Characterization of the complete genomic structure of the human WNT-5A gene, functional analysis of its promoter, chromosomal mapping, and expression in early human embryogenesis

Altered binding affinity of SIX1-Q177R correlates with enhanced WNT5A and WNT pathway effector expression in Wilms tumor

Wilms tumors present as an amalgam of varying proportions of tissues located within the developing kidney, one being the nephrogenic blastema comprising multipotent nephron progenitor cells (NPCs). The recurring missense mutation Q177R in NPC transcription factors SIX1 and SIX2 is most correlated with tumors of blastemal histology and is significantly associated with relapse. Yet, the transcriptional regulatory consequences of SIX1/2-Q177R that might promote tumor progression and recurrence have not been investigated extensively. Utilizing multiple Wilms tumor transcriptomic datasets, we identified upregulation of the gene encoding non-canonical WNT ligand WNT5A in addition to other WNT pathway effectors in SIX1/2-Q177R mutant tumors. SIX1 ChIP-seq datasets from Wilms tumors revealed shared binding sites for SIX1/SIX1-Q177R within a promoter of WNT5A and at putative distal cis-regulatory elements (CREs). We demonstrate colocalization of SIX1 and WNT5A in Wilms tumor tissue and utilize in vitro assays that support SIX1 and SIX1-Q177R activation of expression from the WNT5A CREs, as well as enhanced binding affinity within the WNT5A promoter that may promote the differential expression of WNT5A and other WNT pathway effectors associated with SIX1-Q177R tumors.

Progranulin and EGFR modulate receptor-like tyrosine kinase sorting and stability in mesothelioma cells

Progranulin is a growth factor with pro-tumorigenic activity. We recently demonstrated that in mesothelioma, progranulin regulates cell migration, invasion, adhesion, and in vivo tumor formation by modulating a complex signaling network involving multiple receptor tyrosine kinase (RTK)s. Progranulin biological activity relies on epidermal growth factor receptor (EGFR) and receptor-like tyrosine kinase (RYK), a co-receptor of the Wnt signaling pathway, which are both required for progranulin-induced downstream signaling. However, the molecular mechanism regulating the functional interaction among progranulin, EGFR, and RYK are not known. In this study, we demonstrated that progranulin directly interacted with RYK by specific enzyme-linked immunosorbent assay (ELISA) (KD = 0.67). Using immunofluorescence and proximity ligation assay, we further discovered that progranulin and RYK colocalized in mesothelioma cells in distinct vesicular compartments. Notably, progranulin-dependent downstream signaling was sensitive to endocytosis inhibitors, suggesting that it could depend on RYK or EGFR internalization. We discovered that progranulin promoted RYK ubiquitination and endocytosis preferentially through caveolin-1-enriched pathways, and modulated RYK stability. Interestingly, we also showed that in mesothelioma cells, RYK complexes with the EGFR, contributing to the regulation of RYK stability. Collectively, our results suggest a complex regulation of RYK trafficking/activity in mesothelioma cells, a process that is concurrently regulated by exogenous soluble progranulin and EGFR. NEW & NOTEWORTHY The growth factor progranulin has pro-tumorigenic activity. In mesothelioma, progranulin signaling is mediated by EGFR and RYK, a co-receptor of the Wnt signaling. However, the molecular mechanisms regulating progranulin action are not well defined. Here, we demonstrated that progranulin binds RYK and regulates its ubiquitination, internalization, and trafficking. We also uncovered a role for EGFR in modulating RYK stability. Overall, these results highlight a complex modulation of RYK activity by progranulin and EGFR in mesothelioma.

