ERK-MAPK signaling coordinately regulates activity of Rac1 and RhoA for tumor cell motility

Diversity and functional evolution of the plasminogen activator system

The urokinase plasminogen activator system is a family of serine proteases which consists of uPA (urokinase plasminogen activator), uPAR (urokinase type plasminogen activator receptor) and PAI-1 (plasminogen activator inhibitor 1). In addition to their significant roles in activation, these proteases act as key regulators of the tumor microenvironment and are involved in the metastatic process in many cancers. High levels of uPA system proteases in many human cancer predicts poor patient prognosis and strongly indicated a key role of uPA system in cancer metastasis. Individual components of uPA system are found to be differentially expressed in cancer cells compared to normal cells and therefore are potential therapeutic targets. In this review, we present the molecular and cellular mechanisms underlying the role of uPA system in cancer progression. Epithelial to mesenchymal transitions (EMT) is the main cause of the cancer cell metastasis. We have also attempted to relate the role of uPA signaling in EMT of cancer cells.

FRA1 promotes squamous cell carcinoma growth and metastasis through distinct AKT and c-Jun dependent mechanisms

FRA1 (Fos-like antigen 1) is highly expressed in many epithelial cancers including squamous cell carcinoma of the skin (cSCC) and head and neck (HNSCC). However, the functional importance and the mechanisms mediating FRA1 function in these cancers are not fully understood. Here, we demonstrate that FRA1 gene silencing in HNSCC and cSCC cells resulted in two consequences – impaired cell proliferation and migration. FRA1 regulation of cell growth was distinct from that of c-Jun, a prominent Jun group AP-1 factor. While c-Jun was required for the expression of the G1/S phase cell cycle promoter CDK4, FRA1 was essential for AKT activation and AKT-dependent expression of CyclinB1, a molecule required for G2-M progression. Exogenous expression of a constitutively active form of AKT rescued cancer cell growth defect caused by FRA1-loss. Additionally, FRA1 knockdown markedly slowed cell adhesion and migration, and conversely expression of an active FRA1 mutant (FRA1DD) expedited these processes in a JNK/c-Jun-dependent manner. Through protein and ChIP-PCR analyses, we identified KIND1, a cytoskeletal regulator of the cell adhesion molecule β1-integrin, as a novel FRA1 transcriptional target. Restoring KIND1 expression rescued migratory defects induced by FRA1 loss. In agreement with these in vitro data, HNSCC cells with FRA1 loss displayed markedly reduced rates of subcutaneous tumor growth and pulmonary metastasis. Together, these results indicate that FRA1 promotes cancer growth through AKT, and enhances cancer cell migration through JNK/c-Jun, pinpointing FRA1 as a key integrator of JNK and AKT signaling pathways and a potential therapeutic target for cSCC and HNSCC.

Linear Integration of ERK Activity Predominates over Persistence Detection in Fra-1 Regulation

ERK signaling regulates the expression of target genes, but it is unclear how ERK activity dynamics are interpreted. Here, we investigate this question using simultaneous, live, single-cell imaging of two ERK activity reporters and expression of Fra-1, a target gene controlling epithelial cell identity. We find that Fra-1 is expressed in proportion to the amplitude and duration of ERK activity. In contrast to previous "persistence detector" and "selective filter" models in which Fra-1 expression only occurs when ERK activity persists beyond a threshold duration, our observations demonstrate that the network regulating Fra-1 expression integrates total ERK activity and responds to it linearly. However, exploration of a generalized mathematical model of the Fra-1 coherent feedforward loop demonstrates that it can perform either linear integration or persistence detection, depending on the basal mRNA production rate and protein production delays. Our data indicate that significant basal expression and short delays cause Fra-1 to respond linearly to integrated ERK activity.

Mechanical mismatch between Ras transformed and untransformed epithelial cells

The organization of the actin cytoskeleton plays a key role in regulating cell mechanics. It is fundamentally altered during transformation, affecting how cells interact with their environment. We investigated mechanical properties of cells expressing constitutively active, oncogenic Ras (Ras^V12) in adherent and suspended states. To do this, we utilized atomic force microscopy and a microfluidic optical stretcher. We found that adherent cells stiffen and suspended cells soften with the expression of constitutively active Ras. The effect on adherent cells was reversed when contractility was inhibited with the ROCK inhibitor Y-27632, resulting in softer Ras^V12 cells. Our findings suggest that increased ROCK activity as a result of Ras has opposite effects on suspended and adhered cells. Our results also establish the importance of the activation of ROCK by Ras and its effect on cell mechanics.

The IKK/NF-κB signaling pathway requires Morgana to drive breast cancer metastasis

NF-κB is a transcription factor involved in the regulation of multiple physiological and pathological cellular processes, including inflammation, cell survival, proliferation, and cancer cell metastasis. NF-κB is frequently hyperactivated in several cancers, including triple-negative breast cancer. Here we show that NF-κB activation in breast cancer cells depends on the presence of the CHORDC1 gene product Morgana, a previously unknown component of the IKK complex and essential for IκBα substrate recognition. Morgana silencing blocks metastasis formation in breast cancer mouse models and this phenotype is reverted by IκBα downregulation. High Morgana expression levels in cancer cells decrease recruitment of natural killer cells in the first phases of tumor growth and induce the expression of cytokines able to attract neutrophils in the primary tumor, as well as in the pre-metastatic lungs, fueling cancer metastasis. In accordance, high Morgana levels positively correlate with NF-κB target gene expression and poor prognosis in human patients.

NF-κB regulates inflammation, cell survival, proliferation, and metastasis and is often hyperactivated in triple-negative breast cancer. Here the authors show that Morgana, a protein highly expressed in triple-negative breast cancers, drives NF-kB activation to promote metastasis and neutrophil recruitment.

Multicolor lineage tracing reveals clonal architecture and dynamics in colon cancer

Colon cancers are composed of phenotypically heterogeneous tumor cell subpopulations with variable expression of putative stem cell and differentiation antigens. While in normal colonic mucosa, clonal repopulation occurs along differentiation gradients from crypt base toward crypt apex, the clonal architecture of colon cancer and the relevance of tumor cell subpopulations for clonal outgrowth are poorly understood. Using a multicolor lineage tracing approach in colon cancer xenografts that reflect primary colon cancer architecture, we here demonstrate that clonal outgrowth is mainly driven by tumor cells located at the leading tumor edge with clonal axis formation toward the tumor center. While our findings are compatible with lineage outgrowth in a cancer stem cell model, they suggest that in colorectal cancer tumor cell position may be more important for clonal outgrowth than tumor cell phenotype.

The clonal architecture of colon cancer and the relevance of tumor cell subpopulations for clonal outgrowth are poorly understood. Here, the authors describe the clonal architecture and dynamics in human colon cancer by using a multicolor lineage tracing approach in colon cancer xenografts.

