The E-cadherin/catenin complex in invasion and metastasis

A-Kinase Anchoring Protein 9 Promotes Gastric Cancer Progression as a Downstream Effector of Cadherin 1

Background

Genetic studies identified a dozen of frequently mutated genes in gastric cancer, such as cadherin 1 (CDH1) and A-kinase anchoring protein 9 (AKAP9). Of note, genetic alterations including depletion and amplification frameshift mutations of AKAP9 have been observed in 10–15% of gastric cancer patients. However, it is unknown of the expression and role of AKAP9 in gastric cancer. This study is aimed to characterize the expression and function of AKAP9 in gastric cancer.

Methods

Using qRT-PCR, we analyzed the mRNA levels of AKAP9 in gastric cancer patient samples. We investigated the role of AKAP9 in gastric cancer by performing cell proliferation assay, transwell assay, and mouse xenograft assay.

Results

AKAP9 was upregulated in gastric cancer patients. Overexpression of AKAP9 promoted cell proliferation, migration, and gastric tumor growth. Loss of CDH1 elevated AKAP9 mRNA and protein levels.

Conclusion

Our study demonstrates that AKAP9 functions as an oncoprotein to promote gastric cancer cell proliferation, migration, and tumor growth. Moreover, we reveal a possible molecular link showing that AKAP9 is a critical effector downstream of CDH1 in gastric cancer.

The magic of MAGI-1: A scaffolding protein with multi signalosomes and functional plasticity

MAGI-1 is a critical cellular scaffolding protein with over 110 different cellular and microbial protein interactors. Since the discovery of MAGI-1 in 1997, MAGI-1 has been implicated in diverse cellular functions such as polarity, cell-cell communication, neurological processes, kidney function, and a host of diseases including cancer and microbial infection. Additionally, MAGI-1 has undergone nomenclature changes in response to the discovery of an additional PDZ domain, leading to lack of continuity in the literature. We address the nomenclature of MAGI-1 as well as summarize many of the critical functions of the known interactions. Given the importance of many of the interactors, such as human papillomavirus E6, the Coxsackievirus and adenovirus receptor (CAR), and PTEN, the enhancement or disruption of MAGI-based interactions has the potential to affect cellular functions that can potentially be harnessed as a therapeutic strategy for a variety of diseases.

Cadherin Expression and EMT: A Focus on Gliomas

Cadherins are calcium-binding proteins with a pivotal role in cell adhesion and tissue homeostasis. The cadherin-dependent mechanisms of cell adhesion and migration are exploited by cancer cells, contributing to tumor invasiveness and dissemination. In particular, cadherin switch is a hallmark of epithelial to mesenchymal transition, a complex development process vastly described in the progression of most epithelial cancers. This is characterized by drastic changes in cell polarity, adhesion, and motility, which lead from an E-cadherin positive differentiated epithelial state into a dedifferentiated mesenchymal-like state, prone to metastization and defined by N-cadherin expression. Although vastly explored in epithelial cancers, how these mechanisms contribute to the pathogenesis of other non-epithelial tumor types is poorly understood. Herein, the current knowledge on cadherin expression in normal development in parallel to tumor pathogenesis is reviewed, focusing on epithelial to mesenchymal transition. Emphasis is taken in the unascertained cadherin expression in CNS tumors, particularly in gliomas, where the potential contribution of an epithelial-to-mesenchymal-like process to glioma genesis and how this may be associated with changes in cadherin expression is discussed.

Corneal proteome and differentially expressed corneal proteins in highly myopic chicks using a label-free SWATH-MS quantification approach

Myopia, or short-sightedness, is a highly prevalent refractive disorder in which the eye's focal length is too short for its axial dimension in its relaxed state. High myopia is associated with increased risks of blinding ocular complications and abnormal eye shape. In addition to consistent findings on posterior segment anomalies in high myopia (e.g., scleral remodeling), more recent biometric and biomechanical data in myopic humans and animal models also indicate anterior segment anomalies (e.g., corneal biomechanical properties). Because the cornea is the anterior-most ocular tissue, providing essential refractive power and physiological stability, it is important to understand the biochemical signaling pathway during myopia development. This study first aimed to establish the entire chicken corneal proteome. Then, using the classical form deprivation paradigm to induce high myopia in chicks, state-of-the-art bioinformatics technologies were applied to identify eight differentially expressed proteins in the highly myopic cornea. These results provide strong foundation for future corneal research, especially those using chicken as an animal model for myopia development.

Evaluation of the Effect of Foeniculum vulgare on the Expression of E-Cadherin, Dysadherin and Ki-67 in BALB/C Mice with 4T1 Model of Breast Cancer

Introduction: Breast cancer is described as a serious disease and one of the important factors of cancer-related deaths. Considering the drug resistance, special attention has been paid to natural compounds. This study aimed at evaluating the anti-metastatic activity of fennel in a breast cancer mouse model.Methods: A total of 28 adult female BALB/C mice were used in this study. Breast cancer was induced by subcutaneous injection of 4T1 cells in the right lower flank. The mice received fennel extracts daily via intraperitoneal injection for two weeks. Meanwhile, tumor volume was measured every day using calipers. After two weeks, each animal was anesthetized. The expression levels of ki-67 and dysadherin as tumor markers, as well as E-cadherin as a tumor suppressor, were measured in tumor tissue and ovary. Also the expression of her2 was measured in ovary.Results: Tumor size significantly decreased after nine days treatment of the fennel. Fennel treatment caused an increase in the ratio of the expression of E-cadherin to Ki-67 and dysadherin in the tumor tissues. On the other hand, the expression of Ki-67 and HER2 decreased in the ovary.Conclusion: Based on our findings, fennel has anti-tumor and anti-metastatic activities against aggressive cancers.

The functional activity of E-cadherin controls tumor cell metastasis at multiple steps

E-cadherin is a tumor suppressor protein, and the loss of its expression in association with the epithelial mesenchymal transition (EMT) occurs frequently during tumor metastasis. However, many metastases continue to express E-cadherin, and a full EMT is not always necessary for metastasis; also, positive roles for E-cadherin expression in metastasis have been reported. We hypothesize instead that changes in the functional activity of E-cadherin expressed on tumor cells in response to environmental factors is an important determinant of the ability of the tumor cells to metastasize. We find that E-cadherin expression persists in metastatic lung nodules and circulating tumor cells (CTCs) in two mouse models of mammary cancer: genetically modified MMTV-PyMT mice and orthotopically grafted 4T1 tumor cells. Importantly, monoclonal antibodies that bind to and activate E-cadherin at the cell surface reduce lung metastasis from endogenous genetically driven tumors and from tumor cell grafts. E-cadherin activation inhibits metastasis at multiple stages, including the accumulation of CTCs from the primary tumor and the extravasation of tumor cells from the vasculature. These activating mAbs increase cell adhesion and reduce cell invasion and migration in both cell culture and three-dimensional spheroids grown from primary tumors. Moreover, activating mAbs increased the frequency of apoptotic cells without affecting proliferation. Although the growth of the primary tumors was unaffected by activating mAbs, CTCs and tumor cells in metastatic nodules exhibited increased apoptosis. Thus, the functional state of E-cadherin is an important determinant of metastatic potential beyond whether the gene is expressed.