Different strategies by distinct Wnt-signaling pathways in activating a nuclear transcriptional response

The Wnt family of secreted glycolipo-proteins signals through multiple signal transduction pathways and is essential for embryonic development and organ development and homeostasis. The Wnt-pathways are conserved and critical in all metazoans. Wnt signaling pathways comprise the canonical Wnt/β-catenin pathway and several non-canonical signaling branches, of which Wnt-Planar Cell Polarity (PCP) signaling and the Wnt/Calcium pathway have received the most attention and are best understood. nterestingly, all Wnt-pathways have a nuclear signaling branch and also can affect many cellular processes independent of its nuclear transcriptional regulation. Canonical Wnt/β-catenin signaling is the most critical for a nuclear transcriptional response, in both development and disease, yet the mechanism(s) on how the "business end" of the pathway, β-catenin, translocates to the nucleus to act as co-activator to the TCF/Lef transcription factor family still remains obscure. Here we discuss and compare the very different strategies on how the respective Wnt signaling pathways activate a nuclear transcriptional response. We also highlight some recent new insights into how β-catenin is translocated to the nucleus via an IFT-A, Kinesin-2, and microtubule dependent mechanism and how this aspect of canonical Wnt-signaling uses ciliary proteins in a cilium independent manner, conserved between Drosophila and mammalian cells.

WNT5a in Colorectal Cancer: Research Progress and Challenges

Despite the clinical development of new adjuvant and neoadjuvant chemotherapy drugs, colorectal cancer is still one of the leading causes of cancer-related death in human beings. WNT5a, an autocrine and paracrine β-catenin independent ligand, has been shown to induce tumor inhibition and carcinogenic signals, depending on the type of cancer. In patients with colorectal cancer, WNT5a triggers a variety of downstream signaling pathways, which mainly affect the migration and invasion of tumor cells. This article reviews the mechanism and therapeutic potential of WNT5a in colorectal cancer. In short, an in-depth understanding of the role of WNT5a in colorectal cancer is very helpful to better deal with this disease.

WNT5A as a therapeutic target in breast cancer

Despite the clinical development of novel adjuvant and neoadjuvant chemotherapeutic drugs, metastatic breast cancer is one of the leading causes of cancer-related death among women. The present review focuses on the relevance, mechanisms, and therapeutic potential of targeting WNT5A as a future anti-metastatic treatment strategy for breast cancer patients by restoring WNT5A signaling as an innovative therapeutic option. WNT5A is an auto- and paracrine β-catenin-independent ligand that has been shown to induce tumor suppression as well as oncogenic signaling, depending upon cancer type. In breast cancer patients, WNT5A protein expression has been observed to be significantly reduced in between 45 and 75% of the cases and associated with early relapse and reduced disease-free survival. WNT5A triggers various downstream signaling pathways in breast cancer that primarily affect tumor cell migration and invasion. The accumulated in vitro results reveal that treatment of WNT5A-negative breast cancer cells with recombinant WNT5A caused different tumor-suppressive responses and in particular it impaired migration and invasion. The anti-migratory/invasive and anti-metastatic effects of reconstituting WNT5A signaling by the small WNT5A mimicking peptide Foxy5 form the basis for two successful clinical phase 1-studies aiming at determining safety and pharmacokinetics as well as defining dose-level for a subsequent phase 2-study. We conclude that re-installation of WNT5A signaling is an attractive and promising anti-metastatic therapeutic approach for future treatment of WNT5A-negative breast cancer patients.

The role of AP-1 in self-sufficient proliferation and migration of cancer cells and its potential impact on an autocrine/paracrine loop

