A t-butyloxycarbonyl-modified Wnt5a-derived hexapeptide functions as a potent antagonist of Wnt5a-dependent melanoma cell invasion

Wnt signaling in the pathogenesis of multiple sclerosis-associated chronic pain

Many multiple sclerosis (MS) patients develop chronic pain, but the underlying pathological mechanism is unknown. Mice with experimental autoimmune encephalomyelitis (EAE) have been widely used to model MS-related neurological complications, including CNS demyelination, neuroinflammation and motor impairments. Similar to MS patients, EAE mice also develop chronic pain. We are interested in elucidating the potential involvement of Wnt signaling in the pathogenesis of chronic pain in EAE mice. In this study, we characterized the expression of Wnt signaling proteins in the spinal cord dorsal horn (SCDH) of EAE mice, by immunoblotting and immunostaining. The EAE model was created by immunization of adult mice (C57BL/6, 10 weeks) with myelin oligodendrocyte glycoprotein (MOG) 35-55. Robust mechanical hyperalgesia and allodynia were developed in both fore- and hindpaws of the EAE mice. Wnt3a, a prototypical Wnt ligand for the canonical pathway, was significantly increased in the SCDH of the EAE mice. Another key protein in the canonical pathway, ß-catenin, was also significantly up-regulated. In addition, Wnt5a, a prototypic Wnt ligand for the non-canonical pathway, and its receptor (co-receptor) Ror2 were also up-regulated in the SCDH of the EAE mice. We further found that Wnt5a antagonist Box5 and β-catenin inhibitor indomethacin attenuated mechanical allodynia in the EAE mice. Our data collectively suggest that Wnt signaling pathways are up-regulated in the SCDH of the EAE mice and that aberrant activation of Wnt signaling contributes to the development of EAE-related chronic pain.

Targeting of Noncanonical Wnt5a Signaling by AP-1 Blocker Dominant-Negative Jun When It Inhibits Skin Carcinogenesis

The transcription factor AP-1 (activator protein-1) regulates a number of genes that drive tumor promotion and progression. While basal levels of AP-1 activity are important for normal cell proliferation and cell survival, overactivated AP-1-dependent gene expression stimulates inflammation, angiogenesis, invasion, and other events that propel carcinogenesis. We seek to discover genes targeted by carcinogenesis inhibitors that do not also inhibit cell proliferation or survival. Transgenic TAM67 (dominant-negative c-Jun) inhibits mouse skin tumorigenesis and tumor progression without inhibiting cell proliferation or induced hyperproliferation. Expression profiling of wild-type and K14-TAM67 mouse epidermis has revealed a number of functionally significant genes that are induced by tumor promoters in wild-type mice but not in those expressing the AP-1 blocker. The current study now identifies Wnt5a signaling as a new target of TAM67 when it inhibits DMBA/TPA-induced carcinogenesis. Wnt5a is required to maintain the tumor phenotype in tumorigenic mouse JB6 cells and Ras-transformed human squamous carcinoma HaCaT-II4 cells, as Wnt5a knockdown suppresses anchorage-independent and tumor xenograft growth. The oncogenic Wnt5a-mediated pathway signals through activation of the protein kinase PKCα and oncogenic transcription factor STAT3 phosphorylation and not through the canonical Wnt/β-catenin pathway. Similar to Wnt5a knockdown, inhibitors of PKCα blocked STAT3 activation in both mouse JB6 and human HaCaT-II4 tumor cells. Moreover, expression of STAT3-regulated genes FAS, MMP3, IRF1, and cyclin D1 was suppressed with Wnt5a knockdown. Treatment of mouse Wnt5a knockdown cells with a PKCα-specific activator rescued phosphorylation of STAT3. Thus, Wnt5a signaling is required for maintaining the tumor phenotype in squamous carcinoma cells, Wnt5a targeting by the AP-1 blockade contributes to inhibition of skin carcinogenesis, and the signaling pathway traverses PKCα and STAT3 activation. Coordinate overactivation of Wnt5a expression and STAT3 signaling is observed in human skin and colon cancers as well as glioblastoma.

Wnt5a is strongly expressed at the leading edge in non-melanoma skin cancer, forming active gradients, while canonical Wnt signalling is repressed

