Functional characterization of E- and P-cadherin in invasive breast cancer cells

Reversible photoregulation of cell-cell adhesions with opto-E-cadherin

E-cadherin-based cell-cell adhesions are dynamically and locally regulated in many essential processes, including embryogenesis, wound healing and tissue organization, with dysregulation manifesting as tumorigenesis and metastasis. However, the lack of tools that would provide control of the high spatiotemporal precision observed with E-cadherin adhesions hampers investigation of the underlying mechanisms. Here, we present an optogenetic tool, opto-E-cadherin, that allows reversible control of E-cadherin-mediated cell-cell adhesions with blue light. With opto-E-cadherin, functionally essential calcium binding is photoregulated such that cells expressing opto-E-cadherin at their surface adhere to each other in the dark but not upon illumination. Consequently, opto-E-cadherin provides remote control over multicellular aggregation, E-cadherin-associated intracellular signalling and F-actin organization in 2D and 3D cell cultures. Opto-E-cadherin also allows switching of multicellular behaviour between single and collective cell migration, as well as of cell invasiveness in vitro and in vivo. Overall, opto-E-cadherin is a powerful optogenetic tool capable of controlling cell-cell adhesions at the molecular, cellular and behavioural level that opens up perspectives for the study of dynamics and spatiotemporal control of E-cadherin in biological processes.

Pharmacological Activation of Potassium Channel Kv11.1 with NS1643 Attenuates Triple Negative Breast Cancer Cell Migration by Promoting the Dephosphorylation of Caveolin-1

The prevention of metastasis is a central goal of cancer therapy. Caveolin-1 (Cav-1) is a structural membrane and scaffolding protein shown to be a key regulator of late-stage breast cancer metastasis. However, therapeutic strategies targeting Cav-1 are still lacking. Here, we demonstrate that the pharmacological activation of potassium channel Kv11.1, which is uniquely expressed in MDA-MB-231 triple negative breast cancer cells (TNBCs) but not in normal MCF-10A cells, induces the dephosphorylation of Cav-1 Tyr-14 by promoting the Ca2+-dependent stimulation of protein tyrosine phosphatase 1B (PTP1B). Consequently, the dephosphorylation of Cav-1 resulted in its disassociation from β-catenin, which enabled the accumulation of β-catenin at cell borders, where it facilitated the formation of cell-cell adhesion complexes via interactions with R-cadherin and desmosomal proteins. Kv11.1 activation-dependent Cav-1 dephosphorylation induced with NS1643 also reduced cell migration and invasion, consistent with its ability to regulate focal adhesion dynamics. Thus, this study sheds light on a novel pharmacological mechanism of promoting Cav-1 dephosphorylation, which may prove to be effective at reducing metastasis and promoting contact inhibition.

P-Cadherin Regulates Intestinal Epithelial Cell Migration and Mucosal Repair, but Is Dispensable for Colitis Associated Colon Cancer

Recurrent chronic mucosal inflammation, a characteristic of inflammatory bowel diseases (IBD), perturbs the intestinal epithelial homeostasis resulting in formation of mucosal wounds and, in most severe cases, leads to colitis-associated colon cancer (CAC). The altered structure of epithelial cell-cell adhesions is a hallmark of intestinal inflammation contributing to epithelial injury, repair, and tumorigenesis. P-cadherin is an important adhesion protein, poorly expressed in normal intestinal epithelial cells (IEC) but upregulated in inflamed and injured mucosa. The goal of this study was to investigate the roles of P-cadherin in regulating intestinal inflammation and CAC. P-cadherin expression was markedly induced in the colonic epithelium of human IBD patients and CAC tissues. The roles of P-cadherin were investigated in P-cadherin null mice using dextran sulfate sodium (DSS)-induced colitis and an azoxymethane (AOM)/DSS induced CAC. Although P-cadherin knockout did not affect the severity of acute DSS colitis, P-cadherin null mice exhibited faster recovery after colitis. No significant differences in the number of colonic tumors were observed in P-cadherin null and control mice. Consistently, the CRISPR/Cas9-mediated knockout of P-cadherin in human IEC accelerated epithelial wound healing without affecting cell proliferation. The accelerated migration of P-cadherin depleted IEC was driven by activation of Src kinases, Rac1 GTPase and myosin II motors and was accompanied by transcriptional reprogramming of the cells. Our findings highlight P-cadherin as a negative regulator of IEC motility in vitro and mucosal repair in vivo. In contrast, this protein is dispensable for IEC proliferation and CAC development.

Tumorigenic mesenchymal clusters are less sensitive to moderate osmotic stresses due to low amounts of junctional E-cadherin

The migration of tumorigenic cells is a critical step for metastatic breast cancer progression. Although the role of the extracellular matrix in breast cancer cell migration has been extensively described, the effect of osmotic stress on the migration of tumor breast cohorts remains unclear. Most of our understanding on the effect of osmotic stresses on cell migration comes from studies at the level of the single cell in isolation and does not take cell-cell interactions into account. Here, we study the impact of moderate osmotic stress on the migration of cell clusters composed of either non-tumorigenic or tumorigenic cells. We observe a decrease in migration distance and speed for non-tumorigenic cells but not for tumorigenic ones. To explain these differences, we investigate how osmotic stress impacts the mechanical properties of cell clusters and affects their volumes. Our findings show that tumorigenic mesenchymal cells are less sensitive to osmotic stress than non-tumorigenic cells and suggest that this difference is associated with a lower expression of E-cadherin. Using EGTA treatments, we confirm that the establishment of cell-cell adhesive interactions is a key component of the behavior of cell clusters in response to osmotic stress. This study provides evidence on the low sensitivity of mesenchymal tumorigenic clusters to moderate osmotic stress and highlights the importance of cadherin-based junctions in the response to osmotic stress.

Epithelial Mesenchymal Transition and Immune Response in Metaplastic Breast Carcinoma

Metaplastic breast carcinoma (MBC) is a heterogeneous group of infrequent triple negative (TN) invasive carcinomas with poor prognosis. MBCs have a different clinical behavior from other types of triple negative breast cancer (TNBC), being more resistant to standard chemotherapy. MBCs are an example of tumors with activation of epithelial–mesenchymal transition (EMT). The mechanisms involved in EMT could be responsible for the increase in the infiltrative and metastatic capacity of MBCs and resistance to treatments. In addition, a relationship between EMT and the immune response has been seen in these tumors. In this sense, MBC differ from other TN tumors showing a lower number of tumor-infiltrating lymphocytes (TILS) and a higher percentage of tumor cells expressing programmed death-ligand 1 (PD-L1). A better understanding of the relationship between the immune system and EMT could provide new therapeutic approaches in MBC.

Machine learning reveals mesenchymal breast carcinoma cell adaptation in response to matrix stiffness

Epithelial-mesenchymal transition (EMT) and its reverse process, mesenchymal-epithelial transition (MET), are believed to play key roles in facilitating the metastatic cascade. Metastatic lesions often exhibit a similar epithelial-like state to that of the primary tumour, in particular, by forming carcinoma cell clusters via E-cadherin-mediated junctional complexes. However, the factors enabling mesenchymal-like micrometastatic cells to resume growth and reacquire an epithelial phenotype in the target organ microenvironment remain elusive. In this study, we developed a workflow using image-based cell profiling and machine learning to examine morphological, contextual and molecular states of individual breast carcinoma cells (MDA-MB-231). MDA-MB-231 heterogeneous response to the host organ microenvironment was modelled by substrates with controllable stiffness varying from 0.2kPa (soft tissues) to 64kPa (bone tissues). We identified 3 distinct morphological cell types (morphs) varying from compact round-shaped to flattened irregular-shaped cells with lamellipodia, predominantly populating 2-kPa and >16kPa substrates, respectively. These observations were accompanied by significant changes in E-cadherin and vimentin expression. Furthermore, we demonstrate that the bone-mimicking substrate (64kPa) induced multicellular cluster formation accompanied by E-cadherin cell surface localisation. MDA-MB-231 cells responded to different substrate stiffness by morphological adaptation, changes in proliferation rate and cytoskeleton markers, and cluster formation on bone-mimicking substrate. Our results suggest that the stiffest microenvironment can induce MET.