Bioinformatics analysis of gene expression alterations conferring drug resistance in tumor samples from melanoma patients with EGFR-activating BRAF mutations

Melanoma is a highly malignant tumor of the skin melanocytes. Patients with this cancer have a high frequency (~50%) of oncogenic BRAF mutations, particularly BRAF V600E. Treatments for melanoma often target BRAF mutations or involve mitogen-activated protein kinase kinase/extracellular signal-regulated kinase inhibitors. A major challenge in melanoma treatment is resistance to BRAF inhibitor treatment, which may be enhanced by the BRAF mutation itself and/or epidermal growth factor receptor (EGFR) activation, leading to poor prognosis. However, no effective clinical treatment exists for patients with EGFR-activating feedback. The aim of the present study was to analyze gene expression changes in tumors from patients with EGFR-activating BRAF mutations during development of drug resistance. RNA-seq data was downloaded from the Gene Expression Omnibus (GEO) database for pre- and post-treatment tumor samples from three melanoma patients with EGFR-activating BRAF V600E mutations, and from The Cancer Genome Atlas (TCGA) melanoma database for tumor and non-tumor samples from patients with the BRAF V600E mutation and unknown EGFR activation status. Using functional enrichment and KEGG pathway analyses, the present study analyzed differentially expressed genes (DEGs) between pre- vs. post-treatment data from the GEO database and tumor or non-tumor sample data from the TCGA database. The results of the present study indicated that functional and structural changes to the plasma membrane may be associated with drug resistance. The present study identified 9 DEGs that were significantly different between tumor and non-tumor samples and also between prior to and following treatment. Thus, it was confirmed that patients with EGFR-activating BRAF V600E mutations undergo gene expression changes during disease development, and during therapy. These findings may provide potential directions for melanoma-specific therapy.

Pro-migratory and TGF-β-activating functions of αvβ6 integrin in pancreatic cancer are differentially regulated via an Eps8-dependent GTPase switch

The integrin αvβ6 is up-regulated in numerous carcinomas, where expression commonly correlates with poor prognosis. αvβ6 promotes tumour invasion, partly through regulation of proteases and cell migration, and is also the principal mechanism by which epithelial cells activate TGF-β1; this latter function complicates therapeutic targeting of αvβ6, since TGF-β1 has both tumour-promoting and -suppressive effects. It is unclear how these different αvβ6 functions are linked; both require actin cytoskeletal reorganization, and it is suggested that tractive forces generated during cell migration activate TGF-β1 by exerting mechanical tension on the ECM-bound latent complex. We examined the functional relationship between cell invasion and TGF-β1 activation in pancreatic ductal adenocarcinoma (PDAC) cells, and confirmed that both processes are αvβ6-dependent. Surprisingly, we found that cellular functions could be biased towards either motility or TGF-β1 activation depending on the presence or absence of epidermal growth factor receptor pathway substrate 8 (Eps8), a regulator of actin remodelling, endocytosis, and GTPase activation. Similar to αvβ6, we found that Eps8 was up-regulated in >70% of PDACs. In complex with Abi1/Sos1, Eps8 regulated αvβ6-dependent cell migration through activation of Rac1. Down-regulation of Eps8, Sos1 or Rac1 suppressed cell movement, while simultaneously increasing αvβ6-dependent TGF-β1 activation. This latter effect was modulated through increased cell tension, regulated by Rho activation. Thus, the Eps8/Abi1/Sos1 tricomplex acts as a key molecular switch altering the balance between Rac1 and Rho activation; its presence or absence in PDAC cells modulates αvβ6-dependent functions, resulting in a pro-migratory (Rac1-dependent) or a pro-TGF-β1 activation (Rho-dependent) functional phenotype, respectively. © 2017 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

The role of Lutheran/basal cell adhesion molecule in human bladder carcinogenesis

Background

Lutheran/basal cell adhesion molecule (Lu/BCAM) is a membrane bound glycoprotein. This study was performed to investigate the role and downstream signaling pathway of Lu/BCAM in human bladder tumorigenesis.

Methods

Five human bladder cancer (E6, RT4, TSGH8301, TCCSUP and J82), one stable mouse fibroblast cell line (NIH-Lu) expressing Lu/BCAM transgene and sixty human uroepithelial carcinoma specimens were analyzed by real-time PCR, immunohistochemistry (IHC), immunofluorescence (IFA) staining, Western blotting and promoter luciferase assay for Lu/BCAM, respectively. The tumorigenicity of Lu/BCAM was demonstrated by focus formation, colony-forming ability, tumour formation, cell adhesion and migration.

Results

H-ras^V12 was revealed to up-regulate Lu/BCAM at both transcriptional and translation levels. Lu/BCAM expression was detected on the membrane of primary human bladder cancer cells. Over-expression of Lu/BCAM in NIH-Lu stable cells increased focus number, colony formation and cell adhesion accompanied with F-actin rearrangement and decreased cell migration compared with parental NIH3T3 fibroblasts. In the presence of laminin ligand, Lu/BCAM overexpression further suppressed cell migration accompanied with increased cell adhesion. We further revealed that laminin-Lu/BCAM-induced cell adhesion and F-actin rearrangement were through increased Erk phosphorylation with an increase of RhoA and a decrease of Rac1 activity. Similarly, high Lu/BCAM expression was detected in the tumors of human renal pelvis, ureter and bladder, and was significantly associated with advanced tumor stage (p = 0.02). Patients with high Lu/BCAM expression showed a trend toward larger tumor size (p = 0.07) and lower disease-specific survival (p = 0.08), although not reaching statistical significance.

Conclusion

This is the first report showing that Lu/BCAM, in the presence of its ligand laminin, is oncogenic in human urothelial cancers and may have potential as a novel therapeutic target.

Electronic supplementary material

The online version of this article (doi:10.1186/s12929-017-0360-x) contains supplementary material, which is available to authorized users.

Expression of Fra-1 in human hepatocellular carcinoma and its prognostic significance

This study aimed to explore the clinical significance and prognostic value of Fra-1 in hepatocellular carcinoma patients after curative resection. Fra-1 expression was investigated using a combination of techniques: immunohistochemistry for 66 samples of hepatocellular carcinoma and quantitative real-time polymerase chain reaction and western blotting assays for 19 matched hepatocellular carcinoma specimens. Fra-1 was present in 38 of 66 (57.6%) tumor tissues, with intense staining in the nuclei. There was also positive staining in 14 of 66 (21.2%) adjacent peritumoral tissues, with weak staining in the cytoplasm. Quantitative real-time polymerase chain reaction and western blotting assays confirmed higher expression of Fra-1 messenger RNA and Fra-1 protein in tumor tissues than adjacent non-tumor tissues for 19 hepatocellular carcinoma samples (p < 0.001). Positive expression of Fra-1 was significantly related to vascular invasion and serum alpha-fetoprotein. Kaplan-Meier survival analysis found that overexpressed Fra-1 was correlated with poor overall survival and disease-free survival. Multivariate analysis identified Fra-1 as an independent prognostic factor. Fra-1 may be involved in the progress of hepatocellular carcinoma and could be a promising molecular candidate in the diagnosis and treatment of hepatocellular carcinoma.

Exosomes from metastatic cancer cells transfer amoeboid phenotype to non-metastatic cells and increase endothelial permeability: their emerging role in tumor heterogeneity

The goal of this study was to understand if exosomes derived from high-metastatic cells may influence the behavior of less aggressive cancer cells and the properties of the endothelium. We found that metastatic colon cancer cells are able to transfer their amoeboid phenotype to isogenic primary cancer cells through exosomes, and that this morphological transition is associated with the acquisition of a more aggressive behavior. Moreover, exosomes from the metastatic line (SW620Exos) exhibited higher ability to cause endothelial hyperpermeability than exosomes from the non metastatic line (SW480Exos). SWATH-based quantitative proteomic analysis highlighted that SW620Exos are significantly enriched in cytoskeletal-associated proteins including proteins activating the RhoA/ROCK pathway, known to induce amoeboid properties and destabilization of endothelial junctions. In particular, thrombin was identified as a key mediator of the effects induced by SW620Exos in target cells, in which we also found a significant increase of RhoA activity. Overall, our results demonstrate that in a heterogeneous context exosomes released by aggressive sub-clones can contribute to accelerate tumor progression by spreading malignant properties that affect both the tumor cell plasticity and the endothelial cell behavior.

