Post-transcriptional regulation of cadherin-11 expression by GSK-3 and beta-catenin in prostate and breast cancer cells

Cdh11: Roles in different diseases and potential value in disease diagnosis and treatment

Cadherin is a homophilic, Ca2+-dependent cell adhesion glycoprotein that mediates cell-cell adhesion. Among them, Cadherin-11 (CDH11), as a classical cadherin, participates in and influences many crucial aspects of human growth and development. Furthermore, The involvement of CDH11 has been identified in an increasing number of diseases, primarily including various tumorous diseases, fibrotic diseases, autoimmune diseases, neurodevelopmental disorders, and more. In various tumorous diseases, CDH11 acts not only as a tumor suppressor but can also promote migration and invasion of certain tumors through various mechanisms. Likewise, in non-tumorous diseases, CDH11 remains a pivotal factor in disease progression. In this context, we summarize the specific functionalities and mechanisms of CDH11 in various diseases, aiming to gain a more comprehensive understanding of the potential value of CDH11 in disease diagnosis and treatment. This endeavor seeks to provide more effective diagnostic and therapeutic strategies for clinical management across diverse diseases.

Lithium: A Promising Anticancer Agent

Lithium is a therapeutic cation used to treat bipolar disorders but also has some important features as an anti-cancer agent. In this review, we provide a general overview of lithium, from its transport into cells, to its innovative administration forms, and based on genomic, transcriptomic, and proteomic data. Lithium formulations such as lithium acetoacetate (LiAcAc), lithium chloride (LiCl), lithium citrate (Li3C6H5O7), and lithium carbonate (Li2CO3) induce apoptosis, autophagy, and inhibition of tumor growth and also participate in the regulation of tumor proliferation, tumor invasion, and metastasis and cell cycle arrest. Moreover, lithium is synergistic with standard cancer therapies, enhancing their anti-tumor effects. In addition, lithium has a neuroprotective role in cancer patients, by improving their quality of life. Interestingly, nano-sized lithium enhances its anti-tumor activities and protects vital organs from the damage caused by lipid peroxidation during tumor development. However, these potential therapeutic activities of lithium depend on various factors, such as the nature and aggressiveness of the tumor, the type of lithium salt, and its form of administration and dosage. Since lithium has been used to treat bipolar disorder, the current study provides an overview of its role in medicine and how this has changed. This review also highlights the importance of this repurposed drug, which appears to have therapeutic cancer potential, and underlines its molecular mechanisms.

Regulation of AKT phosphorylation by GSK3β and PTEN to control chemoresistance in breast cancer

BACKGROUND

Phosphorylated AKT is highly expressed or overexpressed in chemoresistant tumor samples. However, the precise molecular mechanism involved in AKT phosphorylation-related chemoresistance in breast cancer is still elusive. The present research was designed to estimate the effect of AKT phosphorylation on cell viability and chemoresistance in breast cancer.

METHODS

We utilized MCF-7 and MDA-MB468 human breast cancer cell lines and developed multidrug-resistant MCF-7/MDR and cisplatin-resistant MDA-MB-468 cells. Immunofluorescence analysis and Western blotting were employed to test the level of glycogen synthase kinase 3 beta (GSK3β), phosphorylated phosphatase and tension homologue (p-PTEN) and phosphorylated AKT (p-AKT) in MCF-7/MDR and MDA-MB468 cells. Xenograft assays in nude mice were performed with MCF-7/MDR cells to verify chemoresistance and the signaling pathway upstream of phosphatidylinositide 3-kinase (PI3K)/AKT.

RESULTS

An increase in GSK3β, p-PTEN and p-AKT expression was strongly induced in MCF-7/MDR and cisplatin-resistant MDA-MB-468 cells, and augmented GSK3β phosphorylation and PTEN inactivation enhanced AKT signaling. The elevation in GSK3β, p-PTEN and p-AKT was associated with cell viability based on a CCK-8 assay. The results of in vivo and in vitro assays indicated that GSK3β knockdown with lentiviral shRNA (shRNA-GSK3β) promoted apoptosis and suppressed the migration of cisplatin-resistant MCF-7/MDR cells, while these effects were reversed by activating p-AKT with the PTEN inhibitor bpV(pic).

