Melanoma chondroitin sulphate proteoglycan regulates cell spreading through Cdc42, Ack-1 and p130cas

Bispecific antibodies redirect synthetic agonistic receptor modified T cells against melanoma

BACKGROUND

Melanoma is an immune sensitive disease, as demonstrated by the activity of immune check point blockade (ICB), but many patients will either not respond or relapse. More recently, tumor infiltrating lymphocyte (TIL) therapy has shown promising efficacy in melanoma treatment after ICB failure, indicating the potential of cellular therapies. However, TIL treatment comes with manufacturing limitations, product heterogeneity, as well as toxicity problems, due to the transfer of a large number of phenotypically diverse T cells. To overcome said limitations, we propose a controlled adoptive cell therapy approach, where T cells are armed with synthetic agonistic receptors (SAR) that are selectively activated by bispecific antibodies (BiAb) targeting SAR and melanoma-associated antigens.

METHODS

Human as well as murine SAR constructs were generated and transduced into primary T cells. The approach was validated in murine, human and patient-derived cancer models expressing the melanoma-associated target antigens tyrosinase-related protein 1 (TYRP1) and melanoma-associated chondroitin sulfate proteoglycan (MCSP) (CSPG4). SAR T cells were functionally characterized by assessing their specific stimulation and proliferation, as well as their tumor-directed cytotoxicity, in vitro and in vivo.

RESULTS

MCSP and TYRP1 expression was conserved in samples of patients with treated as well as untreated melanoma, supporting their use as melanoma-target antigens. The presence of target cells and anti-TYRP1 × anti-SAR or anti-MCSP × anti-SAR BiAb induced conditional antigen-dependent activation, proliferation of SAR T cells and targeted tumor cell lysis in all tested models. In vivo, antitumoral activity and long-term survival was mediated by the co-administration of SAR T cells and BiAb in a syngeneic tumor model and was further validated in several xenograft models, including a patient-derived xenograft model.

CONCLUSION

The SAR T cell-BiAb approach delivers specific and conditional T cell activation as well as targeted tumor cell lysis in melanoma models. Modularity is a key feature for targeting melanoma and is fundamental towards personalized immunotherapies encompassing cancer heterogeneity. Because antigen expression may vary in primary melanoma tissues, we propose that a dual approach targeting two tumor-associated antigens, either simultaneously or sequentially, could avoid issues of antigen heterogeneity and deliver therapeutic benefit to patients.

Chondroitin Sulfate Proteoglycan 4 as a Marker for Aggressive Squamous Cell Carcinoma

Chondroitin sulfate (CS) proteoglycan 4 (CSPG4) is a cell surface proteoglycan that is currently under investigation as a marker of cancer malignancy, and as a potential target of anticancer drug treatment. CSPG4 acts as a driver of tumourigenesis by regulating turnover of the extracellular matrix (ECM) to promote tumour cell invasion, migration as well as inflammation and angiogenesis. While CSPG4 has been widely studied in certain malignancies, such as melanoma, evidence is emerging from global gene expression studies, which suggests a role for CSPG4 in squamous cell carcinoma (SCC). While relatively treatable, lack of widely agreed upon diagnostic markers for SCCs is problematic, especially for clinicians managing certain patients, including those who are aged or infirm, as well as those with underlying conditions such as epidermolysis bullosa (EB), for which a delayed diagnosis is likely lethal. In this review, we have discussed the structure of CSPG4, and quantitatively analysed CSPG4 expression in the tissues and pathologies where it has been identified to determine the usefulness of CSPG4 expression as a diagnostic marker and therapeutic target in management of malignant SCC.

The expression of keratan sulfate in malignant melanoma enhances the adhesion and invasion activity of melanoma cells

Mammals express a wide variety of glycans that include N-glycans, O-glycans, proteoglycans, glycolipids, etc. Glycan expression can modulate the cellular functions, and hence is strongly involved in the onset and progression of numerous diseases. Here, we report the relevance of the ectopic expression of keratan sulfate (KS) glycan chains in human malignant melanomas. Using a human melanoma cell line, we found that the KS enhanced the invasiveness of the cells but caused no change in the growth rate of the cells. The phosphorylation of paxillin, a focal adhesion-associated adaptor protein, was strong at the region where KS was expressed in the melanoma tissues, indicating that KS stimulated the phosphorylation of paxillin. We also observed that KS enhanced the adhesion of melanoma cells and this was accompanied by a greatly increased level of phosphorylation of paxillin. These data suggest that the expression of KS contributes to the development of malignant phenotypes such as strong cell adhesion and the invasiveness of melanoma cells.

Exosome application in tumorigenesis: diagnosis and treatment of melanoma

Melanoma is the most aggressive of skin cancer derived from genetic mutations in the melanocytes. Current therapeutic approaches include surgical resection, chemotherapy, photodynamic therapy, immunotherapy, biochemotherapy, and targeted therapy. However, the efficiency of these strategies may be decreased due to the development of diverse resistance mechanisms. Here, it has been proven that therapeutic monoclonal antibodies (mAbs) can improve the efficiency of melanoma therapies and also, cancer vaccines are another approach for the treatment of melanoma that has already improved clinical outcomes in these patients. The use of antibodies and gene vaccines provides a new perspective in melanoma treatment. Since the tumor microenvironment is another important factor for cancer progression and metastasis, in recent times, a mechanism has been identified to provide an opportunity for melanoma cells to communicate with remote cells. This mechanism is involved by a novel molecular structure, named extracellular vesicles (EVs). Depending on the functional status of origin cells, exosomes contain various cargos and different compositions. In this review, we presented recent progress of exosome applications in the treatment of melanoma. Different aspects of exosome therapy and ongoing efforts in this field will be discussed too.

Small Molecules Targeting Activated Cdc42-Associated Kinase 1 (ACK1/TNK2) for the Treatment of Cancers

Activated Cdc42-associated kinase 1 (ACK1/TNK2) is a nonreceptor tyrosine kinase with a unique structure. It not only can act as an activated transmembrane effector of receptor tyrosine kinases (RTKs) to transmit various RTK signals but also can play a corresponding role in epigenetic regulation. A number of studies have shown that ACK1 is a carcinogenic factor. Blockage of ACK1 has been proven to be able to inhibit cancer cell survival, proliferation, migration, and radiation resistance. Thus, ACK1 is a promising potential antitumor target. To date, despite many efforts to develop ACK1 inhibitors, no specific small molecule inhibitors have entered clinical trials. This Perspective provides an overview of the structural features, biological functions, and association with diseases of ACK1 and in vitro and in vivo activities, selectivity, and therapeutic potential of small molecule ACK1 inhibitors with different chemotypes.

ACK1 is dispensable for development, skin tumor formation, and breast cancer cell proliferation

Activated Cdc42‐associated kinase 1 (ACK1), a widely expressed nonreceptor tyrosine kinase, is often amplified in cancer and has been shown to interact with Cell division cycle 42 (Cdc42), Epidermal growth factor receptor (EGFR), and several other cancer‐relevant molecules, suggesting a possible role for ACK1 in development and tumor formation. To directly address this scenario, we generated mice lacking a functional ACK1 gene (ACK1 ko) using CRISPR genome editing. ACK1 ko mice developed normally, displayed no obvious defect in tissue maintenance, and were fertile. Primary ACK1‐null keratinocytes showed normal phosphorylation of EGFR, but a tendency toward reduced activation of AKT serine/threonine kinase 1 (Akt) and Mitogen‐activated protein kinase 1 (Erk). DMBA/TPA‐induced skin tumor formation did not reveal significant differences between ACK1 ko and control mice. Deletion of the ACK1 gene in the breast cancer cell lines MDA‐MB‐231, 67NR, MCF7, 4T1, and T47D caused no differences in growth. Furthermore, EGF‐induced phosphorylation kinetics of Erk, Akt, and p130Cas were not detectably altered in T47D cells by the loss of ACK1. Finally, loss of ACK1 in MDA‐MB‐231 and T47D breast cancer cells had a very limited or no effect on directed cell migration. These data do not support a major role for ACK1 in Cdc42 and EGFR signaling, development, or tumor formation.