Activating protein-1 (AP-1) family members, especially Fra-1 and c-Jun, are highly expressed in invasive cancers and can mediate enhanced migration and proliferation. The aim of this study was to explore the significance of elevated levels of AP-1 family members under conditions that restrict growth. We observed that invasive MDA-MB-231 cells express high levels of Fra-1, c-Jun, and Jun-D during serum starvation and throughout the cell cycle compared to non-tumorigenic and non-invasive cell lines. We then analyzed Fra-1 levels in additional breast and other cancer cell lines. We found breast and lung cancer cells with higher levels of Fra-1 during serum starvation had relatively higher ability to proliferate and migrate under these conditions. Utilizing a dominant negative construct of AP-1, we demonstrated that proliferation and migration of MDA-MB-231 in the absence of serum requires AP-1 activity. Finally, we observed that MDA-MB-231 cells secrete factors(s) that induce Fra-1 expression and migration in non-tumorigenic and non-metastatic cells and that both the expression of and response to these factors require AP-1 activity. These results suggest the presence of an autocrine/paracrine loop that maintains high Fra-1 levels in aggressive cancer cells, enhancing their proliferative and metastatic ability and affecting neighbors to alter the tumor environment.

A Possible Role for WNT5A Hypermethylation in Pediatric Acute Lymphoblastic Leukemia

Objective:

WNT5A is one of the most studied noncanonical WNT ligands and is shown to be deregulated in different tumor types. Our aim was to clarify whether hypermethylation might be the cause of low WNT5A mRNA levels and whether we could restore this downregulation by reversing the event.

Materials and Methods:

The expression of WNT5A mRNA was studied in a large acute lymphoblastic leukemia (ALL) patient group (n=86) by quantitative real-time PCR. The methylation status was detected by methylation-specific PCR (MSPCR) and bisulphate sequencing. In order to determine whether methylation has a direct effect on WNT5A expression, disease-representative cell lines were treated by 5’-aza-20-deoxycytidine.

Results:

Here we designed a validation experiment of the WNT5A gene, which was previously examined and found to be differentially expressed by microarray study in 31 T-cell ALL patients. The expression levels were confirmed by quantitative real-time PCR and the expression levels were significantly lower in T-cell ALL patients than in control thymic subsets (p=0.007). MSPCR revealed that 86% of the patients were hypermethylated in the WNT5A promoter region. Jurkat and RPMI cell lines were treated with 5’-aza-20-deoxycytidine and WNT5A mRNA expression was restored after treatment.

Conclusion:

According to our results, WNT5A hypermethylation does occur in ALL patients and it has a direct effect on mRNA expression. Our findings show that epigenetic changes of WNT signaling can play a role in ALL pathogenesis and reversing methylation might be useful as a possible treatment of leukemia.

Multiple Roles of WNT5A in Breast Cancer

Breast cancer is one of the most common malignant tumors of women. Modern combinatorial therapeutic regimens can reduce patient tumor burdens to undetectable levels, yet in many cases these tumors will relapse. Understanding of breast cancer biology, developing more potent therapeutic approaches, and overcoming resistance are of great importance. WNT5A is a non-canonical signaling member of the WNT family. Its role in breast cancer still remains unclear. Most of the evidence shows that WNT5A is a suppressor in breast cancer and loss of its expression is associated with poor prognosis, while some evidence suggests the tumorigenicity of WNT5A. WNT signaling molecules are potent targets for treatment of cancer. Therefore, understanding the role of WNT5A in breast cancer may provide new ideas and methods for breast cancer treatment. We review the evidence concerning WNT5A and breast cancer involving the signaling pathways and the molecular-targeted therapy of WNT5A. Our results show that the role WNT5A plays depends on the availability of key receptors and intercellular interactions among different cell types.

Dual mechanisms of action of the RNA-binding protein human antigen R explains its regulatory effect on melanoma cell migration

Overexpression of wingless-type MMTV integration site family 5A (WNT5A) plays a significant role in melanoma cancer progression; however, the mechanism(s) involved remains unknown. In breast cancer, the human antigen R (HuR) has been implicated in the regulation of WNT5A expression. Here, we demonstrate that endogenous expression of WNT5A correlates with levels of active HuR in HTB63 and WM852 melanoma cells and that HuR binds to WNT5A messenger RNA in both cell lines. Although the HuR inhibitor MS-444 significantly impaired migration in both melanoma cell lines, it reduced WNT5A expression only in HTB63 cells, as did small interfering RNA knockdown of HuR. Consistent with this finding, MS-444-induced inhibition of HTB63 cell migration was restored by the addition of recombinant WNT5A, whereas MS-444-induced inhibition of WM852 cell migration was restored by the addition of recombinant matrix metalloproteinase-9, another HuR-regulated protein. Clearly, HuR positively regulates melanoma cell migration via at least 2 distinct mechanisms making HuR an attractive therapeutic target for halting melanoma dissemination.

