Bruton's tyrosine kinase revealed as a negative regulator of Wnt-beta-catenin signaling

Zebrafish and bioactive compounds: a bibliometric review

Bibliometrics has become a crucial tool for evaluating and analyzing researchers' output. In recent decades, zebrafish has demonstrated its potential for studying oxidative stress, and the use of medicinal plants has proven essential in this context, as they are endowed with bioactive compounds that possess antioxidant properties. Thus, the aim of this study was to conduct a bibliometric review to analyze the evolution of publications concerning the concepts of "zebrafish" and "bioactive compounds." The Web of Science (WoS) database was utilized. Data on authors, countries, most cited journals, co-authorship between countries and authors, co-occurrence of keywords, keyword co-occurrence by publication year, and co-citation of references were analyzed using VOSviewer software. A total of 170 documents were retrieved, spanning the years 2004 to 2024. Jean Luc Wolfender, the United States, and PLoS One were prominent among the authors, countries, and journals with the highest citations, respectively. Among the co-occurrence of keywords, the following were noteworthy: zebrafish (n = 60), bioactive compounds (n = 12), angiogenesis (n = 9), antioxidant (n = 8), oxidative stress (n = 8), apoptosis (n = 7), antioxidant activity (n = 7), and toxicity (n = 7). It was concluded that the highest number of published documents was observed in 2022. Moreover, from 2018 onward, there has been an increase in research using the zebrafish model and bioactive compounds, highlighting the field of Pharmacy/Pharmacology in the development of new drugs, with a strong emphasis on the use of medicinal plants.

Combined targeting of Hedgehog/GLI1 and Wnt/β-catenin pathways in mantle cell lymphoma

Mantle cell lymphoma (MCL) is a rare and aggressive form of non-Hodgkin lymphoma. Challenges in its treatment include relapse, drug resistance, and a short survival period. The Hedgehog/GLI1 (Hh/GLI1) and Wnt/β-catenin pathways are crucial in cancer cell proliferation, survival, and drug resistance, making them significant targets for anticancer research. This study aimed to assess the effectiveness of combining inhibitors for both pathways against MCL and investigate the underlying molecular mechanisms. The co-expression of key proteins from the Hh/GLI1 and Wnt/β-catenin pathways was observed in MCL. Targeting the Hh/GLI1 pathway with the GLI1 inhibitor GANT61 and the Wnt/β-catenin pathway with the CBP/β-catenin transcription inhibitor ICG-001, dual-target therapy was demonstrated to synergistically suppressed the activity of MCL cells. This approach promoted MCL cell apoptosis, induced G0/G1 phase blockade, decreased the percentage of S-phase cells, and enhanced the sensitivity of MCL cells to the drugs adriamycin and ibrutinib. Both GANT61 and ICG-001 downregulated GLI1 and β-catenin while upregulating GSK-3β expression. The interaction between Hh/GLI1 and Wnt/β-catenin pathways was mediated by GANT61-dependent Hh/GLI1 inhibition. Moreover, GLI1 knockdown combined with ICG-001 synergistically induced apoptosis and increased drug sensitivity of MCL cells to doxorubicin and ibrutinib. GANT61 attenuated the overexpression of β-catenin and decreased the inhibition of GSK-3β in MCL cells. Overall, the combined targeting of both the Hh/GLI1 and Wnt/β-catenin pathways was more effective in suppressing proliferation, inducing G0/G1 cycle retardation, promoting apoptosis, and increasing drug sensitivity of MCL cells than mono treatments. These findings emphasize the potential of combinatorial therapy for treating MCL patients.

High incidence of imperforate vagina in ADGRA3-deficient mice

BACKGROUND

Ten percent of the female population suffers from congenital abnormalities of the vagina, uterus, or oviducts, with severe consequences for reproductive and psychological health. Yet, the underlying causes of most of these malformations remain largely unknown. ADGRA3 (GPR125) is involved in WNT signaling and planar cell polarity, mechanisms vital to female reproductive tract development. Although ADGRA3 is a well-established spermatogonial stem cell marker, its role within the female urogenital system remains unclear.

RESULTS

In this study, we found Adgra3 to be expressed throughout the murine female urogenital system, with higher expression pre-puberty than after sexual maturation. We generated a global Adgra3-/- mouse line and observed imperforate vagina in 44% of Adgra3-/- females, resulting in distension of the reproductive tract and infertility. Ovarian morphology, plasma estradiol, ovarian Cyp19a1, and vaginal estrogen receptor α (Esr1) expression were unaffected. However, compared to controls, a significantly lower bone mineral density was found in Adgra3-/- mice. Whereas vaginal opening in mice is an estrogen-dependent process, 17β-estradiol treatment failed to induce vaginal canalization in Adgra3-/- mice. Furthermore, a marked reduction in vaginal and ovarian progesterone receptor expression was observed concomitant with an upregulation of apoptotic regulators Bcl2, Bid, and Bmf in adult Adgra3-/- females with a closed vagina.

CONCLUSIONS

Our collective results shed new insights into the complex mechanisms by which the adhesion receptor ADGRA3 regulates distal vaginal tissue remodeling during vaginal canalization via altered sex hormone responsiveness and balance in apoptotic regulators. This highlights the potential of ADGRA3 as a target in diagnostic screening and/or therapy for obstructive vaginal malformations in humans.

The mechanisms of class 1A PI3K and Wnt/β-catenin coupled signaling in breast cancer

The class IA PI3K signaling pathway is activated by growth factor stimulation and regulates a signaling cascade that promotes diverse events including cell growth, proliferation, migration and metabolism. PI3K signaling is one of the most commonly hyperactivated pathways in breast cancer, leading to increased tumor growth and progression. PI3K hyperactivation occurs via a number of genetic and epigenetic mechanisms including mutation or amplification of PIK3CA, the gene encoding the p110α subunit of PI3Kα, as well as via dysregulation of the upstream growth factor receptors or downstream signaling effectors. Over the past decade, extensive efforts to develop therapeutics that suppress oncogenic PI3K signaling have been undertaken. Although FDA-approved PI3K inhibitors are now emerging, their clinical success remains limited due to adverse effects and negative feedback mechanisms which contribute to their reduced efficacy. There is an emerging body of evidence demonstrating crosstalk between the PI3K and Wnt/β-catenin pathways in breast cancer. However, PI3K exhibits opposing effects on Wnt/β-catenin signaling in distinct tumor subsets, whereby PI3K promotes Wnt/β-catenin activation in ER+ cancers, but paradoxically suppresses this pathway in ER- breast cancers. This review discusses the molecular mechanisms for PI3K-Wnt crosstalk in breast cancer, and how Wnt-targeted therapies have the potential to contribute to treatment regimens for breast cancers with PI3K dysregulation.