Chondroitin sulfate proteoglycan 4 enhanced melanoma motility and growth requires a cysteine in the core protein transmembrane domain

Chondroitin sulfate proteoglycan 4 (CSPG4) is a cell surface proteoglycan that enhances malignant potential in melanoma and several other tumor types. CSPG4 functions as a transmembrane scaffold in melanoma cells to activate oncogenic signaling pathways such as focal adhesion kinase (FAK) and extracellular signal regulated kinases 1,2, that control motility, invasion and anchorage independent growth. Here, we demonstrate that CSPG4 promotes directional motility and anchorage independent growth of melanoma cells by organizing and positioning a signaling complex containing activated FAK to lipid rafts within the plasma membrane of migrating cells. This FAK-containing signal transduction platform, which consists of syntenin-1, active Src and caveolin-1 requires the cytoplasmic domain of CSPG4 for assembly. Enhanced directional motility promoted by this complex also requires a CSPG4 transmembrane cysteine residue C2230. Substituting C2230 with alanine (CSPG4) still permits assembly of the signaling complex, however Src remains in an inactive state. CSPG4 also fails to promote anchorage independent growth and activation of extracellular signal regulated kinases 1,2. Therapies that target the transmembrane domain of CSPG4 could be a novel strategy for limiting progression by disrupting its function as a compartmentalized motogenic and growth-promoting oncogenic signaling node.

Chondroitin sulfate proteoglycan 4 regulates zebrafish body axis organization via Wnt/planar cell polarity pathway

Pericellular and extracellular proteoglycans play an important role in modulating morphogen gradients and signal transductions. Chondroitin sulfate proteoglycan 4 (Cspg4) is a membrane spanning proteoglycan expressed in immature progenitor cells and cancer cells. Cspg4 participates in cellular events such as proliferation, migration and signal transduction, and these events are generally important for embryo development. In this study, we characterized Cspg4 for its roles in zebrafish embryonic development. Our results demonstrated that cspg4 was maternally expressed from 0 to 3 hours post fertilization (hpf) and expressed in the anterior and posterior embryo end after 9 hpf. Knocking-down cspg4 resulted in a shorter anterior-posterior axis than control embryo, which could be rescued by co-injecting wnt11 mRNA suggesting that Cspg4 regulates body axis organization through modulating the Wnt/planar cell polarity signaling pathway. In addition, overexpressing cspg4 caused cyclopia. The Cspg4 transmembrane domain mutant embryo phenocopied the global over-expression of cspg4 mRNA and led to cyclopia with a very low penetrance. Our results demonstrated that the quantitatively and spatially accurate distribution of Cspg4 is critical for body axis and midline development during gastrulation.

Chondroitin Sulfate Promotes the Proliferation of Keloid Fibroblasts Through Activation of the Integrin and Protein Kinase B Pathways

Keloids are dermal fibroproliferative tumors that arise beyond the boundary of the original wound edges and invades adjacent tissue. Keloids are characterized by the extensive production of extracellular matrix (ECM) and abnormal fibroblast proliferation. Chondroitin sulfate (CS) is one of the major structural components of cartilage and ECM. Recently, we reported the over-accumulation of CS in keloid lesions. Keloid-derived fibroblasts (KFs) and normal dermal fibroblasts (NFs) were incubated with CS. The fibroblast proliferation rate was analyzed using a tetrazolium salt colorimetric assay. The activation of the intracellular signaling pathway was analyzed by Western blotting. Wortmannin, a PI3K inhibitor, and anti-integrin antibodies were tested to investigate the mechanism of the CS-induced cell proliferation. CS strongly stimulated the proliferation of KFs, but not NFs. The analysis of the intracellular signal transduction pathway revealed that the stimulation effect of CS on KF proliferation was due to the activation of the protein kinase B (AKT) pathway and that integrin α1 was responsible for this phenomenon. We revealed that CS probably activates the AKT pathway through integrin to induce KF proliferation. CS may be a novel clinical therapeutic target in keloids.

The non-receptor tyrosine kinase ACK: regulatory mechanisms, signalling pathways and opportunities for attACKing cancer

Activated Cdc42-associated kinase or ACK, is a non-receptor tyrosine kinase and an effector protein for the small G protein Cdc42. A substantial body of evidence has accumulated in the past few years heavily implicating ACK as a driver of oncogenic processes. Concomitantly, more is also being revealed regarding the signalling pathways involving ACK and molecular details of its modes of action. Some details are also available regarding the regulatory mechanisms of this kinase, including activation and regulation of its catalytic activity, however, a full understanding of these aspects remains elusive. This review considers the current knowledge base concerning ACK and summarizes efforts and future prospects to target ACK therapeutically in cancer.

CSPG4 as Target for CAR-T-Cell Therapy of Various Tumor Entities-Merits and Challenges

Targeting cancer cells using chimeric-antigen-receptor (CAR-)T cells has propelled adoptive T-cell therapy (ATT) to the next level. A plentitude of durable complete responses using CD19-specific CAR-T cells in patients suffering from various lymphoid malignancies resulted in the approval by the food and drug administration (FDA) of CD19-directed CAR-T cells for the treatment of acute lymphoblastic leukemia (ALL) and diffuse large B-cell lymphoma (DLBCL). A substantial portion of this success in hematological malignancies can be traced back to the beneficial properties of the target antigen CD19, which combines a universal presence on target cells with no detectable expression on indispensable host cells. Hence, to replicate response rates achieved in ALL and DLBCL in the realm of solid tumors, where ideal target antigens are scant and CAR-T cells are still lagging behind expectations, the quest for appropriate target antigens represents a crucial task to expedite the next steps in the evolution of CAR-T-cell therapy. In this review, we want to highlight the potential of chondroitin sulfate proteoglycan 4 (CSPG4) as a CAR-target antigen for a variety of different cancer entities. In particular, we discuss merits and challenges associated with CSPG4-CAR-T cells for the ATT of melanoma, leukemia, glioblastoma, and triple-negative breast cancer.

Bispecific Antibody Approach for Improved Melanoma-Selective PD-L1 Immune Checkpoint Blockade

Reactivation of functionally-impaired anticancer T cells by programmed cell death protein 1 (PD-1) and programmed cell death receptor ligand-1 (PD-L1)-blocking antibodies shows prominent therapeutic benefit in advanced melanoma and patients with non-small cell lung cancer. However, current PD-L1-blocking antibodies lack intrinsic tumor selectivity. Therefore, efficacy may be reduced resulting from on-target and off-tumor binding to PD-L1-expressing normal cells. This may lead to indiscriminate activation of antigen-experienced T cells, including those implicated in autoimmune-related adverse events. To direct PD-L1 blockade to chondroitin sulfate proteoglycan 4 (CSPG4)-expressing cancers and to reactivate anticancer T cells more selectively, we constructed bispecific antibody PD-L1xCSPG4. CSPG4 is an established target antigen that is selectively overexpressed on malignant melanoma and various other difficult-to-treat cancers. PD-L1xCSPG4 showed enhanced capacity for CSPG4-directed blockade of PD-L1 on cancer cells. Importantly, treatment of mixed cultures containing primary patient-derived CSPG4-expressing melanoma cells and autologous tumor-infiltrating lymphocytes with PD-L1xCSPG4 significantly enhanced activation status, IFN-γ production, and cytolytic activity of anticancer T cells. In conclusion, tumor-directed blockade of PD-L1 by PD-L1xCSPG4 may improve efficacy and safety of PD-1/PD-L1 checkpoint blockade for treatment of melanoma and other CSPG4-overexpressing malignancies.

