Perinuclear Actin Research Articles

Membrane Microdomains and Cytoskeleton Organization Shape and Regulate the IL-7 Receptor Signalosome in Human CD4 T-cells

Interleukin (IL)-7 is the main homeostatic regulator of CD4 T-lymphocytes (helper) at both central and peripheral levels. Upon activation by IL-7, several signaling pathways, mainly JAK/STAT, PI3K/Akt and MAPK, induce the expression of genes involved in T-cell differentiation, activation, and proliferation. We have analyzed the early events of CD4 T-cell activation by IL-7. We have shown that IL-7 in the first few min induces the formation of cholesterol-enriched membrane microdomains that compartmentalize its activated receptor and initiate its anchoring to the cytoskeleton, supporting the formation of the signaling complex, the signalosome, on the IL-7 receptor cytoplasmic domains. Here we describe by stimulated emission depletion microscopy the key roles played by membrane microdomains and cytoskeleton transient organization in the IL-7-regulated JAK/STAT signaling pathway. We image phospho-STAT5 and cytoskeleton components along IL-7 activation kinetics using appropriate inhibitors. We show that lipid raft inhibitors delay and reduce IL-7-induced JAK1 and JAK3 phosphorylation. Drug-induced disassembly of the cytoskeleton inhibits phospho-STAT5 formation, transport, and translocation into the nucleus that controls the transcription of genes involved in T-cell activation and proliferation. We fit together the results of these quantitative analyses and propose the following mechanism. Activated IL-7 receptors embedded in membrane microdomains induce actin-microfilament meshwork formation, anchoring microtubules that grow radially from rafted receptors to the nuclear membrane. STAT5 phosphorylated by signalosomes are loaded on kinesins and glide along the microtubules across the cytoplasm to reach the nucleus 2 min after IL-7 stimulation. Radial microtubules disappear 15 min later, while transversal microtubules, independent of phospho-STAT5 transport, begin to bud from the microtubule organization center.

The LINC-anchored actin cap connects the extracellular milieu to the nucleus for ultrafast mechanotransduction

Cells continuously sense and respond to external mechanical forces through their cytoskeleton. Here we show that only a small subset of actin fibers, those forming the perinuclear actin cap that wraps around the nucleus, form in response to low physiological mechanical stresses in adherent fibroblasts. While conventional basal stress fibers form only past a threshold shear stress of 0.5 dyn/cm2, actin-cap fibers are formed at shear stresses 50 times lower and orders-of-magnitude faster than biochemical stimulation. This fast differential response is uniquely mediated by focal adhesion protein zyxin at low shear stress and actomyosin fibers of the actin cap. We identify additional roles for lamin A/C of the nuclear lamina and linkers of nucleus to cytoskeleton (LINC) molecules nesprin2giant and nesprin3, which anchor actin cap fibers to the nucleus. These results suggest an interconnected physical pathway for mechanotransduction, from the extracellular milieu to the nucleus.

Cellular Geometry Mediated Apical Stress Fibers Dynamically Couples Nucleus to Focal Adhesion

Cells sense their physical microenvironment and transduce these signals through actin-nuclear links to regulate nuclear functions including gene expression. However, the spatio-temporal coupling between actin cytoskeleton and the nucleus and its modulation by cell geometry are still unclear. using micro-patterned substrates to control cell geometry, we show that perinuclear actin organization at the apical plane remodels from mesh-like structure to stress fibers. The formation of these apical stress fibers (ASF) correlated with significant reduction in nuclear height and was found to exert an active compressive load on the nucleus via direct contact with mature focal adhesion sites. We further show, using quantitative fluorescence spectroscopy experiments, that these ASFs were dynamically coupled to the nucleus via outer nuclear membrane proteins nesprin2G. Taken together, our work provides direct evidence of physical links between the nucleus and focal adhesion sites via ASFs. We suggest that such direct links may underlie nuclear mechanotransduction to regulate genomic programs.