High expression of Collagen Triple Helix Repeat Containing 1 (CTHRC1) facilitates progression of oesophageal squamous cell carcinoma through MAPK/MEK/ERK/FRA-1 activation

Background

Oesophageal cancer is one of the most common malignancies worldwide,and oesophageal squamous cell carcinoma (ESCC) is the predominant histological type both globally and in China. Collagen triple helix repeat containing 1 (CTHRC1) has been found to be upregulated in ESCC. However, its role in tumourigenesis and progression of ESCC remains unclear.

Methods

Using our previous ESCC mRNA profiling data, we screened upregulated genes to identify those required for proliferation. Immunohistochemistry was performed to determine the level of CTHRC1 protein expression in 204 ESCC patients. Correlations between CTHRC1 expression and clinicopathological characteristics were assessed. In addition, pyrosequencing and 5-aza-dC treatment were performed to evaluate methylation status of CTHRC1 promoter. In vitro and in vivo analyses were also conducted to determine the role of CTHRC1 in ESCC cell proliferation, migration and invasion, and RNA sequencing and molecular experiments were performed to study the underlying mechanisms.

Results

Based on mRNA profiling data, CTHRC1 was identified as one of the most significantly upregulated genes in ESCC tissues (n = 119, fold change = 20.5, P = 2.12E-66). RNA interference screening also showed that CTHRC1 was required for cell proliferation. Immunohistochemistry confirmed markedly high CTHRC1 protein expression in tumour tissues, and high CTHRC1 expression was positively correlated with advanced T stage (P = 0.043), lymph node metastasis (P = 0.023), TNM stage (P = 0.024) and poor overall survival (P = 0.020). Promoter hypomethylation at cg07757887 may contribute to increased CTHRC1 expression in ESCC cells and tumours. Forced overexpression of CTHRC1 significantly enhanced cell proliferation, migration and invasion, whereas depletion of CTHRC1 suppressed these cellular functions in three ESCC cell lines and xenografts. CTHRC1 was found to activate FRA-1 (Fos-related antigen 1, also known as FOSL1) through the MAPK/MEK/ERK cascade, which led to upregulation of cyclin D1 and thus promoted cell proliferation. FRA-1 also induced snail1-mediated MMP14 (matrix metallopeptidase 14, also known as MT1-MMP) expression to facilitate ESCC cell invasion, migration, and metastasis.

Conclusions

Our data suggest that CTHRC1 may act as an oncogenic driver in progression and metastasis of ESCC, and may serve as a potential biomarker for prognosis and personalized therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-017-0555-8) contains supplementary material, which is available to authorized users.

Cadmium stimulates metastasis-associated phenotype in triple-negative breast cancer cells through integrin and β-catenin signaling

Cadmium (Cd) is a carcinogenic heavy metal which is implicated in breast cancer development. While the mechanisms of Cd-induced breast cancer initiation and promotion have been studied, the molecular processes involved in breast cancer progression remain to be investigated. The purpose of the present study was to evaluate the influence of Cd on metastasis-associated phenotypes, such as cell adhesion, migration, and invasion in triple-negative breast cancer cells. Treatment of MDA-MB-231 cells with 1μM Cd increased cell spreading and cell migration. This was associated with the activation of integrin β1, FAK, Src, and Rac1. Treatment with Cd also inhibited GSK3β activity and induced T-cell factor/lymphoid enhancer factor (TCF/LEF) transcription, indicating the involvement of β-catenin signaling. Furthermore, treatment with 3μM Cd for 4weeks increased the expression of β-catenin and enhanced TCF/LEF-mediated transcription. Furthermore, enhanced expressions of integrins α5 and β1, paxillin, and vimentin indicated that prolonged Cd treatment reorganized the cytoskeleton, which aided malignancy, as evidenced by enhanced matrix metalloprotease 2/9 (MMP2/9) secretion and cell invasion. Prolonged Cd treatment also caused an increase in cell growth. Together, these results indicate that Cd alters key signaling processes involved in the regulation of cytoskeleton to enhance cancer cell migration, invasion, adhesion, and proliferation.

The Drosophila DOCK family protein Sponge is required for development of the air sac primordium

Dedicator of cytokinesis (DOCK) family genes are known as DOCK1-DOCK11 in mammals. DOCK family proteins mainly regulate actin filament polymerization and/or depolymerization and are GEF proteins, which contribute to cellular signaling events by activating small G proteins. Sponge (Spg) is a Drosophila counterpart to mammalian DOCK3/DOCK4, and plays a role in embryonic central nervous system development, R7 photoreceptor cell differentiation, and adult thorax development. In order to conduct further functional analyses on Spg in vivo, we examined its localization in third instar larval wing imaginal discs. Immunostaining with purified anti-Spg IgG revealed that Spg mainly localized in the air sac primordium (ASP) in wing imaginal discs. Spg is therefore predicted to play an important role in the ASP. The specific knockdown of Spg by the breathless-GAL4 driver in tracheal cells induced lethality accompanied with a defect in ASP development and the induction of apoptosis. The monitoring of ERK signaling activity in wing imaginal discs by immunostaining with anti-diphospho-ERK IgG revealed reductions in the ERK signal cascade in Spg knockdown clones. Furthermore, the overexpression of D-raf suppressed defects in survival and the proliferation of cells in the ASP induced by the knockdown of Spg. Collectively, these results indicate that Spg plays a critical role in ASP development and tracheal cell viability that is mediated by the ERK signaling pathway.

All for one and FOSL1 for all: FOSL1 at the crossroads of lung and pancreatic cancer driven by mutant KRAS

KRAS proto-oncogene, GTPase (KRAS) remains refractory to current therapies. We devised an integrative cross-tumor approach to expose common core elements up-regulated in mutant KRAS cancers that could provide new treatment opportunities. This approach identified FOSL1 (Fos-like antigen 1) as a clinically and functionally relevant gene in mutant KRAS-driven lung and pancreatic cancers, and unveiled downstream transcriptional targets amenable to pharmacological inhibition.

p27Kip1 promotes invadopodia turnover and invasion through the regulation of the PAK1/Cortactin pathway

p27^Kip1 (p27) is a cyclin-CDK inhibitor and negative regulator of cell proliferation. p27 also controls other cellular processes including migration and cytoplasmic p27 can act as an oncogene. Furthermore, cytoplasmic p27 promotes invasion and metastasis, in part by promoting epithelial to mesenchymal transition. Herein, we find that p27 promotes cell invasion by binding to and regulating the activity of Cortactin, a critical regulator of invadopodia formation. p27 localizes to invadopodia and limits their number and activity. p27 promotes the interaction of Cortactin with PAK1. In turn, PAK1 promotes invadopodia turnover by phosphorylating Cortactin, and expression of Cortactin mutants for PAK-targeted sites abolishes p27’s effect on invadopodia dynamics. Thus, in absence of p27, cells exhibit increased invadopodia stability due to impaired PAK1-Cortactin interaction, but their invasive capacity is reduced compared to wild-type cells. Overall, we find that p27 directly promotes cell invasion by facilitating invadopodia turnover via the Rac1/PAK1/Cortactin pathway.

DOI:http://dx.doi.org/10.7554/eLife.22207.001

When animals develop from embryos to adults, or try to heal wounds later in life, their cells have to move. Moving means that the cells must invade into their surroundings, a dense network of proteins called the extracellular matrix. The cell first attaches to the extracellular matrix; degrades it; and then moves into the newly opened space. Cells have developed specialized structures called invadosomes to enable all these steps. Invadosomes are never static, they first assemble where cells interact with extracellular matrix, they then release proteins that loosen the matrix, and finally disassemble again to allow cells to move. Invadosomes in cancer cells often become overactive, and can allow the tumor cells to spread throughout the body.