Wnt5a is one of the so-called non-canonical Wnt ligands which do not act through β-catenin. In normal development, Wnt5a is secreted and directs the migration of target cells along concentration gradients. The effect of Wnt5a on target cells is regulated by many factors, including the expression level of inhibitors and receptors. Dysregulated Wnt5a signalling facilitates invasion of multiple tumor types into adjacent tissue. However, the expression and distribution of Wnt5a in cutaneous squamous cell carcinoma (SCC) and basal cell carcinoma (BCC), as well as the effect of Wnt5a on keratinocyte migration has not been studied in detail to date. We here report that Wnt5a is upregulated in SCC and BCC and localised to the leading edge of tumors, as well as tumor-associated fibroblasts. The Wnt5a-triggered bundling of its receptor Fzd3 provides evidence of Wnt5a concentration gradients projecting into the tumor. In vitro migration assays show that Wnt5a concentration gradients determine its effect on keratinoctye migration: While chemotactic migration is inhibited by Wnt5a present in homogenous concentrations, it is enhanced in the presence of a Wnt5a gradient. Expression profiling of the Wnt pathway shows that the upregulation of Wnt5a in SCC is coupled to repression of canonical Wnt signalling. This is confirmed by immunohistochemistry showing lack of nuclear β-catenin, as well as absent accumulation of Axin2. Since both types of Wnt signalling act mutually antogonistically at multiple levels, the concurrent repression of canonical Wnt signalling suggests hyper-active Wnt5a signal transduction. Significantly, this combination of gene dysregulation is not observed in the benign hyperproliferative inflammatory skin disease psoriasis. Collectively, our data strongly suggest that Wnt5a signalling contributes to tissue invasion by non-melanoma skin cancer.

WNT5A signaling contributes to Aβ-induced neuroinflammation and neurotoxicity

Neurodegenration is a pathological hallmark of Alzheimer's disease (AD), but the underlying molecular mechanism remains elusive. Here, we present evidence that reveals a crucial role of Wnt5a signaling in this process. We showed that Wnt5a and its receptor Frizzled-5 (Fz5) were up-regulated in the AD mouse brain, and that beta-amyloid peptide (Aβ), a major constituent of amyloid plaques, stimulated Wnt5a and Fz5 expression in primary cortical cultures; these observations indicate that Wnt5a signaling could be aberrantly activated during AD pathogenesis. In support of such a possibility, we observed that inhibition of Wnt5a signaling attenuated while activation of Wnt5a signaling enhanced Aβ-evoked neurotoxicity, suggesting a role of Wnt5a signaling in AD-related neurodegeneration. Furthermore, we also demonstrated that Aβ-induced neurotoxicity depends on inflammatory processes, and that activation of Wnt5a signaling elicited the expression of proinflammatory cytokines IL-1β and TNF-α whereas inhibition of Wnt5a signaling attenuated the Aβ-induced expression of the cytokines in cortical cultures. Our findings collectively suggest that aberrantly up-regulated Wnt5a signaling is a crucial pathological step that contributes to AD-related neurodegeneration by regulating neuroinflammation.

Wnt5a as an effector of TGFβ in mammary development and cancer

Wnt5a is a member of the Wingless-related/MMTV-integration family of secreted growth factors, which are involved in a wide range of cellular processes. Wnt signaling can be broadly divided into two categories the canonical, ß-catenin-dependent pathway and the non-canonical ß-catenin-independent pathway. Wnt5a is a non-canonical signaling member of the Wnt family. Loss of Wnt5a is associated with early relapse of invasive breast cancer, increased metastasis, and poor survival in humans. It has been shown that TGF-ß directly regulates expression of Wnt5a in mammary gland and that Wnt5a mediates the effects of TGF-ß on branching during mammary gland development. Here we review the evidence suggesting Wnt5a acts as an effector of TGF-ß actions in breast cancer. It is suggested that the tumor suppressive functions of TGF-ß involve Wnt5a-mediated antagonism of Wnt/ß-catenin signaling and limiting the stem cell population. Interactions between TGF-ß and Wnt5a in metastasis appear to be more complex, and may depend on specific cues from the microenvironment as well as activation of specific intracellular signaling pathways.

WNT/β-catenin signaling is modulated by mechanical ventilation in an experimental model of acute lung injury

PURPOSE

The mechanisms involved in lung injury progression during acute lung injury (ALI) are still poorly understood. Because WNT/β-catenin signaling has been shown to be involved in epithelial cell injury and hyperplasia during inflammation and sepsis, we hypothesized that it would be modulated by mechanical ventilation (MV) in an experimental model of sepsis-induced ALI.

METHODS

This study was a prospective, randomized, controlled animal study performed using adult male Sprague-Dawley rats. Sepsis was induced by cecal ligation and perforation. At 18 h, surviving animals were randomized to spontaneous breathing or two strategies of MV for 4 h: low tidal volume (V (T)) (6 ml/kg) plus 10 cmH2O of positive end-expiratory pressure (PEEP) versus high (20 ml/kg) tidal volume (V (T)) with zero PEEP. Histological evaluation, measurements of WNT5A, total β-catenin, and matrix metalloproteinase-7 (MMP7) protein levels by Western blot, and their immunohistochemical localization in the lungs were analyzed.

RESULTS

Sepsis and high-V (T) MV caused lung inflammation and perivascular edema with cellular infiltrates and collagen deposition. Protein levels of WNT5A, β-catenin, and MMP7 in the lungs were increased in animals with sepsis-induced ALI. High-V (T) MV was associated with higher levels of WNT5A, β-catenin, and MMP7 protein levels (p < 0.001), compared to healthy control animals. By contrast, low-V (T) MV markedly reduced WNT5A, β-catenin, and MMP7 protein levels (p < 0.001).