Overexpression of Bruton Tyrosine Kinase Inhibits the Proliferation, Migration, and Invasion of Non-Small Cell Lung Cancer Cells

Lung cancer is one of the most lethal malignant tumors in the world. Non-small cell lung cancer (NSCLC) is the most common pathological subtype. However, the molecular mechanism of NSCLC progress is still unclear. We extracted the expression data of the Bruton's tyrosine kinase (BTK) gene in NSCLC tissues from the TCGA database. The results of paired t-test showed that the BTK gene was significantly underexpressed in NSCLC tissues. To further verify the above results, we detected the expression of the BTK gene in NSCLC cell lines A549, H1299, and H1650 at the RNA and protein levels by real-time fluorescent quantitative polymerase chain reaction and Western Blot analysis, respectively. The results showed that BTK was low expressed in NSCLC tissues and cells. More importantly, the expression of the BTK gene is also significantly related to the patient's age, gender, tumor range (T), lymph node invasion (N), tumor stage, and prognosis, and its expression level gradually decreases with the progress of the disease. It is speculated that BTK may be an independent prognostic factor of NSCLC. Our experimental results are consistent with the above clinical correlation analysis results. Overexpression of BTK can significantly inhibit the proliferation, migration, and invasion of NSCLC cells and can block the G0/G1 tumor cell cycle, indicating that overexpression of BTK can inhibit the growth, migration, and invasion of NSCLC cells.

Cell-Based Double-Screening Method to Identify a Reliable Candidate for Osteogenesis-Targeting Compounds

Small-molecule compounds strongly affecting osteogenesis can form the basis of effective therapeutic strategies in bone regenerative medicine. A cell-based high-throughput screening system might be a powerful tool for identifying osteoblast-targeting candidates; however, this approach is generally limited with using only one molecule as a cell-based sensor that does not always reflect the activation of the osteogenic phenotype. In the present study, we used the MC3T3-E1 cell line stably transfected with the green fluorescent protein (GFP) reporter gene driven by a fragment of type I collagen promoter (Col-1a1GFP-MC3T3-E1) to evaluate a double-screening system to identify osteogenic inducible compounds using a combination of a cell-based reporter assay and detection of alkaline phosphatase (ALP) activity. Col-1a1GFP-MC3T3-E1 cells were cultured in an osteogenic induction medium after library screening of 1280 pharmacologically active compounds (Lopack¹²⁸⁰). After 7 days, GFP fluorescence was measured using a microplate reader. After 14 days of osteogenic induction, the cells were stained with ALP. Library screening using the Col-1a1/GFP reporter and ALP staining assay detected three candidates with significant osteogenic induction ability. Furthermore, leflunomide, one of the three detected candidates, significantly promoted new bone formation in vivo. Therefore, this double-screening method could identify candidates for osteogenesis-targeting compounds more reliably than conventional methods.

Colonic epithelial adaptation to EGFR-independent growth induces chromosomal instability and is accelerated by prior injury

Although much is known about the gene mutations required to drive colorectal cancer (CRC) initiation, the tissue-specific selective microenvironments in which neoplasia arises remains less characterized. Here, we determined whether modulation of intestinal stem cell niche morphogens alone can exert a neoplasia-relevant selective pressure on normal colonic epithelium. Using adult stem cell-derived murine colonic epithelial organoids (colonoids), we employed a strategy of sustained withdrawal of epidermal growth factor (EGF) and epidermal growth factor receptor (EGFR) inhibition to select for and expand survivors. EGFR-signaling-independent (iEGFR) colonoids emerged over rounds of selection and expansion. Colonoids derived from a mouse model of chronic mucosal injury showed an enhanced ability to adapt to EGFR inhibition. Whole-exome and transcriptomic analyses of iEGFR colonoids demonstrated acquisition of deleterious mutations and altered expression of genes implicated in EGF signaling, pyroptosis, and CRC. iEGFR colonoids acquired dysplasia-associated cytomorphologic changes, an increased proliferative rate, and the ability to survive independently of other required niche factors. These changes were accompanied by emergence of aneuploidy and chromosomal instability; further, the observed mitotic segregation errors were significantly associated with loss of interkinetic nuclear migration, a fundamental and dynamic process underlying intestinal epithelial homeostasis. This study provides key evidence that chromosomal instability and other phenotypes associated with neoplasia can be induced ex vivo via adaptation to EGF withdrawal in normal and stably euploid colonic epithelium, without introducing cancer-associated driver mutations. In addition, prior mucosal injury accelerates this evolutionary process.

NUP153 overexpression suppresses the proliferation of colorectal cancer by negatively regulating Wnt/β-catenin signaling pathway and predicts good prognosis

BACKGROUND

Nucleoporin NUP153 (NUP153) is well known to be involved in the regulating of nuclear transport. Although NUP153 is associated with several cancers, its role in colorectal cancer (CRC) and the underlying mechanism are still unknown.

OBJECTIVE

The aim of this study was to access the effect of NUP153 on the prognosis of patients with CRC, and cancer cell proliferation.

METHODS

The expression levels of NUP153 in CRC tissues and matched normal colon tissues were examined by real-time quantitative PCR and immunohistochemistry. Then the association between NUP153 levels with clinical variables as well as survival time was investigated. Moreover, overexpression of NUP153 in HCT116 cells was established to study its influence on cell proliferation in vitro, and a xenograft model was performed to explore this effect in vivo.

RESULTS

We found that NUP153 was highly expressed in adjacent normal tissues than in cancer tissues, and elevated NUP153 expression was negatively associated with pathological grade (P= 0.015), T stage (P= 0.048) and distant metastasis (P= 0.006). Kaplan-Meier analysis revealed that patients with higher NUP153 expression had a longer overall survival (OS) (P= 0.01) and recurrence free disease (RFS) (P= 0.001). Logistic regression analysis further identified NUP153 as an independent prognostic safe factor for OS and recurrence. Moreover, NUP153 overexpression suppressed CRC cells proliferation and inhibited tumor growth in a xenograft model. Its mechanistic investigations showed that NUP153 overexpression inhibited β-catenin transcriptional activity and down-regulated the mRNA expression levels of Wnt downstream proteins-Axin2, cyclinD1, c-myc and lef-1.

CONCLUSIONS

NUP153 might be a promising prognostic factor, a potential tumor suppressor and therapeutic target in human CRC through an interaction with the Wnt/β-catenin signaling pathway.