EGF-reduced Wnt5a transcription induces epithelial-mesenchymal transition via Arf6-ERK signaling in gastric cancer cells

Wnt5a, a ligand for activating the non-canonical Wnt signaling pathway, is commonly associated with Epithelial-to-mesenchymal transition (EMT) in cancer cell metastasis. Here, we show that downregulation of Wnt5a mRNA and protein by EGF is necessary for EGF-induced EMT in gastric cancer SGC-7901 cells. To further explore the mechanisms, we investigated the effect of EGF signaling on Wnt5a expression. EGF increased Arf6 and ERK activity, while blockade of Arf6 activation repressed ERK activity, up-regulated Wnt5a expression and repressed EMT in response to EGF. We also demonstrate that EGF inactivated Wnt5a transcription by direct recruitment of ERK to the Wnt5a promoter. On the other hand, inhibition of ERK phosphorylation resulted in decreased movement of ERK from the cytoplasm to the nucleus, following rescued Wnt5a mRNA and protein expression and favored an epithelial phenotype of SGC-7901 cells. In addition, we notice that kinase-dead, nuclear-localised ERK has inhibitory effect on Wnt5a transcription. Analysis of gastric cancer specimens revealed an inverse correlation between P-ERK and Wnt5a protein levels and an association between Wnt5a expression and better prognosis. These findings indicate that Wnt5a is a potential suppressor of EMT and identify a novel Arf6/ERK signaling pathway for EGF-regulated Wnt5a expression at transcriptional level of gastric cancer cells.

Immunohistochemical expression of WNT5A and MMPs in odontogenic epithelial tumors and cysts

OBJECTIVE

The aim of this study was compare the expression of WNT5A and MMP2, 7 and 20, in frequent benign odontogenic tumors and odontogenic cysts, since these lesions have a different biological behavior.

MATERIALS AND METHODS

Eighty-one paraffin-embedded specimens of odontogenic tumors, including ameloblastoma and keratocystic odontogenic tumor, and thirty-two odontogenic cysts were used for immunohistochemical analysis.

RESULTS

The expression of WNT5A in odontogenic tumors and inflammatory cyst was higher than in developmental odontogenic cyst. There was no statistical difference (p<0.05) in the expression of WNT5A when comparing the analyzed tumors. The expression of MMP7 was lower in RC with a statistical difference when compared with all tumors and cysts. Statistical differences also occurred when comparing glandular odontogenic cyst (GOC) to keratocyst odontogenic tumor (KOT) and calcifying cystic odontogenic tumor (CCOT). MMP20 expression was higher in ameloblastoma when compared to adenomatoid odontogenic tumor (AOT), DC and GOC. The expression of MMP20 was lower in CCOT when compared to all tumors and cysts.

CONCLUSIONS

The expression of WNT5A in a group of odontogenic lesions suggests the participation of a non-canonical WNT signaling pathway in the progression and maintenance of these lesions. These molecules are possibly involved in the biological differences between odontogenic tumors and cysts. Considering previous studies, WNT5A may help promote the calcification seen in AOT, CCOT and CEOT by activating MMP7.

Anorectal malformation: the etiological factors

Anorectal malformation (ARM) is a congenital anomaly commonly encountered in pediatric surgery practice. Although surgical procedures correct the anatomical anomalies, the post-operative bowel function is not universally satisfactory. The etiology of ARM remains unclear. In this review, we summarize the current understanding of the genetic and epigenetic factors contributing to the pathogenesis of ARM, based on published animal models, human genetics and epidemiological researches. Appreciation of these factors may be helpful in the management of ARM in the future.