CONCLUSIONS

AKT phosphorylation mediated by GSK3β and PTEN were correlated with cell viability, migration and apoptosis, which may promote chemoresistance in breast cancer. Furthermore, GSK3β can regulate cell viability through the PTEN/PI3K/AKT signaling pathway and induce chemoresistance, serving as a valuable molecular strategy for breast cancer therapy.

Potassium channel activity controls breast cancer metastasis by affecting β-catenin signaling

Potassium ion channels are critical in the regulation of cell motility. The acquisition of cell motility is an essential parameter of cancer metastasis. However, the role of K⁺ channels in cancer metastasis has been poorly studied. High expression of the hG1 gene, which encodes for Kv11.1 channel associates with good prognosis in estrogen receptor-negative breast cancer (BC). We evaluated the efficacy of the Kv11.1 activator NS1643 in arresting metastasis in a triple negative breast cancer (TNBC) mouse model. NS1643 significantly reduces the metastatic spread of breast tumors in vivo by inhibiting cell motility, reprogramming epithelial–mesenchymal transition via attenuation of Wnt/β-catenin signaling and suppressing cancer cell stemness. Our findings provide important information regarding the clinical relevance of potassium ion channel expression in breast tumors and the mechanisms by which potassium channel activity can modulate tumor biology. Findings suggest that Kv11.1 activators may represent a novel therapeutic approach for the treatment of metastatic estrogen receptor-negative BC. Ion channels are critical factor for cell motility but little is known about their role in metastasis. Stimulation of the Kv11.1 channel suppress the metastatic phenotype in TNBC. This work could represent a paradigm-shifting approach to reducing mortality by targeting a pathway that is central to the development of metastases.

Discovery and anti-inflammatory evaluation of benzothiazepinones (BTZs) as novel non-ATP competitive inhibitors of glycogen synthase kinase-3β (GSK-3β)

Glycogen synthase kinase-3β (GSK-3β) has been identified to promote inflammation and its inhibitors have also been proven to treat some inflammatory mediated diseases in animal models. Non-ATP competitive inhibitors inherently have better therapeutical value due to their higher specificity than ATP competitive ones. In this paper, we designed and synthesized a series of new BTZ derivatives as non-ATP competitive GSK-3β inhibitors. Kinetic analysis revealed two typical compounds 6j and 3j showed the different non-ATP competitive mechanism of substrate competition or allosteric modulation to GSK-3β, respectively. As expected, the two compounds showed good specificity in a panel test of 16 protein kinases, even to the closest enzymes, like CDK-1/cyclin B and CK-II. The in vivo results proved that both compounds can greatly attenuate the LPS-induced acute lung injury (ALI) and diminish inflammation response in mice by inhibiting the mRNA expression of IL-1β and IL-6. Western blot analysis demonstrated that they negatively regulated GSK-3β, and the mechanism of the observed beneficial effects of the inhibitors may involve both the increased phosphorylation of the Ser9 residue on GSK-3β and protein expression of Sirtuin 1 (SIRT1). The results support that such novel BTZ compounds have a protective role in LPS-induced ALI, and might be attractive candidates for further development of inflammation pharmacotherapy, which greatly thanks to their inherently high selectivities by the non-ATP competitive mode of action. Finally, we proposed suggesting binding modes by Docking study to well explain the impacts of compounds on the target site.

Cadherin-11 expression is upregulated in invasive human breast cancer

Loss of expression of cadherin-11 protein is correlated with a loss of epithelial phenotype and a gain in tumor cell proliferation and invasion. It has been hypothesized that cadherin-11 may be a molecular marker for a more aggressive subtype of breast cancer. The present study examined the expression of the mesenchymal gene/protein cadherin-11 in malignant, benign and healthy breast cancer samples. A paraffin-embedded tissue microarray of both malignant and benign/healthy breast tumor was used. Clinicopathological parameters, including age, grading, tumor size, hormone receptors and HER2 receptors status were obtained from patient medical records. Expression of cadherin-11 was analyzed using the monoclonal mouse anti cadherin-11 IgG2B clone. Total RNA was extracted from each breast cancer sample and subjected to semi-quantitative RT-PCR analysis for cadherin-11. Cadherin-11 was detected in 80/82 malignant breast cancer samples and in 33/70 non-malignant tissue samples. Cadherin-11 expression was observed to be predominantly localized to the membrane of tumor cells. When compared to healthy breast tissue biopsies, both cadherin-11 mRNA and protein were demonstrated to be significantly overexpressed in breast carcinoma (P=0.040 and P<0.0001, respectively). Within malignant tumors, however, protein expression was not identified to be associated with other clinicopathological parameters. Our results indicate that cadherin-11 expression is upregulated in malignant human breast cancer.