MicroRNA-885-5p promotes osteosarcoma proliferation and migration by downregulation of cell division cycle protein 73 homolog expression

Osteosarcoma (OS) is the most common primary malignant bone tumor. Numerous studies have strongly implicated the ectopic expression of microRNAs (miRNAs/miRs), including miR-885-5p, which is aberrantly expressed in several cancer types, in multiple cancer-related processes. However, the role of miR-885-5p in OS remains unknown. In the present study, it was found that the expression of miR-885-5p was markedly upregulated in OS cell lines and clinical tissues. Moreover, high expression of miR-885-5p was significantly associated with the development of OS. The human OS MG-63 cell line was transfected with recombinant lentivirus to regulate miR-885-5p expression. Overexpressed miR-885-5p significantly promoted the proliferation and migration of MG-63 cells in vitro, while downregulating miR-885-5p expression reversed these effects. Furthermore, bioinformatic analysis was used to predict the potential target genes of miR-885-5p, and cell division cycle protein 73 homolog (CDC73) was identified as a novel and direct target of miR-885-5p. This interaction was further confirmed using reverse transcription-quantitative polymerase chain reaction, western blotting and luciferase activity assays. These findings suggest that miR-885-5p serves a critical role in facilitating OS proliferation and migration, and can regulate CDC73 expression in OS cells and tissues. Thus, miR-885-5p could be a promising novel therapeutic biomarker for OS.

Elevated G-Protein Receptor 125 (GPR125) Expression Predicts Good Outcomes in Colorectal Cancer and Inhibits Wnt/β-Catenin Signaling Pathway

Background

G-protein receptor 125 (GPR125), as a transmembrane signal transducer, is involved in regulating cancer development. Although GPR125 is related with several cancers, its role in colorectal cancer (CRC) and the underlying mechanism are still unknown. Here, we investigated the clinical significance of GPR125 in CRC.

Material/Methods

We assessed the expression level of GPR125 in CRC tissues by analyzing 3 datasets in the Gene Expression Omnibus (GEO) database and in human samples. The correlation between GPR125 expression and clinicopathological features was further analyzed. Survival analysis was performed to assess the association between GPR125 expression and recurrence-free survival (RFS). Cox logistic regression analysis was used to analyze the role of GPR125 expression in overall survival (OS). Moreover, we activated the Wnt pathway in HCT116 cells to investigate their potential mechanism.

Results

Analysis of the GEO database showed that the expression of GPR125 was down-regulated in CRC tissues, consistent with our human samples experiments, and patients with higher GPR125 expression had a longer RFS. Also, we found that high GPR125 expression was associated with better tumor outcomes in clinical stage, metastasis, and KRAS status. Cox logistic regression analysis demonstrated that GPR125 was an independent prognostic factor for favorable outcome. Mechanistically, GPR125 overexpression inhibited the β-catenin transcriptional activity, and down-regulated the expression levels of the Wnt downstream proteins-Axin2, c-Myc, cylinD1, and lef-1.

Conclusions

GPR125 may be a potential prognosis-related anti-oncogene and its effects on inactivating Wnt/β-catenin signaling pathway might be a key link to inhibiting CRC formation.

ALPK2 Promotes Cardiogenesis in Zebrafish and Human Pluripotent Stem Cells

Cardiac development requires coordinated biphasic regulation of the WNT/β-catenin signaling pathway. By intersecting gene expression and loss-of-function siRNA screens we identified Alpha Protein Kinase 2 (ALPK2) as a candidate negative regulator of WNT/β-catenin signaling in cardiogenesis. In differentiating human embryonic stem cells (hESCs), ALPK2 is highly induced as hESCs transition from mesoderm to cardiac progenitors. Using antisense knockdown and CRISPR/Cas9 mutagenesis in hESCs and zebrafish, we demonstrate that ALPK2 promotes cardiac function and cardiomyocyte differentiation. Quantitative phosphoproteomics, protein expression profiling, and β-catenin reporter assays demonstrate that loss of ALPK2 led to stabilization of β-catenin and increased WNT signaling. Furthermore, cardiac defects attributed to ALPK2 depletion can be rescued in a dose-dependent manner by direct inhibition of WNT signaling through the small molecule XAV939. Together, these results demonstrate that ALPK2 regulates β-catenin-dependent signaling during developmental commitment of cardiomyocytes.

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ALPK2 is expressed and regulated during hESC cardiomyocyte lineage determination

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Cardiac development in zebrafish embryos and hESCs requires ALPK2

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ALPK2 negatively regulates WNT signaling to promote cardiomyocyte differentiation

Molecular genetics and epigenetics of nonfamilial (sporadic) parathyroid tumours

Primary hyperparathyroidism (pHPT) is a common endocrine disease characterized by excessive secretion of parathyroid hormone and an increased level of serum calcium. Overall, 80-85% of pHPT cases are due to a benign, single parathyroid adenoma (PA), and 15% to multiglandular disease (multiple adenomas/hyperplasia). Parathyroid carcinoma (PC) is rare, accounting for <0.5-1% of pHPT cases. Secondary hyperparathyroidism (sHPT) is a complication of renal failure, with the development of parathyroid tumours and hypercalcaemia. Recurrent mutations in the MEN1 gene have been confirmed by the whole-exome sequencing in 35% of PAs, suggesting that non-protein-coding genes, regulatory elements or epigenetic derangements may also have roles in the majority of PAs. DNA translocations with cyclin D1 overexpression occur in PAs (8%). In PCs, mutations in CDC73/HRPT2 are common. Activation of the WNT/β-catenin signalling pathway (accumulation of nonphosphorylated β-catenin) by an aberrantly truncated LRP5 receptor has been seen for the majority of investigated PAs and sHPT tumours, and possibly by APC inactivation through promoter methylation in PCs. Promoter methylation of several other genes and repressive histone H3 lysine 27 trimethylation by EZH2 of the HIC1 gene may also contribute to parathyroid tumorigenesis. It is possible that a common pathway exists for parathyroid tumour development. CCND1 (cyclin D1) and EZH2 overexpression, accumulation of nonphosphorylated β-catenin and repression of HIC1 have all been observed to occur in PAs, PCs and sHPT tumours. In addition, hypermethylation has been observed for the same genes in PAs and PCs (e.g. SFRP1, CDKN2A and WT1). Whether β-catenin represents a 'hub' in parathyroid tumour development will be discussed.

Cancer stem cells are the cause of drug resistance in multiple myeloma: fact or fiction?