Tumor spheroids under perfusion within a 3D microfluidic platform reveal critical roles of cell-cell adhesion in tumor invasion

Tumor invasion within the interstitial space is critically regulated by the force balance between cell-extracellular matrix (ECM) and cell-cell interactions. Interstitial flows (IFs) are present in both healthy and diseased tissues. However, the roles of IFs in modulating cell force balance and subsequently tumor invasion are understudied. In this article, we develop a microfluidic model in which tumor spheroids are embedded within 3D collagen matrices with well-defined IFs. Using co-cultured tumor spheroids (1:1 mixture of metastatic and non-tumorigenic epithelial cells), we show that IFs downregulate the cell-cell adhesion molecule E-cadherin on non-tumorigenic cells and promote tumor invasion. Our microfluidic model advances current tumor invasion assays towards a more physiologically realistic model using tumor spheroids instead of single cells under perfusion. We identify a novel mechanism by which IFs can promote tumor invasion through an influence on cell-cell adhesion within the tumor and highlight the importance of biophysical parameters in regulating tumor invasion.

E-cadherin to P-cadherin switching in lobular breast cancer with tubular elements

Loss of E-cadherin expression due to mutation of the CDH1 gene is a characteristic feature of invasive lobular breast cancer (ILBC). Beta-catenin, which binds to the cytoplasmic domain of E-cadherin, is simultaneously downregulated, reflecting disassembly of adherens junctions (AJs) and loss of cell adhesion. E-cadherin to P-cadherin expression switching can rescue AJs and cell adhesion. However, P-cadherin has not been implicated in ILBC, so far. We aimed to characterize 13 ILBCs with exceptional histomorphology, which we termed ILBCs with tubular elements. The CDH1 mutational status was determined by next generation sequencing and whole-genome copy number (CN) profiling. Expression of cadherins was assessed by immunohistochemistry. ILBCs with tubular elements were ER-positive (13/13) and HER2-negative (13/13) and harbored deleterious CDH1 mutations (11/13) accompanied by loss of heterozygosity due to deletion of chromosome 16q22.1 (9/11). E-cadherin expression was lost or reduced in noncohesive tumor cells and in admixed tubular elements (13/13). Beta-catenin expression was lost in noncohesive tumor cells, but was retained in tubular elements (11/13), indicating focal rescue of AJ formation. N-cadherin and R-cadherin were always negative (0/13). Strikingly, P-cadherin was commonly positive (12/13) and immunoreactivity was accentuated in tubular elements. Adjacent lobular carcinoma in situ (LCIS) was always P-cadherin-negative (0/7). In a reference cohort of LCIS specimens, P-cadherin was constantly not expressed (0/25). In a reference cohort of invasive mammary carcinomas, P-cadherin-positive cases (36/268, 13%) were associated with triple-negative nonlobular breast cancer (P < 0.001). Compared with ILBCs from the reference cohort, P-cadherin expression was more common in ILBCs with tubular elements (12/13 versus 7/84, P < 0.001). In summary, E-cadherin to P-cadherin switching occurs in a subset of ILBCs. P-cadherin is the molecular determinant of a mixed-appearing histomorphology in ILBCs with tubular elements.

Active wetting of epithelial tissues

Development, regeneration and cancer involve drastic transitions in tissue morphology. In analogy with the behavior of inert fluids, some of these transitions have been interpreted as wetting transitions. The validity and scope of this analogy are unclear, however, because the active cellular forces that drive tissue wetting have been neither measured nor theoretically accounted for. Here we show that the transition between two-dimensional epithelial monolayers and three-dimensional spheroidal aggregates can be understood as an active wetting transition whose physics differs fundamentally from that of passive wetting phenomena. By combining an active polar fluid model with measurements of physical forces as a function of tissue size, contractility, cell-cell and cell-substrate adhesion, and substrate stiffness, we show that the wetting transition results from the competition between traction forces and contractile intercellular stresses. This competition defines a new intrinsic lengthscale that gives rise to a critical size for the wetting transition in tissues, a striking feature that has no counterpart in classical wetting. Finally, we show that active shape fluctuations are dynamically amplified during tissue dewetting. Overall, we conclude that tissue spreading constitutes a prominent example of active wetting - a novel physical scenario that may explain morphological transitions during tissue morphogenesis and tumor progression.

Jiedu Sangen Decoction Inhibits Migration and Invasion of Colon Cancer SW480 Cells via Suppressing Epithelial Mesenchymal Transition

Jiedu Sangen Decoction (JSD), a traditional Chinese medicine (TCM) formula, has been widely used in China to treat gastrointestinal cancer, especially as an adjuvant therapy in colorectal cancer (CRC) patients. This study aimed to evaluate the efficacy of JSD and Jiedu Sangen aqueous extract (JSAE) in colon cancer cells and explored the underlining mechanisms by cytotoxicity assay, scratch assay, transwell migration assay, matrigel invasion assay, confocal laser scanning microscopy, and western blot analysis. We demonstrated that JSAE inhibited the growth of colon cancer SW480 cells in a dose-dependent manner and JSAE repressed cancer cell migration and invasion. Furthermore, epithelial mesenchymal transition (EMT) was reversed by JSAE via enhancing E-cadherin expression and attenuating protein levels of EMT promoting factors such as N-cadherin, Slug, and ZEB1. These findings provided the first experimental evidence confirming the efficacy of JSAE in repressing invasion and metastasis of CRC and paving a way for the broader use of JSD in clinic.

STAT3-coordinated migration facilitates the dissemination of diffuse large B-cell lymphomas

The motile characteristics and mechanisms that drive the dissemination of diffuse large B-cell lymphoma (DLBCL) are elusive. Here, we show that DLBCL initiates dissemination through activating STAT3-mediated amoeboid migration. Mechanistically, STAT3 activates RHOH transcription, which competes with the RhoGDP dissociation inhibitor RhoGDIγ to activate RhoA. In addition, activated STAT3 regulates microtubule dynamics and releases ARHGEF2 to activate RhoA. Both the JAK inhibitor ruxolitinib and the microtubule stabilizer Taxol suppress DLBCL cell dissemination in vivo. A clinical DLBCL sample analysis shows that STAT3-driven amoeboid movement is particularly important for the transition from stage I to stage II. This study elucidates the mechanism of DLBCL dissemination and progression and highlights the potential of combating advanced DLBCL with a JAK/STAT inhibitor or microtubule stabilizer to reduce DLBCL motility; these findings may have a great impact on the development of patient-tailored treatments for DLBCL.

The mechanism underlying the dissemination of diffuse large B-cell lymphoma (DLBCL) is unclear. Here, the authors show that STAT3 controls amoeboid migration in DLBCL via the transcriptional activation of RHOH, which then releases RhoA from RhoGDIγ-mediated suppression, or via regulating microtubule dynamics to activate RhoA.