Inhibition of Cdc42-Interacting Protein 4 (CIP4) Impairs Osteosarcoma Tumor Progression

In patients with Osteosarcoma (OS), larger primary tumor size correlates with higher metastasis incidence and lower overall survival. Identifying the mechanisms that control primary tumor growth can lead to the new therapeutic approaches and improve prognosis. Cytoskeleton regulatory molecules play an important role in tumor cells proliferation and motility. In the current study, we investigated the role of scaffolding protein Cdc42-interacting protein 4 (CIP4) in OS.Murine OS cells, DLM8 were stably transfected with shCIP4 plasmid and their tumorigenic activity was studied in vitro and in vivo. The effect of CIP4 downregulation on cytoskeleton was studied by immunohistochemical analysis.In vivo studies revealed that downregulation of CIP4 in OS tumor cells can inhibit primary subcutaneous tumor growth and delay spontaneous metastases growth in the animal lungs. In vitro studies confirmed that inhibiting CIP4 expression significantly reduced tumor cells invasiveness and migration. Changes in CIP4 expression altered its cellular localization pattern and tumor cell morphology, which could explain changes in OS cell behavior in vivo and in vitro. Cells with downregulated CIP4 showed lower levels of actin in cells along with fewer perinuclear actin stress filaments and actin bridges to the lipid bilayer of the cell membrane than control cells.This study presents compelling evidence that inhibition of CIP4 expression in OS cells impairs metastatic behavior of cells in vitro and prolongs survival of animals by inhibiting primary tumor growth. Although the lack of CIP4 in tumor cells did not prevent formation of metastasis, it did substantially delay their formation in the animals' lungs.

The multi-faceted role of the actin cap in cellular mechanosensation and mechanotransduction

The perinuclear actin cap (or actin cap) is a recently characterized cytoskeletal organelle composed of thick, parallel, and highly contractile acto-myosin filaments that are specifically anchored to the apical surface of the interphase nucleus. The actin cap is present in a wide range of adherent eukaryotic cells, but is disrupted in several human diseases, including laminopathies and cancer. Through its large terminating focal adhesions and anchorage to the nuclear lamina and nuclear envelope through LINC complexes, the perinuclear actin cap plays a critical role both in mechanosensation and mechanotransduction, the ability of cells to sense changes in matrix compliance and to respond to mechanical forces, respectively.

Inhibition of Cdc42-Interacting Protein 4 (CIP4) Impairs Osteosarcoma Tumor Progression

In patients with Osteosarcoma (OS), larger primary tumor size correlates with higher metastasis incidence and lower overall survival. Identifying the mechanisms that control primary tumor growth can lead to the new therapeutic approaches and improve prognosis. Cytoskeleton regulatory molecules play an important role in tumor cells proliferation and motility. In the current study, we investigated the role of scaffolding protein Cdc42-interacting protein 4 (CIP4) in OS. Murine OS cells, DLM8 were stably transfected with shCIP4 plasmid and their tumorigenic activity was studied in vitro and in vivo. The effect of CIP4 downregulation on cytoskeleton was studied by immunohistochemical analysis. In vivo studies revealed that downregulation of CIP4 in OS tumor cells can inhibit primary subcutaneous tumor growth and delay spontaneous metastases growth in the animal lungs. In vitro studies confirmed that inhibiting CIP4 expression significantly reduced tumor cells invasiveness and migration. Changes in CIP4 expression altered its cellular localization pattern and tumor cell morphology, which could explain changes in OS cell behavior in vivo and in vitro. Cells with downregulated CIP4 showed lower levels of actin in cells along with fewer perinuclear actin stress filaments and actin bridges to the lipid bilayer of the cell membrane than control cells. This study presents compelling evidence that inhibition of CIP4 expression in OS cells impairs metastatic behavior of cells in vitro and prolongs survival of animals by inhibiting primary tumor growth. Although the lack of CIP4 in tumor cells did not prevent formation of metastasis, it did substantially delay their formation in the animals' lungs.

Actin cap associated focal adhesions and their distinct role in cellular mechanosensing

The ability for cells to sense and adapt to different physical microenvironments plays a critical role in development, immune responses, and cancer metastasis. Here we identify a small subset of focal adhesions that terminate fibers in the actin cap, a highly ordered filamentous actin structure that is anchored to the top of the nucleus by the LINC complexes; these differ from conventional focal adhesions in morphology, subcellular organization, movements, turnover dynamics, and response to biochemical stimuli. Actin cap associated focal adhesions (ACAFAs) dominate cell mechanosensing over a wide range of matrix stiffness, an ACAFA-specific function regulated by actomyosin contractility in the actin cap, while conventional focal adhesions are restrictively involved in mechanosensing for extremely soft substrates. These results establish the perinuclear actin cap and associated ACAFAs as major mediators of cellular mechanosensing and a critical element of the physical pathway that transduce mechanical cues all the way to the nucleus.