Multiple myeloma (MM) remains a largely incurable, genetically heterogeneous plasma-cell malignancy that contains – just like many other cancers – a small fraction of clonogenic stem cell-like cells that exhibit pronounced self-renewal and differentiation capacities, but also pronounced drug resistance. These MM stem cells (MMSCs) are a controversial but highly significant issue in myeloma research because, in our opinion, they are at the root of the failure of anti-neoplastic chemotherapies to transform myeloma to a manageable chronic disease. Several markers including CD138⁻, ALDH1⁺ and SP have been used to identify MMSCs; however, no single marker is reliable for the isolation of MMSC. Nonetheless, it is now known that MMSCs depend on self-renewal and pro-survival pathways, such as AKT, Wnt/β-catenin, Notch and Hedgehog, which can be targeted with novel drugs that have shown promise in pre-clinical and clinical trials. Here, we review the pathways of myeloma “stemness”, the interactions with the bone marrow microenvironment that promote drug resistance, and the obstacles that must be overcome to eradicate MMSCs and make myeloma a curable disease.

PKA inhibits WNT signalling in adrenal cortex zonation and prevents malignant tumour development

Adrenal cortex physiology relies on functional zonation, essential for production of aldosterone by outer zona glomerulosa (ZG) and glucocorticoids by inner zona fasciculata (ZF). The cortex undergoes constant cell renewal, involving recruitment of subcapsular progenitors to ZG fate and subsequent lineage conversion to ZF identity. Here we show that WNT4 is an important driver of WNT pathway activation and subsequent ZG differentiation and demonstrate that PKA activation prevents ZG differentiation through WNT4 repression and WNT pathway inhibition. This suggests that PKA activation in ZF is a key driver of WNT inhibition and lineage conversion. Furthermore, we provide evidence that constitutive PKA activation inhibits, whereas partial inactivation of PKA catalytic activity stimulates β-catenin-induced tumorigenesis. Together, both lower PKA activity and higher WNT pathway activity lead to poorer prognosis in adrenocortical carcinoma (ACC) patients. These observations suggest that PKA acts as a tumour suppressor in the adrenal cortex, through repression of WNT signalling.

The adrenal cortex undergoes functional zonation to generate an outer zona glomerulosa (ZG) and inner zona fasciculata (ZF), but how this is regulated at a molecular level is unclear. Here, the authors show that ZG differentiation is stimulated by WNT signalling and that PKA blocks WNT signalling to allow ZF differentiation and also prevents WNT-induced cancer development.

Wnt Drug Discovery: Weaving Through the Screens, Patents and Clinical Trials

The Wnt signaling pathway is intricately involved in many aspects of development and is the root cause of an increasing number of diseases. For example, colorectal cancer is the second leading cause of death in the industrialized world and aberration of Wnt signaling within the colonic stem cell is the cause of more than 90% of these cancers. Despite our advances in successfully targeting other pathways, such as Human Epidermal Growth Factor Receptor 2 (HER2), there are no clinically relevant therapies available for Wnt-related diseases. Here, we investigated where research activities are focused with respect to Wnt signaling modulators by searching the United States Patent and Trade Office (USPTO) for patents and patent applications related to Wnt modulators and compared this to clinical trials focusing on Wnt modulation. We found that while the transition of intellectual property surrounding the Wnt ligand-receptor interface to clinical trials is robust, this is not true for specific inhibitors of β-catenin, which is constitutively active in many cancers. Considering the ubiquitous use of the synthetic T-cell Factor/Lymphoid Enhancer Factor (TCF/Lef) reporter system and its success in identifying novel modulators in vitro, we speculate that this model of drug discovery does not capture the complexity of in vivo Wnt signaling that may be required if we are to successfully target the Wnt pathway in the clinic. Notwithstanding, increasingly more complex models are being developed, which may not be high throughput, but more pragmatic in our pursuit to control Wnt signaling.

Comparison of gene expression of the oncogenic Wnt/β-catenin signaling pathway components in the mouse and human epididymis

β-catenin is an integral part of the Wnt signaling pathway and has been linked to tumorigenesis and multiple developmental processes. The high β-catenin expression with low tumor incidence in the human epididymis is thus intriguing. In the present study, the β-catenin gene and protein was found to be highly expressed in the murine caput epididymidis, and the protein mainly localized along the lateral plasma membranes of adjacent epithelial cells throughout both human and mouse epididymides. Furthermore, the adult mouse epididymis was found to express almost all the Wnt/β-catenin signaling pathway genes that were determined previously by our group in the human organ. Despite the differences in epididymal structure, the similar location of β-catenin and the high concordance of this pathway's components’ gene expression in both the adult human and mouse epididymides make the mouse a suitable animal model for studying the anti-tumor mechanism of the epididymis. In addition, both the mRNA and protein expression of β-catenin shared a similar spatial expression as the mRNA of Ros1, a proto-oncogene and a key developmental regulator of the initial segment of the mouse epididymis. The observations on the parallel temporal expression of β-catenin and Ros1 during postnatal development raise the possibility that the canonical Wnt signaling pathway has an additional role in the postnatal development of mouse epididymis.

Bruton's tyrosine kinase inhibitor restrains Wnt signaling in chronic lymphocytic leukemia

The B-cell receptor (BCR) signaling pathway serves an important role in the pathogenesis of chronic lymphocytic leukemia (CLL), and has been identified as a novel and effective therapeutic target of CLL, with particular focus its kinase factor, BTK. Previous studies have focused on combining the BTK inhibitor with additional chemotherapeutic agents to improve the prognosis of patients with CLL. Further investigation into the mechanism of the BTK inhibitor would promote an understanding of the pathogenesis of CLL. The current study investigated the association between ibrutinib and the Wnt signaling pathway, additionally focussing upon one of its regulators, metadherin (MTDH), which has been identified to be overexpressed in CLL and is considered a promoter of the Wnt pathway. The experiments in the current study were performed in the MEC-1 CLL cell line. Results indicated that MTDH, β-catenin and lymphoid-enhancing factor-1 were inhibited subsequent to ibrutinib treatment. The results indicate that in CLL, ibrutinib is likely to possess an inhibitory role in Wnt signaling.