Functions of the APC tumor suppressor protein dependent and independent of canonical WNT signaling: implications for therapeutic targeting

The acquisition of biallelic mutations in the APC gene is a rate-limiting step in the development of most colorectal cancers and occurs in the earliest lesions. APC encodes a 312-kDa protein that localizes to multiple subcellular compartments and performs diverse functions. APC participates in a cytoplasmic complex that promotes the destruction of the transcriptional licensing factor β-catenin; APC mutations that abolish this function trigger constitutive activation of the canonical WNT signaling pathway, a characteristic found in almost all colorectal cancers. By negatively regulating canonical WNT signaling, APC counteracts proliferation, promotes differentiation, facilitates apoptosis, and suppresses invasion and tumor progression. APC further antagonizes canonical WNT signaling by interacting with and counteracting β-catenin in the nucleus. APC also suppresses tumor initiation and progression in the colorectal epithelium through functions that are independent of canonical WNT signaling. APC regulates the mitotic spindle to facilitate proper chromosome segregation, localizes to the cell periphery and cell protrusions to establish cell polarity and appropriate directional migration, and inhibits DNA replication by interacting directly with DNA. Mutations in APC are often frameshifts, insertions, or deletions that introduce premature stop codons and lead to the production of truncated APC proteins that lack its normal functions and possess tumorigenic properties. Therapeutic approaches in development for the treatment of APC-deficient tumors are focused on the inhibition of canonical WNT signaling, especially through targets downstream of APC in the pathway, or on the restoration of wild-type APC expression.

Secretion of N- and O-linked Glycoproteins from 4T1 Murine Mammary Carcinoma Cells

Breast cancer is one of the most common cancers that affect women globally and accounts for ~23% of all cancers diagnosed in women. Breast cancer is also one of the leading causes of death primarily due to late stage diagnoses and a lack of effective treatments. Therefore, discovering protein expression biomarkers is mandatory for early detection and thus, critical for successful therapy. Two-dimensional electrophoresis (2D-E) coupled with lectin-based analysis followed by mass spectrometry were applied to identify potential biomarkers in the secretions of a murine mammary carcinoma cell line. Comparisons of the protein profiles of the murine 4T1 mammary carcinoma cell line and a normal murine MM3MG mammary cell line indicated that cadherin-1 (CDH), collagenase 3 (MMP-13), Viral envelope protein G7e (VEP), Gag protein (GAG) and Hypothetical protein LOC433182 (LOC) were uniquely expressed by the 4T1 cells, and pigment epithelium-derived factor (PEDF) was exclusively secreted by the MM3MG cells. Further analysis by a lectin-based study revealed that aberrant O-glycosylated CDH, N-glycosylated MMP-13 and LOC were present in the 4T1 medium. These differentially expressed N- and O-linked glycoprotein candidates, which were identified by combining lectin-based analysis with 2D-E, could serve as potential diagnostic and prognostic markers for breast cancer.

E-cadherin-negative acinar cell carcinoma of the pancreas: report of a case showing a solid pseudopapillary growth pattern

E-cadherin expression patterns in acinar cell carcinomas (ACCs) of the pancreas have not been well documented. Herein, we present a hitherto undescribed case of E-cadherin-negative ACC with a solid pseudopapillary growth pattern in a 65-year-old man. We used an antibody against the extracellular domain of E-cadherin. As a further unusual status in ACC, faint β-catenin expression was observed in the cytoplasm of carcinoma cells. Morphological distinction from a solid pseudopapillary neoplasm (SPN) of the pancreas might be problematic in such a case, because of their similarities concerned with the growth pattern and E-cadherin negativity. Without nuclear accumulation of β-catenin, a diagnosis of SPN was almost excluded. Immunoreactivity for trypsin and BCL10 made an accurate diagnosis of ACC to this case. The tumor recurred 10 months post-surgery as rapidly enlarging masses in the liver, presumably indicating the aggressiveness of the E-cadherin-negative phenotype among ACCs.

The down-regulation of Notch1 inhibits the invasion and migration of hepatocellular carcinoma cells by inactivating the cyclooxygenase-2/Snail/E-cadherin pathway in vitro

BACKGROUND

The Notch signaling pathway plays an important role in cancer, but the mechanism by which Notch1 participates in invasion and migration of hepatocellular carcinoma (HCC) cells is unclear.

AIMS

Our purpose is to confirm the anti-invasion and anti-migration effects of the down-regulation of Notch1 in HCC cells.

METHODS

The invasion and migration capacities of HCC cells were detected with Transwell cell culture chambers. The expressions of Notch1, Notch1 intracellular domain (N1ICD), E-cadherin, Snail, and cyclooxygenase-2 (COX-2) were analyzed by RT-PCR and/or western blotting. Notch1 and Snail were down-regulated by RNA interference, and COX-2 was inhibited by NS-398. Cell apoptosis was analyzed by MTT and flow cytometry.

RESULTS

In HCC cells, Snail, Notch1, and COX-2 were up-regulated, and E-cadherin was down-regulated in mRNA and/or protein levels. The down-regulation of Snail or Notch1 or the inhibition of COX-2, respectively, can increase the mRNA and protein expressions of E-cadherin and decrease the invasion and migration capabilities of HCC cell. Down-regulated Notch1 or inhibited COX-2 can reduce the mRNA and protein expressions of Snail. The down-regulation of Notch1 can also reduce the protein expression of COX-2. However, exogenous PGE2 can reverse the role of down-regulated Notch1. The results of MTT and flow cytometry showed that down-regulated Notch1 did not affect HCC cell viability.

CONCLUSIONS

Down-regulated Notch1 may be an effective approach to inactivating Snail/E-cadherin by regulating COX-2, which results in inhibiting the invasion and migration of HCC cells. The inhibitory effects of down-regulated Notch1 on cell invasion and migration were independent of apoptosis.

E-Cadherin as a diagnostic biomarker in breast cancer

Background:

E-cadherin is expressed in most normal epithelial tissues. Selective loss of E-cadherin can cause dedifferentiation and invasiveness in human carcinomas, leading E-cadherin to be classified as a tumor suppressor. Loss of E-cadherin has been demonstrated in invasive lobular carcinoma of the breast, but the relationship between E-cadherin expression and breast cancer histopathology and prognosis is less clear.

Aim:

Our objective was to assess loss of E-cadherin as a diagnostic breast cancer biomarker and as an aid to the sub-classification of invasive breast cancer. We also correlated the loss of expression of E-cadherin with various clinical and pathologic prognostic factors.

Material and Methods:

Breast cancer specimens after modified radical mastectomy were obtained from women who underwent surgery at Grant Medical College and Sir J.J Group of Hospitals, Mumbai, India between May 2007 and October 2010. We stained 276 breast cancers specimens with monoclonal antibodies to E-cadherin. The breast cancers were classified by histopathological type.

Results:

A statistical correlation of E-cadherin loss with a positive diagnosis of invasive lobular carcinoma was found, but there was no correlation with any prognostic tumor variables. A negative E-cadherin stain was a sensitive and specific biomarker to confirm the diagnosis of invasive lobular carcinoma (specificity 97.7%; negative predictive value 96.8%; sensitivity 88.1%; and positive predictive value 91.2%). Positive E-cadherin expression was also associated with tubulolobular carcinomas.

Conclusions:

E-cadherin immunohistochemistry is helpful in classifying breast cancer cases with indeterminate histopathologic features. E-cadherin loss is uncommon in non-lobular carcinomas but shows no correlation to currently established prognostic variables.