Immunomagnetic-Enriched Subpopulations of Melanoma Circulating Tumour Cells (CTCs) Exhibit Distinct Transcriptome Profiles

Cutaneous melanoma circulating tumour cells (CTCs) are phenotypically and molecularly heterogeneous. We profiled the gene expression of CTC subpopulations immunomagnetic-captured by targeting either the melanoma-associated marker, MCSP, or the melanoma-initiating marker, ABCB5. Firstly, the expression of a subset of melanoma genes was investigated by RT-PCR in MCSP-enriched and ABCB5-enriched CTCs isolated from a total of 59 blood draws from 39 melanoma cases. Of these, 6 MCSP- and 6 ABCB5-enriched CTC fractions were further analysed using a genome-wide gene expression microarray. The transcriptional programs of both CTC subtypes included cell survival maintenance, cell proliferation, and migration pathways. ABCB5-enriched CTCs were specifically characterised by up-regulation of genes involved in epithelial to mesenchymal transition (EMT), suggesting an invasive phenotype. These findings underscore the presence of at least two distinct melanoma CTC subpopulations with distinct transcriptional programs, which may have distinct roles in disease progression and response to therapy.

Type VI collagen promotes lung epithelial cell spreading and wound-closure

Basement membrane (BM) is an essential part of the extracellular matrix (ECM) that plays a crucial role in mechanical support and signaling to epithelial cells during lung development, homeostasis and repair. Abnormal composition and remodeling of the lung ECM have been associated with developmental abnormalities observed in multiple pediatric and adult respiratory diseases. Collagen VI (COL6) is a well-studied muscle BM component, but its role in the lung and its effect on pulmonary epithelium is largely undetermined. We report the presence of COLVI immediately subjacent to human airway and alveolar epithelium in the pediatric lung, in a location where it is likely to interact with epithelial cells. In vitro, both primary human lung epithelial cells and human lung epithelial cell lines displayed an increased rate of “wound healing” in response to a scratch injury when plated on COL6 as compared to other matrices. For the 16HBE cell line, wounds remained >5-fold larger for cells on COL1 (p<0.001) and >6-fold larger on matrigel (p<0.001), a prototypical basement membrane, when compared to COL6 (>96% closure at 10 hr). The effect of COL6 upon lung epithelial cell phenotype was associated with an increase in cell spreading. Three hours after initial plating, 16HBE cells showed >7-fold less spreading on matrigel (p<0.01), and >4-fold less spreading on COL1 (p<0.01) when compared to COL6. Importantly, the addition of COL6 to other matrices also enhanced cell spreading. Similar responses were observed for primary cells. Inhibitor studies indicated both integrin β1 activity and activation of multiple signaling pathways was required for enhanced spreading on all matrices, with the PI3K/AKT pathway (PI3K, CDC42, RAC1) showing both significant and specific effects for spreading on COL6. Genetic gain-of-function experiments demonstrated enhanced PI3K/AKT pathway activity was sufficient to confer equivalent cell spreading on other matrices as compared to COL6. We conclude that COL6 has significant and specific effects upon human lung epithelial cell-autonomous functions.

Structural deciphering of the NG2/CSPG4 proteoglycan multifunctionality

The chondroitin sulfate proteoglycan 4 ( CSPG4) gene encodes a transmembrane proteoglycan (PG) constituting the largest and most structurally complex macromolecule of the human surfaceome. Its transcript shows an extensive evolutionary conservation and, due to the elaborated intracellular processing of the translated protein, it generates an array of glycoforms with the potential to exert variant-specific functions. CSPG4-mediated molecular events are articulated through the interaction with more than 40 putative ligands and the concurrent involvement of the ectodomain and cytoplasmic tail. Alternating inside-out and outside-in signal transductions may thereby be elicited through a tight functional connection of the PG with the cytoskeleton and its regulators. The potential of CSPG4 to influence both types of signaling mechanisms is also asserted by its lateral mobility along the plasma membrane and its intersection with microdomain-restricted internalization and endocytic trafficking. Owing to the multitude of molecular interplays that CSPG4 may engage, and thanks to a differential phosphorylation of its intracellular domain accounted by crosstalking signaling pathways, the PG stands out for its unique capability to affect numerous cellular phenomena, including those purporting pathologic conditions. We discuss here the progresses made in advancing our understanding about the structural-functional bases for the ability of CSPG4 to widely impact on cell behavior, such as to highlight how its multivalency may be exploited to interfere with disease progression.-Tamburini, E., Dallatomasina, A., Quartararo, J., Cortelazzi, B., Mangieri, D., Lazzaretti, M., Perris, R. Structural deciphering of the NG2/CSPG4 proteoglycan multifunctionality.

Cell surface chondroitin sulphate proteoglycan 4 (CSPG4) binds to the basement membrane heparan sulphate proteoglycan, perlecan, and is involved in cell adhesion

Chondroitin sulphate proteoglycan 4 (CSPG4) is a cell surface proteoglycan highly expressed by tumour, perivascular and oligodendrocyte cells and known to be involved cell adhesion and migration. This study showed that CSPG4 was present as a proteoglycan on the cell surface of two melanoma cell lines, MM200 and Me1007, as well as shed into the conditioned medium. CSPG4 from the two melanoma cell lines differed in the amount of chondroitin sulphate (CS) decoration, as well as the way the protein core was fragmented. In contrast, the CSPG4 expressed by a colon carcinoma cell line, WiDr, was predominantly as a protein core on the cell surface lacking glycosaminoglycan (GAG) chains. This study demonstrated that CSPG4 immunopurified from the melanoma cell lines formed a complex with perlecan synthesized by the same cultured cells. Mechanistic studies showed that CSPG4 bound to perlecan via hydrophobic protein-protein interactions involving multiple sites on perlecan including the C-terminal region. Furthermore, this study revealed that CSPG4 interacted with perlecan to support cell adhesion and actin polymerization. Together these data suggest a novel mechanism by which CSPG4 expressing cells might attach to perlecan-rich matrices so as those found in connective tissues and basement membranes.

Proteoglycans remodeling in cancer: Underlying molecular mechanisms

Extracellular matrix is a highly dynamic macromolecular network. Proteoglycans are major components of extracellular matrix playing key roles in its structural organization and cell signaling contributing to the control of numerous normal and pathological processes. As multifunctional molecules, proteoglycans participate in various cell functions during morphogenesis, wound healing, inflammation and tumorigenesis. Their interactions with matrix effectors, cell surface receptors and enzymes enable them with unique properties. In malignancy, extensive remodeling of tumor stroma is associated with marked alterations in proteoglycans' expression and structural variability. Proteoglycans exert diverse functions in tumor stroma in a cell-specific and context-specific manner and they mainly contribute to the formation of a permissive provisional matrix for tumor growth affecting tissue organization, cell-cell and cell-matrix interactions and tumor cell signaling. Proteoglycans also modulate cancer cell phenotype and properties, the development of drug resistance and tumor stroma angiogenesis. This review summarizes the proteoglycans remodeling and their novel biological roles in malignancies with particular emphasis to the underlying molecular mechanisms.