CONCLUSIONS

Our findings demonstrate that the WNT/β-catenin signaling pathway is modulated early during sepsis and ventilator-induced lung injury, suggesting that activation of this pathway could play an important role in both lung injury progression and repair.

Methylation and loss of Secreted Frizzled-Related Protein 3 enhances melanoma cell migration and invasion

Background

Wnt signaling is important in development and can also contribute to the initiation and progression of cancer. The Secreted Frizzled Related Proteins (SFRPs) constitute a family of Wnt modulators, crucial for controlling Wnt signaling. Here we investigate the expression and role of SFRP3 in melanoma.

Methodology/Principal Findings

We show that SFRP3 mRNA is down-regulated in malignant melanoma tumors as compared to normal/benign tissue. Furthermore, we found that SFRP3 expression was lost in the malignant melanoma cell lines, A2058, HTB63 and A375, but not in the non-transformed melanocyte cell line, Hermes 3A. Methylated CpG rich areas were detected in the SFRP3 gene in melanoma cell lines and their SFRP3 expression could be restored using the demethylating agent, 5′aza-deoxycytidine. Addition of recombinant SFRP3 to melanoma cells had no effect on viable cell numbers, but decreased cell migration and invasion. Wnt5a signaling has been shown to increase the migration and invasion of malignant melanoma cells, and high expression of Wnt5a in melanoma tumors has been connected to a poor prognosis. We found that recombinant SFRP3 could inhibit Wnt5a signaling, and that it inhibited melanoma cell migration and invasion in a Wnt5a-dependent manner.

Conclusion/Significance

We conclude that SFRP3 functions as a melanoma migration and invasion suppressor by interfering with Wnt5a signaling.

International Union of Basic and Clinical Pharmacology. LXXX. The class Frizzled receptors

The receptor class Frizzled, which has recently been categorized as a separate group of G protein-coupled receptors by the International Union of Basic and Clinical Pharmacology, consists of 10 Frizzleds (FZD(1-10)) and Smoothened (SMO). The FZDs are activated by secreted lipoglycoproteins of the Wingless/Int-1 (WNT) family, whereas SMO is indirectly activated by the Hedgehog (HH) family of proteins acting on the transmembrane protein Patched (PTCH). Recent years have seen major advances in our knowledge about these seven-transmembrane-spanning proteins, including: receptor function, molecular mechanisms of signal transduction, and the receptor's role in embryonic patterning, physiology, cancer, and other diseases. Despite intense efforts, many question marks and challenges remain in mapping receptor-ligand interaction, signaling routes, mechanisms of specificity and how these molecular details underlie disease and also the receptor's important role in physiology. This review therefore focuses on the molecular aspects of WNT/FZD and HH/SMO signaling discussing receptor structure, mechanisms of signal transduction, accessory proteins, receptor dynamics, and the possibility of targeting these signaling pathways pharmacologically.

Identification of new genes associated with melanoma

PURPOSE

Repeated failures in melanoma therapy made clear that the molecular mechanisms leading to melanoma are still poorly understood. In this study, we aim to provide a more comprehensive understanding of the transcriptional profiles and signalling pathways associated with melanoma.

METHODS

Gene expression was analysed using the Affymetrix Human Genome U133A 2.0 GeneChip arrays. To avoid culture artifacts, we used microdissected fresh frozen material of 18 melanocytic nevi (MN), 20 primary melanomas (PM) and 20 metastatic melanomas (MM). Statistical analysis was performed with Genomatix Chipinspector, Ingenuity™ Software, SPSS Software and Partek Genomic Suite 6.4. Expression levels of selected transcripts were verified by quantitative real-time RT-PCR and immunostaining of a tissue microarray sampling more than 280 cases of MN, PM and MM with known clinical outcome.

RESULTS

A total of 284 differentially expressed genes was detected in PM compared with MN and 189 genes in MM compared with PM affecting common cancer pathways such as MAPK-, Wnt- and Notch-signalling. Using principal component analysis, the samples could be grouped according to their histological entity. We identified a panel of novel melanoma-associated markers: frizzled-related protein, an antagonist of Wnt; tranducin-like enhancer of split 1, a transcription factor partner of TCF/LEF-1; CNTN1, an activator of Notch signalling; two Serpin peptidase inhibitors, Serpin B3/B4 and the TGF-β family member GDF15, the latter with association to MAPK-signalling.

Wnt and related signaling pathways in melanomagenesis

Given the pivotal roles of morphogen pathways including Wnt, Notch, Hedgehog, and BMP pathways in the development of the neural crest lineage, it is not surprising that these signaling networks have also been implicated in the biology of malignant melanoma. Understanding the mechanisms by which these pathways can alter cell fate and other biological properties in tumor cells will be essential for determining whether the therapeutic targeting of these pathways has a potential role in melanoma treatment. This review highlights some of the recent findings with regards to how morphogen signaling may regulate melanoma cell biology.

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.