A Metabolic Inhibitory Cocktail for Grave Cancers: Metformin, Pioglitazone and Lithium Combination in Treatment of Pancreatic Cancer and Glioblastoma Multiforme

Pancreatic cancer (PC) and glioblastoma multiforme (GBM) are among the human cancers with worst prognosis which require an urgent need for efficient therapies. Here, we propose to apply to treat both malignancies with a triple combination of drugs, which are already in use for different indications. Recent studies demonstrated a considerable link between risk of PC and diabetes. In experimental models, anti-diabetogenic agents suppress growth of PC, including metformin (M), pioglitazone (P) and lithium (L). L is used in psychiatric practice, yet also bears anti-diabetic potential and selectively inhibits glycogen synthase kinase-3 beta (GSK-3β). M, a biguanide class anti-diabetic agent shows anticancer activity via activating AMP-activated protein kinase (AMPK). Glitazones bind to PPAR-γ and inhibit NF-κB, triggering cell proliferation, apoptosis resistance and synthesis of inflammatory cytokines in cancer cells. Inhibition of inflammatory cytokines could simultaneously decrease tumor growth and alleviate cancer cachexia, having a major role in PC mortality. Furthermore, mutual synergistic interactions exist between PPAR-γ and GSK-3β, between AMPK and GSK-3β and between AMPK and PPAR-γ. In GBM, M blocks angiogenesis and migration in experimental models. Very noteworthy, among GBM patients with type 2 diabetes, usage of M significantly correlates with better survival while reverse is true for sulfonylureas. In experimental models, P synergies with ligands of RAR, RXR and statins in reducing growth of GBM. Further, usage of P was found to be lesser in anaplastic astrocytoma and GBM patients, indicating a protective effect of P against high-grade gliomas. L is accumulated in GBM cells faster and higher than in neuroblastoma cells, and its levels further increase with chronic exposure. Recent studies revealed anti-invasive potential of L in GBM cell lines. Here, we propose that a triple-agent regime including drugs already in clinical usage may provide a metabolic adjuvant therapy for PC and GBM.

AP-1 Transcription Factors c-FOS and c-JUN Mediate GnRH-Induced Cadherin-11 Expression and Trophoblast Cell Invasion

GnRH is expressed in first-trimester human placenta and increases cell invasion in extravillous cytotrophoblasts (EVTs). Invasive phenotypes have been reported to be regulated by transcription factor activator protein 1 (AP-1) and mesenchymal cadherin-11. The aim of our study was to investigate the roles of AP-1 components (c-FOS/c-JUN) and cadherin-11 in GnRH-induced cell invasion in human EVT cells. Phosphorylated c-FOS and phosphorylated c-JUN were detected in the cell column regions of human first-trimester placental villi by immunohistochemistry. GnRH treatment increased c-FOS, c-JUN, and cadherin-11 mRNA and protein levels in immortalized EVT (HTR-8/SVneo) cells. Moreover, GnRH treatment induced c-FOS and c-JUN protein phosphorylation and nuclear accumulation. Pretreatment with antide, a GnRH antagonist, attenuated GnRH-induced cadherin-11 expression. Importantly, basal and GnRH-induced cadherin-11 expression and cell invasion were reduced by small interfering RNA-mediated knockdown of c-FOS, c-JUN, and cadherin-11 in HTR-8/SVneo cells. Our results suggest that GnRH induces the expression and phosphorylation of the AP-1 transcription factors c-FOS and c-JUN in trophoblast cells, which contributes to GnRH-induced elevation of cadherin-11 expression and cell invasion.

Notch1 Mutation Leads to Valvular Calcification Through Enhanced Myofibroblast Mechanotransduction

OBJECTIVE

Calcific aortic valve disease (CAVD) is a significant cardiovascular disorder, and controversy exists as to whether it is primarily a dystrophic or osteogenic process in vivo. In this study, we sought to clarify the mechanism of CAVD by assessing a genetic mutation, Notch1 heterozygosity, which leads to CAVD with 100% penetrance in humans.

