Homophilic Cell Adhesion Molecule Research Articles

IGSF3 is a homophilic cell adhesion molecule that drives lung metastasis of melanoma by promoting adhesion to vascular endothelium.

The immunoglobulin superfamily (IgSF) is one of the largest families of cell-surface molecules involved in various cell-cell interactions, including cancer-stromal interactions. In this study, we undertook a comprehensive RT-PCR-based screening for IgSF molecules that promote experimental lung metastasis in mice. By comparing the expression of 325 genes encoding cell-surface IgSF molecules between mouse melanoma B16 cells and its highly metastatic subline, B16F10 cells, we found that expression of the immunoglobulin superfamily member 3 gene (Igsf3) was significantly enhanced in B16F10 cells than in B16 cells. Knockdown of Igsf3 in B16F10 cells significantly reduced lung metastasis following intravenous injection into C57BL/6 mice. IGSF3 promoted adhesion of B16F10 cells to vascular endothelial cells and functioned as a homophilic cell adhesion molecule between B16F10 cells and vascular endothelial cells. Notably, the knockdown of IGSF3 in either B16F10 cells or vascular endothelial cells suppressed the transendothelial migration of B16F10 cells. Moreover, IGSF3 knockdown suppressed the extravasation of B16F10 cells into the lungs after intravenous injection. These results suggest that IGSF3 promotes the metastatic potential of B16F10 cells in the lungs by facilitating their adhesion to vascular endothelial cells.

Nectin-3 and Nectin-4: potential prognostic biomarkers for therapeutic targeting of cancer

Nectin-3 and nectin-4 belong to the immunoglobulin (Ig) superfamily, and are Ca2+ -independent homophilic cell adhesion molecules. Nectin-3 is ubiquitous in adult tissues, and it enhances normal levels of synaptic formation. In contrast, nectin-4 is weakly-to-moderately expressed in normal human tissues. In recent years, studies have shown that nectin-3 is highly expressed in the nervous system. Moreover, it is associated with poor prognostic factors in distant metastases and malignant tumors with high vascular invasion such as pancreatic, lung and breast cancers. In particular, nectin-4 is overexpressed in various malignant tumors, and it is associated with proliferation, angiogenesis, metastasis, drug resistance, tumor relapse, DNA repair, cancer stemness, and poor prognosis. Unlike nectin-3, nectin-4 has become a potential prognostic biomarker and specific therapeutic target for cancer as there is no consensus on the significance of abnormal expression of nectin-3 in various cancers.

ASD/OCD-Linked Protocadherin-10 Regulates Synapse, But Not Axon, Development in the Amygdala and Contributes to Fear- and Anxiety-Related Behaviors.

The Protocadherin-10 (PCDH10) gene is associated with autism spectrum disorder (ASD), obsessive-compulsive disorder (OCD), and major depression (MD). The PCDH10 protein is a homophilic cell adhesion molecule that belongs to the δ2-protocadherin family. PCDH10 is highly expressed in the developing brain, especially in the basolateral nucleus of the amygdala (BLA). However, the role of PCDH10 in vivo has been debatable: one paper reported that a Pcdh10 mutant mouse line showed changes in axonal projections; however, another Pcdh10 mutant mouse line was reported to have failed to detect axonal phenotypes. Therefore, the actual roles of PCDH10 in the brain remain to be elucidated. We established a new Pcdh10 KO mouse line using the CRISPR/Cas9 system, without inserting gene cassettes to avoid nonspecific effects, examined the roles of PCDH10 in the brain, and studied the behavioral consequences of Pcdh10 inactivation. Here, we show that Pcdh10 KO mice do not show defects in axonal development. Instead, we find that Pcdh10 KO mice exhibit impaired development of excitatory synapses in the dorsal BLA. We further demonstrate that male Pcdh10 KO mice exhibit reduced anxiety-related behaviors, impaired fear conditioning, decreased stress-coping responses, and mildly impaired social recognition and communication. These results indicate that PCDH10 plays a critical role in excitatory synapse development, but not axon development, in the dorsal BLA and that PCDH10 regulates anxiety-related, fear-related, and stress-related behaviors. Our results reveal the roles of PCDH10 in the brain and its relationship to relevant psychiatric disorders such as ASD, OCD, and MD.SIGNIFICANCE STATEMENTProtocadherin-10 (PCDH10) encodes a cell adhesion molecule and is implicated in autism spectrum disorder (ASD), obsessive-compulsive disorder (OCD), and major depression (MD). PCDH10 is highly expressed in the basolateral nucleus of the amygdala (BLA). However, the phenotypes of previously published Pcdh10 mutant mice are debatable, and some are possibly because of the nonspecific effects of the LacZ/Neo cassette inserted in the mice. We have generated a new Pcdh10 mutant mouse line without the LacZ/Neo cassette. Using our new mouse line, we reveal the roles of PCDH10 for excitatory synapse development in the BLA. The mutant mice exhibit anxiety-related, fear-related, and stress-related behaviors, which are relevant to ASD, OCD, and MD, suggesting a possible treatment strategy for such psychiatric disorders.