Melanoma differentiation-associated gene-7 suppresses human gastric cancer cell invasion and migration

Gastric cancer is one of the most common types of cancer in the world. Patients with gastric cancer often respond poorly to conventional chemotherapies, therefore more comprehensive therapy is required. Melanoma differentiation-associated gene-7 (MDA-7), also termed interleukin-24, is a potent tumor suppressor gene. Numerous studies have demonstrated that MDA-7 suppresses the growth and induces the apoptosis of cancer cells. In the present study, the MDA-7 gene was transfected into human gastric cancer AGS cells using adenovirus. Transwell and wound healing assays were performed to evaluate AGS cell invasion and migration, respectively. Western blotting was used to detect the expression of epithelial (E)-cadherin, cluster of differentiation (CD)44 and matrix metalloproteinase (MMP)-2 and MMP-9 proteins. A recombinant virus package was successfully constructed, and it was verified using western blotting that exogenous MDA-7 was highly expressed in the AGS cells. MDA-7 overexpression inhibited invasion and migration, decreased CD44, MMP-2 and MMP-9 expression, and increased epithelial (E-)cadherin expression in the AGS cells. Results of the present study revealed that MDA-7 inhibits gastric cancer invasion and metastasis by inhibiting CD44, MMP-2 and MMP-9 expression and by promoting E-cadherin expression.

Exclusion from spheroid formation identifies loss of essential cell-cell adhesion molecules in colon cancer cells

Many cell lines derived from solid cancers can form spheroids, which recapitulate tumor cell clusters and are more representative of the in vivo situation than 2D cultures. During spheroid formation, a small proportion of a variety of different colon cancer cell lines did not integrate into the sphere and lost cell-cell adhesion properties. An enrichment protocol was developed to augment the proportion of these cells to 100% purity. The basis for the separation of spheroids from non-spheroid forming (NSF) cells is simple gravity-sedimentation. This protocol gives rise to sub-populations of colon cancer cells with stable loss of cell-cell adhesion. SW620 cells lacked E-cadherin, DLD-1 cells lost α-catenin and HCT116 cells lacked P-cadherin in the NSF state. Knockdown of these molecules in the corresponding spheroid-forming cells demonstrated that loss of the respective proteins were indeed responsible for the NSF phenotypes. Loss of the spheroid forming phenotype was associated with increased migration and invasion properties in all cell lines tested. Hence, we identified critical molecules involved in spheroid formation in different cancer cell lines. We present here a simple, powerful and broadly applicable method to generate new sublines of tumor cell lines to study loss of cell-cell adhesion in cancer progression.

Slug/Pcad pathway controls epithelial cell dynamics in mammary gland and breast carcinoma

Mammary gland morphogenesis results from the coordination of proliferation, cohort migration, apoptosis and stem/progenitor cell dynamics. We showed earlier that the transcription repressor Slug is involved in these functions during mammary tubulogenesis. Slug is expressed by a subpopulation of basal epithelial cells, co-expressed with P-cadherin (Pcad). Slug-knockout mammary glands showed excessive branching, similarly to Pcad-knockout. Here, we found that Slug unexpectedly binds and activates Pcad promoter through E-boxes, inducing Pcad expression. We determined that Pcad can mediate several functions of Slug: Pcad promoted clonal mammosphere growth, basal epithelial differentiation, cell-cell dissociation and cell migration, rescuing Slug depletion. Pcad also promoted cell migration in isolated cells, in association with Src activation, focal adhesion reorganization and cell polarization. Pcad, similarly to Slug, was required for in vitro 3D tubulogenesis. Therefore, Pcad appears to be responsible for epithelial-mesenchymal transition-linked plasticity in mammary epithelial cells. In addition, we found that genes from the Slug/Pcad pathway components were co-expressed and specifically correlated in human breast carcinomas subtypes, carrying pathophysiological significance.

Inflammatory breast cancer: a model for investigating cluster-based dissemination

Metastases claim more than 90% of cancer-related patient deaths and are usually seeded by a subset of circulating tumor cells shed off from the primary tumor. In circulation, circulating tumor cells are found both as single cells and as clusters of cells. The clusters of circulating tumor cells, although many fewer in number, possess much higher metastatic potential as compared to that of individual circulating tumor cells. In this review, we highlight recent insights into molecular mechanisms that can enable the formation of these clusters—(a) hybrid epithelial/mesenchymal phenotype of cells that couples their ability to migrate and adhere, and (b) intercellular communication that can spatially coordinate the cluster formation and provide survival signals to cancer cells. Building upon these molecular mechanisms, we also offer a possible mechanistic understanding of why clusters are endowed with a higher metastatic potential. Finally, we discuss the highly aggressive Inflammatory Breast Cancer as an example of a carcinoma that can metastasize via clusters and corroborates the proposed molecular mechanisms.

The role of Slit-Robo signaling in the regulation of tissue barriers

The role of Slit/Robo signaling has extended from initial axon repulsion in the developing nervous system to organ morphogenesis, cancer development and angiogenesis. Slit/Robo signaling regulates similar pathways within these processes. Slit/Robo ensures the homeostasis of the dynamic interaction between cell-cell and cell-matrix interactions. The dysregulation of Slit/Robo signaling damages the tissue barrier, resulting in developmental abnormalities or disease. Here, we summarize how Slit/Robo controls kidney morphogenesis and describe the dual roles of Slit/Robo signaling in the regulation of tumorigenesis and angiogenesis.

Identification of Novel Signal Transduction, Immune Function, and Oxidative Stress Genes and Pathways by Topiramate for Treatment of Methamphetamine Dependence Based on Secondary Outcomes

BACKGROUND

Topiramate (TPM) is suggested to be a promising medication for treatment of methamphetamine (METH) dependence, but the molecular basis remains to be elucidated.

METHODS

Among 140 METH-dependent participants randomly assigned to receive either TPM (N = 69) or placebo (N = 71) in a previously conducted randomized controlled trial, 50 TPM- and 49 placebo-treated participants had a total 212 RNA samples available at baseline, week 8, and week 12 time points. Following our primary analysis of gene expression data, we reanalyzed the microarray expression data based on a latent class analysis of binary secondary outcomes during weeks 1-12 that provided a classification of 21 responders and 31 non-responders with consistent responses at both time points.

RESULTS

Based on secondary outcomes, 1,381, 576, 905, and 711 differentially expressed genes at nominal P values < 0.05 were identified in responders versus non-responders for week 8 TPM, week 8 placebo, week 12 TPM, and week 12 placebo groups, respectively. Among 1,381 genes identified in week 8 TPM responders, 359 genes were identified in both week 8 and week 12 TPM groups, of which 300 genes were exclusively detected in TPM responders. Of them, 32 genes had nominal P values < 5 × 10^-3 at either week 8 or week 12 and false discovery rates < 0.15 at both time points with consistent directions of gene expression changes, which include GABARAPL1, GPR155, and IL15RA in GABA receptor signaling that represent direct targets for TPM. Analyses of these 300 genes revealed 7 enriched pathways belonging to neuronal function/synaptic plasticity, signal transduction, inflammation/immune function, and oxidative stress response categories. No pathways were enriched for 72 genes exclusively detected in both week 8 and week 12 placebo groups.

CONCLUSION

This secondary analysis study of gene expression data from a TPM clinical trial not only yielded consistent results with those of primary analysis but also identified additional new genes and pathways on TPM response to METH addiction.

E-cadherin downregulation sensitizes PTEN-mutant tumors to PI3Kβ silencing

Alterations in phosphatidylinositol 3-kinase (PI3K) and in PTEN (phosphatase and tensin homolog), the negative regulator of the PI3K pathway, are found in nearly half of human tumors. As PI3Kβ, the main isoform activated in PTEN-mutant tumors, has kinase-dependent and -independent activities, we compared the effects of depleting vs. drug-inhibiting PI3Kβ kinase activity in a collection of diverse tumor types and in a set of bladder carcinoma cell lines grown as xenografts in mice. PI3Kβ depletion (by intratumor injection of PIK3CB siRNA) induced apoptosis and triggered regression of PTEN-mutant tumors more efficiently than PI3Kβ inhibition. A small proportion of these tumors was resistant to PI3Kβ downregulation; we analyzed what determined resistance in these cases. Using add-back experiments, we show that both PTEN mutation and low E-cadherin expression are necessary for PI3Kβ dependence. In bladder carcinoma, loss of E-cadherin expression coincides with N-cadherin upregulation. We found that PI3Kβ associated with N-cadherin and that PIK3CB depletion selectively disrupted N-cadherin cell adhesions in PTEN-mutant bladder carcinoma. These results support the use of PIK3CB interfering RNA as a therapeutic approach for high-risk bladder cancers that show E-cadherin loss and express mutant PTEN.