Consumption of high-fat diet induces tumor progression and epithelial-mesenchymal transition of colorectal cancer in a mouse xenograft model

Epidemiologic studies suggest that intake of high-fat diet (HFD) promotes colon carcinogenesis. Epithelial-mesenchymal transition (EMT) and inflammation play important roles during tumor progression of colorectal cancer (CRC). Oncogenic pathways such as phosphatidylinositol-3-kinase (PI3K)/Akt/mTOR and mitogen-activated protein kinase (MAPK)/ERK signaling cascades induce EMT and inflammation in cancer. No experimental evidence has been demonstrated regarding HFD-mediated tumor progression including EMT in CRC so far. Our results demonstrated that HFD consumption could induce tumor growth and progression, including EMT and inflammation, in a mouse xenograft tumor model. The molecular mechanisms were through activation of MAPK/ERK and PI3K/Akt/mTOR signaling pathways. HFD induced up-regulation of cyclooxygenase-2, cyclin D1 and proliferating cell nuclear antigen proteins concomitant with increases in expression of nuclear factor-κB p65 (RelA) and β-catenin proteins. Surprisingly, HFD consumption could suppress p21(CIP1/WAF1) expression through increases in nuclear histone deacetylase complex (HDAC). Moreover, HFD could mediate the disassembly of E-cadherin adherent complex and the up-regulation of Vimentin and N-cadherin proteins in tumor tissues. Taken together, our novel findings support evidence for HFD-mediated modulation of HDAC activity and activation of oncogenic cascades, which involve EMT and inflammation in CRC, playing important roles in tumor growth and progression in a mouse xenograft model.

Distinct roles of cadherin-6 and E-cadherin in tubulogenesis and lumen formation

Classic cadherins are important regulators of tissue morphogenesis. The predominant cadherin in epithelial cells, E-cadherin, has been extensively studied because of its critical role in normal epithelial development and carcinogenesis. Epithelial cells may also coexpress other cadherins, but their roles are less clear. The Madin Darby canine kidney (MDCK) cell line has been a popular mammalian model to investigate the role of E-cadherin in epithelial polarization and tubulogenesis. However, MDCK cells also express relatively high levels of cadherin-6, and it is unclear whether the functions of this cadherin are redundant to those of E-cadherin. We investigate the specific roles of both cadherins using a knockdown approach. Although we find that both cadherins are able to form adherens junctions at the basolateral surface, we show that they have specific and mutually exclusive roles in epithelial morphogenesis. Specifically, we find that cadherin-6 functions as an inhibitor of tubulogenesis, whereas E-cadherin is required for lumen formation. Ablation of cadherin-6 leads to the spontaneous formation of tubules, which depends on increased phosphoinositide 3-kinase (PI3K) activity. In contrast, loss of E-cadherin inhibits lumen formation by a mechanism independent of PI3K.

Preparation and characterization of a novel skin substitute

Autologous epidermal cell cultures (CEA) represent a possibility to treat extensive burn lesions, since they allow a significative surface expansion which cannot be achieved with other surgical techniques based on autologous grafting. Moreover currently available CEA preparations are difficult to handle and their take rate is unpredictable. This study aimed at producing and evaluating a new cutaneous biosubstitute made up of alloplastic acellular glycerolized dermis (AAGD) and CEA to overcome these difficulties. A procedure that maintained an intact basement membrane was developed, so as to promote adhesion and growth of CEA on AAGD. Keratinocytes were seeded onto AAGD and cultured up to 21 days. Viability tests and immunohistochemical analysis with specific markers were carried out at 7, 14, and 21 days, to evaluate keratinocyte adhesion, growth, and maturation. Our results support the hypothesis that this newly formed skin substitute could allow its permanent engraftment in clinical application.

P-cadherin counteracts myosin II-B function: implications in melanoma progression

BACKGROUND

Malignant transformation of melanocytes is frequently attended by a switch in cadherin expression profile as shown for E- and N-cadherin. For P-cadherin, downregulation in metastasizing melanoma has been demonstrated, and over-expression of P-cadherin in melanoma cell lines has been shown to inhibit invasion. The strong invasive and metastatic nature of cutaneous melanoma implies a deregulated interplay between intercellular adhesion and migration-related molecules

RESULTS

In this study we performed a microarray analysis to compare the mRNA expression profile of an invasive BLM melanoma cell line (BLM LIE) and the non-invasive P-cadherin over-expression variant (BLM P-cad). Results indicate that nonmuscle myosin II-B is downregulated in BLM P-cad. Moreover, myosin II-B plays a major role in melanoma migration and invasiveness by retracting the tail during the migratory cycle, as shown by the localization of myosin II-B stress fibers relative to Golgi and the higher levels of phosphorylated myosin light chain. Analysis of P-cadherin and myosin II-B in nodular melanoma sections and in a panel of melanoma cell lines further confirmed that there is an inverse relationship between both molecules.

CONCLUSIONS

Therefore, we conclude that P-cadherin counteracts the expression and function of myosin II-B, resulting in the suppression of the invasive and migratory behaviour of BLM melanoma cells.

Cytokines and growth factors expressed by human cutaneous melanoma

Cytokines and growth factors have biologic effects that could stimulate tumor growth, invasion and angiogenesis. The incidence of 24 factors was investigated in 25 cultured human melanoma cell lines and in 62 fixed tissues at different stages of the disease. Over 80% of the human melanoma cell lines expressed TGF-β, IL-8, IL-6, VEGF, PDGF-AA and OPN. Significantly higher TGF-β, IGF-1 and IL-15 were determined in primary lesions compared to distant metastases by immunohistochemistry. Illustrating the complexity of the milieu of the tumor microenvironment, some of these factors may have to be considered in targeted therapy.

The detection, treatment, and biology of epithelial ovarian cancer

Ovarian cancer is particularly insidious in nature. Its ability to go undetected until late stages coupled with its non-descript signs and symptoms make it the seventh leading cause of cancer related deaths in women. Additionally, the lack of sensitive diagnostic tools and resistance to widely accepted chemotherapy regimens make ovarian cancer devastating to patients and families and frustrating to medical practitioners and researchers. Here, we provide an in-depth review of the theories describing the origin of ovarian cancer, molecular factors that influence its growth and development, and standard methods for detection and treatment. Special emphasis is focused on interactions between ovarian tumors and the innate and adaptive immune system and attempts that are currently underway to devise novel immunotherapeutic approaches for the treatment of ovarian tumors.

Molecular events associated with epithelial to mesenchymal transition of nasopharyngeal carcinoma cells in the absence of Epstein-Barr virus genome

Epithelial-mesenchymal transition (EMT) is an important process in tumor metastasis. The EMT-related events associated with metastasis of NPC in the absence of EBV have not been elucidated. We established an EBV-negative NPC cell line from a bone marrow biopsy of an NPC patient. Using a Matrigel system we isolated an invasive and non-invasive sublines, designated NPC-BM29 and NPC-BM00. NPC-BM29 acquired an invasive-like phenotype characterized by EMT, marked by down-regulation of E-cadherin and β-catenin with concomitant increased expression of Ets1. NPC-BM29 cells expressed ≥ 10-fold higher of MMP-9 than NPC-BM00 cells. NPC-BM29 cells grew better in 2% serum than NPC-BM00 cells, with a population doubling-time of 26.8 h and 30.7 h, respectively. A marked reduction in colony-formation ability of NPC-BM00 cells compared to NPC-BM29 was observed. Wound-healing assay revealed that NPC-BM29 cells displayed higher motility than NPC-BM00 and the motility was further enhanced by cell treatment with TPA, a PKC activator. Cell surface markers and tumor-associated molecules, AE3, MAK6 and sialyl-Tn, were up-regulated in NPC-BM29 cells, whereas the expression of HLA-DR and CD54 was significantly increased in NPC-BM00 cells. NPC-BM29 consistently released higher levels of IL-8 and IL-10 than NPC-BM00, with low levels of IL-1α expression in both cell lines. Higher level of VEGF production was detected in NPC-BM00 than NPC-BM29 cells. These data show that EBV is not required for exhibiting multiple metastatic phenotypes associated with EMT. More studies that target right molecules/signalings associated with the EMT may offer new therapeutic intervention options for NPC invasion and metastasis.