CSPG4: a prototype oncoantigen for translational immunotherapy studies

Thanks to striking progress in both the understanding of anti-tumor immune response and the characterization of several tumor associated antigens (TAA), a more rational design and more sophisticated strategies for anti-tumor vaccination have been possible. However, the effectiveness of cancer vaccines in clinical trial is still partial, indicating that additional studies are needed to optimize their design and their pre-clinical testing. Indeed, anti-tumor vaccination success relies on the choice of the best TAA to be targeted and on the translational power of the pre-clinical model used to assess its efficacy. The chondroitin sulfate proteoglycan-4 (CSPG4) is a cell surface proteoglycan overexpressed in a huge range of human and canine neoplastic lesions by tumor cells, tumor microenvironment and cancer initiating cells. CSPG4 plays a central role in the oncogenic pathways required for malignant progression and metastatization. Thanks to these features and to its poor expression in adult healthy tissues, CSPG4 represents an ideal oncoantigen and thus an attractive target for anti-tumor immunotherapy. In this review we explore the potential of CSPG4 immune-targeting. Moreover, since it has been clearly demonstrated that spontaneous canine tumors mimic the progression of human malignancies better than any other pre-clinical model available so far, we reported also our results indicating that CSPG4 DNA vaccination is safe and effective in significantly increasing the survival of canine melanoma patients. Therefore, anti-CSPG4 vaccination strategy could have a substantial impact for the treatment of the wider population of spontaneous CSPG4-positive tumor affected dogs with a priceless translational value and a revolutionary implication for human oncological patients.

Functional ferritin nanoparticles for biomedical applications

Ferritin, a major iron storage protein with a hollow interior cavity, has been reported recently to play many important roles in biomedical and bioengineering applications. Owing to the unique architecture and surface properties, ferritin nanoparticles offer favorable characteristics and can be either genetically or chemically modified to impart functionalities to their surfaces, and therapeutics or probes can be encapsulated in their interiors by controlled and reversible assembly/disassembly. There has been an outburst of interest regarding the employment of functional ferritin nanoparticles in nanomedicine. This review will highlight the recent advances in ferritin nanoparticles for drug delivery, bioassay, and molecular imaging with a particular focus on their biomedical applications.

Ack1 overexpression promotes metastasis and indicates poor prognosis of hepatocellular carcinoma

Despite the substantial data supporting the oncogenic role of Ack1, the predictive value and biologic role of Ack1 in hepatocellular carcinoma (HCC) metastasis remains unknown. In this study, both correlations of Ack1 expression with prognosis of HCC, and the role of Ack1 in metastasis of HCC were investigated in vitro and in vivo. Our results showed that Ack1 was overexpressed in human HCC tissues and cell lines. High Ack1 expression was associated with HCC metastasis and determined as a significant and independent prognostic factor for HCC after liver resection. Ack1 promoted HCC invasion and metastasis in vitro and in vivo. Mechanistically, we confirmed that Ack1 enhanced invasion and metastasis of HCC via EMT by mediating AKT phosphorylation. In conclusion, our study shows Ack1 is a novel prognostic biomarker for HCC and promotes metastasis of HCC via EMT by activating AKT signaling.

Chimeric Aptamer-Gelatin Hydrogels as an Extracellular Matrix Mimic for Loading Cells and Growth Factors

It is important to synthesize materials to recapitulate critical functions of biological systems for a variety of applications such as tissue engineering and regenerative medicine. The purpose of this study was to synthesize a chimeric hydrogel as a promising extracellular matrix (ECM) mimic using gelatin, a nucleic acid aptamer, and polyethylene glycol. This hydrogel had a macroporous structure that was highly permeable for fast molecular transport. Despite its high permeability, it could strongly sequester and sustainably release growth factors with high bioactivity. Notably, growth factors retained in the hydrogel could maintain ∼ 50% bioactivity during a 14-day release test. It also provided cells with effective binding sites, which led to high efficiency of cell loading into the macroporous hydrogel matrix. When cells and growth factors were coloaded into the chimeric hydrogel, living cells could still be observed by day 14 in a static serum-reduced culture condition. Thus, this chimeric aptamer-gelatin hydrogel constitutes a promising biomolecular ECM mimic for loading cells and growth factors.

Stonin1 mediates endocytosis of the proteoglycan NG2 and regulates focal adhesion dynamics and cell motility

Cellular functions, ranging from focal adhesion (FA) dynamics and cell motility to tumour growth, are orchestrated by signals cells receive from outside via cell surface receptors. Signalling is fine-tuned by the exo–endocytic cycling of these receptors to control cellular responses such as FA dynamics, which determine cell motility. How precisely endocytosis regulates turnover of the various cell surface receptors remains unclear. Here we identify Stonin1, an endocytic adaptor of unknown function, as a regulator of FA dynamics and cell motility, and demonstrate that it facilitates the internalization of the oncogenic proteoglycan NG2, a co-receptor of integrins and platelet-derived growth factor receptor. Embryonic fibroblasts obtained from Stonin1-deficient mice display a marked surface accumulation of NG2, increased cellular signalling and defective FA disassembly as well as altered cellular motility. These data establish Stonin1 as a specific adaptor for the endocytosis of NG2 and as an important factor for FA dynamics and cell migration.

Signalling is often fine-tuned by the exo-endocytic cycling of cell surface receptors. Here, the authors show that the endocytic adaptor protein Stonin1 is important for the endocytosis of NG2, a co-receptor for extracellular matrix and growth factors, and that loss of Stonin1 alters cell motility.

Chondroitin sulfate effects on neural stem cell differentiation

We have investigated the role chondroitin sulfate has on cell interactions during neural plate formation in the early chick embryo. Using tissue culture isolates from the prospective neural plate, we have measured neural gene expression profiles associated with neural stem cell differentiation. Removal of chondroitin sulfate from stage 4 neural plate tissue leads to altered associations of N-cadherin-positive neural progenitors and causes changes in the normal sequence of neural marker gene expression. Absence of chondroitin sulfate in the neural plate leads to reduced Sox2 expression and is accompanied by an increase in the expression of anterior markers of neural regionalization. Results obtained in this study suggest that the presence of chondroitin sulfate in the anterior chick embryo is instrumental in maintaining cells in the neural precursor state.

FH535 inhibited metastasis and growth of pancreatic cancer cells

FH535 is a small-molecule inhibitor of the Wnt/β-catenin signaling pathway, which a substantial body of evidence has proven is activated in various cancers, including pancreatic cancer. Activation of the Wnt/β-catenin pathway plays an important role in tumor progression and metastasis. We investigated the inhibitory effect of FH535 on the metastasis and growth of pancreatic cancer cells. Western blotting and luciferase reporter gene assay indicated that FH535 markedly inhibited Wnt/β-catenin pathway viability in pancreatic cancer cells. In vitro wound healing, invasion, and adhesion assays revealed that FH535 significantly inhibited pancreatic cancer cell metastasis. We also observed the inhibitory effect of FH535 on pancreatic cancer cell growth via the tetrazolium and plate clone formation assays. Microarray analyses suggested that changes in the expression of multiple genes could be involved in the anti-cancer effect of FH535 on pancreatic cancer cells. Our results indicate for the first time that FH535 inhibits pancreatic cancer cell metastasis and growth, providing new insight into therapy of pancreatic cancer.