Microelectrode bioimpedance analysis distinguishes basal and claudin-low subtypes of triple negative breast cancer cells

Triple negative breast cancer (TNBC) is highly aggressive and has a poor prognosis when compared to other molecular subtypes. In particular, the claudin-low subtype of TNBC exhibits tumor-initiating/cancer stem cell like properties. Here, we seek to find new biomarkers to discriminate different forms of TNBC by characterizing their bioimpedance. A customized bioimpedance sensor with four identical branched microelectrodes with branch widths adjusted to accommodate spreading of individual cells was fabricated on silicon and pyrex/glass substrates. Cell analyses were performed on the silicon devices which showed somewhat improved inter-electrode and intra-device reliability. We performed detailed analysis of the bioimpedance spectra of four TNBC cell lines, comparing the peak magnitude, peak frequency and peak phase angle between claudin-low TNBC subtype represented by MDA-MB-231 and Hs578T with that of two basal cells types, the TNBC MDA-MB-468, and an immortalized non-malignant basal breast cell line, MCF-10A. The claudin-low TNBC cell lines showed significantly higher peak frequencies and peak phase angles than the properties might be useful in distinguishing the clinically significant claudin-low subtype of TNBC.

Cell adhesion and urothelial bladder cancer: the role of cadherin switching and related phenomena

Cadherins are mediators of cell-cell adhesion in epithelial tissues. E-cadherin is a known tumour suppressor and plays a central role in suppressing the invasive phenotype of cancer cells. However, the abnormal expression of N- and P-cadherin ('cadherin switching', CS) has been shown to promote a more invasive and m̀alignant phenotype of cancer, with P-cadherin possibly acting as a key mediator of invasion and metastasis in bladder cancer. Cadherins are also implicated in numerous signalling events related to embryonic development, tissue morphogenesis and homeostasis. It is these wide ranging effects and the serious implications of CS that make the cadherin cell adhesion molecules and their related pathways strong candidate targets for the inhibition of cancer progression, including bladder cancer. This review focuses on CS in the context of bladder cancer and in particular the switch to P-cadherin expression, and discusses other related molecules and phenomena, including EpCAM and the development of the cancer stem cell phenotype.

Active Tensile Modulus of an Epithelial Monolayer

A general trait of cell monolayers is their ability to exert contractile stresses on their surroundings. The scaling laws that link such contractile stresses with the size and geometry of constituent cells remain largely unknown. In this Letter, we show that the active tension of an epithelial monolayer scales linearly with the size of the constituent cells, a surprisingly simple relationship. The slope of this relationship defines an active tensile modulus, which depends on the concentration of myosin and spans more than 2 orders of magnitude across cell types and molecular perturbations.

Review: Cell Dynamics in Malignant Pleural Effusions

Malignant pleural effusions (MPEs) are a common manifestation found in patients with lung cancer. After cytological and histological confirmation of malignancy, talc pleurodesis still remains the treatment of choice in patients with MPEs resistant to chemotherapy. Despite this, primary challenges include reduced quality of life and life expectancy in general. Therefore, a better understanding of the cell biology of MPEs, along with improvements in treatment is greatly needed. It has recently been demonstrated that MPEs may represent an excellent source for identification of molecular mechanisms within the tumor and its environment. The present review summarizes the current understanding of MPEs cells and tumor microenvironment, and particularly focuses on dissecting the cross-talk between MPEs and epithelial to mesenchymal transition (EMT), inflammation and cancer stem cells.

P-cadherin and the journey to cancer metastasis

P-cadherin is a classical cell-to-cell adhesion molecule with a homeostatic function in several normal tissues. However, its behaviour in the malignant setting is notably dependent on the cellular context. In some tumour models, such as melanoma and oral squamous cell carcinoma, P-cadherin acts as a tumour suppressor, since its absence is associated with a more aggressive cancer cell phenotype; nevertheless, the overexpression of this molecule is linked to significant tumour promoting effects in the breast, ovarian, prostate, endometrial, skin, gastric, pancreas and colon neoplasms. Herein, we review the role of P-cadherin in cancer cell invasion, as well as in loco-regional and distant metastatic dissemination. We focus in P-cadherin signalling pathways that are activated to induce invasion and metastasis, as well as cancer stem cell properties. The signalling network downstream of P-cadherin is notably dependent on the cellular and tissue context and includes the activation of integrin molecules, receptor tyrosine kinases, small molecule GTPases, EMT transcription factors, and crosstalk with other cadherin family members. As new oncogenic molecular pathways mediated by P-cadherin are uncovered, putative therapeutic options can be tested, which will allow for the targeting of invasion or metastatic disease, depending on the tumour model.

Expression array analysis of the hepatocyte growth factor invasive program

Signaling by human hepatocyte growth factor (hHGF) via its cell surface receptor (MET) drives mitogenesis, motogenesis and morphogenesis in a wide spectrum of target cell types and embryologic, developmental and homeostatic contexts. Oncogenic pathway activation also contributes to tumorigenesis and cancer progression, including tumor angiogenesis and metastasis, in several prevalent malignancies. The HGF gene encodes full-length hHGF and two truncated isoforms known as NK1 and NK2. NK1 induces all three HGF activities at modestly reduced potency, whereas NK2 stimulates only motogenesis and enhances HGF-driven tumor metastasis in transgenic mice. Prior studies have shown that mouse HGF (mHGF) also binds with high affinity to human MET. Here we show that, like NK2, mHGF stimulates cell motility, invasion and spontaneous metastasis of PC3M human prostate adenocarcinoma cells in mice through human MET. To identify target genes and signaling pathways associated with motogenic and metastatic HGF signaling, i.e., the HGF invasive program, gene expression profiling was performed using PC3M cells treated with hHGF, NK2 or mHGF. Results obtained using Ingenuity Pathway Analysis software showed significant overlap with networks and pathways involved in cell movement and metastasis. Interrogating The Cancer Genome Atlas project also identified a subset of 23 gene expression changes in PC3M with a strong tendency for co-occurrence in prostate cancer patients that were associated with significantly decreased disease-free survival.

MicroRNA-10b Triggers the Epithelial-Mesenchymal Transition (EMT) of Laryngeal Carcinoma Hep-2 Cells by Directly Targeting the E-cadherin

Laryngeal carcinoma is the second most common malignancy of the head and neck squamous cell carcinoma. Therefore, there is an urgent need to understand the molecular mechanism of its metastasis. The present study was designed to investigate effects of miR-10b on the invasion and migration of laryngeal Hep-2 cells. We found that miR-10b had limited effects on cell proliferation; however, it can significantly promote the migration and invasion of Hep-2 cells. Further studies revealed that overexpression of miR-10b can induce the epithelial-mesenchymal transition (EMT) of Hep-2 cells by acquiring mesenchymal spindle-like morphology and increasing the expression of N-cadherin (N-Cad) with a concomitant decrease of E-cadherin (E-Cad). However, the messenger RNA (mRNA) and protein level of transcription factors such as Snail, Slug, Twist and ZEB was not changed during this process. Bioinformatic analysis revealed that miR-10b can directly target CDH1 (E-Cad gene) at nucleotides 461 and 481 within the 3'-UTR. This was confirmed by the results that miR-10 downregulated the protein and mRNA levels of E-Cad via a time-dependent manner and luciferase analysis by use of four-nucleotide substitution in the core binding sites. The present study provided a better understanding of laryngeal carcinoma metastasis and the roles of miR-10b during this process.