Defining the role of laminin-332 in carcinoma

The deadly feature of cancer, metastasis, requires invasion of cells through basement membranes (BM), which normally act as barriers between tissue compartments. In the case of many epithelially-derived cancers (carcinomas), laminin-332 (Ln-332) is a key component of the BM barrier. This review provides a historical examination of Ln-332 from its discovery through identification of its functions in BM and possible role in carcinomas. Current understanding points to distinct roles for the three Ln-332 subunits (alpha3, beta3, gamma2) in cell adhesion, extracellular matrix stability, and cell signaling processes in cancer. Given the large number of studies linking Ln-332 gamma2 subunit with cancer prognosis, particular attention is given to the crucial role of this subunit in cancer invasion and to the unanswered questions in this area.

Loss of retinal cadherin facilitates mammary tumor progression and metastasis

The mammary epithelium is thought to be stabilized by cell-cell adhesion mediated mainly by E-cadherin (E-cad). Here, we show that another cadherin, retinal cadherin (R-cad), is critical for maintenance of the epithelial phenotype. R-cad is expressed in nontransformed mammary epithelium but absent from tumorigenic cell lines. In vivo, R-cad was prominently expressed in the epithelium of both ducts and lobules. In human breast cancer, R-cad was down-regulated with tumor progression, with high expression in ductal carcinoma in situ and reduced expression in invasive duct carcinomas. By comparison, E-cad expression persisted in invasive breast tumors and cell lines where R-cad was lost. Consistent with these findings, R-cad knockdown in normal mammary epithelium stimulated invasiveness and disrupted formation of acini despite continued E-cad expression. Conversely, R-cad overexpression in aggressive cell lines induced glandular morphogenesis and inhibited invasiveness, tumor formation, and lung colonization. R-cad also suppressed the matrix metalloproteinase 1 (MMP1), MMP2, and cyclooxygenase 2 gene expression associated with pulmonary metastasis. The data suggest that R-cad is an adhesion molecule of the mammary epithelium, which acts as a critical regulator of the normal phenotype. As a result, R-cad loss contributes to epithelial suppression and metastatic progression.

NGAL decreases E-cadherin-mediated cell-cell adhesion and increases cell motility and invasion through Rac1 in colon carcinoma cells

Expression of neutrophil gelatinase-associated lipocalin (NGAL)/lipocalin2, a recently recognized iron regulatory protein that binds to matrix metalloproteinase-9 (MMP9), is increased in a spectrum of cancers, including those of the colorectum. Using colon carcinoma cell lines stably transfected with NGAL or antisense NGAL, we showed that NGAL overexpression altered subcellular localization of E-cadherin and catenins, decreased E-cadherin-mediated cell-cell adhesion, enhanced cell-matrix attachment, and increased cell motility and in vitro invasion. Conversely, a decrease in NGAL enhanced more aggregated growth pattern and decreased in vitro invasion. We further showed that NGAL exerted these effects through the alteration of the subcellular localization of Rac1 in an extracellular matrix-dependent, but MMP9-independent, manner. Furthermore, we observed that the NGAL-overexpressing cells tolerated increased iron levels in the culture environment, whereas the NGAL-underexpressing cells showed significant cell death after prolonged incubation in high-iron condition. Thus, overexpressing NGAL in colon carcinomas is an important regulatory molecule that integrates extracellular environment cues, iron metabolism, and intracellular small GTPase signaling in cancer migration and invasion. NGAL may therefore be a new target for therapeutic intervention in colorectal carcinoma.

Tumor necrosis factor receptor-associated factor 4 is a dynamic tight junction-related shuttle protein involved in epithelium homeostasis

Background

Despite numerous in vivo evidences that Tumor Necrosis Factor Receptor-Associated Factor 4 (TRAF4) plays a key biological function, how it works at the cellular and molecular level remains elusive.

Methodology/Principal Findings

In the present study, we show using immunofluorescence and immuohistochemistry that TRAF4 is a novel player at the tight junctions (TJs). TRAF4 is connected to assembled TJs in confluent epithelial cells, but accumulates in the cytoplasm and/or nucleus when TJs are open in isolated cells or EGTA-treated confluent cells. In vivo, TRAF4 is consistently found at TJs in normal human mammary epithelia as well as in well-differentiated in situ carcinomas. In contrast, TRAF4 is never localized at the plasma membrane of poorly-differentiated invasive carcinomas devoid of correct TJs, but is observed in the cytoplasm and/or nucleus of the cancer cells. Moreover, TRAF4 TJ subcellular localization is remarkably dynamic. Fluorescence recovery after photobleaching (FRAP) experiments show that TRAF4 is highly mobile and shuttles between TJs and the cytoplasm. Finally, we show that intracellular TRAF4 potentiates ERK1/2 phosphorylation in proliferating HeLa cells, an epithelial cell line known to be devoid of TJs.

Conclusions/Significance

Collectively, our data strongly support the new concept of TJs as a dynamic structure. Moreover, our results implicate TRAF4 in one of the emerging TJ-dependent signaling pathways that responds to cell polarity by regulating the cell proliferation/differentiation balance, and subsequently epithelium homeostasis. Drastic phenotypes or lethality in TRAF4-deficient mice and drosophila strongly argue in favor of such a function.

Lupeol Suppresses Cisplatin-Induced Nuclear Factor-κB Activation in Head and Neck Squamous Cell Carcinoma and Inhibits Local Invasion and Nodal Metastasis in an Orthotopic Nude Mouse Model

A poor prognosis in head and neck squamous cell carcinoma (HNSCC) patients is commonly associated with the presence of regional metastasis. Cisplatin-based chemotherapy concurrent with radiation therapy is commonly used in the treatment of locally advanced HNSCC. However, the result is dismal due to common acquisition of chemoresistance and radioresistance. Epidemiologic studies have shown the importance of dietary substances in the prevention of HNSCC. Here, we found that lupeol, a triterpene found in fruits and vegetables, selectively induced substantial HNSCC cell death but exhibited only a minimal effect on a normal tongue fibroblast cell line in vitro. Down-regulation of NF-kappaB was identified as the major mechanism of the anticancer properties of lupeol against HNSCC. Lupeol alone was not only found to suppress tumor growth but also to impair HNSCC cell invasion by reversal of the NF-kappaB-dependent epithelial-to-mesenchymal transition. Lupeol exerted a synergistic effect with cisplatin, resulting in chemosensitization of HNSCC cell lines with high NF-kappaB activity in vitro. In in vivo studies, using an orthotopic metastatic nude mouse model of oral tongue squamous cell carcinoma, lupeol at a dose of 2 mg/animal dramatically decreased tumor volume and suppressed local metastasis, which was more effective than cisplatin alone. Lupeol exerted a significant synergistic cytotoxic effect when combined with low-dose cisplatin without side effects. Our results suggest that lupeol may be an effective agent either alone or in combination for treatment of advanced tumors.