A lot of different proteins are involved in controlling how and when cells move. p27 is a well-known protein usually found in a cell’s nucleus along with the cell’s DNA. Inside the nucleus, p27 suppresses tumor growth by stopping cells from dividing. However, often in cancer cells p27 moves outside of the cell’s nucleus where it contributes to cell movement via an unknown mechanism.

To answer how p27 controls cell invasion, Jeannot et al. used a biochemical technique to uncover which proteins p27 binds to when it is outside of the nucleus. One of its interaction partners was called Cortactin. This protein is known to be an important building block of invadosomes, and is involved in both the assembly and disassembly of these structures. In further experiments, Jeannot studied mouse cells with or without p27 and human cancer cells that can be grown in the laboratory. The experiments revealed that p27 promotes an enzyme called PAK1 to also bind to Cortactin. PAK1 then modified Cortactin, causing whole invadosomes to disassemble, which in turn allowed cells to de-attach from the matrix and move forward. In contrast, cells lacking p27 had more stable invadosomes, attached more strongly to the matrix and were better at degrading it, but could not invade as well as cells with p27.

Overall these experiments showed a new way that p27 promotes cell invasion. The next steps will include finding out exactly how the modification of Cortactin causes the invadosomes to disassemble. Furthermore, it will be important to study whether forcing p27 back into the nucleus can reduce the spread of cancer cells in the body.

DOI:http://dx.doi.org/10.7554/eLife.22207.002

An integrative approach unveils FOSL1 as an oncogene vulnerability in KRAS-driven lung and pancreatic cancer

KRAS mutated tumours represent a large fraction of human cancers, but the vast majority remains refractory to current clinical therapies. Thus, a deeper understanding of the molecular mechanisms triggered by KRAS oncogene may yield alternative therapeutic strategies. Here we report the identification of a common transcriptional signature across mutant KRAS cancers of distinct tissue origin that includes the transcription factor FOSL1. High FOSL1 expression identifies mutant KRAS lung and pancreatic cancer patients with the worst survival outcome. Furthermore, FOSL1 genetic inhibition is detrimental to both KRAS-driven tumour types. Mechanistically, FOSL1 links the KRAS oncogene to components of the mitotic machinery, a pathway previously postulated to function orthogonally to oncogenic KRAS. FOSL1 targets include AURKA, whose inhibition impairs viability of mutant KRAS cells. Lastly, combination of AURKA and MEK inhibitors induces a deleterious effect on mutant KRAS cells. Our findings unveil KRAS downstream effectors that provide opportunities to treat KRAS-driven cancers.

Progression of Human Renal Cell Carcinoma via Inhibition of RhoA-ROCK Axis by PARG1

Renal cell carcinoma (RCC) is the most lethal urological malignancy with high risk of recurrence; thus, new prognostic biomarkers are needed. In this study, a new RCC antigen, PTPL1 associated RhoGAP1 (PARG1), was identified by using serological identification of recombinant cDNA expression cloning with sera from RCC patients. PARG1 protein was found to be differentially expressed in RCC cells among patients. High PARG1 expression is significantly correlated with various clinicopathological factors relating to cancer cell proliferation and invasion, including G3 percentage (P = .0046), Ki-67 score (p expression is also correlated with high recurrence of N0M0 patients (P = .0084) and poor prognosis in RCC patients (P = .0345). Multivariate analysis has revealed that high PARG1 expression is an independent factor for recurrence (P = .0149) of N0M0 RCC patients. In in vitro studies, depletion of PARG1by siRNA in human RCC cell lines inhibited their proliferation through inducing G1 cell cycle arrest via upregulation of p53 and subsequent p21^Cip1/Waf1, which are mediated by increased RhoA-ROCK activities. Similarly, PARG1 depletion cells inhibited invasion ability via increasing RhoA-ROCK activities in the RCC cell lines. Conversely, overexpression of PARG1 on human embryonic kidney cell line HEK293T promotes its cell proliferation and invasion. These results indicate that PARG1 plays crucial roles in progression of human RCC in increasing cell proliferation and invasion ability via inhibition of the RhoA-ROCK axis, and PARG1 is a poor prognostic marker, particularly for high recurrence of N0M0 RCC patients.

Tumour-suppressor microRNAs regulate ovarian cancer cell physical properties and invasive behaviour

The activities of pathways that regulate malignant transformation can be influenced by microRNAs (miRs). Recently, we showed that increased expression of five tumour-suppressor miRs, miR-508-3p, miR-508-5p, miR-509-3p, miR-509-5p and miR-130b-3p, correlate with improved clinical outcomes in human ovarian cancer patients, and that miR-509-3p attenuates invasion of ovarian cancer cell lines. Here, we investigate the mechanism underlying this reduced invasive potential by assessing the impact of these five miRs on the physical properties of cells. Human ovarian cancer cells (HEYA8, OVCAR8) that are transfected with miR mimics representing these five miRs exhibit decreased invasion through collagen matrices, increased cell size and reduced deformability as measured by microfiltration and microfluidic assays. To understand the molecular basis of altered invasion and deformability induced by these miRs, we use predicted and validated mRNA targets that encode structural and signalling proteins that regulate cell mechanical properties. Combined with analysis of gene transcripts by real-time PCR and image analysis of F-actin in single cells, our results suggest that these tumour-suppressor miRs may alter cell physical properties by regulating the actin cytoskeleton. Our findings provide biophysical insights into how tumour-suppressor miRs can regulate the invasive behaviour of ovarian cancer cells, and identify potential therapeutic targets that may be implicated in ovarian cancer progression.

mTORC2 activation is regulated by the urokinase receptor (uPAR) in bladder cancer

Mammalian target of rapamycin complex 2 (mTORC2) has been identified as a major regulator of bladder cancer cell migration and invasion. Upstream pathways that mediate mTORC2 activation remain poorly defined. Urokinase-type plasminogen activator receptor (uPAR) is a GPI-anchored membrane protein and known activator of cell-signaling. We identified increased uPAR expression in 94% of invasive human bladder cancers and in 54-71% of non-invasive bladder cancers, depending on grade. Normal urothelium was uPAR-immunonegative. Analysis of publicly available datasets identified uPAR gene amplification or mRNA upregulation in a subset of bladder cancer patients with reduced overall survival. Using biochemical approaches, we showed that uPAR activates mTORC2 in bladder cancer cells. Highly invasive bladder cancer cell lines, including T24, J82 and UM-UC-3 cells, showed increased uPAR mRNA expression and protein levels compared with the less aggressive cell lines, UROtsa and RT4. uPAR gene-silencing significantly reduced phosphorylation of Serine-473 in Akt, an mTORC2 target. uPAR gene-silencing also reduced bladder cancer cell migration and Matrigel invasion. S473 phosphorylation was observed by immunohistochemistry in human bladder cancers only when the tumors expressed high levels of uPAR. S473 phosphorylation was not controlled by uPAR in bladder cancer cell lines that are PTEN-negative; however, this result probably did not reflect altered mTORC2 regulation. Instead, PTEN deficiency de-repressed alternative kinases that phosphorylate S473. Our results suggest that uPAR and mTORC2 are components of a single cell-signaling pathway. Targeting uPAR or mTORC2 may be beneficial in patients with bladder cancer.