P-Cadherin Linking Breast Cancer Stem Cells and Invasion: A Promising Marker to Identify an "Intermediate/Metastable" EMT State

Epithelial–mesenchymal transition (also known as EMT) is a fundamental mechanism occurring during embryonic development and tissue differentiation, being also crucial for cancer progression. Actually, the EMT program contributes to the dissemination of cancer cells from solid tumors and to the formation of micro-metastasis that subsequently develop into clinically detectable metastases. Besides being a process that is defined by the progressive loss of epithelial cell characteristics and the acquisition of mesenchymal features, EMT has also been implicated in therapy resistance, immune escape, and maintenance of cancer stem cell properties, such as self-renewal capacity. However, the majority of the studies usually neglect the progressive alterations occurring during intermediate EMT states, which imply a range of phenotypic cellular heterogeneity that can potentially generate more metastable and plastic tumor cells. In fact, few studies have tried to identify these transitory states, partly due to the current lack of a detailed understanding of EMT, as well as of reliable readouts for its progression. Herein, a brief review of evidences is presented, showing that P-cadherin expression, which has been already identified as a breast cancer stem cell marker and invasive promoter, is probably able to identify an intermediate EMT state associated with a metastable phenotype. This hypothesis is based on our own work, as well as on the results described by others, which suggest the use of P-cadherin as a promising EMT marker, clearly functioning as an important clinical prognostic factor and putative therapeutic target in breast carcinogenesis.

The tetraindole SK228 reverses the epithelial-to-mesenchymal transition of breast cancer cells by up-regulating members of the miR-200 family

The results of recent studies have shown that metastasis, the most common malignancy and primary cause of mortality promoted by breast cancer in women, is associated with the epithelial-to-mesenchymal transition (EMT). The results of the current study show that SK228, a novel indole containing substance, exhibits anti-cancer activity. In addition, the effects of SK228 on the regulation of EMT in breast cancer cells as well as the underlying mechanism have been explored. SK228 was observed to induce a fibroblastoid to epithelial-like change in the appearance of various breast cancer cell lines and to suppress the migration and invasion of these cancer cells in vitro. Moreover, expression of E-cadherin was found to increase following SK228 treatment whereas ZEB1 expression was repressed. Expression of other major EMT inducers, including ZEB2, Slug and Twist1, is also repressed by SK228 as a consequence of up-regulation of members of the miR-200 family, especially miR-200c. The results of animal studies demonstrate that SK228 treatment leads to effective suppression of breast cancer growth and metastasis in vivo. The observations made in this investigation show that SK228 reverses the EMT process in breast cancer cells via an effect on the miR-200c/ZEB1/E-cadherin signalling pathway. In addition, the results of a detailed analysis of the in vivo anti-cancer activities of SK228, carried out using a breast cancer xenograft animal model, show that this substance is a potential chemotherapeutic agent for the treatment of breast cancer.

Brain metastases from lung cancer show increased expression of DVL1, DVL3 and beta-catenin and down-regulation of E-cadherin

The susceptibility of brain to secondary formation from lung cancer primaries is a well-known phenomenon. In contrast, the molecular basis for invasion and metastasis to the brain is largely unknown. In the present study, 31 brain metastases that originated from primary lung carcinomas were analyzed regarding over expression of Dishevelled-1 (DVL1), Dishevelled-3 (DVL3), E-cadherin (CDH1) and beta-catenin (CTNNB1). Protein expressions and localizations were analyzed by immunohistochemistry. Genetic alterations of E-cadherin were tested by polymerase chain reaction (PCR)/loss of heterozygosity (LOH). Heteroduplex was used to investigate mutations in beta-catenin. DVL1 and DVL3 showed over expression in brain metastasis in 87.1% and 90.3% of samples respectively. Nuclear staining was observed in 54.8% of cases for DVL1 and 53.3% for DVL3. The main effector of the Wnt signaling, beta-catenin, was up-regulated in 56%, and transferred to the nucleus in 36% of metastases. When DVL1 and DVL3 were up-regulated the number of cases with nuclear beta-catenin significantly increased (p=0.0001). Down-regulation of E-cadherin was observed in 80% of samples. Genetic analysis showed 36% of samples with LOH of the CDH1. In comparison to other lung cancer pathologies, the diagnoses adenocarcinoma and small cell lung cancer (SCLC) were significantly associated to CDH1 LOH (p=0.001). Microsatellite instability was detected in one metastasis from adenocarcinoma. Exon 3 of beta-catenin was not targeted. Altered expression of Dishevelled-1, Dishevelled-3, E-cadherin and beta-catenin were present in brain metastases which indicates that Wnt signaling is important and may contribute to better understanding of genetic profile conditioning lung cancer metastasis to the brain.

MiR-203 is downregulated in laryngeal squamous cell carcinoma and can suppress proliferation and induce apoptosis of tumours

MicroRNAs (miRNAs) have been recognised to regulate cancer development and progression in carcinogenesis as either oncogenes or tumour suppressor genes. However, whether miR-203 plays a crucial role in human laryngeal squamous cell carcinoma (LSCC) remains largely unclear. In the study, we have found that miR-203 expression was significantly lower in LSCC tissues than that in corresponding adjacent non-neoplastic tissues and was negatively correlated with ASAP1 expression level. Lower expression of miR-203 was significantly related to poor differentiation, advanced clinical stages, T3-4 tumour grade, lymph node metastasis and decreased 5-year overall survival. Transfection with miR-203 inhibited proliferation, reduced invasion, induced apoptosis and caused G1 phase cell cycle arrest of Hep-2 cells in vitro, suggesting that miR-203 functioned as a tumour suppressor. We have also tested that over-expression of miR-203 may both suppress the growth of xenograft tumours in mice and downregulate the expressions of ASAP1 in vivo. Furthermore, miR-203 may regulate the expressions of mesenchymal transition (EMT) marker of E-cadherin and cancer stem cells (CSCs) marker of CD44. These findings suggest that miR-203 plays a role as a tumour suppressor in LSCC, likely by regulating ASAP1, probably in relation to EMT and CSCs and may serve as a potential target for therapeutic intervention.

Ductal barriers in mammary epithelium

Tissue barriers play an integral role in the biology and pathobiology of mammary ductal epithelium. In normal breast physiology, tight and adherens junctions undergo dynamic changes in permeability in response to hormonal and other stimuli, while several of their proteins are directly involved in mammary tumorigenesis. This review describes first the structure of mammary ductal epithelial barriers and their role in normal mammary development, examining the cyclical changes in response to puberty, pregnancy, lactation and involution. It then examines the role of adherens and tight junctions and the participation of their constituent proteins in mammary tumorigenic functions such as migration, invasion and metastasis. Finally, it discusses the potential of these adhesion proteins as both prognostic biomarkers and potential therapeutic targets in breast cancer.

P-cadherin functional role is dependent on E-cadherin cellular context: a proof of concept using the breast cancer model

P-cadherin overexpression is associated with worse breast cancer survival, being a poor prognostic marker as well as a putative therapeutic target for the aggressive triple-negative and basal-like carcinomas (TNBCs). Previously, we have shown that P-cadherin promotes breast cancer invasion of cells where membrane E-cadherin was maintained; however, it suppresses invasion in models without endogenous cadherins, like melanomas. Here, we investigated if P-cadherin expression would interfere with the normal adhesion complex and which were the cellular/molecular consequences, constituting, in this way, a new mechanism by which E-cadherin invasive-suppressor function was disrupted. Using breast TNBC models, we demonstrated, for the first time, that P-cadherin co-localizes with E-cadherin, promoting cell invasion due to the disruption caused in the interaction between E-cadherin and cytoplasmic catenins. P-cadherin also induces cell migration and survival, modifying the expression profile of cells expressing wild-type E-cadherin and contributing to alter their cellular behaviour. Additionally, E- and P-cadherin co-expressing cells significantly enhanced in vivo tumour growth, compared with cells expressing only E- or only P-cadherin. Finally, we still found that co-expression of both molecules was significantly correlated with high-grade breast carcinomas, biologically aggressive, and with poor patient survival, being a strong prognostic factor in this disease. Our results show a role for E- and P-cadherin co-expression in breast cancer progression and highlight the potential benefit of targeting P-cadherin in the aggressive tumours expressing high levels of this protein.