Evaluation of immunohistochemical expression of E-cadherin in pleomorphic adenoma and adenoid cystic carcinoma

Background:Pleomorphic adenoma (PA) and adenoid cystic carcinoma (ADCC) are benign and malignant salivary gland tumors, respectively, with distinct behavior. They have similar origins and cell components. E-cadherins are the main homophilic cell adhesion molecules, which play a central role in maintaining epithelial integrity, functioning in intercellular adhesion and differentiation. Hence, changes in E-cadherin function are reflected in the morphologic events associated with the cellular arrangement, movement and wound healing.Aim:To study and compare the expression of E-cadherin immunostaining in PA and ADCC.Materials and Methods:Fifteen cases of each PA and ADCC were immunohistochemically stained with E-cadherin. Five cases of normal salivary gland tissues were taken as the positive control.Mann–Whitney U-test was used for statistical analysis.Results:About 86.6% of PA cases showed homogeneous staining. 66.6% of cases of ADCC showed heterogeneous staining. PA, cribriform and tubular patterns of ADCC predominantly showed moderate immune-staining and solid patterns of ADCC exhibited predominantly mild immunostaining. Depending on the intensity of staining, we found a significant P value between PA and the solid variant of ADCC.Conclusion:E-cadherin proved to be a better marker for epithelial phenotypes in PAs. In ADCC difference in staining intensity between different histological subtypes suggests that further studies should be done to assess the usefulness of an immuno-marker to know the aggressive behavior of ADCC.

Expression of FLRT2 in Postnatal Central Nervous System Development and After Spinal Cord Injury.

Fibronectin and leucine-rich transmembrane (FLRT) proteins are necessary for various developmental processes and in pathological conditions. FLRT2 acts as a homophilic cell adhesion molecule, a heterophilic repulsive ligand of Unc5/Netrin receptors, and a synaptogenic molecule; the last feature is mediated by binding to latrophilins. Although the function of FLRT2 in regulating cortical migration at the late gestation stage has been analyzed, little is known about the expression pattern of FLRT2 during postnatal central nervous system (CNS) development. In this study, we used Flrt2-LacZ knock-in (KI) mice to analyze FLRT2 expression during CNS development. At the early postnatal stage, FLRT2 expression was largely restricted to several regions of the striatum and deep layers of the cerebral cortex. In adulthood, FLRT2 expression was more prominent in the cerebral cortex, hippocampus, piriform cortex (PIR), nucleus of the lateral olfactory tract (NLOT), and ventral medial nucleus (VM) of the thalamus, but lower in the striatum. Notably, in the hippocampus, FLRT2 expression was confined to the CA1 region and partly localized on pre- and postsynapses whereas only few expression was observed in CA3 and dentate gyrus (DG). Finally, we observed temporally limited FLRT2 upregulation in reactive astrocytes around lesion sites 7 days after thoracic spinal cord injury. These dynamic changes in FLRT2 expression may enable multiple FLRT2 functions, including cell adhesion, repulsion, and synapse formation in different regions during CNS development and after spinal cord injury.