The distinct roles of the nucleus and nucleus-cytoskeleton connections in three-dimensional cell migration

Cells often migrate in vivo in an extracellular matrix that is intrinsically three-dimensional (3D) and the role of actin filament architecture in 3D cell migration is less well understood. Here we show that, while recently identified linkers of nucleoskeleton to cytoskeleton (LINC) complexes play a minimal role in conventional 2D migration, they play a critical role in regulating the organization of a subset of actin filament bundles – the perinuclear actin cap - connected to the nucleus through Nesprin2giant and Nesprin3 in cells in 3D collagen I matrix. Actin cap fibers prolong the nucleus and mediate the formation of pseudopodial protrusions, which drive matrix traction and 3D cell migration. Disruption of LINC complexes disorganizes the actin cap, which impairs 3D cell migration. A simple mechanical model explains why LINC complexes and the perinuclear actin cap are essential in 3D migration by providing mechanical support to the formation of pseudopodial protrusions.

The Differential Formation of the LINC-Mediated Perinuclear Actin Cap in Pluripotent and Somatic Cells

The actin filament cytoskeleton mediates cell motility and adhesion in somatic cells. However, whether the function and organization of the actin network are fundamentally different in pluripotent stem cells is unknown. Here we show that while conventional actin stress fibers at the basal surface of cells are present before and after onset of differentiation of mouse (mESCs) and human embryonic stem cells (hESCs), actin stress fibers of the actin cap, which wrap around the nucleus, are completely absent from undifferentiated mESCs and hESCs and their formation strongly correlates with differentiation. Similarly, the perinuclear actin cap is absent from human induced pluripotent stem cells (hiPSCs), while it is organized in the parental lung fibroblasts from which these hiPSCs are derived and in a wide range of human somatic cells, including lung, embryonic, and foreskin fibroblasts and endothelial cells. During differentiation, the formation of the actin cap follows the expression and proper localization of nuclear lamin A/C and associated linkers of nucleus and cytoskeleton (LINC) complexes at the nuclear envelope, which physically couple the actin cap to the apical surface of the nucleus. The differentiation of hESCs is accompanied by the progressive formation of a perinuclear actin cap while induced pluripotency is accompanied by the specific elimination of the actin cap, and that, through lamin A/C and LINC complexes, this actin cap is involved in progressively shaping the nucleus of hESCs undergoing differentiation. While, the localization of lamin A/C at the nuclear envelope is required for perinuclear actin cap formation, it is not sufficient to control nuclear shape.

Nuclear Localization of mDia2 Formin and its Possible Regulation by Rho Family GTPases

Formin family proteins are potent activators of actin filament nucleation and elongation. While numerous studies indicate the possible roles of actin inside the nucleus and the tight association of the nucleus with cytoplasmic actin cytoskeleton, the role of actin-associated proteins and, in particular, regulators of actin polymerization in the organization of nuclear and perinuclear actin remains obscure. Nuclear localization of some formins, such as formin-1 and mDia2 was detected in some previous studies. Particularly, it was recently shown that mDia2 has both nuclear localization and nuclear export signals, and is accumulated in the nucleus upon inhibition of nuclear export by leptomycin B (LMB) (Miki et al, J Biol Chem. 2009). We confirmed and extended these results; in particular, we have measured the kinetics of nuclear accumulation of some formins upon LMB treatment and have found that mDia2 accumulates in the nucleus very fast while mDia1 does not accumulate. Since mDia2 activity is regulated by the Rho family GTPases, we further studied the nuclear localization of RhoA, Rac1, and Cdc42 and found that significant amounts of the wild type Rho GTPases were localized to the nucleus, while constitutively active Rho GTPases demonstrated essentially cytoplasmic localization. Moreover, active Cdc42 was shown to augment localization of mDia2 to cell plasma membrane and slow down its nuclear shuttling. Finally, we have found that even without LMB treatment, GFP-fused full length mDia2 is accumulated to the nuclear rim, where it colocalizes with nesprin, a protein involved in linking nucleus with actin cytoskeleton. Constitutively active Rac1 was also enriched in the nuclear rim. The experiments using cell treatment with digitonin, which permeabilizes plasma- but not the nuclear membrane, suggested that mDia2-enriched nuclear rim was located at the cytoplasmic side of the nuclear membrane.