Identification of Differentially Expressed Proteins in the Serum of Colorectal Cancer Patients Using 2D-DIGE Proteomics Analysis

Early detection of colorectal cancer (CRC) is vital for the improvement of disease prognosis. However to date there are no blood-based biomarkers sensitive and specific enough for early diagnosis. We analysed the differences in serum protein expression of early stage CRC (Dukes’ A and B) and late stage CRC (Dukes’ C and D) against normal controls using 2D Fluorescence Difference Gel Electrophoresis (2D-DIGE). Analysis of the 2D maps showed that 23 proteins were differentially expressed between groups (p ≤ 0.05) and these proteins were identified with LC-MS/MS. Eight proteins were up-regulated and 2 down-regulated in patients with early CRC, whereas 14 proteins were up-regulated and 4 down-regulated in those with late CRC compared to normal controls (p ≤ 0.05). Five proteins, namely apolipoprotein A1 (APOA1), apolipoprotein E (APOE), complement factor H (CFH), galectin-7 (GAL7) and synaptojanin-2 (SYNJ2) were validated using ELISA and only APOA1 and GAL-7 showed consistent findings. Further validation using immunohistochemistry showed negative immunoreactivity for GAL-7 in CRC tissues, suggesting that GAL-7 detected in the serum did not originate from the CRC tumour. APOA1 showed positive immunoreactivity but its expression did not correlate with Dukes’ staging (p = 0.314), tumour grading (p = 0.880) and lymph node involvement (p = 0.108). Differences in APOA1 isoforms and/or conformation between serum and tissue samples as well as tumour heterogeneity may explain for the discrepancies between DIGE and ELISA when compared to immunohistochemistry. Structural and functional studies of APOA1 in future would best describe the role of APOA1 in CRC.

The GAS6-AXL signaling network is a mesenchymal (Mes) molecular subtype-specific therapeutic target for ovarian cancer

Ovarian cancer is a complex disease with heterogeneity among the gene expression molecular subtypes (GEMS) between patients. Patients with tumors of a mesenchymal ("Mes") subtype have a poorer prognosis than patients with tumors of an epithelial ("Epi") subtype. We evaluated GEMS of ovarian cancer patients for molecular signaling profiles and assessed how the differences in these profiles could be leveraged to improve patient clinical outcome. Kinome enrichment analysis identified AXL as a particularly abundant kinase in Mes-subtype tumor tissue and cell lines. In Mes cells, upon activation by its ligand GAS6, AXL coclustered with and transactivated the receptor tyrosine kinases (RTKs) cMET, EGFR, and HER2, producing sustained extracellular signal-regulated kinase (ERK) activation. In Epi-A cells, AXL was less abundant and induced a transient activation of ERK without evidence of RTK transactivation. AXL-RTK crosstalk also stimulated sustained activation of the transcription factor FRA1, which correlated with the induction of the epithelial-mesenchymal transition (EMT)-associated transcription factor SLUG and stimulation of motility exclusively in Mes-subtype cells. The AXL inhibitor R428 attenuated RTK and ERK activation and reduced cell motility in Mes cells in culture and reduced tumor growth in a chick chorioallantoic membrane model. A higher concentration of R428 was needed to inhibit ERK activation and cell motility in Epi-A cells. Silencing AXL in Mes-subtype cells reversed the mesenchymal phenotype in culture and abolished tumor formation in an orthotopic xenograft mouse model. Thus, AXL-targeted therapy may improve clinical outcome for patients with Mes-subtype ovarian cancer.

Presence of Cx43 in extracellular vesicles reduces the cardiotoxicity of the anti-tumour therapeutic approach with doxorubicin

Extracellular vesicles (EVs) are major conveyors of biological information, mediating local and systemic cell-to-cell communication under physiological and pathological conditions. These endogenous vesicles have been recognized as prominent drug delivery vehicles of several therapeutic cargoes, including doxorubicin (dox), presenting major advantages over the classical approaches. Although dox is one of the most effective anti-tumour agents in the clinical practice, its use is very often hindered by its consequent dramatic cardiotoxicity. Despite significant advances witnessed in the past few years, more comprehensive studies, supporting the therapeutic efficacy of EVs, with decreased side effects, are still scarce. The main objective of this study was to evaluate the role of the gap junction protein connexin43 (Cx43) in mediating the release of EV content into tumour cells. Moreover, we investigated whether Cx43 improves the efficiency of dox-based anti-tumour treatment, with a concomitant decrease of cardiotoxicity. In the present report, we demonstrate that the presence of Cx43 in EVs increases the release of luciferin from EVs into tumour cells in vitro and in vivo. In addition, using cell-based approaches and a subcutaneous mouse tumour model, we show that the anti-tumour effect of dox incorporated into EVs is similar to the administration of the free drug, regardless the presence of Cx43. Strikingly, we demonstrate that the presence of Cx43 in dox-loaded EVs reduces the cardiotoxicity of the drug. Altogether, these results bring new insights into the concrete potential of EVs as therapeutic vehicles and open new avenues toward the development of strategies that help to reduce unwanted side effects.

The role of aquaporin-5 in cancer cell migration: A potential active participant

Emerging data identifies the water channel aquaporin-5 as a major player in multiple cancers. Over-expression of aquaporin-5 has been associated with increased metastasis and poor prognosis, suggesting that aquaporin-5 may enhance cancer cell migration. This review aims to highlight the current knowledge and hypothesis regarding downstream signaling partners of aquaporin-5 in relation to cancer cell migration. The molecular mechanisms that link aquaporin-5 to cell migration are not completely understood. Aquaporin-5 may promote cell movement by increasing water uptake into the front of the cell allowing local swelling. Aquaporin-5 may also activate extracellular-regulated kinases, increasing proliferation and potentially stimulating the migration machinery. Thus, further studies are warranted to identify the underlying mechanisms and signaling pathways. This will reveal whether aquaporin-5 and downstream effectors could be targets for developing new cancer therapeutics.

ROCK inhibition stimulates SOX9/Smad3-dependent COL2A1 expression in inner meniscus cells

BACKGROUND

Proper functioning of the meniscus depends on the composition and organization of its fibrocartilaginous extracellular matrix. We previously demonstrated that the avascular inner meniscus has a more chondrocytic phenotype compared with the outer meniscus. Inhibition of the Rho family GTPase ROCK, the major regulator of the actin cytoskeleton, stimulates the chondrogenic transcription factor Sry-type HMG box (SOX) 9-dependent α1(II) collagen (COL2A1) expression in inner meniscus cells. However, the crosstalk between ROCK inhibition, SOX9, and other transcription modulators on COL2A1 upregulation remains unclear in meniscus cells. The aim of this study was to investigate the role of SOX9-related transcriptional complex on COL2A1 expression under the inhibition of ROCK in human meniscus cells.

METHODS

Human inner and outer meniscus cells were prepared from macroscopically intact lateral menisci. Cells were cultured in the presence or absence of ROCK inhibitor (ROCKi, Y27632). Gene expression, collagen synthesis, and nuclear translocation of SOX9 and Smad2/3 were analyzed.

RESULTS

Treatment of ROCKi increased the ratio of type I/II collagen double positive cells derived from the inner meniscus. In real-time PCR analyses, expression of SOX9 and COL2A1 genes was stimulated by ROCKi treatment in inner meniscus cells. ROCKi treatment also induced nuclear translocation of SOX9 and phosphorylated Smad2/3 in immunohistological analyses. Complex formation between SOX9 and Smad3 was increased by ROCKi treatment in inner meniscus cells. Chromatin immunoprecipitation analyses revealed that association between SOX9/Smad3 transcriptional complex with the COL2A1 enhancer region was increased by ROCKi treatment.

CONCLUSIONS

This study demonstrated that ROCK inhibition stimulated SOX9/Smad3-dependent COL2A1 expression through the immediate nuclear translocation of Smad3 in inner meniscus cells. Our results suggest that ROCK inhibition can stimulates type II collagen synthesis through the cooperative activation of Smad3 in inner meniscus cells. ROCKi treatment may be useful to promote the fibrochondrocytic healing of the injured inner meniscus.