δ-Protocadherins regulate neural progenitor cell division by antagonizing Ryk and Wnt/β-catenin signaling

SummaryThe division of neural progenitor cells provides the cellular substrate from which the nervous system is sculpted during development. The δ-protocadherin family of homophilic cell adhesion molecules is essential for the development of the vertebrate nervous system and is implicated in an array of neurodevelopmental disorders. We show that lesions in any of six, individual δ-protocadherins increases cell divisions of neural progenitors in the hindbrain. This increase is due to mis-regulation of Wnt/β-catenin signaling, as this pathway is upregulated in δ-protocadherin mutants and inhibition of this pathway blocks the increase in cell division. Furthermore, the δ-protocadherins can be present in complex with the Wnt receptor Ryk, and Ryk is required for the increased proliferation in protocadherin mutants. Thus, δ-protocadherins are novel regulators of Wnt/β-catenin signaling that may control the development of neural circuits by defining a molecular code for the identity of neural progenitor cells and differentially regulating their proliferation.

IgSF11 homophilic adhesion proteins promote layer-specific synaptic assembly of the cortical interneuron subtype.

The most prominent structural hallmark of the mammalian neocortical circuitry is the layer-based organization of specific cell types and synaptic inputs. Accordingly, cortical inhibitory interneurons (INs), which shape local network activity, exhibit subtype-specific laminar specificity of synaptic outputs. However, the underlying molecular mechanisms remain unknown. Here, we demonstrate that Immunoglobulin Superfamily member 11 (IgSF11) homophilic adhesion proteins are preferentially expressed in one of the most distinctive IN subtypes, namely, chandelier cells (ChCs) that specifically innervate axon initial segments of pyramidal neurons (PNs), and their synaptic laminar target. Loss-of-function experiments in either ChCs or postsynaptic cells revealed that IgSF11 is required for ChC synaptic development in the target layer. While overexpression of IgSF11 in ChCs enlarges ChC presynaptic boutons, expressing IgSF11 in nontarget layers induces ectopic ChC synapses. These findings provide evidence that synapse-promoting adhesion proteins, highly localized to synaptic partners, determine the layer-specific synaptic connectivity of the cortical IN subtype.

Mice with cleavage-resistant N-cadherin exhibit synapse anomaly in the hippocampus and outperformance in spatial learning tasks

N-cadherin is a homophilic cell adhesion molecule that stabilizes excitatory synapses, by connecting pre- and post-synaptic termini. Upon NMDA receptor (NMDAR) activation by glutamate, membrane-proximal domains of N-cadherin are cleaved serially by a-disintegrin-and-metalloprotease 10 (ADAM10) and then presenilin 1(PS1, catalytic subunit of the γ-secretase complex). To assess the physiological significance of the initial N-cadherin cleavage, we engineer the mouse genome to create a knock-in allele with tandem missense mutations in the mouse N-cadherin/Cadherin-2 gene (Cdh2R714G, I715D, or GD) that confers resistance on proteolysis by ADAM10 (GD mice). GD mice showed a better performance in the radial maze test, with significantly less revisiting errors after intervals of 30 and 300 s than WT, and a tendency for enhanced freezing in fear conditioning. Interestingly, GD mice reveal higher complexity in the tufts of thorny excrescence in the CA3 region of the hippocampus. Fine morphometry with serial section transmission electron microscopy (ssTEM) and three-dimensional (3D) reconstruction reveals significantly higher synaptic density, significantly smaller PSD area, and normal dendritic spine volume in GD mice. This knock-in mouse has provided in vivo evidence that ADAM10-mediated cleavage is a critical step in N-cadherin shedding and degradation and involved in the structure and function of glutamatergic synapses, which affect the memory function.

Current View on EpCAM Structural Biology.

EpCAM, a carcinoma cell-surface marker protein and a therapeutic target, has been primarily addressed as a cell adhesion molecule. With regard to recent discoveries of its role in signaling with implications in cell proliferation and differentiation, and findings contradicting a direct role in mediating adhesion contacts, we provide a comprehensive and updated overview on the available structural data on EpCAM and interpret it in the light of recent reports on its function. First, we describe the structure of extracellular part of EpCAM, both as a subunit and part of a cis-dimer which, according to several experimental observations, represents a biologically relevant oligomeric state. Next, we provide a thorough evaluation of reports on EpCAM as a homophilic cell adhesion molecule with a structure-based explanation why direct EpCAM participation in cell–cell contacts is highly unlikely. Finally, we review the signaling aspect of EpCAM with focus on accessibility of signaling-associated cleavage sites.