APPROACH AND RESULTS

Murine immortalized Notch1(+/-) aortic valve interstitial cells (AVICs) were isolated and expanded in vitro. Molecular signaling of wild-type and Notch1(+/-) AVICs were compared to identify changes in pathways that have been linked to CAVD-transforming growth factor-β1/bone morphogenetic protein, mitogen-activated protein kinase, and phosphoinositide 3-kinase/protein kinase B-and assessed for calcification potential. Additionally, AVIC mechanobiology was studied in a physiologically relevant, dynamic mechanical environment (10% cyclic strain) to investigate differences in responses between the cell types. We found that Notch1(+/-) AVICs resembled a myofibroblast-like phenotype expressing higher amounts of cadherin-11, a known mediator of dystrophic calcification, and decreased Runx2, a known osteogenic marker. We determined that cadherin-11 expression is regulated by Akt activity, and inhibition of Akt phosphorylation significantly reduced cadherin-11 expression. Moreover, in the presence of cyclic strain, Notch1(+/-) AVICs exhibited significantly upregulated phosphorylation of Akt at Ser473 and smooth muscle α-actin expression, indicative of a fully activated myofibroblast. Finally, these Notch1-mediated alterations led to enhanced dystrophic calcific nodule formation.

CONCLUSIONS

This study presents novel insights in our understanding of Notch1-mediated CAVD by demonstrating that the mutation leads to AVICs that are fully activated myofibroblasts, resulting in dystrophic, but not osteogenic, calcification.

Deregulation of the EGFR/PI3K/PTEN/Akt/mTORC1 pathway in breast cancer: possibilities for therapeutic intervention

The EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway plays prominent roles in malignant transformation, prevention of apoptosis, drug resistance and metastasis. The expression of this pathway is frequently altered in breast cancer due to mutations at or aberrant expression of: HER2, ERalpha, BRCA1, BRCA2, EGFR1, PIK3CA, PTEN, TP53, RB as well as other oncogenes and tumor suppressor genes. In some breast cancer cases, mutations at certain components of this pathway (e.g., PIK3CA) are associated with a better prognosis than breast cancers lacking these mutations. The expression of this pathway and upstream HER2 has been associated with breast cancer initiating cells (CICs) and in some cases resistance to treatment. The anti-diabetes drug metformin can suppress the growth of breast CICs and herceptin-resistant HER2+ cells. This review will discuss the importance of the EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway primarily in breast cancer but will also include relevant examples from other cancer types. The targeting of this pathway will be discussed as well as clinical trials with novel small molecule inhibitors. The targeting of the hormone receptor, HER2 and EGFR1 in breast cancer will be reviewed in association with suppression of the EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway.

Cadherin-11 in poor prognosis malignancies and rheumatoid arthritis: common target, common therapies

Cadherin-11 (CDH11), associated with epithelial to mesenchymal transformation in development, poor prognosis malignancies and cancer stem cells, is also a major therapeutic target in rheumatoid arthritis (RA). CDH11 expressing basal-like breast carcinomas and other CDH11 expressing malignancies exhibit poor prognosis. We show that CDH11 is increased early in breast cancer and ductal carcinoma in-situ. CDH11 knockdown and antibodies effective in RA slowed the growth of basal-like breast tumors and decreased proliferation and colony formation of breast, glioblastoma and prostate cancer cells. The repurposed arthritis drug celecoxib, which binds to CDH11, and other small molecules designed to bind CDH11 without inhibiting COX-2 preferentially affect the growth of CDH11 positive cancer cells in vitro and in animals. These data suggest that CDH11 is important for malignant progression, and is a therapeutic target in arthritis and cancer with the potential for rapid clinical translation

Cadherin 11, a miR-675 target, induces N-cadherin expression and epithelial-mesenchymal transition in melasma

Cadherin 11 (CDH11) was identified as a target of miR-675 by using a luciferase reporter assay. CDH11 expression and miR-675 expression were inversely correlated. CDH11 expression was not detected in melanocytes, but CDH11 expression in fibroblasts and keratinocytes positively influenced melanogenesis via the canonical Wnt and AKT activation pathways in cocultured melanocytes. CDH11 in fibroblasts or keratinocytes induced N-cadherin and Twist1 expression, while decreasing E-cadherin expression. This suggests a role for CDH11 in epithelial-mesenchymal transition. CDH11 in fibroblasts also induced the migration of cocultured melanocytes. N-cadherin knockdown abolished the tyrosinase expression that was induced in CDH11-overexpressing fibroblasts. Collectively, our data indicate that CDH11 in fibroblasts and keratinocytes is a target of miR-675, and could be involved in melanogenesis through the induction of N-cadherin during epithelial-mesenchymal transition.