A novel PI3K/AKT signaling axis mediates Nectin-4-induced gallbladder cancer cell proliferation, metastasis and tumor growth

Nectin-4 is a Ca(2+)-independent immunoglobulin-like cell adhesion molecule which has diverse functions in cell-cell adhesion via homophilic and heterophilic interactions. Cell-cell adhesive processes are central to cell polarization, differentiation, proliferation, survival and movement. Here we report that Nectin-4 is substantially overexpressed in gallbladder cancer (GBC), the most common biliary tract malignancy with a high risk of local tumor spread and invasion. Further, Nectin-4 high expression in GBC patients was associated with pathologic T stage and lymph node metastasis status, and the expression level of the downstream target Rac1 and poor prognoses were also correlated with Nectin-4. Ectopic expression of Nectin-4 promoted GBC cell growth, motility and tumor growth in a mouse model. The depletion of Nectin-4 inhibited GBC cell proliferation and migration both in cell culture and in mice. Our data suggest that activation of the PI3K/AKT pathway was involved in the oncogenic function of Nectin-4 to activate Rac1 in GBC. Inhibition of PI3K/AKT with LY294002 and/or Rac1 with NSC23766 impaired Nectin-4-mediated GBC cell proliferation and motility. We hypothesize that Nectin-4 is critical for GBC progression via PI3K/AKT pathway activation of Rac1. Nectin-4 may be a novel prognostic factor and therapeutic target in GBC patients.

RAS signalling through PI3-Kinase controls cell migration via modulation of Reelin expression

RAS signalling through phosphoinositide 3-kinase (PI3-Kinase) has been shown to have an essential role in tumour initiation and maintenance. RAS also regulates cell motility and tumour invasiveness, but the role of direct RAS binding to PI3-Kinase in this remains uncertain. Here, we provide evidence that disruption of RAS interaction with PI3-Kinase p110α decreases cell motility and prevents activation of Rac GTPase. Analysis of gene expression in cells lacking RAS interaction with p110α reveals increased levels of the extracellular matrix glycoprotein Reelin and activation of its downstream pathway resulting in upregulation of E-cadherin expression. Induction of the Reelin/E-cadherin axis is also observed in Kras mutant lung tumours that are regressing due to blockade of RAS interaction with PI3-Kinase. Furthermore, loss of Reelin correlates with decreased survival of lung and breast cancer patients. Reelin thus plays a role in restraining RAS and PI3-kinase promotion of cell motility and potentially tumour metastasis.

The Correlation Between RhoA Expression and Clinicopathological Characteristics in Gastric Cancer Patients After Curative Surgery

BACKGROUND

The expression of RhoA, a member of the ras homologue family, is reported to be involved in tumorigenesis in some cancers; however, its prognostic value in gastric cancer is controversial.

METHODS

Between April 1988 and January 2005, a total of 206 gastric cancer patients receiving curative surgery were enrolled in this study. Immunohistochemical staining of the RhoA protein was performed, and the clinicopathological characteristics and initial recurrence patterns were compared between low RhoA expression (n = 55) and high RhoA expression (n = 151) gastric cancer patients.

RESULTS

For intestinal-type (n = 134) gastric cancer, there is no significant difference between the clinicopathological characteristics and RhoA expression. However, for diffuse-type (n = 82) gastric cancer, high RhoA expression was associated with more advanced pathological N category compared to low RhoA expression. A multivariate analysis revealed that age, pathological T and N categories, and RhoA expression were independent prognostic factors for overall survival after curative surgery. For all patients, the five-year overall survival rates and disease-free survival rates were higher in patients with low RhoA expression compared to those with high RhoA expression, which was observed in diffuse-type gastric cancer, not in intestinal-type gastric cancer. With regard to the initial recurrence pattern, patients with high RhoA expression had more distant metastasis compared to those with low RhoA expression, especially more liver metastasis.

CONCLUSIONS

RhoA expression is an independent prognostic factor for gastric cancer, especially for diffuse-type. We should be aware of liver metastasis during the follow-up of gastric cancer with high RhoA expression.

Targeting the MAP kinase pathway in astrocytoma cells using a recombinant anthrax lethal toxin as a way to inhibit cell motility and invasion

Malignant astrocytomas are highly invasive into adjacent and distant regions of the normal brain. Understanding and targeting cancer cell invasion is an important therapeutic approach. Cell invasion is a complex process that replies on many signaling pathways including the mitogen-activated protein (MAP) kinase (MAPK). In many cell lines, the use of MAPK-targeted drugs proved to be a potential method to inhibit cancer cell motility. In the present study, we use a recombinant anthrax lethal toxin (LeTx), which selectively inhibits the MAPK pathway, in order to target invasion. LeTx proved ineffective on cell survival in astrocytoma (as well as normal cells). However, astrocytoma cells that were treated with LeTx showed a significant decrease in cell motility as seen by wound healing as well as random 2D motility in serum. The cells also showed a decrease in invasion across a collagen matrix. The effect of LeTx on cell migration was mediated though the deregulation of Rho GTPases, which play a role in cell motility. Finally, the effect of LeTx on cell migration and Rho GTPases was mimicked by the inhibition of the MAPK pathway. In this study, we describe for the first time the effect of the LeTx on cancer cell motility and invasion not cell survival making it a potentially selective brain tumor invasion inhibitor.

SNX9 promotes metastasis by enhancing cancer cell invasion via differential regulation of RhoGTPases

Despite current advances in cancer research, metastasis remains the leading factor in cancer-related deaths. Here, we identify sorting nexin 9 (SNX9) as a new regulator of breast cancer metastasis. We detected an increase in SNX9 expression in human breast cancer metastases compared with primary tumors and demonstrated that SNX9 expression in MDA-MB-231 breast cancer cells is necessary to maintain their ability to metastasize in a chick embryo model. Reciprocally, SNX9 knockdown impairs the process. In vitro studies using several cancer cell lines derived from a variety of human tumors revealed a role for SNX9 in cell invasion and identified mechanisms responsible for this novel function. We showed that SNX9 controls the activation of RhoA and Cdc42 GTPases and also regulates cell motility via the modulation of well-known molecules involved in metastasis, namely RhoA-ROCK and N-WASP. In addition, we have discovered that SNX9 is required for RhoGTPase-dependent, clathrin-independent endocytosis, and in this capacity, can functionally substitute to the bona fide Rho GAP, GRAF1 (GTPase Regulator Associated with Focal Adhesion Kinase). Together, our data establish novel roles for SNX9 as a multifunctional protein scaffold that regulates, and potentially coordinates, several cellular processes that together can enhance cancer cell metastasis.

NME2 associates with PTPσ to transduce signals from chondroitin sulfate proteoglycans

Chondroitin sulfate proteoglycans (CSPGs) are a major component of glial scars, inhibiting axonal growth in the central nervous system. Protein tyrosine phosphatase, receptor type S (PTPσ) has been identified as a receptor for CSPGs, whereas its downstream signaling pathway remains to be fully understood. Here, we report that nucleoside diphosphate kinase 2 (NME2) interacts with PTPσ. We screened proteins associated with PTPσ by mass spectrometry, and obtained NME2. Immunoprecipitation analysis revealed that NME2 associated with the PTPσ intracellular domain in HEK-293T cells. NME2 was expressed in the cytoplasm and nucleus of cortical neurons, and knockdown of NME2 in the cortical neurons completely rescued neurite outgrowth inhibition induced by CSPGs. These results demonstrate that NME2 associates with PTPσ to elicit neurite outgrowth inhibition in response to CSPGs.