Quantitative proteomics identify DAB2 as a cardiac developmental regulator that inhibits WNT/β-catenin signaling

To reveal the molecular mechanisms involved in cardiac lineage determination and differentiation, we quantified the proteome of human embryonic stem cells (hESCs), cardiac progenitor cells (CPCs), and cardiomyocytes during a time course of directed differentiation by label-free quantitative proteomics. This approach correctly identified known stage-specific markers of cardiomyocyte differentiation, including SRY-box2 (SOX2), GATA binding protein 4 (GATA4), and myosin heavy chain 6 (MYH6). This led us to determine whether our proteomic screen could reveal previously unidentified mediators of heart development. We identified Disabled 2 (DAB2) as one of the most dynamically expressed proteins in hESCs, CPCs, and cardiomyocytes. We used clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) mutagenesis in zebrafish to assess whether DAB2 plays a functional role during cardiomyocyte differentiation. We found that deletion of Dab2 in zebrafish embryos led to a significant reduction in cardiomyocyte number and increased endogenous WNT/β-catenin signaling. Furthermore, the Dab2-deficient defects in cardiomyocyte number could be suppressed by overexpression of dickkopf 1 (DKK1), an inhibitor of WNT/β-catenin signaling. Thus, inhibition of WNT/β-catenin signaling by DAB2 is essential for establishing the correct number of cardiomyocytes in the developing heart. Our work demonstrates that quantifying the proteome of human stem cells can identify previously unknown developmental regulators.

Functional Crosstalk Between WNT Signaling and Tyrosine Kinase Signaling in Cancer

Extensive molecular characterization of tumors has revealed that the activity of multiple signaling pathways is often simultaneously dampened or enhanced in cancer cells. Aberrant WNT signaling and tyrosine kinase signaling are two pathways that are frequently up- or downregulated in cancer. Although signaling pathways regulated by WNTs, tyrosine kinases, and other factors are often conceptualized as independent entities, the biological reality is likely much more complex. Understanding the mechanisms of crosstalk between multiple signal transduction networks is a key challenge for cancer researchers. The overall goals of this review are to describe mechanisms of crosstalk between WNT and tyrosine kinase pathways in cancer and to discuss how understanding intersections between WNT and tyrosine kinase signaling networks might be exploited to improve current therapies.

Targeting Wnt pathway in mantle cell lymphoma-initiating cells

BACKGROUND

Mantle cell lymphoma (MCL) is an aggressive and incurable form of non-Hodgkin's lymphoma. Despite initial intense chemotherapy, up to 50% of cases of MCL relapse often in a chemoresistant form. We hypothesized that the recently identified MCL-initiating cells (MCL-ICs) are the main reason for relapse and chemoresistance of MCL. Cancer stem cell-related pathways such as Wnt could be responsible for their maintenance and survival.

METHODS

We isolated MCL-ICs from primary MCL cells on the basis of a defined marker expression pattern (CD34-CD3-CD45+CD19-) and investigated Wnt pathway expression. We also tested the potential of Wnt pathway inhibitors in elimination of MCL-ICs.

RESULTS

We showed that MCL-ICs are resistant to genotoxic agents vincristine, doxorubicin, and the newly approved Burton tyrosine kinase (BTK) inhibitor ibrutinib. We confirmed the differential up-regulation of Wnt pathway in MCL-ICs. Indeed, MCL-ICs were particularly sensitive to Wnt pathway inhibitors. Targeting β-catenin-TCF4 interaction with CCT036477, iCRT14, or PKF118-310 preferentially eliminated the MCL-ICs.

CONCLUSIONS

Our results suggest that Wnt signaling is critical for the maintenance and survival of MCL-ICs, and effective MCL therapy should aim to eliminate MCL-ICs through Wnt signaling inhibitors.

Genome-wide identification of phospho-regulators of Wnt signaling in Drosophila

Evolutionarily conserved intercellular signaling pathways regulate embryonic development and adult tissue homeostasis in metazoans. The precise control of the state and amplitude of signaling pathways is achieved in part through the kinase- and phosphatase-mediated reversible phosphorylation of proteins. In this study, we performed a genome-wide in vivo RNAi screen for kinases and phosphatases that regulate the Wnt pathway under physiological conditions in the Drosophila wing disc. Our analyses have identified 54 high-confidence kinases and phosphatases capable of modulating the Wnt pathway, including 22 novel regulators. These candidates were also assayed for a role in the Notch pathway, and numerous phospho-regulators were identified. Additionally, each regulator of the Wnt pathway was evaluated in the wing disc for its ability to affect the mechanistically similar Hedgehog pathway. We identified 29 dual regulators that have the same effect on the Wnt and Hedgehog pathways. As proof of principle, we established that Cdc37 and Gilgamesh/CK1γ inhibit and promote signaling, respectively, by functioning at analogous levels of these pathways in both Drosophila and mammalian cells. The Wnt and Hedgehog pathways function in tandem in multiple developmental contexts, and the identification of several shared phospho-regulators serve as potential nodes of control under conditions of aberrant signaling and disease.

Bruton tyrosine kinase is a therapeutic target in stem-like cells from multiple myeloma

Ibrutinib (Imbruvica), a small-drug inhibitor of Bruton tyrosine kinase (BTK), is currently undergoing clinical testing in patients with multiple myeloma, yet important questions on the role of BTK in myeloma biology and treatment are outstanding. Using flow-sorted side population cells from human myeloma cell lines and multiple myeloma primary samples as surrogate for the elusive multiple myeloma stem cell, we found that elevated expression of BTK in myeloma cells leads to AKT/WNT/β-catenin-dependent upregulation of key stemness genes (OCT4, SOX2, NANOG, and MYC) and enhanced self-renewal. Enforced transgenic expression of BTK in myeloma cells increased features of cancer stemness, including clonogenicity and resistance to widely used myeloma drugs, whereas inducible knockdown of BTK abolished them. Furthermore, overexpression of BTK in myeloma cells promoted tumor growth in laboratory mice and rendered side population-derived tumors that contained high levels of BTK more sensitive to the selective, second-generation BTK inhibitor, CGI1746, than side population-derived tumors that harbored low levels of BTK. Taken together, these findings implicate BTK as a positive regulator of myeloma stemness and provide additional support for the clinical testing of BTK-targeted therapies in patients with myeloma.