Beta-catenin/HuR post-transcriptional machinery governs cancer stem cell features in response to hypoxia

Hypoxia has been long-time acknowledged as major cancer-promoting microenvironment. In such an energy-restrictive condition, post-transcriptional mechanisms gain importance over the energy-expensive gene transcription machinery. Here we show that the onset of hypoxia-induced cancer stem cell features requires the beta-catenin-dependent post-transcriptional up-regulation of CA9 and SNAI2 gene expression. In response to hypoxia, beta-catenin moves from the plasma membrane to the cytoplasm where it binds and stabilizes SNAI2 and CA9 mRNAs, in cooperation with the mRNA stabilizing protein HuR. We also provide evidence that the post-transcriptional activity of cytoplasmic beta-catenin operates under normoxia in basal-like/triple-negative breast cancer cells, where the beta-catenin knockdown suppresses the stem cell phenotype in vitro and tumor growth in vivo. In such cells, we unravel the generalized involvement of the beta-catenin-driven machinery in the stabilization of EGF-induced mRNAs, including the cancer stem cell regulator IL6. Our study highlights the crucial role of post-transcriptional mechanisms in the maintenance/acquisition of cancer stem cell features and suggests that the hindrance of cytoplasmic beta-catenin function may represent an unprecedented strategy for targeting breast cancer stem/basal-like cells.

Development of a method to isolate circulating tumor cells using mesenchymal-based capture

Epithelial tumor cells can become mesenchymal cells and vice versa via phenotypic transitions, a process known as epithelial plasticity. We postulate that during the process of metastasis, circulating tumor cells (CTCs) lose their epithelial phenotype and acquire a mesenchymal phenotype that may not be sufficiently captured by existing epithelial-based CTC technologies. We report here on the development of a novel CTC capture method, based on the biology of epithelial plasticity, which isolates cells based on OB-cadherin cell surface expression. Using this mesenchymal-based assay, OB-cadherin cellular events are detectable in men with metastatic prostate cancer and are less common in healthy volunteers. This method may complement existing epithelial-based methods and may be particularly useful in patients with bone metastases.

Role of cadherin-11 in synovial joint formation and rheumatoid arthritis pathology

Cadherin-11 is a classic cadherin adhesion molecule that mediates homophilic cell-to-cell adhesion. Cadherin-11 is involved in the function of embryonic development, tissue morphogenesis, tumor invasion and metastasis, and signal transduction. This review summarizes the function of cadherin-11 in synovial joint formation and rheumatoid arthritis (RA), including its relative function with bone and cartilage development and growth plate, synovial, and tendon formation. The role of cadherin-11 in RA is also discussed, both in fibroblasts inflammation and fibroblast-like synoviocyte (FLSs) migration and invasion. The potential of anti-cadherin-11 therapy for RA is introduced in comparison with the other current RA therapies.

Biomarkers of epithelial-mesenchymal transition in squamous cell carcinoma

An understanding of the process by which tumor cells destroy the basement membrane of the surface epithelium, invade, and metastasize is essential to the development of novel treatment of head and neck squamous cell carcinoma (HNSCC). In recent years, there has been increased interest in the role of epithelial-mesenchymal transition (EMT) in invasion. EMT is a process that describes the development of motile, mesenchymal-like cells from non-motile parent epithelial cells. There are 3 known types of EMT that mediate development, wound healing, and carcinogenesis. This review summarizes studies of known EMT biomarkers in the context of HNSCC progression. The biomarkers discussed come from a wide range of proteins, including cell-surface proteins (E-cadherin, N-cadherin, and Integrins), cytoskeletal proteins (α-Smooth Muscle Actin, Vimentin, and β-catenin), extracellular matrix proteins (Collagens, Fibronectin, and Laminin), and transcription factors (SNAIL1, SNAIL2, TWIST, and LEF-1). Overall, the findings of these studies suggest that EMT mediates HNSCC progression. The mechanistic role of the EMT markers that have been associated with HNSCC should be more clearly defined if new anti-HNSCC therapies to block EMT progression are to be developed.