Induction of EMT-like response by BMP4 via up-regulation of lysyl oxidase is required for adipocyte lineage commitment

The developmental pathway that gives rise to mature adipocytes involves commitment and terminal differentiation. Our previous findings indicate that BMP4 (bone morphogenetic protein 4) induces nearly complete commitment of C3H10T1/2 pluripotent stem cells to the adipocyte lineage and knockdown of lysyl oxidase (Lox) disrupts this commitment process. Here, we found that an epithelial-mesenchymal transition (EMT)-like response is required for adipocyte lineage commitment and that Lox is indispensable for this process. When C3H10T1/2 cells were treated with BMP4, Vim and Cdh2 showed up-regulated expression while Cdh1 and Ocln were down-regulated along with enhanced cell migration, which are EMT-like responses. Silencing of Lox in BMP4-treated C3H10T1/2 cells induced a mesenchymal-epithelial transition (MET)-like response associated with the repression of mesenchymal markers, induction of epithelial markers and decreased cell migration. Importantly, blocking the EMT-like response by knocking down Cdh2 or over-expression of Cdh1 impairs adipocyte lineage commitment. EMT is regulated by distinct transcription factors such as Snai1, Snai2 and Twist. In this study, we also found that only Twist was down-regulated after Lox silencing in C3H10T1/2 cells treated with BMP4. This study provides new insights into adipocyte lineage commitment.

MicroRNA-10b targets E-cadherin and modulates breast cancer metastasis

BACKGROUND

Recent studies have suggested that microRNA-10b (miR-10b) acts as a promoter of metastasis in breast cancer, although the underlying mechanism remains largely unknown. In this study, we provide the first evidence that E-cadherin (E-cad) is a potential target of miR-10b.

MATERIAL/METHOD

By applying gain-of-function and loss-of-function approaches in the metastatic breast cancer cell line MDA-MB-231, we demonstrated that miR-10b is necessary and sufficient to regulate the cellular expression of E-cad and in vitro tumor cell invasion.

RESULTS

Comparative expression analysis of miR-10b in benign breast lesions (N=16), primary breast cancers (N=21), and metastatic breast carcinomas (N=23) revealed that miR-10b transcription was uniquely up-regulated in metastatic cancers. The expression level of miR-10b positively correlated with tumor size, pathological grading, clinical staging, lymph node metastasis, Her2-positivity and tumor proliferation, but was negatively associated with estrogen receptor-positivity, progesterone receptor-positivity and E-cad mRNA and protein levels.

CONCLUSIONS

These findings indicate the existence of a novel E-cadherin-related mechanism by which miR-10b modulates breast cancer metastasis. In addition, miR-10b may be a useful biomarker of advanced progression and metastasis of breast cancer.

Epithelial E- and P-cadherins: role and clinical significance in cancer

E-cadherin and P-cadherin are major contributors to cell-cell adhesion in epithelial tissues, playing pivotal roles in important morphogenetic and differentiation processes during development, and in maintaining integrity and homeostasis in adult tissues. It is now generally accepted that alterations in these two molecules are observed during tumour progression of most carcinomas. Genetic or epigenetic alterations in E- and P-cadherin-encoding genes (CDH1 and CDH3, respectively), or alterations in their proteins expression, often result in tissue disorder, cellular de-differentiation, increased invasiveness of tumour cells and ultimately in metastasis. In this review, we will discuss the major properties of E- and P-cadherin molecules, its regulation in normal tissue, and their alterations and role in cancer, with a specific focus on gastric and breast cancer models.

MicroRNA-30a inhibits cell migration and invasion by downregulating vimentin expression and is a potential prognostic marker in breast cancer

Tumor recurrence and metastasis result in an unfavorable prognosis for cancer patients. Recent studies have suggested that specific microRNAs (miRNAs) may play important roles in the development of cancer cells. However, prognostic markers and the outcome prediction of the miRNA signature in breast cancer patients have not been comprehensively assessed. The aim of this study was to identify miRNA biomarkers relating to clinicopathological features and outcome of breast cancer. A miRNA microarray analysis was performed on breast tumors of different lymph node metastasis status and with different progression signatures, indicated by overexpression of cyclin D1 and β-catenin genes, to identify miRNAs showing a significant difference in expression. The functional interaction between the candidate miRNA, miR-30a, and the target gene, Vim, which codes for vimentin, a protein involved in epithelial-mesenchymal transition, was examined using the luciferase reporter assay, western blotting, and migration and invasion assays. The association between the decreased miR-30a levels and breast cancer progression was examined in a survival analysis. miR-30a negatively regulated vimentin expression by binding to the 3'-untranslated region of Vim. Overexpression of miR-30a suppressed the migration and invasiveness phenotypes of breast cancer cell lines. Moreover, reduced tumor expression of miR-30a in breast cancer patients was associated with an unfavorable outcome, including late tumor stage, lymph node metastasis, and worse progression (mortality and recurrence) (p < 0.05). In conclusion, these findings suggest a role for miR-30a in inhibiting breast tumor invasiveness and metastasis. The finding that miR-30a downmodulates vimentin expression might provide a therapeutic target for the treatment of breast cancer.

P-cadherin expression and basal-like subtype in breast cancers

Breast cancer is considered as one of the multifactorial diseases. The aim of the current study is to investigate the association between P-cadherin and molecular subtypes of breast cancer, especially the basal-like subtype. Two hundred and thirteen breast-invasive ductal carcinomas were involved in this study. The expressions of P-cadherin were detected via immunohistochemistry. The 213 cases were divided into luminal A, luminal B, HER2 overexpression subtype, and normal breast-like and basal-like subtypes according to the standard of molecular breast cancer subtypes. In addition, the expressions of CK5/6 and CK14 were detected to distinguish between the normal breast-like and the basal-like subtypes. P-cadherin expression was found in 91 cases of 213 breast-invasive ductal carcinomas, with a positive rate of 42.7%. P-cadherin correlated negatively with estrogen receptor (ER) (p=0.001) and progesterone receptor (p=0.001), whereas it positively correlated with histologic grade (p=0.003), NPI (p=0.005), p53 (p=0.038), and Ki67 (p=0.022). P-cadherin expression showed a strong correlation with recurrence and distant metastasis (p=0.009), and invasion of the vascular and soft tissues (p=0.004). Moreover, P-cadherin expression existed in the basal-like and non-basal-like subtypes. During prognosis, P-cadherin expression was associated with decreased disease-free survival in patients (p=0.009) and overall survival (OS) (p=0.005). In addition, multivariate analysis showed that tumor grade (p=0.021), ER (p=0.015), clinical stage (p=0.001), and P-cadherin (p=0.033) were significant predictors of OS. The current data suggest that P-cadherin may be used to distinguish the basal-like subtype and to predict the outcome in view of the relationship with DFS and OS. Furthermore, P-cadherin expression may be useful in making treatment decisions.