Approaches of targeting Rho GTPases in cancer drug discovery

INTRODUCTION

Rho GTPases are master regulators of actomyosin structure and dynamics and play pivotal roles in a variety of cellular processes including cell morphology, gene transcription, cell cycle progression, and cell adhesion. Because aberrant Rho GTPase signaling activities are widely associated with human cancer, key components of Rho GTPase signaling pathways have attracted increasing interest as potential therapeutic targets. Similar to Ras, Rho GTPases themselves were, until recently, deemed "undruggable" because of structure-function considerations. Several approaches to interfere with Rho GTPase signaling have been explored and show promise as new ways for tackling cancer cells.

AREAS COVERED

This review focuses on the recent progress in targeting the signaling activities of three prototypical Rho GTPases, that is, RhoA, Rac1, and Cdc42. The authors describe the involvement of these Rho GTPases, their key regulators and effectors in cancer. Furthermore, the authors discuss the current approaches for rationally targeting aberrant Rho GTPases along their signaling cascades, upstream and downstream of Rho GTPases, and posttranslational modifications at a molecular level.

EXPERT OPINION

To date, while no clinically effective drugs targeting Rho GTPase signaling for cancer treatment are available, tool compounds and lead drugs that pharmacologically inhibit Rho GTPase pathways have shown promise. Small-molecule inhibitors targeting Rho GTPase signaling may add new treatment options for future precision cancer therapy, particularly in combination with other anti-cancer agents.

Pericytes, microvasular dysfunction, and chronic rejection

Chronic rejection of transplanted organs remains the main obstacle in the long-term success of organ transplantation. Thus, there is a persistent quest for development of antichronic rejection therapies and identification of novel molecular and cellular targets. One of the potential targets is the pericytes, the mural cells of microvessels, which regulate microvascular permeability, development, and maturation by controlling endothelial cell functions and regulating tissue fibrosis and inflammatory response. In this review, we discuss the potential of targeting pericytes in the development of microvasular dysfunction and the molecular pathways involved in regulation of pericyte activities for antichronic rejection intervention.

Theranostic impact of NG2/CSPG4 proteoglycan in cancer

NG2/CSPG4 is an unusual cell-membrane integral proteoglycan widely recognized to be a prognostic factor, a valuable tool for ex vivo and non-invasive molecular diagnostics and, by virtue of its tight association with malignancy, a tantalizing therapeutic target in several tumour types. Although the biology behind its involvement in cancer progression needs to be better understood, implementation of NG2/CSPG4 in the routine clinical practice is attainable and has the potential to contribute to an improved individualized management of cancer patients. In this context, its polymorphic nature seems to be particularly valuable in the effort to standardize informative diagnostic procedures and consolidate forcible immunotherapeutic treatment strategies. We discuss here the underpinnings for this potential and highlight the benefits of taking advantage of the intra-tumour and inter-patient variability in the regulation of NG2/CSPG4 expression. We envision that NG2/CSPG4 may effectively be exploited in therapeutic interventions aimed at averting resistance to target therapy agents and at interfering with secondary lesion formation and/or tumour recurrence.

Chondroitin sulfate proteoglycan 4 functions as the cellular receptor for Clostridium difficile toxin B

As a gram-positive, spore-forming anaerobic bacillus, Clostridium difficile (C. difficile) is responsible for severe and fatal pseudomembranous colitis, and poses the most urgent antibiotic resistance threat worldwide. Epidemic C. difficile is the leading cause of antibiotic-associated diarrhoea globally, especially diarrhoea due to the emergence of hypervirulent strains associated with high mortality and morbidity. TcdB, one of the key virulence factors secreted by this bacterium, enters host cells through a poorly understood mechanism to elicit its pathogenic effect. Here we report the first identification of the TcdB cellular receptor, chondroitin sulfate proteoglycan 4 (CSPG4). CSPG4 was initially isolated from a whole-genome human shRNAmir library screening, and its role was confirmed by both TALEN- and CRISPR/Cas9-mediated gene knockout in human cells. CSPG4 is critical for TcdB binding to the cell surface, inducing cytoskeleton disruption and cell death. A direct interaction between the N-terminus of CSPG4 and the C-terminus of TcdB was confirmed, and the soluble peptide of the toxin-binding domain of CSPG4 could protect cells from the action of TcdB. Notably, the complete loss of CSPG4/NG2 decreased TcdB-triggered interleukin-8 induction in mice without significantly affecting animal mortality. Based on both the in vitro and in vivo studies, we propose a dual-receptor model for TcdB endocytosis. The discovery of the first TcdB receptor reveals a previously unsuspected role for CSPG4 and provides a new therapeutic target for the treatment of C. difficile infection.

Cell adhesion properties of neural stem cells in the chick embryo

The nervous system of vertebrates is derived from an early embryonic region referred to as the neural plate. In the chick embryo, the neural plate is populated by neural stem cells specified from the epiblast shortly after the onset of gastrulation. Accompanying the formation of the plate, chondroitin sulfate glycosaminoglycans are expressed in the basal extracellular matrix. We describe in vitro experiments measuring cell adhesion of epiblast cells during the formation of the neural plate. Our findings may suggest that neural stem cells are set apart from non-neural epiblast by changes in relative cell-cell and cell-substrate adhesion. Specifically, changes in cell adhesion separating neural stem cells from the non-neural epiblast may be augmented by the presence of exogenous chondroitin-6-sulfate in the epiblast basal lamina at the time neural progenitors are specified in the epiblast.

Role for chondroitin sulfate glycosaminoglycan in NEDD9-mediated breast cancer cell growth

There are lines of evidence demonstrating that NEDD9 (Cas-L, HEF-1) plays a key role in the development, progression, and metastasis of breast cancer cells. We previously reported that NEDD9 plays a critical role for promoting migration and growth of MDA-MB-231. In order to further characterize the mechanisms of NEDD9-mediated cancer migration and growth, stable cells overexpressing NEDD9 were generated using HCC38 as a parental cell line which expresses low level of endogenous NEDD9. Microarray studies demonstrated that core proteins of CD44 and Serglycin were markedly upregulated in HCC38(NEDD9) cells compared to HCC38(Vector) cells, while those of Syndecan-1, Syndecan-2, and Versican were downregulated in HCC38(NEDD9). Importantly, enzymes generating chondroitin sulfate glycosaminoglycans (CS) such as CHST11, CHST15, and CSGALNACT1 were upregulated in HCC38(NEDD9) compared to HCC38(Vector). Immunofluorescence studies using specific antibody, GD3G7, confirmed the enhanced expression of CS-E subunit in HCC38(NEDD9). Immunoprecipitation and western blotting analysis demonstrated that CS-E was attached to CD44 core protein. We demonstrated that removing CS by chondroitinase ABC significantly inhibited anchorage-independent colony formation of HCC38(NEDD9) in methylcellulose. Importantly, the fact that GD3G7 significantly inhibited colony formation of HCC38(NEDD9) cells suggests that CS-E subunit plays a key role in this process. Furthermore, treatment of HCC38(NEDD9) cells with chondroitinase ABC or GD3G7 significantly inhibited mammosphere formation. Exogenous addition of CS-E enhanced colony formation and mammosphere formation of HCC38 parental and HCC38(Vector) cells. These results suggest that NEDD9 regulates the synthesis and expression of tumor associated glycocalyx structures including CS-E, which plays a key role in promoting and regulating breast cancer progression and metastasis and possibly stem cell phenotypes.