In Vitro Monolayer Culture of Dispersed Neural Stem Cells on the E-Cadherin-Based Substrate with Long-Term Stemness Maintenance.

Neural stem cells (NSCs) play an important role in neural tissue engineering because of their capacity of self-renewal and differentiation to multiple cell lineages. The in vitro conventional neurosphere culture protocol has some limitations such as limited nutrition and oxygen penetration and distribution causing the heterogeneity of cells inside, inaccessibility of internal cells, and inhomogeneous cellular morphology and properties. As a result, cultivation as a monolayer is a better way to study NSCs and obtain a homogeneous cell population. The cadherins are a classical family of homophilic cell adhesion molecules mediating cell-cell adhesion. Here, we used a recombinant human E-cadherin mouse IgG Fc chimera protein that self-assembles on a hydrophobic polystyrene surface via hydrophobic interaction to obtain an E-cadherin-coated culture plate (ECP). The rat fetal NSCs were cultured on the ECP and routine tissue culture plate (TCP) from passage 2 to passage 5. NSCs on TCP formed uniform floating neurospheres and grew up over time, while cells on the ECP adhered on the bottom of the plate and exhibited individual cells with scattering morphology, forming intercellular connections between cells. The cell proliferation and differentiation behaviors that were evaluated by Cell Counting Kit-8 assay (CCK-8), immunofluorescence staining, and real-time quantitative polymerase chain reaction showed NSCs could maintain the capacity for self-renewal and ability to differentiate into neurons, oligodendrocytes, and astrocytes after the long-term in vitro cell culture and passaging. Therefore, our study indicated that hE-cad-Fc could provide a homogeneous environment for individual cells in monolayer conditions to maintain the capacity of self-renewal and differentiation by mimicking the cell–cell interaction.

Multiplane Calcium Imaging Reveals Disrupted Development of Network Topology in Zebrafish pcdh19 Mutants.

Functional brain networks self-assemble during development, although the molecular basis of network assembly is poorly understood. Protocadherin-19 (pcdh19) is a homophilic cell adhesion molecule that is linked to neurodevelopmental disorders, and influences multiple cellular and developmental events in zebrafish. Although loss of PCDH19 in humans and model organisms leads to functional deficits, the underlying network defects remain unknown. Here, we employ multiplane, resonant-scanning in vivo two-photon calcium imaging of developing zebrafish, and use graph theory to characterize the development of resting state functional networks in both wild-type and pcdh19 mutant larvae. We find that the brain networks of pcdh19 mutants display enhanced clustering and an altered developmental trajectory of network assembly. Our results show that functional imaging and network analysis in zebrafish larvae is an effective approach for characterizing the developmental impact of lesions in genes of clinical interest.

EpCAM homo-oligomerization is not the basis for its role in cell-cell adhesion

Cell-surface tumor marker EpCAM plays a key role in proliferation, differentiation and adhesion processes in stem and epithelial cells. It is established as a cell-cell adhesion molecule, forming intercellular interactions through homophilic association. However, the mechanism by which such interactions arise has not yet been fully elucidated. Here, we first show that EpCAM monomers do not associate into oligomers that would resemble an inter-cellular homo-oligomer, capable of mediating cell-cell adhesion, by using SAXS, XL-MS and bead aggregation assays. Second, we also show that EpCAM forms stable dimers on the surface of a cell with pre-formed cell-cell contacts using FLIM-FRET; however, no inter-cellular homo-oligomers were detectable. Thus, our study provides clear evidence that EpCAM indeed does not function as a homophilic cell adhesion molecule and therefore calls for a significant revision of its role in both normal and cancerous tissues. In the light of this, we strongly support the previously suggested name Epithelial Cell Activating Molecule instead of the Epithelial Cell Adhesion Molecule.

Neuronal cell adhesion molecule (NrCAM) is expressed by sensory cells in the cochlea and is necessary for proper cochlear innervation and sensory domain patterning during development.