Quantitative and robust assay to measure cell-cell contact assembly and maintenance

Epithelial junction formation and maintenance are multistep processes that rely on the clustering of macromolecular complexes. These events are highly regulated by signalling pathways that involve Rho small GTPases. Usually, when analysing the contribution of different components of Rho-dependent pathways to cell-cell adhesion, the localisation of adhesion receptors at junctions is evaluated by immunofluorescence. However, we find that this method has limitations on the quantification (dynamic range), ability to detect partial phenotypes and to differentiate between the participation of a given regulatory protein in assembly and/or maintenance of cell-cell contacts.In this chapter, we describe a suitable method, the aggregation assay, in which we adapted a quantitative strategy to allow objective and reproducible detection of partial phenotypes. Importantly, this methodology estimates the ability of cells to form junctions and their resistance to mechanical shearing forces (stabilisation).

Targets of the tumor suppressor miR-200 in regulation of the epithelial-mesenchymal transition in cancer

The microRNA-200 (miR-200) family restricts epithelial-mesenchymal transition (EMT) and metastasis in tumor cell lines derived from mice that develop metastatic lung adenocarcinoma. To determine the mechanisms responsible for EMT and metastasis regulated by this microRNA, we conducted a global liquid chromatography/tandem mass spectrometry analysis to compare metastatic and nonmetastatic murine lung adenocarcinoma cells which had undergone EMT because of loss of miR-200. An analysis of syngeneic tumors generated by these cells identified multiple novel proteins linked to metastasis. In particular, the analysis of conditioned media, cell surface proteins, and whole-cell lysates from metastatic and nonmetastatic cells revealed large-scale modifications in the tumor microenvironment. Specific increases were documented in extracellular matrix (ECM) proteins, peptidases, and changes in distribution of cell adhesion proteins in the metastatic cell lines. Integrating proteomic data from three subproteomes, we defined constituents of a multilayer protein network that both regulated and mediated the effects of TGFβ. Lastly, we identified ECM proteins and peptidases that were directly regulated by miR-200. Taken together, our results reveal how expression of miR-200 alters the tumor microenvironment to inhibit the processes of EMT and metastasis.

A novel human ghrelin variant (In1-ghrelin) and ghrelin-O-acyltransferase are overexpressed in breast cancer: potential pathophysiological relevance

The human ghrelin gene, which encodes the ghrelin and obestatin peptides, contains 5 exons (Ex), with Ex1-Ex4 encoding a 117 amino-acid (aa) preproprotein that is known to be processed to yield a 28-aa (ghrelin) and/or a 23-aa (obestatin) mature peptides, which possess biological activities in multiple tissues. However, the ghrelin gene also encodes additional peptides through alternative splicing or post-translational modifications. Indeed, we previously identified a spliced mRNA ghrelin variant in mouse (In2-ghrelin-variant), which is regulated in a tissue-dependent manner by metabolic status and may thus be of biological relevance. Here, we have characterized a new human ghrelin variant that contains Ex0-1, intron (In) 1, and Ex2 and lacks Ex3-4. This human In1-ghrelin variant would encode a new prepropeptide that conserves the first 12aa of native-ghrelin (including the Ser3-potential octanoylation site) but has a different C-terminal tail. Expression of In1-variant was detected in 22 human tissues and its levels were positively correlated with those of ghrelin-O-acyltransferase (GOAT; p = 0.0001) but not with native-ghrelin expression, suggesting that In1-ghrelin could be a primary substrate for GOAT in human tissues. Interestingly, levels of In1-ghrelin variant expression in breast cancer samples were 8-times higher than those of normal mammary tissue, and showed a strong correlation in breast tumors with GOAT (p = 0.0001), ghrelin receptor-type 1b (GHSR1b; p = 0.049) and cyclin-D3 (a cell-cycle inducer/proliferation marker; p = 0.009), but not with native-ghrelin or GHSR1a expression. Interestingly, In1-ghrelin variant overexpression increased basal proliferation of MDA-MB-231 breast cancer cells. Taken together, our results provide evidence that In1-ghrelin is a novel element of the ghrelin family with a potential pathophysiological role in breast cancer.

Estrogen receptor silencing induces epithelial to mesenchymal transition in human breast cancer cells

We propose the hypothesis that loss of estrogen receptor function which leads to endocrine resistance in breast cancer, also results in trans-differentiation from an epithelial to a mesenchymal phenotype that is responsible for increased aggressiveness and metastatic propensity. siRNA mediated silencing of the estrogen receptor in MCF7 breast cancer cells resulted in estrogen/tamoxifen resistant cells (pII) with altered morphology, increased motility with rearrangement and switch from a keratin/actin to a vimentin based cytoskeleton, and ability to invade simulated components of the extracellular matrix. Phenotypic profiling using an Affymetrix Human Genome U133 plus 2.0 GeneChip indicated geometric fold changes ≥ 3 in approximately 2500 identifiable unique sequences, with about 1270 of these being up-regulated in pII cells. Changes were associated with genes whose products are involved in cell motility, loss of cellular adhesion and interaction with the extracellular matrix. Selective analysis of the data also showed a shift from luminal to basal cell markers and increased expression of a wide spectrum of genes normally associated with mesenchymal characteristics, with consequent loss of epithelial specific markers. Over-expression of several peptide growth factors and their receptors are indicative of an increased contribution to the higher proliferative rates of pII cells as well as aiding their potential for metastatic activity. Signalling molecules that have been identified as key transcriptional drivers of epithelial to mesenchymal transition were also found to be elevated in pII cells. These data support our hypothesis that induced loss of estrogen receptor in previously estrogen/antiestrogen sensitive cells is a trigger for the concomitant loss of endocrine dependence and onset of a series of possibly parallel events that changes the cell from an epithelial to a mesenchymal type. Inhibition of this transition through targeting of specific mediators may offer a useful supplementary strategy to circumvent the effects of loss of endocrine sensitivity.

The cadherin switch in ovarian high-grade serous carcinoma is associated with disease progression

Ovarian high-grade serous carcinoma (HGSC) often has a poor prognosis because of late presentation, lack of sensitivity and specificity of screening modalities and the development of chemoresistance. New targeted therapy is required if survival in these cases is to improve. The profile of E-, P- and N-cadherins in ovarian cancer and its association with survival remain poorly understood. Reduced expression of E-cadherin in prostate cancer associated with increase in the expression of N- and P-cadherins is described as cadherin switch. We hypothesised that there is a switch in the expression of cadherins that regulates the behaviour of HGSC and possibly its outcome. To identify the stages of the cadherin switch in HGSC, we studied the immunoexpression of E-, P- and N-cadherins in a cohort of 177 cases of HGSC. High expression of P-cadherin was associated with poor patient survival and was significantly higher in stage 2 disease when compared with stage 1 and stage 3 disease (P = 0.033). In contrast, loss of E-cadherin was observed in stage 3 HGSC when compared with other stages (P = 0.050). E-, P- and N- cadherin expressions were significantly associated with disease outcome when assessed individually and in various combinations with an interesting profile. Our results indicate that the cadherin switch alters through progression of HGSC. The profile of combined cadherin expressions in association with survival raises expectations in targeted therapy.