PDGFR-β-activated ACK1-AKT signaling promotes glioma tumorigenesis

Aberrant PDGF-PDGFR signaling and its effects on downstream effectors have been implicated in glioma development. A crucial AKT regulator, ACK1 (TNK2) has been shown to be a downstream mediator of PDGF signaling; however, the exact underlying mechanisms in gliomas remain elusive. Here, we report that in glioma cells, PDGFR-β activation enhanced the interaction between ACK1 and AKT, resulting in AKT activation. PDGF treatment consistently promoted the formation of complexes containing PDGFR-β and ACK1. Mutational analysis suggested that Y635 of ACK1 is a PDGFR-β phosphorylation site and that the ACK1 Y635F mutant abrogated the sequential activation of AKT. Moreover, PDK1 interacted with ACK1 during PDGF stimulation, which is required for the binding of ACK1 to PDGFR-β. Further mutational analysis showed that T325 of ACK1 was crucial for the ACK1 and PDK1 interaction. ACK1 Y635F or T325A mutants abolished PDGFR-β-induced AKT activation, the subsequent nuclear translocation of β-catenin and the expression of cyclin D1. Glioma cell cycle progression, proliferation and tumorigenesis were accordingly blocked by ACK1 Y635F or T325A. In glioblastoma multiforme samples from 51 patients, increased ACK1 tyrosine phosphorylation correlated with upregulated PDGFR-β activity and AKT activation. Taken together, our data demonstrate that ACK1 plays a pivotal role in PDGF-PDGFR-induced AKT signaling in glioma tumorigenesis. This knowledge contributes to our understanding of glioma progression and may facilitate the identification of novel therapeutic targets for future glioma treatment.

Overexpression of activated Cdc42-associated kinase1 (Ack1) predicts tumor recurrence and poor survival in human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers in China. Recent research suggested that activated Cdc42-associated kinase 1 (Ack1) played an important role in facilitating tumorigenesis, tumor invasion and metastasis. However, the role of Ack1 in HCC is not clear. Herein, the expression level of Ack1 mRNA in 30 fresh HCC specimens (carcinoma, peri-carcinoma and distal-carcinoma tissues) was detected by reverse transcription-polymerase chain reaction (RT-PCR), while the expression of Ack1 protein in 18 fresh HCC specimens (carcinoma, peri-carcinoma and distal-carcinoma tissues) was analyzed by Western blotting. Immunohistochemical (IHC) staining was also employed to assess both the expression level and distribution of Ack1 protein in HCC tissues collected from 173 lesions, so as to study the correlations between Ack1 protein expression and other HCC-related clinicopathologic parameters. The results showed that both Ack1 mRNA and protein were significantly over-expressed in HCC tissues than that of either peri-carcinoma or distal-carcinoma tissues (P < 0.001, P = 0.012, respectively), while there was no significant difference between peri-carcinoma and distal-carcinoma tissues. Furthermore, the results of IHC indicated that the rates of Ack1 expressions in the patients with capsular invasion, hepatic vessel involvement and recurrence were higher than without above three conditions (P = 0.037, P = 0.036, P = 0.019, respectively), whereas the patients with overexpression of Ack1 protein had low survival rate (P = 0.007). Ack1 expression, tumor size and recurrence were independently related to survival (P = 0.014, P = 0.018, P < 0.001, respectively). Thus, the level of Ack1 is associated with tumor invasion potential, and the expression of Ack1 plays an important role as predictor of recurrence and poor outcome in HCC patients.

DNA aptamers against exon v10 of CD44 inhibit breast cancer cell migration

CD44 adhesion molecules are expressed in many breast cancer cells and have been demonstrated to play a key role in regulating malignant phenotypes such as growth, migration, and invasion. CD44 is an integral transmembrane protein encoded by a single 20-exon gene. The diversity of the biological functions of CD44 is the result of the various splicing variants of these exons. Previous studies suggest that exon v10 of CD44 plays a key role in promoting cancer invasion and metastasis, however, the molecular mechanisms are not clear. Given the fact that exon v10 is in the ectodomain of CD44, we hypothesized that CD44 forms a molecular complex with other cell surface molecules through exon v10 in order to promote migration of breast cancer cells. In order to test this hypothesis, we selected DNA aptamers that specifically bound to CD44 exon v10 using Systematic Evolution of Ligands by Exponential Enrichment (SELEX). We selected aptamers that inhibited migration of breast cancer cells. Co-immunoprecipitation studies demonstrated that EphA2 was co-precipitated with CD44. Pull-down studies demonstrated that recombinant CD44 exon v10 bound to EphA2 and more importantly aptamers that inhibited migration also prevented the binding of EphA2 to exon v10. These results suggest that CD44 forms a molecular complex with EphA2 on the breast cancer cell surface and this complex plays a key role in enhancing breast cancer migration. These results provide insight not only for characterizing mechanisms of breast cancer migration but also for developing target-specific therapy for breast cancers and possibly other cancer types expressing CD44 exon v10.

Bosutinib inhibits migration and invasion via ACK1 in KRAS mutant non-small cell lung cancer

The advent of effective targeted therapeutics has led to increasing emphasis on precise biomarkers for accurate patient stratification. Here, we describe the role of ACK1, a non-receptor tyrosine kinase in abrogating migration and invasion in KRAS mutant lung adenocarcinoma. Bosutinib, which inhibits ACK1 at 2.7 nM IC₅₀, was found to inhibit cell migration and invasion but not viability in a panel of non-small cell lung cancer (NSCLC) cell lines. Knockdown of ACK1 abrogated bosutinib-induced inhibition of cell migration and invasion specifically in KRAS mutant cells. This finding was further confirmed in an in vivo zebrafish metastatic model. Tissue microarray data on 210 Singaporean lung adenocarcinomas indicate that cytoplasmic ACK1 was significantly over-expressed relative to paired adjacent non-tumor tissue. Interestingly, ACK1 expression in “normal” tissue adjacent to tumour, but not tumour, was independently associated with poor overall and relapse-free survival. In conclusion, inhibition of ACK1 with bosutinib attenuates migration and invasion in the context of KRAS mutant NSCLC and may fulfil a therapeutic niche through combinatorial treatment approaches.

Transduction of extracellular cues into cell polarity: the role of the transmembrane proteoglycan NG2

Resident progenitor cells expressing nerve/glial antigen 2 (NG2) such as oligodendrocyte precursor cells (OPC) and pericytes persist in the adult brain. The transmembrane proteoglycan NG2 regulates migration of both these cell types in response to growth factors or specific components of the extracellular matrix. This role of NG2 is linked to the control of cell polarity. The polarization of OPC toward an acute lesion in the brain is impaired in NG2-deficient mice, supporting this concept. A review of the signaling pathways impinged on by NG2 reveals key proteins of cell polarity: phosphatidylinositol 3-kinase, focal adhesion kinase, Rho GTPases, and polarity complex proteins. In the scope of cell migration, I discuss here how the interplay of NG2 with signaling transmitted by extracellular cues can control the establishment of cell polarity, and I propose a model to integrate the apparent opposite effects of NG2 on cellular dynamics.