TARGETgene: a tool for identification of potential therapeutic targets in cancer

The vast array of in silico resources and data of high throughput profiling currently available in life sciences research offer the possibility of aiding cancer gene and drug discovery process. Here we propose to take advantage of these resources to develop a tool, TARGETgene, for efficiently identifying mutation drivers, possible therapeutic targets, and drug candidates in cancer. The simple graphical user interface enables rapid, intuitive mapping and analysis at the systems level. Users can find, select, and explore identified target genes and compounds of interest (e.g., novel cancer genes and their enriched biological processes), and validate predictions using user-defined benchmark genes (e.g., target genes detected in RNAi screens) and curated cancer genes via TARGETgene. The high-level capabilities of TARGETgene are also demonstrated through two applications in this paper. The predictions in these two applications were then satisfactorily validated by several ways, including known cancer genes, results of RNAi screens, gene function annotations, and target genes of drugs that have been used or in clinical trial in cancer treatments. TARGETgene is freely available from the Biomedical Simulations Resource web site (http://bmsr.usc.edu/Software/TARGET/TARGET.html).

Mitochondrial DNA maintenance is regulated in human hepatoma cells by glycogen synthase kinase 3β and p53 in response to tumor necrosis factor α

During chronic liver inflammation, up-regulated Tumor Necrosis Factor alpha (TNF-α) targets hepatocytes and induces abnormal reactive oxygen species (ROS) production responsible for mitochondrial DNA (mtDNA) alterations. The serine/threonine Glycogen Synthase Kinase 3 beta (GSK3β) plays a pivotal role during inflammation but its involvement in the maintenance of mtDNA remains unknown. The aim of this study was to investigate its involvement in TNF-α induced mtDNA depletion and its interrelationship with p53 a protein known to maintain mtDNA copy numbers. Using quantitative polymerase chain reaction (qPCR) we found that at 30 min in human hepatoma HepG2 cells TNF-α induced 0.55±0.10 mtDNA lesions per 10 Kb and a 52.4±2.8% decrease in mtDNA content dependent on TNF-R1 receptor and ROS production. Both lesions and depletion returned to baseline from 1 to 6 h after TNF-α exposure. Luminol-amplified chemiluminescence (LAC) was used to measure the rapid (10 min) and transient TNF-α induced increase in ROS production (168±15%). A transient 8-oxo-dG level of 1.4±0.3 ng/mg DNA and repair of abasic sites were also measured by ELISA assays. Translocation of p53 to mitochondria was observed by Western Blot and co-immunoprecipitations showed that TNF-α induced p53 binding to GSK3β and mitochondrial transcription factor A (TFAM). In addition, mitochondrial D-loop immunoprecipitation (mtDIP) revealed that TNF-α induced p53 binding to the regulatory D-loop region of mtDNA. The knockdown of p53 by siRNAs, inhibition by the phosphoSer(15)p53 antibody or transfection of human mutant active GSK3βS9A pcDNA3 plasmid inhibited recovery of mtDNA content while blockade of GSK3β activity by SB216763 inhibitor or knockdown by siRNAs suppressed mtDNA depletion. This study is the first to report the involvement of GSK3β in TNF-α induced mtDNA depletion. We suggest that p53 binding to GSK3β, TFAM and D-loop could induce recovery of mtDNA content through mtDNA repair.