Increased expression of colonic Wnt9A through Sp1-mediated transcriptional effects involving arylsulfatase B, chondroitin 4-sulfate, and galectin-3

In cultured human colonic epithelial cells and mouse colonic tissue, exposure to the common food additive carrageenan leads to inflammation, activation of Wnt signaling, increased Wnt9A expression, and decline in the activity of the enzyme arylsulfatase B (ARSB; N-acetylgalactosamine-4-sulfatase). In this study, the novel transcriptional mechanism by which carrageenan and decline in ARSB increase Wnt9A expression in NCM460 and HT-29 human colonic epithelial cells and in mouse colon is presented. Increased expression of Wnt9A has been associated with multiple malignancies, including colon carcinoma, and with ectodermal and mesoendodermal morphogenesis. When ARSB activity was reduced by siRNA or by exposure to carrageenan (1 μg/ml for 24 h), degradation of chondroitin 4-sulfate (C4S) was inhibited, leading to accumulation of more highly sulfated C4S, which binds less galectin-3, a β-galactoside-binding protein. Nuclear galectin-3 increased and mediated increased binding of Sp1 to the Sp1 consensus sequence in the Wnt9A promoter, shown by oligonucleotide-binding assay and by chromatin immunoprecipitation assay. When galectin-3 was silenced, the increases in Sp1 binding to the Wnt9A promoter and in Wnt9A expression, which followed carrageenan or ARSB silencing, were inhibited. Mithramycin A, a specific inhibitor of Sp1 oligonucleotide binding, and Sp1 siRNA blocked the carrageenan- and ARSB siRNA-induced increases in Wnt9A expression. These studies reveal how carrageenan exposure can lead to transcriptional events in colonic epithelial cells through decline in arylsulfatase B activity, with subsequent impact on C4S, galectin-3, Sp1, and Wnt9A and can exert significant effects on Wnt-initiated signaling and related vital cell processes.

Challenging role of Wnt5a and its signaling pathway in cancer metastasis (Review)

Wnt5a is a noncanonical signaling member of the wingless-related/mouse mammary tumor virus integration family, which is involved in a wide range of cellular processes, particularly in cancer development and metastasis. Accumulating evidence indicates that Wnt5a exhibits paradoxical effects in various types of cancer metastasis. Therefore, the Wnt5a signaling cascade in cancer metastasis appears to be complex and may depend on binding receptors, downstream effectors, exogenous inhibitors and tumor microenvironments, as well as the extracellular matrix, particularly cell/tissue-tropic contexts. The aim of the present study was to summarize the previous findings on the roles of Wnt5a and the potential mechanisms in various types of cancer metastasis. Furthermore, it is reasonable to hypothesize that Wnt5a and the involved signaling pathways may become molecular targets in the treatment of cancer metastasis.

TGF-β-activated kinase 1 (TAK1) signaling regulates TGF-β-induced WNT-5A expression in airway smooth muscle cells via Sp1 and β-catenin

WNT-5A, a key player in embryonic development and post-natal homeostasis, has been associated with a myriad of pathological conditions including malignant, fibroproliferative and inflammatory disorders. Previously, we have identified WNT-5A as a transcriptional target of TGF-β in airway smooth muscle cells and demonstrated its function as a mediator of airway remodeling. Here, we investigated the molecular mechanisms underlying TGF-β-induced WNT-5A expression. We show that TGF-β-activated kinase 1 (TAK1) is a critical mediator of WNT-5A expression as its pharmacological inhibition or siRNA-mediated silencing reduced TGF-β induction of WNT-5A. Furthermore, we show that TAK1 engages p38 and c-Jun N-terminal kinase (JNK) signaling which redundantly participates in WNT-5A induction as only simultaneous, but not individual, inhibition of p38 and JNK suppressed TGF-β-induced WNT-5A expression. Remarkably, we demonstrate a central role of β-catenin in TGF-β-induced WNT-5A expression. Regulated by TAK1, β-catenin is required for WNT-5A induction as its silencing repressed WNT-5A expression whereas a constitutively active mutant augmented basal WNT-5A abundance. Furthermore, we identify Sp1 as the transcription factor for WNT-5A and demonstrate its interaction with β-catenin. We discover that Sp1 is recruited to the WNT-5A promoter in a TGF-β-induced and TAK1-regulated manner. Collectively, our findings describe a TAK1-dependent, β-catenin- and Sp1-mediated signaling cascade activated downstream of TGF-β which regulates WNT-5A induction.