Keeping the LINC: the importance of nucleocytoskeletal coupling in intracellular force transmission and cellular function.

Providing a stable physical connection between the nucleus and the cytoskeleton is essential for a wide range of cellular functions and it could also participate in mechanosensing by transmitting intra- and extra-cellular mechanical stimuli via the cytoskeleton to the nucleus. Nesprins and SUN proteins, located at the nuclear envelope, form the LINC (linker of nucleoskeleton and cytoskeleton) complex that connects the nucleus to the cytoskeleton; underlying nuclear lamins contribute to anchoring LINC complex components at the nuclear envelope. Disruption of the LINC complex or loss of lamins can result in disturbed perinuclear actin and intermediate filament networks and causes severe functional defects, including impaired nuclear positioning, cell polarization and cell motility. Recent studies have identified the LINC complex as the major force-transmitting element at the nuclear envelope and suggest that many of the aforementioned defects can be attributed to disturbed force transmission between the nucleus and the cytoskeleton. Thus mutations in nesprins, SUN proteins or lamins, which have been linked to muscular dystrophies and cardiomyopathies, may weaken or completely eliminate LINC complex function at the nuclear envelope and result in impaired intracellular force transmission, thereby disrupting critical cellular functions.

A novel actin–microtubule cross‐linking kinesin, NtKCH, functions in cell expansion and division

• Kinesins with a calponin homology domain (KCHs) have been identified recently as a plant-specific subgroup of the kinesin-14 family and are suspected to act as microtubule-actin filament cross-linkers. The cellular function, however, has remained elusive. • In order to address the function of KCHs, we isolated NtKCH, a novel KCH homologue from tobacco BY-2 cells. Following synchronization, NtKCH transcripts were shown to be abundant during mitosis, whereas, during interphase, expression was low. • Using fluorescent-tagged cell lines and immunolabelling techniques, the localization of tobacco KCH was found to differ depending on the cell cycle. During interphase, NtKCH mainly associated with cortical microtubules, whereas a subfraction also co-localized with perinuclear actin cables. In dividing cells, NtKCH accumulated at the pre-prophase band and at the phragmoplast. However, it remained absent from spindle microtubules, but, instead, concentrated at two agglomerations in proximity to the two cell poles. • This work develops a detailed model for the dual localization and function of NtKCH during cell division vs cell expansion. This model implies two dynamic states of KCHs that differ with regard to actin interaction. This allows the modulation of force generation by KCH in a cell cycle-dependent capture mechanism.

Refilin holds the cap

The Refilins (RefilinA and RefilinB) are a novel family of short-lived actin regulatory proteins that are expressed during changes in cellular phenotype such as epithelial to mesenchymal transition (EMT). The Refilins promote to the formation of actin- and myosin-rich perinuclear bundles that are characteristic of cellular phenotypic switches. In epithelial cells, RefilinB is up-regulated in response to TGF-β stimulation and function in organization of apical perinuclear actin fibers during early stage of the EMT process1. In fibroblasts, RefilinB stabilizes perinuclear parallel actin bundles which resemble actin cap 2. Refilins bind and modulate the function of Filamin A (FLNA). Upon binding to Refilins, FLNA is capable of assembling actin filaments into parallel bundles, possibly by undergoing conformational changes at the C-terminal. Perinuclear actin structures determine nuclear shape, cell morphology, cell adhesion and possibly cell proliferation and gene regulation. Identifying the role of Refilins in organizing perinuclear actin networks provides additional insight in the process of intracellular mechanotransduction that regulate changes in cellular phenotype such as those observed during EMT.

A Critical Role of Perinuclear Filamentous Actin in Spatial Repositioning and Mutually Exclusive Expression of Virulence Genes in Malaria Parasites

Many microbial pathogens, including the malaria parasite Plasmodium falciparum, vary surface protein expression to evade host immune responses. P. falciparium antigenic variation is linked to var gene family-encoded clonally variant surface protein expression. Mututally exclusive var gene expression is partially controlled by spatial positioning; silent genes are retained at distinct perinuclear sites and relocated to transcriptionally active locations for monoallelic expression. We show that var introns can control this process and that var intron addition relocalizes episomes from a random to a perinuclear position. This var intron-regulated nuclear tethering and repositioning is linked to an 18 bp nuclear protein-binding element that recruits an actin protein complex. Pharmacologically induced F-actin formation, which is restricted to the nuclear periphery, repositions intron-carrying episomes and var genes and disrupts mutually exclusive var gene expression. Thus, actin polymerization relocates var genes from a repressive to an active perinuclear compartment, which is crucial for P. falciparium phenotypic variation and pathogenesis.