Large scale phosphoproteome analysis of LNCaP human prostate cancer cells

Prostate cancer is the most frequently diagnosed cancer among men in the western world. The androgen receptor, a phosphoprotein, is suspected to be involved in all stages of the prostate cancer. Androgen receptor activity can be modulated by various kinases such as PKA, MAPK, AKT, and Src. Phosphorylation is an important post-translational modification and serves as a molecular on-off switch to regulate signaling. Disruptions of cellular phosphorylation are associated with various diseases such as cancer and kinases provide important drug targets. Here we present an analysis of the phosphoproteome in LNCaP human prostate cancer cells. The analytical strategy employed here used proteomics based methodologies with a combination of detergents and chaotropic reagents during trypsin digestion followed by titanium dioxide enrichment of phosphopeptides. Over the course of multiple analyses by mass spectrometry we identified a total of 746 phosphorylation sites in 540 phosphopeptides corresponding to 116 phosphoproteins, of which 56 had not been previously reported. Phosphoproteins identified included transcription factors, co-regulators of the androgen receptor, and cancer-related proteins that include β-catenin, USP10, and histone deacetylase-2. The information of signaling pathways, motifs of phosphorylated peptides, biological processes, molecular functions, cellular components, and protein interactions from the identified phosphoproteins established a map of phosphoproteome and signaling pathways in LNCaP cells.

The role and function of cadherins in the mammary gland

Cadherins are transmembrane receptors that function through calcium-dependent homophilic and heterophilic interactions that provide cell-cell contact and communication in many different organ systems. In the mammary gland only a few of the cadherins that make up this large superfamily of proteins have been characterized. Frequently in metastatic breast cancer, the genes for cadherins are epigenetically silenced, mutated, or regulated differently. During epithelial-mesenchymal transition, cadherins that are expressed normally in the epithelial cells are down-regulated, while cadherins expressed in the mesenchyme are up-regulated. This process is known as cadherin switching, and its regulation can sometimes facilitate the increased motility, invasiveness and proliferation that occurs in metastatic cancer cells. Depending on the context, however, cell motility, invasiveness, proliferation and expression of mesenchymal markers can be independently modulated from cadherin expression, leading to partial epithelial-mesenchymal transitions and even mesenchymal-epithelial transitions (METs). This review will summarize the current understanding of cadherins found in the mammary gland and what is known about their mechanism of regulation in the mammary gland during normal physiological conditions and in breast cancer.

Upregulation of glycogen synthase kinase 3β in human colorectal adenocarcinomas correlates with accumulation of CTNNB1

INTRODUCTION

Mutations of the adenomatous polyposis coli (APC) tumor suppressor gene or the CTNNB1 protooncogene have been implicated in the initiation of most human colorectal epithelial neoplasms. Glycogen synthase kinase 3β (GSK3B) serves a critical role in regulating their functions by phosphorylating both APC and CTNNB1 to facilitate CTNNB1 degradation. The current studies were performed to investigate whether GSK3B itself is regulated during the process of colorectal tumorigenesis.

PATIENTS AND METHODS

We examined the expression of GSK3B and CTNNB1 in tissue samples from 24 human colorectal adenocarcinomas by Western immunoblotting analysis, kinase activity assays and immunohistochemistry. Normal colonic mucosa from the same colectomy specimens were used as a reference for comparison.

RESULTS

We demonstrated that GSK3B expression levels and kinase activities were markedly and significantly increased in colorectal adenocarcinomas in all 24 cases compared with paired adjacent normal-appearing colonic mucosa. These increases correlated with significantly increased expression of CTNNB1 in the same tumors. Similar results were obtained in several cultured human colon cancer cell lines, demonstrating GSK3B levels correlated with CTNNB1 expression.

CONCLUSION

Though APC and CTNNB1 regulation by GSK3B are frequently disrupted by mutations in colon cancers, our observations suggest that increased functional GSK3B might drive other growth-promoting signals in colorectal tumorigenesis.

Profilin-1 overexpression restores adherens junctions in MDA-MB-231 breast cancer cells in R-cadherin-dependent manner

Profilin-1 (Pfn1), a ubiquitously expressed actin-binding protein, is downregulated in several different types of adenocarcinoma and elicits tumor-suppressive effect on breast cancer cell lines. MDA-MB-231 (MDA-231), a breast cancer cell line that displays all the characteristics of post-epithelial-to-mesenchymal transition and does not form cell-cell adhesion, can be reverted to an epithelioid phenotype by Pfn1 overexpression. This morphological transition is caused by restoration of adherens junctions (AJ) requiring Pfn1's interaction with actin. Pfn1 overexpression increases the expression level of R-cadherin (a type of cadherin that is endogenously expressed in the parental cell line) and restores AJ in MDA-231 cells in R-cadherin-dependent manner. These findings highlight important role of Pfn1 in the regulation of epithelial cell-cell adhesion.