WNT5A encodes two isoforms with distinct functions in cancers

WNT5A, a member of the WNT family of secreted lipid-modified glycoproteins, is a critical regulator of a host of developmental processes, including limb formation, lung morphogenesis, intestinal elongation and mammary gland development. Altered WNT5A expression has been associated with a number of cancers. Interestingly, in certain types of cancers, such as hematological malignancies and colorectal carcinoma, WNT5A is inactivated and exerts a tumor suppressive function, while in other cancers, such as melanoma and gastric carcinoma, WNT5A is overexpressed and promotes tumor progression. The mechanism by which WNT5A achieves these distinct activities in cancers is poorly understood. Here, we provide evidence that the WNT5A gene produces two protein isoforms, WNT5A-long (WNT5A-L) and WNT5A-short (WNT5A-S). Amino-terminal sequencing and a WNT5A-L specific antibody demonstrate that the mature and secreted isoforms are distinct, with WNT5A-L carrying an additional 18 N-terminal amino acids. Biochemical analysis indicates that both purified proteins are similar with respect to their stability, hydrophobicity and WNT/β-catenin signaling activity. Nonetheless, modulation of these two WNT5A isoforms, either through ectopic expression or knockdown, demonstrates that they exert distinct activities in cancer cell lines: while WNT5A-L inhibits proliferation of tumor cell lines, WNT5A-S promotes their growth. Finally, we show that expression of these two WNT5A isoforms is altered in breast and cervix carcinomas, as well as in the most aggressive neuroblastoma tumors. In these cancers, WNT5A-L is frequently down-regulated, whereas WNT5A-S is found overexpressed in a significant fraction of tumors. Altogether, our study provides evidence that the distinct activities of WNT5A in cancer can be attributed to the production of two WNT5A isoforms.

Down-regulation of canonical and up-regulation of non-canonical Wnt signalling in the carcinogenic process of squamous cell lung carcinoma

The majority of lung cancers (LC) belong to the non-small cell lung carcinoma (NSCLC) type. The two main NSCLC sub-types, namely adenocarcinoma (AC) and squamous cell carcinoma (SCC), respond differently to therapy. Whereas the link between cigarette smoke and lung cancer risk is well established, the relevance of non-canonical Wnt pathway up-regulation detected in SCC remains poorly understood. The present study was undertaken to investigate further the molecular events in canonical and non-canonical Wnt signalling during SCC development. A total of 20 SCC and AC samples with matched non-cancerous controls were obtained after surgery. TaqMan array analysis confirmed up-regulation of non-canonical Wnt5a and Wnt11 and identified down-regulation of canonical Wnt signalling in SCC samples. The molecular changes were tested in primary small airway epithelial cells (SAEC) and various lung cancer cell lines (e.g. A549, H157, etc). Our studies identified Wnt11 and Wnt5a as regulators of cadherin expression and potentiated relocation of β-catenin to the nucleus as an important step in decreased cellular adhesion. The presented data identifies additional details in the regulation of SCC that can aid identification of therapeutic drug targets in the future.