In the cochlea, auditory development depends on precise patterns of innervation by afferent and efferent nerve fibers, as well as a stereotyped arrangement of hair and supporting cells. Neuronal cell adhesion molecule (NrCAM) is a homophilic cell adhesion molecule that controls diverse aspects of nervous system development, but the function of NrCAM in cochlear development is not well understood. Throughout cochlear innervation, NrCAM is detectable on spiral ganglion neuron (SGN) afferent and olivocochlear efferent fibers, and on the membranes of developing hair and supporting cells. Neonatal Nrcam-null cochleae show errors in type II SGN fasciculation, reduced efferent innervation, and defects in the stereotyped packing of hair and supporting cells. Nrcam loss also leads to dramatic changes in the profiles of presynaptic afferent and efferent synaptic markers at the time of hearing onset. Despite these numerous developmental defects, Nrcam-null adults do not show defects in auditory acuity, and by postnatal day 21, the developmental deficits in ribbon synapse distribution and sensory domain structure appear to have been corrected. NrCAM is expressed by several neural and sensory epithelial subtypes within the developing cochlea, and the loss of Nrcam confers numerous, but nonpermanent, developmental defects in innervation and sensory domain patterning. Developmental Dynamics 247:934-950, 2018. © 2018 Wiley Periodicals, Inc.

Regional Cellular Environment Shapes Phenotypic Variations of Hippocampal and Neocortical Chandelier Cells.

Different cortical regions processing distinct information, such as the hippocampus and the neocortex, share common cellular components and circuit motifs but form unique networks by modifying these cardinal units. Cortical circuits include diverse types of GABAergic interneurons (INs) that shape activity of excitatory principal neurons (PNs). Canonical IN types conserved across distinct cortical regions have been defined by their morphological, electrophysiological, and neurochemical properties. However, it remains largely unknown whether canonical IN types undergo specific modifications in distinct cortical regions and display "regional variants." It is also poorly understood whether such phenotypic variations are shaped by early specification or regional cellular environment. The chandelier cell (ChC) is a highly stereotyped IN type that innervates axon initial segments of PNs and thus serves as a good model with which to address this issue. Here, we show that Cadherin-6 (Cdh6), a homophilic cell adhesion molecule, is a reliable marker of ChCs and Cdh6-CreER mice (both sexes) provide genetic access to hippocampal ChCs (h-ChCs). We demonstrate that, compared with neocortical ChCs (nc-ChCs), h-ChCs cover twice as much area and innervate twice as many PNs. Interestingly, a subclass of h-ChCs exhibits calretinin (CR) expression, which is not found in nc-ChCs. Furthermore, we find that h-ChCs appear to be born earlier than nc-ChCs. Surprisingly, despite the difference in temporal origins, ChCs display host-region-dependent axonal/synaptic organization and CR expression when transplanted heterotopically. These results suggest that local cellular environment plays a critical role in shaping terminal phenotypes of regional IN variants in the hippocampus and the neocortex.SIGNIFICANCE STATEMENT Canonical interneuron (IN) types conserved across distinct cortical regions such as the hippocampus and the neocortex are defined by morphology, physiology, and gene expression. However, it remains unknown whether they display phenotypic variations in different cortical regions. In addition, it is unclear whether terminal phenotypes of regional IN variants belonging to a canonical IN type are determined intrinsically or extrinsically. Our results provide evidence of striking differences in axonal/synaptic organization and calretinin expression between hippocampal chandelier cells (ChCs) and neocortical ChCs. They also reveal that local cellular environment in distinct cortical regions regulates these terminal phenotypes. Therefore, our study suggests that local cortical environment shapes the phenotypes of regional IN variants, which may be required for unique circuit operations in distinct cortical regions.

Differential gene expression profiles in neurons generated from lymphoblastoid B-cell line-derived iPS cells from monozygotic twin cases with treatment-resistant schizophrenia and discordant responses to clozapine

Schizophrenia is a chronic psychiatric disorder with complex genetic and environmental origins. While many antipsychotics have been demonstrated as effective in the treatment of schizophrenia, a substantial number of schizophrenia patients are partially or fully unresponsive to the treatment. Clozapine is the most effective antipsychotic drug for treatment-resistant schizophrenia; however, clozapine has rare but serious side-effects. Furthermore, there is inter-individual variability in the drug response to clozapine treatment. Therefore, the identification of the molecular mechanisms underlying the action of clozapine and drug response predictors is imperative. In the present study, we focused on a pair of monozygotic twin cases with treatment-resistant schizophrenia, in which one twin responded well to clozapine treatment and the other twin did not. Using induced pluripotent stem (iPS) cell-based technology, we generated neurons from iPS cells derived from these patients and subsequently performed RNA-sequencing to compare the transcriptome profiles of the mock or clozapine-treated neurons. Although, these iPS cells similarly differentiated into neurons, several genes encoding homophilic cell adhesion molecules, such as protocadherin genes, showed differential expression patterns between these two patients. These results, which contribute to the current understanding of the molecular mechanisms of clozapine action, establish a new strategy for the use of monozygotic twin studies in schizophrenia research.