N-cadherin expression in breast cancer: correlation with an aggressive histologic variant--invasive micropapillary carcinoma

Upregulation of N-cadherin in epithelial tumor cells has been shown to contribute to the invasive/metastatic phenotype. It remains however to be determined whether N-cadherin is increased in human breast cancers with enhanced malignant potential. We examined a large number of invasive breast cancer specimens (n = 114) for N- and E-cadherin. These specimens compared invasive duct carcinomas (IDCs) of varying histologic grades with an aggressive subtype, invasive micropapillary carcinoma of the breast (MPAP), which has a high propensity for lymphatic invasion and lymph node metastasis. Staining scores for N- and E-cadherin were compared between non-MPAP and MPAP IDCs, and between the invasive and ductal carcinoma in situ (DCIS) of each IDC using statistical analysis. We found that N-cadherin was expressed in 76% of MPAP and 52% of non-MPAP carcinomas, and E-cadherin in 57% of MPAP and 36% of non-MPAP tumors. More MPAP (25%) compared to non-MPAP (5%) tumors expressed both cadherins. Of the two cadherins, N-cadherin was significantly associated with MPAP tumors (p = 0.033) compared to E-cad (p = 0.171). Moreover, in the majority of tumors that were positive for N-cadherin, the staining scores were increased in the IDC relative to intraductal components, and this effect was more dramatic in the MPAP carcinomas. This difference for N-cadherin was greater than the corresponding difference for E-cadherin in the MPAP group (p = 0.005), whereas such changes were not significant in the non-MPAP group (p = 0.10). Thus, N-cadherin is associated with tumor aggressiveness and metastatic potential and may contribute to tumor progression.

N-cadherin switching occurs in high Gleason grade prostate cancer

BACKGROUND

The inappropriate expression of non-epithelial N-(neural) cadherin by epithelial cells, called cadherin switching, has been suggested to play a role in prostate cancer (PC) progression. We explored the role of N-cadherin as a biomarker in PC by correlating the expression with clinical parameters.

METHODS

Two pathologists blinded to patients' history independently reviewed and scored the intensity and extent of staining of N-cadherin expression in 44 randomly selected radical prostatectomy specimens. The expression was correlated with total Gleason grade, individual Gleason patterns, tumor stage, and preoperative serum prostate specific antigen (PSA) levels and P-values < 0.05 were considered statistically significant.

RESULTS

Of the 44 PC specimens, 14 (32%), 23 (52%), 7 (16%) consisted of Gleason grade 5-6, 7, and 8-10, respectively and 20/44 (45%) demonstrated N-cadherin expression. N-cadherin was expressed in 1/14 (7%) of Gleason 5-6 compared to 15/23 (65%) of Gleason grade 7, and 4/7 (57%) of Gleason grade 8-10, demonstrating a significant correlation between N-cadherin switching and higher Gleason grade (P = 0.001). While only about a third of primary or secondary Gleason pattern 3 demonstrated N-cadherin expression, a majority of Gleason patterns of > or = 4 expressed N-cadherin (P > 0.05), further suggesting that N-cadherin switching occurs with higher Gleason pattern. However, N-cadherin expression did not significantly correlate with preoperative serum PSA levels or tumor stage in our study cohort.

CONCLUSIONS

We have demonstrated for the first time that N-cadherin switching occurs in higher grade PC and correlates significantly with increasing Gleason patterns. N-cadherin may be as a useful biomarker of aggressive PC.

Cadherins and catenins in clival chordomas: correlation of expression with tumor aggressiveness

The local invasiveness and occasional rapid growth of chordomas, despite optimal treatment, highlight the need to develop ways to predict their biologic behavior. Alterations in adhesion proteins have been shown to participate in proliferation, invasiveness, and metastasis in epithelial tumors. We therefore analyzed the expression of E-cadherin, N-cadherin, as well as their cytosolic binding proteins alpha-catenin, beta-catenin, and gamma-catenin, in 51 paraffin archived and 17 cryopreserved chordoma specimens. In the majority of chordomas, E-cadherin and N-cadherin expression was inversely correlated, whereas beta-catenin and gamma-catenin expression was directly correlated. By multivariate analysis, N-cadherin up-regulation correlated with a diminished recurrence-free survival, and E-cadherin down-regulation strongly correlated with increased probabilities of death as determined by the Kaplan-Meier log-rank test. There was a 3.28-fold increased probability of having a tumor recurrence and a 10.98-fold increased probability of dying when, respectively, N-cadherin was up-regulated and E-cadherin down-regulated. These results suggest that changes in the relative expression of the cadherin-catenin complex reflect chordoma aggressiveness; and that decreased expression of E-cadherin and increased expression of N-cadherin may underlie the transition from a less to a more aggressive tumor phenotype.

Pleiotropic effects of FGFR1 on cell proliferation, survival, and migration in a 3D mammary epithelial cell model

Members of the fibroblast growth factor (FGF) family and the FGF receptors (FGFRs) have been implicated in mediating various aspects of mammary gland development and transformation. To elucidate the molecular mechanisms of FGFR1 action in a context that mimics polarized epithelial cells, we have developed an in vitro three-dimensional HC11 mouse mammary epithelial cell culture model expressing a drug-inducible FGFR1 (iFGFR1). Using this conditional model, iFGFR1 activation in these growth-arrested and polarized mammary acini initially led to reinitiation of cell proliferation, increased survival of luminal cells, and loss of cell polarity, resulting in the disruption of acinar structures characterized by the absence of an empty lumen. iFGFR1 activation also resulted in a gain of invasive properties and the induction of matrix metalloproteinase 3 (MMP-3), causing the cleavage of E-cadherin and increased expression of smooth muscle actin and vimentin. The addition of a pan MMP inhibitor abolished these phenotypes but did not prevent the effects of iFGFR1 on cell proliferation or survival.

Automated quantitative analysis of E-cadherin expression in lymph node metastases is predictive of survival in invasive ductal breast cancer

PURPOSE

The tumor suppressor adhesion molecule E-cadherin is believed to have an anti-invasive role in breast cancer. Lymph node involvement is the best prognostic marker known, yet there is variability in outcome among node-positive patients. We investigated the relationship between E-cadherin expression in primary invasive ductal tumors and corresponding nodal metastases, and determined the prognostic value of E-cadherin expression in node-positive breast cancer.

EXPERIMENTAL DESIGN

Membrane E-cadherin expression was studied by immunohistochemical staining of tissue microarrays with fluorescent-labeled antibodies. An objective method of automated quantitative analysis (AQUA) was used. AQUA uses cytokeratin to define pixels as breast cancer (tumor mask) within the array spot, and measures E-cadherin expression using a Cy5-conjugated antibody within the mask.

RESULTS

We employed a tissue microarray containing 207 primary and matched nodal metastases suitable for AQUA analysis. There was no significant difference in mean staining intensity between the primary and nodal specimens (P = 0.8). A scattergram was generated which identified a subset of patients (25%) with high E-cadherin expression in nodal metastases, and this top quartile had improved survival (P = 0.028). On univariate analysis, increased E-cadherin expression in nodal metastases was strongly associated with improved survival (P = 0.007), whereas expression in primary tumors was not (P = 0.13). On multivariate analysis, nodal E-cadherin expression retained its independent association with survival, as did tumor size and HER2/neu status.

CONCLUSIONS

Strong E-cadherin expression in lymph node metastases was highly predictive of improved survival. This suggests that expression of adhesion molecules at metastatic sites portends less aggressive tumor behavior.