Dynamics and evolution of β-catenin-dependent Wnt signaling revealed through massively parallel clonogenic screening

Wnt/β-catenin signaling is of significant interest due to the roles it plays in regulating development, tissue regeneration and disease. Transcriptional reporters have been widely employed to study Wnt/β-catenin signal transduction in live cells and whole organisms and have been applied to understanding embryonic development, exploring oncogenesis and developing therapeutics. Polyclonal heterogeneity in reporter cell lines has historically been seen as a challenge to be overcome in the development of novel cell lines and reporter-based assays, and monoclonal reporter cell lines are commonly employed to reduce this variability. A375 cell lines infected with a reporter for Wnt/β-catenin signaling were screened over short (<6) and long (>25) generational timescales. To characterize phenotypic divergence over these time-scales, a microfabricated cell array-based screen was developed enabling characterization of 1119 clonal colonies in parallel. This screen revealed phenotypic divergence after <6 generations at a similar scale to that observed in monoclonal cell lines cultured for >25 generations. Not only were reporter dynamics observed to diverge widely, but monoclonal cell lines were observed with seemingly opposite signaling phenotypes. Additionally, these observations revealed a generational-dependent trend in Wnt signaling in A375 cells that provides insight into the pathway's mechanisms of positive feedback and self-inhibition.

Loss of connectivity in cancer co-expression networks

Differential gene expression profiling studies have lead to the identification of several disease biomarkers. However, the oncogenic alterations in coding regions can modify the gene functions without affecting their own expression profiles. Moreover, post-translational modifications can modify the activity of the coded protein without altering the expression levels of the coding gene, but eliciting variations to the expression levels of the regulated genes. These considerations motivate the study of the rewiring of networks co-expressed genes as a consequence of the aforementioned alterations in order to complement the informative content of differential expression. We analyzed 339 mRNAomes of five distinct cancer types to find single genes that presented co-expression patterns strongly differentiated between normal and tumor phenotypes. Our analysis of differentially connected genes indicates the loss of connectivity as a common topological trait of cancer networks, and unveils novel candidate cancer genes. Moreover, our integrated approach that combines the differential expression together with the differential connectivity improves the classic enrichment pathway analysis providing novel insights on putative cancer gene biosystems not still fully investigated.

Transcriptional repression of tumor suppressor CDC73, encoding an RNA polymerase II interactor, by Wilms tumor 1 protein (WT1) promotes cell proliferation: implication for cancer therapeutics

The Wilms tumor 1 gene (WT1) can either repress or induce the expression of genes. Inconsistent with its tumor suppressor role, elevated WT1 levels have been observed in leukemia and solid tumors. WT1 has also been suggested to act as an oncogene by inducing the expression of MYC and BCL-2. However, these are only the correlational studies, and no functional study has been performed to date. Consistent with its tumor suppressor role, CDC73 binds to RNA polymerase II as part of a PAF1 transcriptional regulatory complex and causes transcriptional repression of oncogenes MYC and CCND1. It also represses β-catenin-mediated transcription. Based on the reduced level of CDC73 in oral squamous cell carcinoma (OSCC) samples in the absence of loss-of-heterozygosity, promoter methylation, and mutations, we speculated that an inhibitory transcription factor is regulating its expression. The bioinformatics analysis predicted WT1 as an inhibitory transcription factor to regulate the CDC73 level. Our results showed that overexpression of WT1 decreased CDC73 levels and promoted proliferation of OSCC cells. ChIP and EMSA results demonstrated binding of WT1 to the CDC73 promoter. The 5-azacytidine treatment of OSCC cells led to an up-regulation of WT1 with a concomitant down-regulation of CDC73, further suggesting regulation of CDC73 by WT1. Exogenous CDC73 attenuated the protumorigenic activity of WT1 by apoptosis induction. An inverse correlation between expression levels of CDC73 and WT1 was observed in OSCC samples. These observations indicated that WT1 functions as an oncogene by repressing the expression of CDC73 in OSCC. We suggest that targeting WT1 could be a therapeutic strategy for cancer, including OSCC.

Protein kinase PKN1 represses Wnt/β-catenin signaling in human melanoma cells

Advances in phosphoproteomics have made it possible to monitor changes in protein phosphorylation that occur at different steps in signal transduction and have aided the identification of new pathway components. In the present study, we applied this technology to advance our understanding of the responses of melanoma cells to signaling initiated by the secreted ligand WNT3A. We started by comparing the phosphopeptide patterns of cells treated with WNT3A for different periods of time. Next, we integrated these data sets with the results from a siRNA screen that targeted protein kinases. This integration of siRNA screening and proteomics enabled us to identify four kinases that exhibit altered phosphorylation in response to WNT3A and that regulate a luciferase reporter of β-catenin-responsive transcription (β-catenin-activated reporter). We focused on one of these kinases, an atypical PKC kinase, protein kinase N1 (PKN1). Reducing the levels of PKN1 with siRNAs significantly enhances activation of β-catenin-activated reporter and increases apoptosis in melanoma cell lines. Using affinity purification followed by mass spectrometry, we then found that PKN1 is present in a protein complex with a WNT3A receptor, Frizzled 7, as well as with proteins that co-purify with Frizzled 7. These data establish that the protein kinase PKN1 inhibits Wnt/β-catenin signaling and sensitizes melanoma cells to cell death stimulated by WNT3A.

Oncogenic microRNA-155 down-regulates tumor suppressor CDC73 and promotes oral squamous cell carcinoma cell proliferation: implications for cancer therapeutics

The CDC73 gene is mutationally inactivated in hereditary and sporadic parathyroid tumors. It negatively regulates β-catenin, cyclin D1, and c-MYC. Down-regulation of CDC73 has been reported in breast, renal, and gastric carcinomas. However, the reports regarding the role of CDC73 in oral squamous cell carcinoma (OSCC) are lacking. In this study we show that CDC73 is down-regulated in a majority of OSCC samples. We further show that oncogenic microRNA-155 (miR-155) negatively regulates CDC73 expression. Our experiments show that the dramatic up-regulation of miR-155 is an exclusive mechanism for down-regulation of CDC73 in a panel of human cell lines and a subset of OSCC patient samples in the absence of loss of heterozygosity, mutations, and promoter methylation. Ectopic expression of miR-155 in HEK293 cells dramatically reduced CDC73 levels, enhanced cell viability, and decreased apoptosis. Conversely, the delivery of a miR-155 antagonist (antagomir-155) to KB cells overexpressing miR-155 resulted in increased CDC73 levels, decreased cell viability, increased apoptosis, and marked regression of xenografts in nude mice. Cotransfection of miR-155 with CDC73 in HEK293 cells abrogated its pro-oncogenic effect. Reduced cell proliferation and increased apoptosis of KB cells were dependent on the presence or absence of the 3'-UTR in CDC73. In summary, knockdown of CDC73 expression due to overexpression of miR-155 not only adds a novelty to the list of mechanisms responsible for its down-regulation in different tumors, but the restoration of CDC73 levels by the use of antagomir-155 may also have an important role in therapeutic intervention of cancers, including OSCC.

