein (12,14) and Ack2 an 83-kDa isoform (13). Multiple interactions have been identified for Ack1. In vitro binding to the proline-rich region has been demonstrated for Nck (15), Grb2 (16), Src (15), and Hck (17), whereas the SH3 domain binds HSH2, an adaptor in hematopoietic cells (18). Ack1 can also be co-immunoprecipitated with clathrin (16) and sorting nexin 9 (19), components of vesicle dynamics. Ack kinases have been implicated in a variety of signaling pathways. Tyrosine phosphorylation of Ack1 and Ack2 has been demonstrated downstream of growth factors (13, 16), cell adhesion (14, 20), and muscarinic receptors (21). Ack1 phosphorylates and activates Dbl, an exchange factor for Rho (22), as well as Ras/GRF1, an exchange factor for Ras (23). Ack1 also mediates p130Cas phosphorylation downstream of melanoma chondroitin sulfate proteoglycan (24), whereas Ack2 is implicated...

Malignant brain tumors are the leading cause of cancer-related deaths in children. Primitive neuroectodermal tumors of the CNS (CNS-PNETs) are particularly aggressive embryonal tumors of unknown cellular origin. Recent genomic studies have classified CNS-PNETs into molecularly distinct subgroups that promise to improve diagnosis and treatment; however, the lack of cell- or animal-based models for these subgroups prevents testing of rationally designed therapies. Here, we show that a subset of CNS-PNETs co-express oligoneural precursor cell (OPC) markers OLIG2 and SOX10 with coincident activation of the RAS/MAPK (mitogen-activated protein kinase) pathway. Modeling NRAS activation in embryonic OPCs generated malignant brain tumors in zebrafish that closely mimic the human oligoneural/NB-FOXR2 CNS-PNET subgroup by histology and comparative oncogenomics. The zebrafish CNS-PNET model was used to show that MEK inhibitors selectively eliminate Olig2/Sox10 CNS-PNET tumors in vivo without impacting normal brain development. Thus, MEK inhibitors represent a promising rationally designed therapy for children afflicted with oligoneural/NB-FOXR2 CNS-PNETs.