Divergent behaviors and underlying mechanisms of cell migration and invasion in non-metastatic T24 and its metastatic derivative T24T bladder cancer cell lines

Previous studies on cancer cell invasion were primarily focused on its migration because these two events were often considered biologically equivalent. Here we found that T24T cells exhibited higher invasion but lower migration abilities than T24 cells. Expression of Rho-GDPases was much lower and expression of SOD2 was much higher in T24T cells than those in T24 cells. Indeed, knockdown of SOD2 in T24T cells can reverse the cell migration but without affecting cell invasion. We also found that SOD2 inhibited the JNK/c-Jun cascade, and the inhibition of c-Jun activation by ectopic expression of TAM67 impaired Rho-GDPases expression and cell migration in T24T shSOD2 cells. Further, we found that Sp1 can upregulate SOD2 transcription in T24T cells. Importantly, matrix metalloproteinase-2 (MMP-2) was overexpressed in T24T and participated in increasing its invasion, and MMP-2 overexpression was mediated by increasing nuclear transport of nucleolin, which enhanced mmp-2 mRNA stability. Taken together, our study unravels an inverse relationship between cell migration and invasion in human bladder cancer T24T cells and suggests a novel mechanism underlying the divergent roles of SOD2 and MMP-2 in regulating metastatic behaviors of human bladder T24T in cell migration and invasion.

Csk/Src/EGFR signaling regulates migration of myofibroblasts and alveolarization

Bronchopulmonary dysplasia (BPD) is characterized by premature alveolar developmental arrest. Antenatal exposure to inflammation inhibits lung morphogenesis, thus increasing the risk of developing BPD. Alveolar myofibroblasts are thought to migrate into the septal tips and elongate secondary septa during alveolarization. Here we found lipopolysaccharide (LPS) disrupted the directional migration of myofibroblasts and increased actin stress fiber expression and focal adhesion formation. In addition, COOH-terminal Src kinase (Csk) activity was downregulated in myofibroblasts treated with LPS, while activation of Src or epidermal growth factor receptor (EGFR) was upregulated by LPS treatment. Specifically, decreased Csk activity and increased activation of Src or EGFR was also observed in primary myofibroblasts isolated from newborn rat lungs with intra-amniotic LPS exposure, a model for BPD. Further investigation revealed that EGFR was involved in cell migration impairment induced by LPS, and Src inhibition blocked LPS-induced activation of EGFR or cell migration impairment. Csk silencing also resulted in EGFR activation and cell migration impairment. Besides, we found the effect of EGFR on myofibroblast migration was mediated through RhoA activation. EGFR inhibition alleviated the abnormal localization of myofibroblasts and improved alveolar development in antenatal LPS-treated rats. Taken together, our data suggest that the Csk/Src/EGFR signaling pathway is critically involved in regulating directional migration of myofibroblasts and may contribute to arrested alveolar development in BPD.

Localized translation regulates cell adhesion and transendothelial migration

By progressing through the epithelial to mesenchymal transition (EMT), cancer cells gain the ability to leave the primary tumor site and invade surrounding tissues. These metastatic cancers cells can further increase their plasticity by adopting an amoeboid-like morphology, by undergoing mesenchymal to amoeboid transition (MAT). We found that adhering cells producing spreading initiation centers (SIC), a transient structure localized above nascent adhesion complexes, share common biological and morphological characteristics associated with amoeboid cells. Meanwhile, spreading cells seem to return to a mesenchymal-like morphology. Thus, our results indicate that SIC-induced adhesion recapitulate events associated with amoeboid to mesenchymal transition (AMT). We found that polyadenylated RNAs were enriched within SIC and blocking their translation decreased adhesion potential of metastatic cells that progressed through EMT. These results point to a novel checkpoint regulating cell adhesion and allowing metastatic cells to alter adhesion strength in order to modulate their dissemination.

Fra-1 is a key driver of colon cancer metastasis and a Fra-1 classifier predicts disease-free survival

Fra-1 (Fos-related antigen-1) is a member of the AP-1 (activator protein-1) family of transcription factors. We previously showed that Fra-1 is necessary for breast cancer cells to metastasize in vivo, and that a classifier comprising genes that are expressed in a Fra-1-dependent fashion can predict breast cancer outcome. Here, we show that Fra-1 plays an important role also in colon cancer progression. Whereas Fra-1 depletion does not affect 2D proliferation of human colon cancer cells, it impairs growth in soft agar and in suspension. Consistently, subcutaneous tumors formed by Fra-1-depleted colon cancer cells are three times smaller than those produced by control cells. Most remarkably, when injected intravenously, Fra-1 depletion causes a 200-fold reduction in tumor burden. Moreover, a Fra-1 classifier generated by comparing RNA profiles of parental and Fra-1-depleted colon cancer cells can predict the prognosis of colon cancer patients. Functional pathway analysis revealed Wnt as one of the central pathways in the classifier, suggesting a possible mechanism of Fra-1 function in colon cancer metastasis. Our results demonstrate that Fra-1 is an important determinant of the metastatic potential of human colon cancer cells, and that the Fra-1 classifier can be used as a prognostic predictor in colon cancer patients.

Cancer Cell Invasion in Three-dimensional Collagen Is Regulated Differentially by Gα13 Protein and Discoidin Domain Receptor 1-Par3 Protein Signaling

Cancer cells can invade in three-dimensional collagen as single cells or as a cohesive group of cells that require coordination of cell-cell junctions and the actin cytoskeleton. To examine the role of Gα13, a G12 family heterotrimeric G protein, in regulating cellular invasion in three-dimensional collagen, we established a novel method to track cell invasion by membrane type 1 matrix metalloproteinase-expressing cancer cells. We show that knockdown of Gα13 decreased membrane type 1 matrix metalloproteinase-driven proteolytic invasion in three-dimensional collagen and enhanced E-cadherin-mediated cell-cell adhesion. E-cadherin knockdown reversed Gα13 siRNA-induced cell-cell adhesion but failed to reverse the effect of Gα13 siRNA on proteolytic invasion. Instead, concurrent knockdown of E-cadherin and Gα13 led to an increased number of single cells rather than groups of cells. Significantly, knockdown of discoidin domain receptor 1 (DDR1), a collagen-binding protein that also co-localizes to cell-cell junctions, reversed the effects of Gα13 knockdown on cell-cell adhesion and proteolytic invasion in three-dimensional collagen. Knockdown of the polarity protein Par3, which can function downstream of DDR1, also reversed the effects of Gα13 knockdown on cell-cell adhesion and proteolytic invasion in three-dimensional collagen. Overall, we show that Gα13 and DDR1-Par3 differentially regulate cell-cell junctions and the actin cytoskeleton to mediate invasion in three-dimensional collagen.

Dynamic membrane depolarization is an early regulator of ependymoglial cell response to spinal cord injury in axolotl

Salamanders, such as the Mexican axolotl, are some of the few vertebrates fortunate in their ability to regenerate diverse structures after injury. Unlike mammals they are able to regenerate a fully functional spinal cord after injury. However, the molecular circuitry required to initiate a pro-regenerative response after spinal cord injury is not well understood. To address this question we developed a spinal cord injury model in axolotls and used in vivo imaging of labeled ependymoglial cells to characterize the response of these cells to injury. Using in vivo imaging of ion sensitive dyes we identified that spinal cord injury induces a rapid and dynamic change in the resting membrane potential of ependymoglial cells. Prolonged depolarization of ependymoglial cells after injury inhibits ependymoglial cell proliferation and subsequent axon regeneration. Using transcriptional profiling we identified c-Fos as a key voltage sensitive early response gene that is expressed specifically in the ependymoglial cells after injury. This data establishes that dynamic changes in the membrane potential after injury are essential for regulating the specific spatiotemporal expression of c-Fos that is critical for promoting faithful spinal cord regeneration in axolotl.