Structural determinants of adhesion by Protocadherin-19 and implications for its role in epilepsy.

Non-clustered δ-protocadherins are homophilic cell adhesion molecules essential for the development of the vertebrate nervous system, as several are closely linked to neurodevelopmental disorders. Mutations in protocadherin-19 (PCDH19) result in a female-limited, infant-onset form of epilepsy (PCDH19-FE). Over 100 mutations in PCDH19 have been identified in patients with PCDH19-FE, about half of which are missense mutations in the adhesive extracellular domain. Neither the mechanism of homophilic adhesion by PCDH19, nor the biochemical effects of missense mutations are understood. Here we present a crystallographic structure of the minimal adhesive fragment of the zebrafish Pcdh19 extracellular domain. This structure reveals the adhesive interface for Pcdh19, which is broadly relevant to both non-clustered δ and clustered protocadherin subfamilies. In addition, we show that several PCDH19-FE missense mutations localize to the adhesive interface and abolish Pcdh19 adhesion in in vitro assays, thus revealing the biochemical basis of their pathogenic effects during brain development.

Abstract 5065: Role of EpCAM in EGFR signaling and tumorigenesis

Abstract EpCAM is a transmembrane glycoprotein that functions as a homophilic cell adhesion molecule. EpCAM is expressed in normal epithelium and at even higher levels in epithelial cancers, including breast, pancreatic and lung cancers. Since its discovery in the 1980s, EpCAM has been targeted in several different epithelial cancers. Even though numerous novel therapeutic strategies targeting EpCAM have been investigated, the biological role and functional significance of EpCAM expression in cancer remains unclear. EpCAM expression appears to be associated with prognosis in several epithelial cancers -in some cancers it is associated with a favorable prognosis (renal cell, rectal) and in others it is associated with a poor prognosis (lung, pancreatic, breast). Thus, the function of EpCAM appears to be context-dependent in epithelial cancers. To understand the impact of EpCAM in human cancer, we specifically ablated EpCAM expression in over 40 cancer cell lines, and assessed the impact on invasion. We identified the A431 epidermoid cancer cell line as a cell line that overexpresses EpCAM, but is exquisitely sensitive to manipulation of EpCAM expression. A431 is known to overexpress EGFR and serves as a model cell line for EGFR signaling. Specific ablation of EpCAM significantly enhanced the migration and invasion of the A431 cell line. Specific ablation of EpCAM was also associated with increased EGFR activity, as demonstrated by phospho-immunoblot. Immunoprecipitation studies demonstrate that EpCAM binds directly to EGFR. Using specific EpCAM mutant constructs, we showed that the N-terminal domain of EpCAM is required for binding and suppression of EGFR activity. Using a soft agar colony growth assay, we were able to confirm that N-terminal EpCAM domain mutants (NTD288) inhibited colony growth in 3T3-transfected cells relative to the wildtype. In addition, a transformation assay showed that the same N-terminal mutant was able to inhibit transformation of 3T3 cells. To assess the effects of EpCAM ablation on in vivo tumor growth, we specifically ablated EpCAM and then performed tumor challenge experiments using immunocompromised mice. Specific ablation of EpCAM increased tumor growth relative to control. These data suggest that EpCAM may modulate EGFR signaling. Further studies are ongoing to define the mechanisms by which EpCAM inhibits EGFR activity. Citation Format: Lincoln Muhoro, Timothy Fleming, Narendra Sankpal, William Gillanders. Role of EpCAM in EGFR signaling and tumorigenesis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5065.

Local translation of cell adhesion molecules in axons.