A temporal chromatin signature in human embryonic stem cells identifies regulators of cardiac development

Directed differentiation of human embryonic stem cells (ESCs) into cardiovascular cells provides a model for studying molecular mechanisms of human cardiovascular development. Although it is known that chromatin modification patterns in ESCs differ markedly from those in lineage-committed progenitors and differentiated cells, the temporal dynamics of chromatin alterations during differentiation along a defined lineage have not been studied. We show that differentiation of human ESCs into cardiovascular cells is accompanied by programmed temporal alterations in chromatin structure that distinguish key regulators of cardiovascular development from other genes. We used this temporal chromatin signature to identify regulators of cardiac development, including the homeobox gene MEIS2. Using the zebrafish model, we demonstrate that MEIS2 is critical for proper heart tube formation and subsequent cardiac looping. Temporal chromatin signatures should be broadly applicable to other models of stem cell differentiation to identify regulators and provide key insights into major developmental decisions.

Inhibitors of B-cell receptor signaling for patients with B-cell malignancies

The B-cell receptor (BCR) complex and its associated protein tyrosine kinases play a critical role in the development, proliferation, and survival of normal or malignant B cells. Regulated activity of the BCR complex promotes the expansion of selected B cells and the deletion of unwanted or self-reactive ones. Compounds that inhibit various components of this pathway, including spleen tyrosine kinase, Bruton's tyrosine kinase, and phosphoinositol-3 kinase, have been developed. We summarize the rationale for use of agents that can inhibit BCR signaling to treat patients with either indolent or aggressive B-cell lymphomas, highlight early clinical results, and speculate on the future application of such agents in the treatment of patients with various B-cell lymphomas.

Identification of a Wnt-induced protein complex by affinity proteomics using an antibody that recognizes a sub-population of β-catenin

β-catenin is a signaling protein with diverse functions in cell adhesion and Wnt signaling. Although β-catenin has been shown to participate in many protein-protein interactions, it is not clear which combinations of β-catenin-interacting proteins form discrete complexes. We have generated a novel antibody, termed 4B3, which recognizes only a small subset of total cellular β-catenin. Affinity proteomics using 4B3, in combination with subcellular fractionation, has allowed us to define a discrete trimeric complex of β-catenin, α-catenin and the tumor suppressor APC, which forms in the cytoplasm in response to Wnt signaling. Depletion of the limiting component of this complex, APC, implicates the complex in mediating Wnt-induced changes in cell-cell adhesion. APC is also essential for N-terminal phosphorylation of β-catenin within this complex. Each component of β-catenin/APC/α-catenin complex co-exists in other protein complexes, thus use of a selective antibody for affinity proteomics has allowed us to go beyond the generation of a list of potential β-catenin-interacting proteins, and define when and where a specific complex forms.

Identification of four novel variants that influence central corneal thickness in multi-ethnic Asian populations

Central corneal thickness (CCT) is a highly heritable trait. Genes that significantly influence CCT can be candidate genes for common disorders in which CCT has been implicated, such as primary open-angle glaucoma (POAG) and keratoconus. Because the genetic factors controlling CCT in different Asian populations are unclear, we have built on previous work conducted on Singaporean Indians and Malays and extended our hypothesis to individuals of Chinese descent. We have followed up on all suggestive signals of association with CCT (P < 10(-4)) from the previously reported meta-analysis comprising Indians and Malays in a sample of Chinese individuals (n= 2681). In the combined sample (n= 7711), strong evidence of association was observed at four novel loci: IBTK on chromosome 6q14.1; CHSY1 on chromosome 15q26.3; and intergenic regions on chromosomes 7q11.2 and 9p23 (8.01 × 10(-11) < λ(GC) corrected P(meta) < 8.72 × 10(-8)). These four new loci explain an additional 4.3% of the total CCT variance across the sample cohorts over and above that of previously identified loci. We also extend on a previous finding at a fifth locus (AKAP13) where a new single-nucleotide polymorphism (rs1821481, P(meta) = 9.99 × 10(-9)) was found to be significantly more informative compared with the previously reported rs6496932 (P(meta) = 3.64 × 10(-5)). Performing association analysis in Asians may lead to the discovery of ethnic-specific genes that control CCT, offering further mechanistic insights into the regulation of CCT. In addition, it may also provide several candidate genes for interrogation for POAG, keratoconus and possible racial/ethnic variations.

Postgenomic technologies targeting the Wnt signaling network

The recent development of high-throughput sequencing technologies and the availability of whole genome sequences of a variety of living organisms, including that of humans, have led to an enormous push in the quest for a comprehensive inquiry for the function of each and every gene discovered in different model organisms. A major conclusion from the sequencing projects was that while forward genetics had been extremely successful in identifying key genes/components of many biological processes, such as signal transduction cascades, the function(s) of the majority of genes in the genome remains a mystery. In this article, we discuss the use of a variety of high-throughput postgenomic tools, including functional genomics, proteomics, and chemical genetics that are being implemented in an exhaustive molecular dissection of a key evolutionarily conserved signal transduction pathway, namely the Wnt/wingless (wg) pathway and its associated signaling network.

Wnt signaling signaling at and above the receptor level

Wnt signaling is one of the most important developmental signaling pathways that controls cell fate decisions and tissue patterning during early embryonic and later development. It is activated by highly conserved Wnt proteins that are secreted as palmitoylated glycoproteins and act as morphogens to form a concentration gradient across a developing tissue. Wnt proteins regulate transcriptional and posttranscriptional processes depending on the distance of their origin and activate distinct intracellular cascades, commonly referred to as canonical (β-catenin-dependent) and noncanonical (β-catenin-independent) pathways. Therefore, the secretion and the diffusion of Wnt proteins needs to be tightly regulated to induce short- and long-range downstream signaling. Even though the Wnt signaling cascade has been studied intensively, key aspects and principle mechanisms, such as transport of Wnt growth factors or regulation of signaling specificity between different Wnt pathways, remain unresolved. Here, we introduce basic principles of Wnt/Wg signal transduction and highlight recent discoveries, such as the involvement of vacuolar ATPases and vesicular acidification in Wnt signaling. We also discuss recent findings regarding posttranslational modifications of Wnts, trafficking through the secretory pathway and developmental consequences of impaired Wnt secretion. Understanding the detailed mechanism and regulation of Wnt protein secretion will provide valuable insights into many human diseases based on overactivated Wnt signaling.