Bowes melanoma cells secrete heregulin, which can promote aggregation and counteract invasion of human mammary cancer cells

Invasiveness, the ability of cancer cells to migrate beyond the normal tissue boundaries, often leads to metastasis and thereby usually turns cancer into a fatal disease. At the molecular level, the E-cadherin/catenin complex is an example of a powerful invasion suppressor in epithelial cells. Since the absence of melanocytes has been associated with disturbances in epithelial organization, we decided to investigate the influence of molecules secreted by melanocytes on the function of the E-cadherin/catenin complex. We used the Bowes melanoma cell line as a source of such molecules. The conditioned medium of Bowes melanoma stimulated aggregation of human MCF-7/6 mammary adenocarcinoma cells at short (30 min) and long (24-72 hr) notice. This effect could be inhibited by MB2, an antibody against human E-cadherin. Conditioned medium of Bowes melanoma also inhibited invasion of MCF-7/6 cells into precultured chick heart fragments. Candidate molecules such as insulin, insulin-like growth factor I, follistatin and interleukins were ruled out to be responsible for the effects, but heregulin mimicked some of the effects of the conditioned medium. Our data indicate that heregulin stimulates aggregation and inhibits invasion of MCF-7/6 cells via activation of the E-cadherin/catenin complex.

Antiinvasive effect of xanthohumol, a prenylated chalcone present in hops (Humulus lupulus L.) and beer

The female inflorescences of the hop plant (Humulus lupulus L.) are essential during brewing to add taste and flavor to beer and to stabilize beer foam. Xanthohumol, the main prenylated chalcone in hops, was investigated for its antiinvasive activity on human breast cancer cell lines (MCF-7 and T47-D) in vitro. Xanthohumol was able to inhibit the invasion of MCF-7/6 cells at 5 microM in the chick heart invasion assay and of T47-D cells in the collagen invasion assay. Xanthohumol inhibited growth of MCF-7/6 and T47-D cells, but not of chick heart cells. Moreover, it induced apoptosis of these tumor cells as demonstrated by the cleavage of nuclear PARP after 48 hr treatment. To probe the mechanism of the antiinvasive effect of xanthohumol, involvement of the E-cadherin/catenin invasion-suppressor complex was investigated. An aggregation assay demonstrated stimulation of aggregation of MCF-7/6 cells in the presence of 5 microM xanthohumol and this could be completely inhibited by an antibody against E-cadherin. Xanthohumol upregulates the function of the E-cadherin/catenin complex and inhibits invasion in vitro, indicating a possible role as an antiinvasive agent in vivo as well.

Protein kinase C alpha expression in breast and ovarian cancer

In recent years research has focused on the development of specific, targeted drugs to treat cancer. One approach has been to block intracellular signaling proteins, such as protein kinase C alpha (PKC-alpha). To help support the rationale for clinical studies of a PKC-alpha-targeted therapy in breast and ovarian cancers, we reviewed publications studying PKC-alpha expression in these tumors. Since these investigations were mostly performed in cell lines, we supplemented this review with some preliminary findings from studies examining PKC-alpha expression in tumor tissue biopsies obtained from patients with breast and ovarian cancer. Based on the reviewed publications using representative cell lines and our preliminary findings on tumor tissue of patients with breast cancer, we infer that PKC-alpha levels may especially be increased in breast cancer patients with low or negative estrogen receptor (ER) levels. Thus, clinical studies determining efficacy of selective or specific inhibitors of PKC-alpha should include determination of ER status in order to help answer whether blocking PKC-alpha in patients with low or absent ER can result in clinical benefit.

Overexpression of the thymosin beta-4 gene is associated with increased invasion of SW480 colon carcinoma cells and the distant metastasis of human colorectal carcinoma

Cell-matrix and cell-cell adhesive interactions play important roles in the normal organization and stabilization of the cell layer in epithelial tissue. Alterations in the expression and function of these adhesion systems that cause a switch to a migratory phenotype in tumor invasion and metastasis are critical for the malignant conversion of epithelial cells. Thymosin beta-4 (Tbeta-4) is the major actin-sequestering protein that has been shown to be upregulated in a wide variety of human carcinomas and has been implicated to be involved in altering the motility of certain tumors. We have recently demonstrated that the growth rate, colony formation in soft agar, and motility, all good indicators for malignant progression, of SW480 colon carcinoma cells are dramatically increased by enforced Tbeta-4 expression. To test the hypothesis that overexpression of this G-actin sequestering peptide also promotes tumor invasion, we examined not only the invasion capability of Tbeta-4-overexpressing SW480 cells, but also the expression levels of Tbeta-4 as well as several proteins that participate in different stages of tumor progression in matched samples of human primary colorectal adenocarcinoma and liver metastases from several patients. A marked increase on the invasiveness in Tbeta-4-overexpressing SW480 cells with increased levels and activity of matrix metalloproteinase-7 (MMP-7) was observed. Furthermore, the levels of Fas as well as the susceptibility to Fas ligand-mediated apoptosis in Tbeta-4-overexpressing cells were significantly decreased. Interestingly, the levels of Tbeta-4 mRNA, beta-catenin, c-Myc, and MMP-7 in metastatic liver lesions were relatively higher, whereas the levels of E-cadherin and Fas were significantly lower than those in the matched primary colorectal tumors. These results suggest that upregulation of Tbeta-4, by promoting the disruption of cell-cell adhesion and a consequential activation of the beta-catenin signaling, could be a key event in the acquisition of growth advantages as well as invasive phenotypes in human colorectal carcinomas.

Prognostic significance of E-cadherin protein expression in pathological stage I-III endometrial cancer

PURPOSE

Decreased expression of E-cadherin in endometrial cancer cells is associated with adverse prognostic features. This study aimed to evaluate the prognostic significance of decreased E-cadherin expression in patients with endometrial cancer.

EXPERIMENTAL DESIGN

Between 1992 and 1999, 102 endometrial cancer patients with stage I-III disease underwent primary surgery at the University of Chicago. Representative tissue specimens were immunostained with a monoclonal antibody to E-cadherin. A semiquantitative evaluation scale was developed based on the percentage of endometrial cancer cells with membranous E-cadherin staining. Tissue sections were scored as "3" if >75%, "2" if 25-75%, "1" if 5-25%, and "0" if <5% of cells stained. E-Cadherin staining was correlated with overall survival (OS), cause-specific survival (CSS), progression-free survival (PFS), and extrapelvic progression. Multivariate Cox proportional hazards modeling was used to estimate hazard ratios, controlling for clinicopathological characteristics and adjuvant treatment. Median follow-up for the study group was 58.5 months.

RESULTS

E-Cadherin staining was scored as 0, 1, 2, and 3 in 29.4%, 18.6%, 26.5%, 25.5% of cases, respectively. E-Cadherin expression was positively correlated with myometrial invasion (Kendall tau: 0.30, P < 0.01), and negatively correlated with grade (Kendall tau: -0.13, P = 0.15) and papillary serous or clear cell histology (Kendall tau: -0.14, P = 0.12). Five-year actuarial OS, CSS, PFS, and extrapelvic recurrence rates for negative (score = 0), heterogeneous (score = 1-2), and positive (score = 3) staining were as follows: OS, 69.2 versus 75.7 versus 81.0% (P = 0.64); CSS, 78.8 versus 91.2 versus 95.5% (P = 0.19); PFS, 69.1 versus 88.6 versus 92.2% (P = 0.079), and extrapelvic progression, 20.8 versus 7.3 versus 4.0% (P = 0.17). On multivariate Cox regression, a higher E-cadherin expression score was associated with decreased overall mortality [hazard ratio (HR), 0.59; 95% confidence interval (CI), 0.34-1.03; P = 0.066), and statistically significant decreases in endometrial cancer mortality (HR, 0.23; 95% CI, 0.055-0.94; P = 0.040), disease progression (HR, 0.28; 95% CI, 0.10-0.77; P = 0.014), and extrapelvic recurrence (HR, 0.24; 95% CI, 0.062-0.97; P = 0.045).