Refilins

Actin cytoskeleton dynamics lie at the heart of cell mechanosensing signaling. In fibroblast cells, two perinuclear acto-myosin structures, the actin cap and the transmembrane actin-associated nuclear (TAN) line, are components of a physical pathway transducing extracellular physical signals to changes in nuclear shape and movements. We recently demonstrated the existence of a previously uncharacterized third apical perinuclear actin organization in epithelial cells that forms during epithelial–mesenchymal transition (EMT) mediated by TGFβ (TGFβ). A common regulatory mechanism for these different perinuclear actin architectures has emerged with the identification of a novel family of actin bundling proteins, the Refilins. Here we provide updates on some characteristics of Refilin proteins, and we discuss potential function of the Refilins in cell mechanosensing signaling.

The Interaction between Nesprins and Sun Proteins at the Nuclear Envelope Is Critical for Force Transmission between the Nucleus and Cytoskeleton

Maintaining physical connections between the nucleus and the cytoskeleton is important for many cellular processes that require coordinated movement and positioning of the nucleus. Nucleo-cytoskeletal coupling is also necessary to transmit extracellular mechanical stimuli across the cytoskeleton to the nucleus, where they may initiate mechanotransduction events. The LINC (Linker of Nucleoskeleton and Cytoskeleton) complex, formed by the interaction of nesprins and SUN proteins at the nuclear envelope, can bind to nuclear and cytoskeletal elements; however, its functional importance in transmitting intracellular forces has never been directly tested. This question is particularly relevant since recent findings have linked nesprin mutations to muscular dystrophy and dilated cardiomyopathy. Using biophysical assays to assess intracellular force transmission and associated cellular functions, we identified the LINC complex as a critical component for nucleo-cytoskeletal force transmission. Disruption of the LINC complex caused impaired propagation of intracellular forces and disturbed organization of the perinuclear actin and intermediate filament networks. Although mechanically induced activation of mechanosensitive genes was normal (suggesting that nuclear deformation is not required for mechanotransduction signaling) cells exhibited other severe functional defects after LINC complex disruption; nuclear positioning and cell polarization were impaired in migrating cells and in cells plated on micropatterned substrates, and cell migration speed and persistence time were significantly reduced. Taken together, our findings suggest that the LINC complex is critical for nucleo-cytoskeletal force transmission and that LINC complex disruption can result in defects in cellular structure and function that may contribute to the development of muscular dystrophies and cardiomyopathies.

RefilinB (FAM101B) targets FilaminA to organize perinuclear actin networks and regulates nuclear shape

The intracellular localization and shape of the nucleus plays a central role in cellular and developmental processes. In fibroblasts, nuclear movement and shape are controlled by a specific perinuclear actin network made of contractile actin filament bundles called transmembrane actin-associated nuclear (TAN) lines that form a structure called the actin cap. The identification of regulatory proteins associated with this specific actin cytoskeletal dynamic is a priority for understanding actin-based changes in nuclear shape and position in normal and pathological situations. Here, we first identify a unique family of actin regulators, the refilin proteins (RefilinA and RefilinB), that stabilize specifically perinuclear actin filament bundles. We next identify the actin-binding filamin A (FLNA) protein as the downstream effector of refilins. Refilins act as molecular switches to convert FLNA from an actin branching protein into one that bundles. In NIH 3T3 fibroblasts, the RefilinB/FLNA complex organizes the perinuclear actin filament bundles forming the actin cap. Finally, we demonstrate that in epithelial normal murine mammary gland (NmuMG) cells, the RefilinB/FLNA complex controls formation of a new perinuclear actin network that accompanies nuclear shape changes during the epithelial-mesenchymal transition (EMT). Our studies open perspectives for further functional analyses of this unique actin-based network and shed light on FLNA function during development and in human syndromes associated with FLNA mutations.