Striking the target in Wnt-y conditions: intervening in Wnt signaling during cancer progression

Wnt signaling can be divided into three pathways, namely the canonical Wnt/beta-catenin pathway, and the non-canonical (or heretical) Wnt/Ca(2+) and planar cell polarity (PCP) pathways. Although the canonical Wnt/beta-catenin pathway is the best described in cancer, increasing data points to the importance of the heretical Wnt pathways in several aspects of tumor progression. The recent advances in understanding the players and mechanisms by which these Wnt pathways contribute to cancer progression have led to the identification of numerous molecules that are already, or could be considered, targets for cancer therapy.

Quantification of beta-catenin signaling components in colon cancer cell lines, tissue sections, and microdissected tumor cells using reaction monitoring mass spectrometry

Reaction monitoring mass spectrometry has emerged as a powerful tool for targeted detection and quantification of proteins in clinical samples. Here, we report the use of gel electrophoresis for protein fractionation and liquid chromatography coupled to multiple reaction monitoring mass spectrometry (LC-MRM) screening for quantitative analysis of components from the Wnt/beta-catenin signaling pathway, which contributes to colon tumor formation and progression. In silico tools are used to design LC-MRM screens for each target protein. Following successful peptide detection, stable isotope labeled peptides are synthesized and developed as internal standards. Then, the assays are implemented in colon cancer cell lines to achieve detection in minimal amounts of cells, compatible with direct translation to clinical specimens. Selected assays are compared with qualitative results from immunoblotting (Westerns) and translated to individual frozen colon tissue sections and laser capture microdissected tumor cells. This LC-MRM platform has been translated from in vitro models to clinical specimens, forming the basis for future experiments in patient assessment.

Targeting the undruggable proteome: the small molecules of my dreams

Biologically active small molecules have long proven useful in the exploration of cell biology. Although many early compounds were by-products of drug development efforts, recent increased small molecule screening efforts in academia have expanded the repertoire of biological processes investigated to include areas of biology that are not of immediate pharmaceutical interest. Many of these new bioassays score for small molecule-induced phenotypic changes at the cellular or even organismal level and thus have been described as "chemical genetic" screens. However, this analogy with traditional genetic screens is misleading; although each gene has roughly an equivalent chance of being mutated in a traditional genetic screen, the amount of "proteomic space" that a chemical genetics approach can reach using current small molecule libraries is considerably smaller. Thus, new chemical biology methodologies are needed to target the remaining "undruggable proteome" with small druglike molecules.

Genomic screening with RNAi: results and challenges

RNA interference (RNAi) is an effective tool for genome-scale, high-throughput analysis of gene function. In the past five years, a number of genome-scale RNAi high-throughput screens (HTSs) have been done in both Drosophila and mammalian cultured cells to study diverse biological processes, including signal transduction, cancer biology, and host cell responses to infection. Results from these screens have led to the identification of new components of these processes and, importantly, have also provided insights into the complexity of biological systems, forcing new and innovative approaches to understanding functional networks in cells. Here, we review the main findings that have emerged from RNAi HTS and discuss technical issues that remain to be improved, in particular the verification of RNAi results and validation of their biological relevance. Furthermore, we discuss the importance of multiplexed and integrated experimental data analysis pipelines to RNAi HTS.

Identification of beta-catenin as a target of the intracellular tyrosine kinase PTK6

Disruption of the gene encoding protein tyrosine kinase 6 (PTK6) leads to increased growth, impaired enterocyte differentiation and higher levels of nuclear beta-catenin in the mouse small intestine. Here, we demonstrate that PTK6 associates with nuclear and cytoplasmic beta-catenin and inhibits beta-catenin- and T-cell factor (TCF)-mediated transcription. PTK6 directly phosphorylates beta-catenin on Tyr64, Tyr142, Tyr331 and/or Tyr333, with the predominant site being Tyr64. However, mutation of these sites does not abrogate the ability of PTK6 to inhibit beta-catenin transcriptional activity. Outcomes of PTK6-mediated regulation appear to be dependent on its intracellular localization. In the SW620 colorectal adenocarcinoma cell line, nuclear-targeted PTK6 negatively regulates endogenous beta-catenin/TCF transcriptional activity, whereas membrane-targeted PTK6 enhances beta-catenin/TCF regulated transcription. Levels of TCF4 and the transcriptional co-repressor TLE/Groucho increase in SW620 cells expressing nuclear-targeted PTK6. Knockdown of PTK6 in SW620 cells leads to increased beta-catenin/TCF transcriptional activity and increased expression of beta-catenin/TCF target genes Myc and Survivin. Ptk6-null BAT-GAL mice, containing a beta-catenin-activated LacZ reporter transgene, have increased levels of beta-galactosidase expression in the gastrointestinal tract. The ability of PTK6 to negatively regulate beta-catenin/TCF transcription by modulating levels of TCF4 and TLE/Groucho could contribute to its growth-inhibitory activities in vivo.

Hear the Wnt Ror: how melanoma cells adjust to changes in Wnt

The interplay between canonical and non-canonical Wnt pathways in development and tumorigenesis is tightly regulated. In this review we will describe the yin and the yang of canonical and non-canonical Wnt signaling pathways during melanocyte development, and melanoma genesis. Canonical Wnt signaling, represented by Wnts such as Wnt1 and Wnt3A, signals via beta-catenin to promote melanocyte differentiation and tumor development. Non-canonical Wnt signaling, specifically Wnt5A, regulates canonical pathways, and signals to induce melanoma metastasis. This review will focus on the role of Wnt5A during melanoma progression, and its relationship to canonical Wnt signaling.

Application of an integrated physical and functional screening approach to identify inhibitors of the Wnt pathway

Large-scale proteomic approaches have been used to study signaling pathways. However, identification of biologically relevant hits from a single screen remains challenging due to limitations inherent in each individual approach. To overcome these limitations, we implemented an integrated, multi-dimensional approach and used it to identify Wnt pathway modulators. The LUMIER protein-protein interaction mapping method was used in conjunction with two functional screens that examined the effect of overexpression and siRNA-mediated gene knockdown on Wnt signaling. Meta-analysis of the three data sets yielded a combined pathway score (CPS) for each tested component, a value reflecting the likelihood that an individual protein is a Wnt pathway regulator. We characterized the role of two proteins with high CPSs, Ube2m and Nkd1. We show that Ube2m interacts with and modulates beta-catenin stability, and that the antagonistic effect of Nkd1 on Wnt signaling requires interaction with Axin, itself a negative pathway regulator. Thus, integrated physical and functional mapping in mammalian cells can identify signaling components with high confidence and provides unanticipated insights into pathway regulators.