Common glycoproteins expressing polylactosamine-type glycans on matched patient primary and metastatic melanoma cells show different glycan profiles

Recently, we reported comparative analysis of glycoproteins which express cancer-specific N-glycans on various cancer cells and identified 24 glycoproteins having polylactosamine (polyLacNAc)-type N-glycans that are abundantly present in malignant cells [ Mitsui et al., J. Pharm. Biomed. Anal. 2012 , 70 , 718 - 726 ]. In the present study, we applied the technique to comparative studies on common glycoproteins present in the matched patient primary and metastatic melanoma cell lines. Metastatic melanoma cells (WM266-4) contained a large amount of polyLacNAc-type N-glycans in comparison with primary melanoma cells (WM115). To identify the glycoproteins expressing these N-glycans, glycopeptides having polyLacNAc-type N-glycans were captured by a Datura stramonium agglutinin (DSA)-immobilized agarose column. The captured glycopeptides were analyzed by LC/MS after removing N-glycans, and some glycoproteins such as basigin, lysosome-associated membrane protein-1 (LAMP-1), and chondroitin sulfate proteoglycan 4 (CSPG4) were identified in both WM115 and WM266-4 cells. The expression level of polyLacNAc of CSPG4 in WM266-4 cells was significantly higher than that in WM115 cells. In addition, sulfation patterns of chondroitin sulfate (CS) chains in CSPG4 showed dramatic changes between these cell lines. These data show that characteristic glycans attached to common proteins observed in different stages of cancer cells will be useful markers for determining degree of malignancies of tumor cells.

Activated Cdc42-associated kinase 1 (Ack1) is required for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor recruitment to lipid rafts and induction of cell death

TNF-related apoptosis-inducing ligand (TRAIL) holds promise for treatment of cancer due to its ability to selectively kill cancer cells while sparing normal cells. Ligand-induced translocation of TRAIL receptors (TRAIL-R) 1 and 2 (also called DR4 and DR5, respectively) into lipid raft membrane microdomains is required for TRAIL-induced cell death by facilitating receptor clustering and formation of the death-inducing signaling complex, yet the underlying regulatory mechanisms remain largely unknown. We show here that the non-receptor tyrosine kinase Ack1, previously implicated in the spatiotemporal regulation of the EGF receptor, is required for TRAIL-induced cell death in multiple epithelial cell lines. TRAIL triggered a transient up-regulation of Ack1 and its recruitment to lipid rafts along with TRAIL-R1/2. siRNA-mediated depletion of Ack1 disrupted TRAIL-induced accumulation of TRAIL-R1/2 in lipid rafts and efficient recruitment of caspase-8 to the death-inducing signaling complex. Pharmacological inhibition of Ack1 did not affect TRAIL-induced cell death, indicating that Ack1 acts in a kinase-independent manner to promote TRAIL-R1/2 accumulation in lipid rafts. These findings identify Ack1 as an essential player in the spatial regulation of TRAIL-R1/2.

Melanoma biomolecules: independently identified but functionally intertwined

The majority of patients diagnosed with melanoma present with thin lesions and generally these patients have a good prognosis. However, 5% of patients with early melanoma (<1 mm thick) will have recurrence and die within 10 years, despite no evidence of local or metastatic spread at the time of diagnosis. Thus, there is a need for additional prognostic markers to help identify those patients that may be at risk of recurrent disease. Many studies and several meta-analyses have compared gene and protein expression in melanocytes, naevi, primary, and metastatic melanoma in an attempt to find informative prognostic markers for these patients. However, although a large number of putative biomarkers have been described, few of these molecules are informative when used in isolation. The best approach is likely to involve a combination of molecules. We believe one approach could be to analyze the expression of a group of interacting proteins that regulate different aspects of the metastatic pathway. This is because a primary lesion expressing proteins involved in multiple stages of metastasis may be more likely to lead to secondary disease than one that does not. This review focuses on five putative biomarkers – melanoma cell adhesion molecule (MCAM), galectin-3 (gal-3), matrix metalloproteinase 2 (MMP-2), chondroitin sulfate proteoglycan 4 (CSPG4), and paired box 3 (PAX3). The goal is to provide context around what is known about the contribution of these biomarkers to melanoma biology and metastasis. Although each of these molecules have been independently identified as likely biomarkers, it is clear from our analyses that each are closely linked with each other, with intertwined roles in melanoma biology.

NG2 regulates directional migration of oligodendrocyte precursor cells via Rho GTPases and polarity complex proteins

The transmembrane proteoglycan NG2 is expressed by oligodendrocyte precursor cells (OPC), which migrate to axons during developmental myelination and remyelinate in the adult after migration to injured sites. Highly invasive glial tumors also express NG2. Despite the fact that NG2 has been implicated in control of OPC migration, its mode of action remains unknown. Here, we show in vitro and in vivo that NG2 controls migration of OPC through the regulation of cell polarity. In stab wounds in adult mice we show that NG2 controls orientation of OPC toward the wound. NG2 stimulates RhoA activity at the cell periphery via the MUPP1/Syx1 signaling pathway, which favors the bipolar shape of migrating OPC and thus directional migration. Upon phosphorylation of Thr-2256, downstream signaling of NG2 switches from RhoA to Rac stimulation. This triggers process outgrowth through regulators of front-rear polarity and we show using a phospho-mimetic form of NG2 that indeed NG2 recruits proteins of the CRB and the PAR polarity complexes to stimulate Rac activity via the GEF Tiam1. Our findings demonstrate that NG2 is a core organizer of Rho GTPase activity and localization in the cell, which controls OPC polarity and directional migration. This work also reveals CRB and PAR polarity complexes as new effectors of NG2 signaling in the establishment of front-rear polarity.

A role for the tyrosine kinase ACK1 in neurotrophin signaling and neuronal extension and branching

Neurotrophins are involved in many crucial cellular functions, including neurite outgrowth, synapse formation, and plasticity. Although these events have long been known, the molecular determinants underlying neuritogenesis have not been fully characterized. Ack1 (activated Cdc42-associated tyrosine kinase) is a non-receptor tyrosine kinase that is highly expressed in the brain. Here, we demonstrate that Ack1 is a molecular constituent of neurotrophin signaling cascades in neurons and PC12 cells. We report that Ack1 interacts with Trk receptors and becomes tyrosine phosphorylated and its kinase activity is increased in response to neurotrophins. Moreover, our data indicate that Ack1 acts upstream of the Akt and MAPK pathways. We show that Ack1 overexpression induces neuritic outgrowth and promotes branching in neurotrophin-treated neuronal cells, whereas the expression of Ack1 dominant negatives or short-hairpin RNAs counteract neurotrophin-stimulated differentiation. Our results identify Ack1 as a novel regulator of neurotrophin-mediated events in primary neurons and in PC12 cells.

Activated Cdc42 kinase regulates Dock localization in male germ cells during Drosophila spermatogenesis

Deregulation of the non-receptor tyrosine kinase ACK1 (Activated Cdc42-associated kinase) correlates with poor prognosis in cancers and has been implicated in promoting metastasis. To further understand its in vivo function, we have characterized the developmental defects of a null mutation in Drosophila Ack, which bears a high degree of sequence similarity to mammalian ACK1 but lacks a CRIB domain. We show that Ack, while not essential for viability, is critical for sperm formation. This function depends on Ack tyrosine kinase activity and is required cell autonomously in differentiating male germ cells at or after the spermatocyte stage. Ack associates predominantly with endocytic clathrin sites in spermatocytes, but disruption of Ack function has no apparent effect on clathrin localization and receptor-mediated internalization of Boss (Bride of sevenless) protein in eye discs. Instead, Ack is required for the subcellular distribution of Dock (dreadlocks), the Drosophila homolog of the SH2- and SH3-containing adaptor protein Nck. Moreover, Dock forms a complex with Ack, and the localization of Dock in male germ cells depends on its SH2 domain. Together, our results suggest that Ack-dependent tyrosine phosphorylation recruits Dock to promote sperm differentiation.