During development and regeneration, axonal growth depends on a rapid response to extracellular growth and guidance molecules. One mechanism underlying this rapid response is local protein synthesis (Jung et al., 2012). Local protein synthesis is a highly tuned, multi-step process by which mRNA binding proteins bind to specific sequences within the untranslated regions of particular mRNAs in the soma; mRNAs are then transported to axons and growth cones and translated at the appropriate spatial location in response to specific guidance cues. Many studies have now demonstrated that stimulus-induced local translation is critical to appropriate axon growth, guidance and regeneration. Multiple types of proteins are locally translated within axons, including those regulating the cytoskeleton, retrograde signaling, regeneration and cellular survival.

Breast cancer cell adhesome and degradome interact to drive metastasis.

Background:Although primary breast tumors are detected early in most cases, it is inevitable that many patients remain at risk for future recurrence and death due to micrometastases. We investigated interactions between the degradome and the adhesome that drive metastasis, and have focused on matrix metalloproteases (MMPs) within the degradome and integrins and E-cadherin within the adhesome.Aims:The aim of this study is to identify interaction networks between adhesion molecules and degradative enzymes in breast cancer metastasis.Methods:We compared non-metastatic (BT-474, T47D, MCF7) and metastatic (MDA-MB-231, SUM149, SUM159) human breast cancer cell lines and xenografts, in which we measured growth rate, migration, invasion, colony formation, protein expression, and enzyme activity in vitro and in vivo.Results:The metastatic breast cancer lines and xenografts displayed higher expression and activity levels of MMPs, which was also confirmed by noninvasive imaging in vivo. These metastatic breast cancer models also displayed elevated heterophilic cell-extracellular matrix (ECM) and lower homophilic cell–cell adhesion compared with those of non-metastatic models. This was conferred by an increased expression of the heterophilic cell adhesion molecule integrin β1 (ITGB1) and a decreased expression of the homophilic cell adhesion molecule E-cadherin. Inhibition of MMPs in metastatic cells led to a reduced expression of ITGB1, and stimulation of ITGB1 resulted in higher MMP activities in metastatic cancer cells, demonstrating reciprocal dependencies between degradome and adhesome. Re-expression of E-cadherin (CDH1) led to an increased expression of the precursor form of ITGB1.Conclusions:Our results point toward a concerted interdependence of MMPs, ITGB1, and CDH1 that is critical for breast cancer metastasis.

Abstract 341: Breast cancer cell adhesion and degradome interact to drive metastasis

Abstract Although primary breast tumors are detected early in most cases, it is inevitable that many patients remain at risk for future recurrence and death due to micrometastases. We investigated the metastatic process with a focus on matrix metalloproteases (MMPs) within the degradome and on integrins and E-cadherin within the adhesome. We have performed comparative studies with a set of non-metastatic (BT-474, T47D, MCF7) versus metastatic (MDA-MB-231, SUM149, SUM159) human breast cancer cell lines and xenografts. Experiments were performed to measure growth rate, migration, invasion, and colony formation. Immunoblotting and immunohistochemistry revealed a higher expression of MMPs and heterophilic cell adhesion molecules integrin β1 and lower expression of homophilic cell adhesion molecule E-cadherin in the metastatic tumor cells and xenografts. Using zymography and activatable fluorescent probes for noninvasive imaging of MMPs, we demonstrated that metastatic breast cancer cells and tumors displayed an elevated degradome activity as compared to non-metastatic cells and tumors. Cell adhesion and cell aggregation assays showed an increased heterophilic and decreased homophilic adhesion in the metastatic models. Inhibiting MMPs reduced the expression of integrin β1, and stimulating integrin β1 resulted in higher MMP activities in metastatic cells. Re-expression of E-cadherin in metastatic cells led to a reduced expression of active integrin β1. Finally, circulating breast cancer cells and cells from lung metastatic nodules generated from metastatic tdTomato-fluorescing breast cancer cells displayed a reduced expression of active integrin β1 and less epithelial-mesenchymal-transition (EMT) marker protein S100A4. Our results indicate that proteolytic ECM remodeling by MMPs and cell adhesion by integrin β1 and E-cadherin are interdependent processes that control transformation from benign to invasive carcinoma and are critical for metastasis. Citation Format: Asif Rizwan, Menglin Cheng, Zaver M. Bhujwalla, Balaji Krishnamachary, Lu Jiang, Kristine Glunde. Breast cancer cell adhesion and degradome interact to drive metastasis. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 341. doi:10.1158/1538-7445.AM2015-341