FRA-1 as a driver of tumour heterogeneity: a nexus between oncogenes and embryonic signalling pathways in cancer

Tumour heterogeneity is a major factor undermining the success of therapies targeting metastatic cancer. Two major theories are thought to explain the phenomenon of heterogeneity in cancer--clonal evolution and cell plasticity. In this review, we examine a growing body of work implicating the transcription factor FOS-related antigen 1 (FRA-1) as a central node in tumour cell plasticity networks, and discuss mechanisms regulating its activity in cancer cells. We also discuss evidence from the FRA-1 perspective supporting the notion that clonal selection and cell plasticity represent two sides of the same coin. We propose that FRA-1-overexpressing clones featuring high plasticity undergo positive selection during consecutive stages of multistep tumour progression. This model underscores a potential mechanism through which tumour cells retaining elevated levels of plasticity acquire a selective advantage over other clonal populations within a tumour.

Erythropoietin dampens injury-induced microglial motility

Traumatic brain injury causes progressive brain atrophy and cognitive decline. Surprisingly, an early treatment with erythropoietin (EPO) prevents these consequences of secondary neurodegeneration, but the mechanisms have remained obscure. Here we show by advanced imaging and innovative analytical tools that recombinant human EPO, a clinically established and neuroprotective growth factor, dampens microglial activity, as visualized also in vivo by a strongly attenuated injury-induced cellular motility.

Snail promotes cell migration through PI3K/AKT-dependent Rac1 activation as well as PI3K/AKT-independent pathways during prostate cancer progression

Snail, a zinc-finger transcription factor, induces epithelial-mesenchymal transition (EMT), which is associated with increased cell migration and metastasis in cancer cells. Rac1 is a small G-protein which upon activation results in formation of lamellipodia, the first protrusions formed by migrating cells. We have previously shown that Snail promotes cell migration through down-regulation of maspin tumor suppressor. We hypothesized that Snail's regulation of cell migration may also involve Rac1 signaling regulated by PI3K/AKT and/or MAPK pathways. We found that Snail overexpression in LNCaP and 22Rv1 prostate cancer cells increased Rac1 activity associated with increased cell migration, and the Rac1 inhibitor, NSC23766, could inhibit Snail-mediated cell migration. Conversely, Snail downregulation using shRNA in the aggressive C4-2 prostate cancer cells decreased Rac1 activity and cell migration. Moreover, Snail overexpression increased ERK and PI3K/AKT activity in 22Rv1 prostate cancer cells. Treatment of Snail-overexpressing 22Rv1 cells with LY294002, PI3K/AKT inhibitor or U0126, MEK inhibitor, decreased cell migration significantly, but only LY294002 significantly reduced Rac1 activity, suggesting that Snail promotes Rac1 activation via the PI3K/AKT pathway. Furthermore, 22Rv1 cells overexpressing Snail displayed decreased maspin levels, while inhibition of maspin expression in 22Rv1 cells with siRNA, led to increased PI3K/AKT, Rac1 activity and cell migration, without affecting ERK activity, suggesting that maspin is upstream of PI3K/AKT. Overall, we have dissected signaling pathways by which Snail may promote cell migration through MAPK signaling or alternatively through PI3K/AKT-Rac1 signaling that involves Snail inhibition of maspin tumor suppressor. This may contribute to prostate cancer progression.

A Rac/Cdc42 exchange factor complex promotes formation of lateral filopodia and blood vessel lumen morphogenesis

During angiogenesis, Rho-GTPases influence endothelial cell migration and cell-cell adhesion; however it is not known whether they control formation of vessel lumens, which are essential for blood flow. Here, using an organotypic system that recapitulates distinct stages of VEGF-dependent angiogenesis, we show that lumen formation requires early cytoskeletal remodelling and lateral cell-cell contacts, mediated through the RAC1 guanine nucleotide exchange factor (GEF) DOCK4 (dedicator of cytokinesis 4). DOCK4 signalling is necessary for lateral filopodial protrusions and tubule remodelling prior to lumen formation, whereas proximal, tip filopodia persist in the absence of DOCK4. VEGF-dependent Rac activation via DOCK4 is necessary for CDC42 activation to signal filopodia formation and depends on the activation of RHOG through the RHOG GEF, SGEF. VEGF promotes interaction of DOCK4 with the CDC42 GEF DOCK9. These studies identify a novel Rho-family GTPase activation cascade for the formation of endothelial cell filopodial protrusions necessary for tubule remodelling, thereby influencing subsequent stages of lumen morphogenesis.

Gene expression profile analysis of colorectal cancer to investigate potential mechanisms using bioinformatics

This study aimed to explore the underlying molecular mechanisms of colorectal cancer (CRC) using bioinformatics analysis. Using GSE4107 datasets downloaded from the Gene Expression Omnibus, the differentially expressed genes (DEGs) were screened by comparing the RNA expression from the colonic mucosa between 12 CRC patients and ten healthy controls using a paired t-test. The Gene Ontology (GO) functional and pathway enrichment analyses of DEGs were performed using the Database for Annotation, Visualization and Integrated Discovery (DAVID) software followed by the construction of a protein–protein interaction (PPI) network. In addition, hub gene identification and GO functional and pathway enrichment analyses of the modules were performed. A total of 612 up- and 639 downregulated genes were identified. The upregulated DEGs were mainly involved in the regulation of cell growth, migration, and the MAPK signaling pathway. The downregulated DEGs were significantly associated with oxidative phosphorylation, Alzheimer’s disease, and Parkinson’s disease. Moreover, FOS, FN1, PPP1CC, and CYP2B6 were selected as hub genes in the PPI networks. Two modules (up-A and up-B) in the upregulated PPI network and three modules (d-A, d-B, and d-C) in the downregulated PPI were identified with the threshold of Molecular Complex Detection (MCODE) Molecular Complex Detection (MCODE) score ≥4 and nodes ≥6. The genes in module up-A were significantly enriched in neuroactive ligand–receptor interactions and the calcium signaling pathway. The genes in module d-A were enriched in four pathways, including oxidative phosphorylation and Parkinson’s disease. DEGs, such as FOS, FN1, PPP1CC, and CYP2B6, may be used as potential targets for CRC diagnosis and treatment.

microRNA-148a dysregulation discriminates poor prognosis of hepatocellular carcinoma in association with USP4 overexpression

Hepatocellular carcinoma (HCC) is classified as a poor prognostic tumor, and becomes frequently aggressive. MicroRNAs emerge as key contributors to tumor progression. This study investigated whether miR-148a dysregulation differentiates poor prognosis of HCC, exploring new targets of miR-148a. miR-148a dysregulation discriminated not only the overall survival and recurrence free survival rates of HCC, but the microvascular invasion. In the human HCC samples, ubiquitin specific protease 4 (USP4) and sphingosine 1-phosphate receptor 1 (S1P1) were up-regulated as the new targets of miR-148a. USP4 and S1P1 were up-regulated in mesenchymal-type liver-tumor cells with miR-148a dysregulation, facilitating migration and proliferation of tumor cells. The inverse relationship between miR-148a and the identified targets was verified in a tumor xenograft model. In the analysis of human samples, the expression of USP4, but not S1P1, correlated with the decrease of miR-148a. In a heterotropic patient-derived HCC xenograft model, USP4 was also overexpressed in G1 and G2 tumors when miR-148a was dysregulated, reflecting the closer link between miR-148a and USP4 for a shift in the expansion phase of tumorgraft. In conclusion, miR-148a dysregulation affects the poor prognosis of HCC. Of the identified targets of miR-148a, USP4 overexpression may contribute to HCC progression towards more aggressive feature.