CONCLUSIONS

Decreased E-cadherin expression is an independent prognostic factor for disease progression and mortality in pathological stage I-III endometrial cancer. Evaluation of E-cadherin expression may aid in the selection of patients for more aggressive adjuvant therapy.

Cadherin switch in tumor progression

The loss of E-cadherin expression or function in epithelial carcinomas has long been thought as a primary reason for disruption of tight epithelial cell-cell contacts and release of invasive tumor cells from the primary tumor. Indeed, E-cadherin serves as a widely acting suppressor of invasion and growth of epithelial cancers, and its functional elimination represents a key step in the acquisition of the invasive phenotype for many tumors. Recent evidence indicates, however, that in addition to the loss of the "invasion-suppressor" E-cadherin, another adhesion molecule, N-cadherin, becomes upregulated in invasive tumor cell lines. N-cadherin was shown to be present in the most invasive and dedifferentiated breast cancer cell lines, and its exogenous expression in tumor cells induces a scattered morphology and heightened motility, invasion, and metastasis. N-cadherin cooperates with the FGF receptor, resulting in signals that lead to the up-modulation of MMP-9 and, hence, cellular invasion. In addition to a signaling function in metastasis, N-cadherin probably also supports the systemic dissemination of tumor cells by enabling circulating tumor cells to associate with the stroma and the endothelium at distant sites. Here, we summarize the various aspects of the E- to N-cadherin switching in epithelial carcinomas and its potential impact on metastatic progression.

Wnt11 signaling promotes proliferation, transformation, and migration of IEC6 intestinal epithelial cells

Wnts are morphogens with well recognized functions during embryogenesis. Aberrant Wnt signaling has been demonstrated to be important in colorectal carcinogenesis. However, the role of Wnt in regulating normal intestinal epithelial cell proliferation is not well established. Here we determine that Wnt11 is expressed throughout the mouse intestinal tract including the epithelial cells. Conditioned media from Wnt11-secreting cells stimulated proliferation and migration of IEC6 intestinal epithelial cells. Co-culture of Wnt11-secreting cells with IEC6 cells resulted in morphological transformation of the latter as evidenced by the formation of foci, a condition also accomplished by stable transfection of IEC6 with a Wnt11-expressing construct. Treatment of IEC6 cells with Wnt11 conditioned media failed to induce nuclear translocation of beta-catenin but led to increased activities of protein kinase C and Ca(2+)/calmodulin-dependent protein kinase II. Inhibition of protein kinase C resulted in a decreased ability of Wnt11 to induce foci formation in IEC6 cells. Finally, E-cadherin was redistributed in Wnt11-treated IEC6 cells, resulting in diminished E-cadherin-mediated cell-cell contact. We conclude that Wnt11 stimulates proliferation, migration, cytoskeletal rearrangement, and contact-independent growth of IEC6 cells by a beta-catenin-independent mechanism. These findings may help understand the molecular mechanisms that regulate proliferation and migration of intestinal epithelial cells.

Promoter hypermethylation of E-cadherin and its abnormal expression in Epstein-Barr virus-associated gastric carcinoma

Promoter hypermethylation of various tumor-related genes is extremely frequent in Epstein-Barr virus (EBV)-associated gastric carcinoma (EBVaGC). To investigate the significance of the promoter methylation in EBVaGC, we focused on one of the important proteins in the carcinogenesis of the stomach, E-cadherin. Methylation-specific PCR analysis (MSP) was applied to surgically resected gastric carcinomas, together with immunohistochemistry, PCR-based analysis of mutations and allelic loss, and site-specific MSP of E-cadherin gene. By MSP, nearly all of the carcinomas showed aberrant methylation of E-cadherin promoter in EBVaGC (21/22), and the frequency of this aberration was significantly higher than that in EBV-negative gastric carcinoma (GC; 45/81; p = 0.0003). According to immunohistochemistry of E-cadherin, the frequency of abnormal staining pattern in EBVaGC (87%) was comparable to that in the diffuse type (80%), but higher than that in the intestinal type of EBV-negative GC (47%). Promoter methylation was well correlated with abnormal staining pattern in EBVaGC, but not in EBV-negative GC. Neither mutation nor allelic loss of E-cadherin was observed in EBVaGC. Methylation status of E-cadherin within each carcinoma was heterogeneous as far as examined. Thus, in addition to the known association involving p16, we determined that promoter methylation-mediated silencing of E-cadherin gene was also closely associated with the development of EBVaGC, although it becomes heterogeneous within a given tumor along its progression.

The epithelial cell adhesion molecule (Ep-CAM) as a morphoregulatory molecule is a tool in surgical pathology

Cell adhesion receptors (CAMs) are actively involved in regulating various cell processes, including growth, differentiation, and cell death. Therefore, CAMs represent a large group of morphoregulating molecules, mediating cross-talk between cells and of cells with their environment. From this perspective, CAMs do contribute to cells and tissue organization, and in diseased tissue, to the disease development and biological characteristics. Therefore, observed changes in expression patterns of adhesion molecules may contribute to establish a diagnosis. A distinct shift in expression patterns in neoplastic epithelium has been described, for example for cadherins, integrins, and CD44. A relatively novel cell CAM, Ep-CAM, was first reported to be a pan-carcinoma antigen, although it is rather a marker of epithelial lineage. Several antibodies directed to Ep-CAM have been generated, and many epithelial tissues and their neoplastic appendages have been studied. This article outlines the results of these studies. Based on the results of these studies, we conclude that Ep-CAM immunohistochemistry can be a useful tool in the diagnosis of disturbed epithelial tissues.

Functional and molecular characterization of the epithelioid to round transition in human colorectal cancer LoVo cells

In subclones of the human colon cancer LoVo cell line, there is a reproducible spontaneous transition from an epithelioid (E) to a round (R) morphotype. The E to R transition is associated with increased cell growth, absence of E-cadherin-dependent compaction in a slow aggregation assay, loss of contact inhibition of motility and directional migration in a wound filling motility assay. Furthermore, none of the E subclones from LoVo was invasive into chick heart fragments. This is in contrast to the R subclones that were either nonadherent or adherent and invasive. Macroarray analysis demonstrated transcriptional downregulation of plakoglobin in R type LoVo cells and this was confirmed at the level of the mRNA by quantitative RT-PCR. Western blotting showed lower expression of all components of the E-cadherin/catenin complex in R subclones. Interestingly, treatment of R subclones with the demethylating agent 5-aza-2'-deoxycytidine resulted in restoration of the E morphotype, higher expression of E-cadherin, but not plakoglobin mRNA, and higher expression of E-cadherin and plakoglobin at the protein level.

IQGAP proteins are integral components of cytoskeletal regulation

IQGAP1 is a scaffolding protein that binds to a diverse array of signalling and structural molecules. By interacting with its target proteins, human IQGAP1 participates in multiple cellular functions, including Ca(2+)/calmodulin signalling, cytoskeletal architecture, CDC42 and Rac signalling, E-cadherin-mediated cell-cell adhesion and beta-catenin-mediated transcription. Yeast IQGAP homologues are important regulators of cellular morphogenesis because they are required for budding and cytokinesis. Here we discuss the structure and function of IQGAP1 as a member of the family of IQGAP proteins and summarize the current knowledge about IQGAP1 and IQGAP2. Collectively, these data reveal that IQGAP1 is a fundamental regulator of cytoskeletal function.