P-cadherin expression as a prognostic biomarker in a 3992 case tissue microarray series of breast cancer

P-cadherin is a calcium-dependent cell-cell adhesion glycoprotein. P-cadherin expression is restricted to the myoepithelial cells in normal breast tissue, and aberrant staining has also been described in invasive tumors. Several small studies have reported P-cadherin as a marker of poor outcome in breast cancer patients but its prognostic significance in relation to other variables has not been established in a large series of breast cancers. A tissue microarray was constructed from 3992 cases of invasive breast carcinoma, and P-cadherin expression was evaluated using immunohistochemistry. Median follow-up was 12.5 years. The immunohistochemistry-based definitions of cancer subtypes were luminal (ER+ or PR+/HER2-), luminal/HER2+ (ER+ or PR+/HER2+), HER2+ (ER-/PR-/HER2+), and basal (ER-/PR-/HER2-/CK5/6+ or EGFR+). Clinical covariate and biomarker associations were assessed using contingency tables, and Pearson's χ(2) or Fisher's exact test. Survival associations were assessed using Kaplan-Meier plots, logrank and Breslow tests, and Cox proportional hazards regression analysis. P-cadherin was expressed in 34.8% (1290/3710, 50% cut point) of cases. P-cadherin staining was strongly associated with HER2+ and basal carcinoma subtypes (P<0.0005). P-cadherin-positive patients showed significantly poorer short-term (0-10 years) overall survival, disease-specific survival, distant relapse-free interval, and locoregional relapse-free interval in univariable models (P<0.05). In multivariable Cox models containing standard clinical covariates and cancer subtypes, P-cadherin did not show independent prognostic value. P-cadherin expression was positively associated with histological grade, chemotherapy, Ki-67, EGFR, CK5/6, p53, YB-1, and HER2 expression (P<0.002), and negatively associated with age at diagnosis, ER, PR, and Bcl-2 expression (P<0.0005). This study shows the value of P-cadherin as a marker of poor prognosis. The large sample size of this series clarifies contradictory findings of many smaller studies. P-cadherin positivity is associated with high-grade tumor subtypes and well-established markers of poor prognosis, and may represent a promising antibody therapeutic target.

Down-regulation of the oncogene cyclin D1 increases migratory capacity in breast cancer and is linked to unfavorable prognostic features

The oncogene cyclin D1 is highly expressed in many breast cancers and, despite its proliferation-activating properties, it has been linked to a less malignant phenotype. To clarify this observation, we focused on two key components of malignant behavior, migration and proliferation, and observed that quiescent G(0)/G(1) cells display an increased migratory capacity compared to cycling cells. We also found that the down-regulation of cyclin D1 in actively cycling cells significantly increased migration while also decreasing proliferation. When analyzing a large set of premenopausal breast cancers, we observed an inverse proliferation-independent link between cyclin D1 and tumor size and recurrence, suggesting that this protein might abrogate infiltrative malignant behavior in vivo. Finally, gene expression analysis after cyclin D1 down-regulation by siRNA confirmed changes in processes associated with migration and enrichment of our gene set in a metastatic poor prognosis signature. This novel function of cyclin D1 illustrates the interplay between tumor proliferation and migration and may explain the attenuation of malignant behavior in breast cancers with high cyclin D1 levels.

p120ctn and P-cadherin but not E-cadherin regulate cell motility and invasion of DU145 prostate cancer cells

Background

Adherens junctions consist of transmembrane cadherins, which interact intracellularly with p120ctn, ß-catenin and α-catenin. p120ctn is known to regulate cell-cell adhesion by increasing cadherin stability, but the effects of other adherens junction components on cell-cell adhesion have not been compared with that of p120ctn.

Methodology/Principal Findings

We show that depletion of p120ctn by small interfering RNA (siRNA) in DU145 prostate cancer and MCF10A breast epithelial cells reduces the expression levels of the adherens junction proteins, E-cadherin, P-cadherin, ß-catenin and α-catenin, and induces loss of cell-cell adhesion. p120ctn-depleted cells also have increased migration speed and invasion, which correlates with increased Rap1 but not Rac1 or RhoA activity. Downregulation of P-cadherin, β-catenin and α-catenin but not E-cadherin induces a loss of cell-cell adhesion, increased migration and enhanced invasion similar to p120ctn depletion. However, only p120ctn depletion leads to a decrease in the levels of other adherens junction proteins.

Conclusions/Significance

Our data indicate that P-cadherin but not E-cadherin is important for maintaining adherens junctions in DU145 and MCF10A cells, and that depletion of any of the cadherin-associated proteins, p120ctn, ß-catenin or α-catenin, is sufficient to disrupt adherens junctions in DU145 cells and increase migration and cancer cell invasion.

Breast carcinoma cells re-express E-cadherin during mesenchymal to epithelial reverting transition

BACKGROUND

Epithelial to mesenchymal transition (EMT), implicated as a mechanism for tumor dissemination, is marked by loss of E-cadherin, disruption of cell adhesion, and induction of cell motility and invasion. In most intraductal breast carcinomas E-cadherin is regulated epigenetically via methylation of the promoter. E-cadherin expression is therefore dynamic and open to modulation by the microenvironment. In addition, it has been observed that metastatic foci commonly appear more differentiated than the primary tumor, suggesting that cancer cells may further undergo a mesenchymal to epithelial reverting transition (MErT) in the secondary organ environment following the EMT that allows for escape.

RESULTS

We first examined E-cadherin expression in primary breast tumors and their corresponding metastases to liver, lung and brain and discovered that 62% (10/16) of cases showed increased E-cadherin expression in the metastases compared to the primaries. These observations led to the question of whether the positive metastatic foci arose from expansion of E-cadherin-positive cells or from MErT of originally E-cadherin-negative disseminated cells. Thus, we aimed to determine whether it was possible for the mesenchymal-like MDA-MB-231 breast cancer cells to undergo an MErT through the re-expression of E-cadherin, either through exogenous introduction or induction by the microenvironment. Ectopic expression of full-length E-cadherin in MDA-MB-231 cells resulted in a morphological and functional reversion of the epithelial phenotype, with even just the cytosolic domain of E-cadherin yielding a partial phenotype. Introduction of MDA-MB-231 cells or primary explants into a secondary organ environment simulated by a hepatocyte coculture system induced E-cadherin re-expression through passive loss of methylation of the promoter. Furthermore, detection of E-cadherin-positive metastatic foci following the spontaneous metastasis of MDA-MB-231 cells injected into the mammary fat pad of mice suggests that this re-expression is functional.

CONCLUSIONS

Our clinical observations and experimental data indicate that the secondary organ microenvironment can induce the re-expression of E-cadherin and consequently MErT. This phenotypic change is reflected in altered cell behavior and thus may be a critical step in cell survival at metastatic sites.

The E-cadherin repressor slug and progression of human extrahepatic hilar cholangiocarcinoma

OBJECTIVES

This study explored the expression and function of Slug in human extrahepatic hilar cholangiocarcinoma (EHC) to identify its role in tumor progression.

METHODS

The expression of Snail and Slug mRNA in 52 human tissue samples of EHC was investigated. The mRNA of Snail and Slug were quantified using reverse transcriptase-PCR, and correlations with E-cadherin expression and clinicopathological factors were investigated. We then investigated transfection of Slug cDNA in endogenous E-cadherin-positive human EHC FRH0201 cells, selectively induced the loss of E-cadherin protein expression, and then small interfering RNA (siRNA) for inhibition of Slug expression in endogenous Slug-positive human EHC QBC939 cells, selectively induced the loss of Slug protein expression. A Boyden chamber transwell assay was used for invasion.

RESULTS

Slug mRNA was overexpressed in 18 cases (34.6%) of EHC compared with adjacent noncancerous tissue. E-Cadherin protein expression determined in the same 52 cases by immunohistochemistry was significantly down-regulated in those cases with Slug mRNA overexpression (P = 0.0001). The tumor and nontumor ratio of Slug mRNA was correlated with nodal metastasis(p = 0.0102), distant metastasis (p = 0.0001)and Survival time(p = 0.0443). However, Snail mRNA correlated with neither E-cadherin expression nor tumor invasiveness. By inhibiting Slug expression by RNA interference, we found that reduced Slug levels upregulated E-cadherin and decreased invasion in QBC939 cell. When the QBC939 cells was infected with Slug cDNA,, significant E-cadherin was downregulated and increased invasion in QBC939 cell.

CONCLUSIONS

The results suggested that Slug expression plays an important role in both the regulation of E-cadherin expression and in the acquisition of invasive potential in human EHC. Slug is possibly a potential target for an antitumor therapy blocking the functions of invasion and metastasis in human EHCs.