Physical properties of mesenchymal stem cells are coordinated by the perinuclear actin cap

Mesenchymal stem cells (MSCs) have been extensively investigated for their applications in regenerative medicine. Successful use of MSCs in cell-based therapies will rely on the ability to effectively identify their properties and functions with a relatively non-destructive methodology.In this study, we measured the surface stiffness and thickness of rat MSCs with atomic force microscopy and clarified their relation at a single-cell level. The role of the perinuclear actin cap in regulating the thickness, stiffness, and proliferative activity of these cells was also determined by using several actin cytoskeleton-modifying reagents. This study has helped elucidate a possible link between the physical properties and the physiological function of the MSCs, and the corresponding regulatory role of the actin cytoskeleton.

MiR-145-dependent targeting of Junctional Adhesion Molecule A and modulation of fascin expression are associated with reduced breast cancer cell motility and invasiveness

Micro RNAs are small non-coding RNAs, which regulate fundamental cellular and developmental processes at the transcriptional and translational level. In breast cancer, miR-145 expression is downregulated compared with healthy control tissue. As several predicted targets of miR-145 potentially regulate cell motility, we aimed at investigating a potential role for miR-145 in breast cancer cell motility and invasiveness. Assisted by Affymetrix array technology, we demonstrate that overexpression of miR-145 in MDA-MB-231, MCF-7, MDA-MB-468 and SK-BR-3 breast cancer cells and in Ishikawa endometrial carcinoma cells leads to a downregulation of the cell-cell adhesion protein JAM-A and of the actin bundling protein fascin. Moreover, podocalyxin and Serpin E1 mRNA levels were downregulated, and gamma-actin, transgelin and MYL9 were upregulated upon miR-145 overexpression. These miR-145-dependent expression changes drastically decreased cancer cell motility, as revealed by time-lapse video microscopy, scratch wound closure assays and matrigel invasion assays. Immunofluorescence microscopy demonstrated restructuring of the actin cytoskeleton and a change in cell morphology by miR-145 overexpression, resulting in a more cortical actin distribution, and reduced actin stress fiber and filopodia formation. Nuclear rotation was observed in 10% of the pre-miR-145 transfected MDA-MB-231 cells, accompanied by a reduction of perinuclear actin. Luciferase activation assays confirmed direct miR-145-dependent regulation of the 3'UTR of JAM-A, whereas siRNA-mediated knockdown of JAM-A expression resulted in decreased motility and invasiveness of MDA-MB-231 and MCF-7 breast cancer cells. Our data identify JAM-A and fascin as novel targets of miR-145, firmly establishing a role for miR-145 in modulating breast cancer cell motility. Our data provide a rationale for future miR-145-targeted approaches of antimetastatic cancer therapy.

Abstract 5115: The role of Cdc42-interacting protein 4 (CIP4) in osteosarcoma tumorigenesis

Abstract Osteosarcoma (OS) remains a devastating disease and requires better understanding of its biology for the development of novel therapeutic approaches. Tumor growth and metastases formation require an ability of cells to have a flexible cytoskeletal organization. Cdc42-interacting protein 4 (CIP4) is one of the scaffolding cytoskeleton-regulatory protein, whose role in tumors remains unknown. In the current study we investigated the role of CIP4 in OS tumorigenesis. We transfected highly aggressive mouse OS cells, DLM8 with the plasmid that downregulated expression of CIP4 protein (DLM8/shCIP4). We found that the growth rate of DLM8/shCIP4 clones was reduced by 30% when compared with non-transfected DLM8 cells or DLM8 cells transfected with control plasmid (DLM8/sh). When DLM8/shCIP4 cells were injected into mice subcutaneously they formed tumors that grew significantly slower than DLM8 or DLM8/sh control cells (p<0.02). We also found that inhibition of CIP4 expression in DLM8 cells decreased their motility and invasion properties in vitro, indicating on its ability to impair metastases growth. Fluorescent immunostaining for actin in DLM8/shCIP4 cells revealed lower perinuclear actin stress filaments formation and lower actin bridge to the lipid bilayer of the lipid cell membrane when compared with wild-type DLM8 or DLM8/sh. We also observed that downregulation of CIP4 changed cell membrane morphology in DLM8 cells - they had less protrusions and smoother cell surface than control cells. All these findings indicate that CIP4 may also play a role in metastatic behavior of OS cells and needs further investigation. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5115.