NG2/CSPG4-collagen type VI interplays putatively involved in the microenvironmental control of tumour engraftment and local expansion

In soft-tissue sarcoma patients, enhanced expression of NG2/CSPG4 proteoglycan in pre-surgical primary tumours predicts post-surgical metastasis formation and thereby stratifies patients into disease-free survivors and patients destined to succumb to the disease. Both primary and secondary sarcoma lesions also up-regulate collagen type VI, a putative extracellular matrix ligand of NG2, and this matrix alteration potentiates the prognostic impact of NG2. Enhanced constitutive levels of the proteoglycan in isolated sarcoma cells closely correlate with a superior engraftment capability and local growth in xenogenic settings. This apparent NG2-associated malignancy was also corroborated by the diverse tumorigenic behaviour in vitro and in vivo of immunoselected NG2-expressing and NG2-deficient cell subsets, by RNAi-mediated knock down of endogenous NG2, and by ectopic transduction of full-length or deletion constructs of NG2. Cells with modified expression of NG2 diverged in their interaction with purified Col VI, matrices supplemented with Col VI, and cell-free matrices isolated from wild-type and Col VI null fibroblasts. The combined use of dominant-negative NG2 mutant cells and purified domain fragments of the collagen allowed us to pinpoint the reciprocal binding sites within the two molecules and to assert the importance of this molecular interaction in the control of sarcoma cell adhesion and motility. The NG2-mediated binding to Col VI triggered activation of convergent cell survival- and cell adhesion/migration-promoting signal transduction pathways, implicating PI-3K as a common denominator. Thus, the findings point to an NG2-Col VI interplay as putatively involved in the regulation of the cancer cell-host microenvironment interactions sustaining sarcoma progression.

Characterisation of novel uveal melanoma cell lines under serum-free conditions

BACKGROUND

The establishment of long-term uveal melanoma (UM) cell lines is difficult. However, studying living cells and their behaviour in the presence of other cells and the extracellular matrix is important in terms of understanding tumour biology and malignant behaviour. We have established three UM cell lines and report a first characterisation of these cell lines.

METHODS

Three established UM cell lines (UMT2, UMT26 and UMT33) were analysed according to their morphologic characteristics, melanocytic differentiation, adhesion on different extracellular matrices and proliferative activity. Copy number changes of chromosomes 1, 3, 6 and 8 were studied by multiplex ligation-dependent probe amplification (MLPA). Oncogenic mutations in UM involving exons 4 and 5 of GNAQ and GNA11, respectively, were analysed by sequencing.

RESULTS

All cell lines grew in suspension. UMT2 cells were homogeneous, UMT26 and UMT33 cells heterogeneous with regard to cell size and pigmentation. All UM cell lines revealed a melanocytic differentiation. UMT2 and 33 adhered on various extracellular matrices, while UMT26 only adhered to basal membrane extract (BME). This difference corresponded to the different expression of various integrins. Ki67 was expressed by 89% of UMT2 and 95% of UMT33 cells, which thus were in a proliferative stage, while only 2% of UMT26 cells revealed immunostaining for this proliferation marker. The doubling time of UMT2 was 3 days, 12 days for UMT33, and circa 3-4 months for UMT26. MLPA revealed disomy 3 in UMT2 and monosomy 3 in UMT33. The same point mutation was found in UMT2, 26 and 33, in exon 5 of GNA11 at codon 209 (p.Q209L).

CONCLUSIONS

The establishment of UM cell lines under serum-free conditions is possible. Characterisation of UMT2, 26, and 33 revealed obvious differences in cytomorphology, melanocytic differentiation, adhesion on extracellular matrices, and proliferative activity. UMT2, 26 and 33 showed the same oncogenic mutation in exon 5 of GNA11.

Ack1: activation and regulation by allostery

The non-receptor tyrosine kinase Ack1 belongs to a unique multi-domain protein kinase family, Ack. Ack is the only family of SH3 domain containing kinases to have an SH3 domain following the kinase domain; others have their SH3 domains preceding the kinase domain. Previous reports have suggested that Ack1 does not require phosphorylation for activation and the enzyme activity of the isolated kinase domain is low relative to other kinases. It has been shown to dimerize in the cellular environment, which augments its enzyme activity. The molecular mechanism of activation, however, remains unknown. Here we present structural and biochemical data on Ack1 kinase domain, and kinase domain+SH3 domain that suggest that Ack1 in its monomeric state is autoinhibited, like EGFR and CDK. The activation of the kinase domain may require N-lobe mediated symmetric dimerization, which may be facilitated by the N-terminal SAM domain. Results presented here show that SH3 domain, unlike in Src family tyrosine kinases, does not directly control the activation state of the enzyme. Instead we speculate that the SH3 domain may play a regulatory role by facilitating binding of the MIG6 homologous region to the kinase domain. We postulate that features of Ack1 activation and regulation parallel those of receptor tyrosine kinase EGFR with some interesting differences.

p130Cas: a key signalling node in health and disease

p130Cas/breast cancer anti-oestrogen resistance 1 (BCAR1) is a member of the Cas (Crk-associated substrate) family of adaptor proteins, which have emerged as key signalling nodes capable of interactions with multiple proteins, with important regulatory roles in normal and pathological cell function. The Cas family of proteins is characterised by the presence of multiple conserved motifs for protein-protein interactions, and by extensive tyrosine and serine phosphorylations. Recent studies show that p130Cas contributes to migration, cell cycle control and apoptosis. p130Cas is essential during early embryogenesis, with a critical role in cardiovascular development. Furthermore, p130Cas has been reported to be involved in the development and progression of several human cancers. p130Cas is able to perform roles in multiple processes due to its capacity to regulate a diverse array of signalling pathways, transducing signals from growth factor receptor tyrosine kinases, non-receptor tyrosine kinases, and integrins. In this review we summarise the current understanding of the structure, function, and regulation of p130Cas, and discuss the importance of p130Cas in both physiological and pathophysiological settings, with a focus on the cardiovascular system and cancer.

NSP-CAS Protein Complexes: Emerging Signaling Modules in Cancer

The CAS (CRK-associated substrate) family of adaptor proteins comprises 4 members, which share a conserved modular domain structure that enables multiple protein-protein interactions, leading to the assembly of intracellular signaling platforms. Besides their physiological role in signal transduction downstream of a variety of cell surface receptors, CAS proteins are also critical for oncogenic transformation and cancer cell malignancy through associations with a variety of regulatory proteins and downstream effectors. Among the regulatory partners, the 3 recently identified adaptor proteins constituting the NSP (novel SH2-containing protein) family avidly bind to the conserved carboxy-terminal focal adhesion-targeting (FAT) domain of CAS proteins. NSP proteins use an anomalous nucleotide exchange factor domain that lacks catalytic activity to form NSP-CAS signaling modules. Additionally, the NSP SH2 domain can link NSP-CAS signaling assemblies to tyrosine-phosphorylated cell surface receptors. NSP proteins can potentiate CAS function by affecting key CAS attributes such as expression levels, phosphorylation state, and subcellular localization, leading to effects on cell adhesion, migration, and invasion as well as cell growth. The consequences of these activities are well exemplified by the role that members of both families play in promoting breast cancer cell invasiveness and resistance to antiestrogens. In this review, we discuss the intriguing interplay between the NSP and CAS families, with a particular focus on cancer signaling networks.

High-throughput quantitative imaging of cell spreading dynamics by multi-step microscopy projection photolithography based on a cell-friendly photoresist

A new method for the high-throughput study of cell spreading dynamics is devised by multi-step microscopy projection photolithography based on a cell-friendly photoresist. By releasing a large number of rounded cells in single cell arrays and monitoring their spreading dynamics by interference reflection microscopy, a large number of cell spreading data can be acquired by a single experiment.