Synthesis, characterization and in vitro anti-invasive activity screening of polyphenolic and heterocyclic compounds

Invasion is the hallmark of malignant tumors, and is responsible for the bad prognosis of the untreated cancer patients. The search for anti-invasive treatments led us to screen compounds of different classes for their effect in an assay for invasion. Thirty-nine new compounds synthesized in the present study along with 56 already reported compounds belonging mainly to the classes of lactones, pyrazoles, isoxazoles, coumarins, desoxybenzoins, aromatic ketones, chalcones, chromans, isoflavanones have been tested against organotypic confronting cultures of invasive human MCF-7/6 mammary carcinoma cells with embryonic chick heart fragments in vitro. Three of them (a pyrazole derivative, an isoxazolylcoumarin and a prenylated desoxybenzoin) inhibited invasion at concentrations as low as 1 microM; instead of occupying and replacing the heart tissue within 8 days, the MCF-7/6 cells grew around the heart fragments and left it intact, when treated with these compounds. At the anti-invasive concentration of 1 microM, the three compounds did not affect the growth of the MCF-7/6 cells, as shown in the sulforhodamine B assay. Aggregate formation on agar was not stimulated by any of the three anti-invasive compounds, making an effect on the E-cadherin/catenin complex improbable. This is an invasion suppressor that can be activated in MCF-7/6 cells by a number of other molecules. Our data indicate that some polyphenolic and heterocyclic compounds are anti-invasive without being cytotoxic for the cancer cells.

The molecular perspective: cadherin

Learning Objectives

After completing this course, the reader will be able to: Gain a basic understanding of the structure and function of cadherins and their role in cancer metastasis.

Access and take the CME test online and receive one hour of AMA PRA category 1 credit at CME.TheOncologist.com

Overexpression of Hsp27 in a human melanoma cell line: regulation of E-cadherin, MUC18/MCAM, and plasminogen activator (PA) system

Hsp27 is considered a potential marker for cell differentiation in diverse tissues. Several aspects linked to the differentiation process and to the transition from high to low metastatic potential were analyzed in melanoma cells transfected with Hsp27. E-cadherin plays a central role in cell differentiation, migration, and normal development. Loss of expression or function of E-cadherin has been documented in a variety of human malignancies. We observed by fluorescence-activated cell sorter (FACS) as well as immunofluorescence (IF) analysis a pronounced expression of E-cadherin in Hsp27-transfected A375 melanoma cells compared with control melanoma cells. The expression of the adhesion molecule MUC18/MCAM correlates directly with the metastatic potential of melanoma cells. In contrast to wild-type and neotransfected melanoma cells, in Hsp27-transfected cells the expression of MUC18/MCAM could not be detected by FACS and IF analysis. The plasminogen activator (PA) system plays a central role in mediating extracellular proteolysis and also in nonproteolytic events such as cell adhesion, migration, and transmembrane signaling. Hsp27 transfectants revealed elevated messenger ribonucleic acid expression of the urokinase-type PA (uPA) and its inhibitor, PA inhibitor type 1, which might indicate a neutralization effect of the proteolytic activity of uPA. Control cells failed to express both these molecules. The influence of Hsp27 expression on uPA activity and the involvement of E-cadherin could be demonstrated by use of anti-E-cadherin-blocking antibody. Our data provide evidence for an inhibitory-regulatory role of Hsp27 in tumor progression as found in our system.

Expression of S100A4, E-cadherin, alpha- and beta-catenin in breast cancer biopsies

In 66 breast cancer biopsies, the expression of the Ca(2+)-binding protein S100A4, E-cadherin, alpha- and beta-catenin was examined by immunohistochemistry, and the results were related to clinical and pathological parameters. High levels of S100A4 were found to significantly correlate with histological grade (P=0.030) and loss of oestrogen receptor (P=0.046), but not to the time interval between surgery and development of distant metastasis (P=0.51) or to patient survival (P=0.89). Loss of E-cadherin expression, associated with altered cell-cell adhesion, showed a highly significant association to overall survival (P=0.020) and metastasis-free period (P=0.0052). In multivariate analysis, only lymph node involvement was a more significant predictor of patient demise. No association was found between expression of S100A4 and any single member of the cadherin-catenin complex, but a trend (P=0.053) towards reduced expression of one or several of these proteins and S100A4 immunoreactivity was observed. In conclusion, although our results suggest an association between S100A4 expression and an aggressive tumour phenotype, no relationship to overall survival was found. Deregulation of E-cadherin expression, however, was of high prognostic significance.

Smad4 induces the tumor suppressor E-cadherin and P-cadherin in colon carcinoma cells

Smad4 is an intracellular transmitter of TGF-beta signals and its tumor suppressor function is presumed to reside in its capacity to mediate TGF-beta-induced growth inhibition. However, there is accumulating evidence that this hypothesis may be too simple. The roles of TGF-beta in carcinogenesis are complex and also comprise tumor promoting functions particularly in late stage carcinogenesis. Importantly, functional inactivation of Smad4 in colon carcinomas frequently occurs at late stages when tumors acquire invasive and metastatic capabilities. We have previously reported that stable re-expression of Smad4 in SW480 human colon carcinoma cells was adequate to suppress tumor growth in nude mice. However, it did not affect cell growth in vitro nor did it restore TGF-beta responsiveness. Here, we report that Smad4 transcriptionally induced classical cadherins including the invasion suppressor E-cadherin, presumably re-establishing epithelial morphology. Smad4-induced cadherins were able to recruit catenins to the plasma membrane and were functionally active in cell-cell adhesion. These results indicate a novel pathway of Smad4-mediated tumor suppression and suggest that Smad4 in colon cells may be involved in the maintenance of epithelial traits.

Turn-off, drop-out: functional state switching of cadherins

The classic cadherins are a group of calcium dependent, homophilic cell-cell adhesion molecules that drive morphogenetic rearrangements and maintain the integrity of cell groups through the formation of adherens junctions. The formation and maintenance of cadherin-mediated adhesions is a multistep process and mechanisms have evolved to regulate each step. This suggests that functional state switching plays an important role in development. Among the many challenges ahead is to determine the developmental role that functional state switching plays in tissue morphogenesis and to define the roles of each of the several regulatory interactions that participate in switching. One correlate of the loss of cadherin-mediated adhesion, the "turn-off" of cadherin function, is the exit, or "drop-out" of cells from neural and epithelial layers and their conversion to a motile phenotype. We suggest that epithelial mesenchymal conversions may be initiated by signaling pathways that result in the loss of cadherin function. Tyrosine phosphorylation of beta-catenin is one such mechanism. Enhanced phosphorylation of tyrosine residues on beta-catenin is almost invariably associated with loss of the cadherin-actin connection concomitant with loss of adhesive function. There are several tyrosine kinases and phosphatases that have been shown to have the potential to alter the phosphorylation state of beta-catenin and thus the function of cadherins. Our laboratory has focused on the role of the nonreceptor tyrosine phosphatase PTP1B in regulating the phosphorylation of beta-catenin on tyrosine residues. Our data suggest that PTP1B is crucial for maintenance of N-cadherin-mediated adhesions in embryonic neural retina cells. By using an L-cell model system constitutively expressing N-cadherin, we have worked out many of the molecular interactions essential for this regulatory interaction. Extracellular cues that bias this critical regulatory interaction toward increased phosphorylation of beta-catenin may be a critical component of many developmental events.