Multilocus genetic characterization of two ant vectors (Group II "Dirty 22" species) known to contaminate food and food products and spread foodborne pathogens

The U.S. Food and Drug Administration utilizes the presence of filth and extraneous materials as one of the criteria for implementing regulatory actions and assessing adulteration of food products of public health importance. Twenty-two prevalent pest species (also known as the ''Dirty 22'' species) have been considered by this agency as possible vehicles for the spread of foodborne diseases, and the presence of these species is considered an indicator of unsanitary conditions in food processing and storage facilities. In a previous study, we further categorized the Dirty 22 species into four groups: group I includes four cockroach species, group II includes two ant species, group III includes 12 fly species, and group IV includes four rodent species. Here, we describe the development of three nested PCR primer sets and multilocus genetic characterization by amplifying the small subunit rRNA, elongation factor 1-alpha, and wingless (WNT-1) genes of group II Dirty 22 ant species Monomorium pharaonis and Solenopsis molesta. These novel group II Dirty 22 species-specific nested PCR primer sets can be used when the specimens cannot be identified using conventional microscopic methods. These newly developed assays will provide correct identification of group II Dirty 22 ant species, and the information can be used in the control of foodborne pathogens.

Diverse mechanisms for activation of Wnt signalling in the ovarian tumour microenvironment

Wnt signalling pathways have been shown to play key roles in both normal development and tumorigenesis. Progression of many human cancers is associated with defined mutations in Wnt pathway components that result in dysregulated β-catenin-mediated gene transcription. Although Wnt pathway mutations are rare in epithelial ovarian cancer (with the exception of the endometrioid histotype), accumulating evidence supports a role for Wnt signalling in ovarian tumorigenesis in the absence of genetic mutations. The present review summarizes evidence in support of activated Wnt signalling in ovarian tumours and discusses alternative mechanisms for Wnt pathway activation in the ovarian tumour microenvironment.

Integrin regulation of beta-catenin signaling in ovarian carcinoma

Reversible modulation of integrin-regulated cell-matrix adhesion and epithelial (E)-cadherin-mediated cell-cell adhesion plays a critical role in the establishment of ovarian cancer metastases. In contrast to most epithelial cell-derived tumors that down-regulate E-cadherin expression during progression, acquisition of E-cadherin expression accompanies malignant transformation of the ovarian surface epithelium and is maintained in peritoneal metastases. Metastatic epithelial ovarian cancer cells are disseminated intraperitoneally and preferentially adhere via integrins to interstitial collagens in the peritoneal cavity. This study was undertaken to determine whether integrin engagement influences E-cadherin and β-catenin localization and function. The data demonstrate that multivalent integrin engagement results in increased internalization of E-cadherin, inhibition of GSK-3β, elevated levels of nuclear β-catenin, increased β-catenin-regulated promoter activation, and transcriptional activation of Wnt/β-catenin target genes. Blocking β-catenin transcriptional control with inhibitor of β-catenin and Tcf-4 reduces cellular invasion, suggesting a key role for β-catenin nuclear signaling in EOC invasion and metastasis. These studies support a model wherein cell-matrix engagement regulates the functional integrity of cell-cell contacts, leading to increased β-catenin nuclear signaling and enhanced cellular invasive activity. Furthermore, these results provide a mechanism for activation of Wnt/β-catenin signaling in the absence of activating mutations in this pathway.

WNT5A expression in ameloblastoma and its roles in regulating enamel epithelium tumorigenic behaviors

Odontogenic tumors originate from the remains of migrating enamel epithelium after the completion of normal tooth genesis. These enamel epithelium remnants exhibit the ability to recapitulate the events that occur during tooth formation. Several lines of evidence suggest that aberrance in the signaling pathways similar to the ones that are used during tooth development, including the WNT pathway, might be the cause of odontogenic tumorigenesis and maintenance. In this study we demonstrated that WNT5A expression was intense in both the epithelial component of ameloblastomas, the most common epithelial odontogenic tumor, and in this tumor's likely precursor cell, the enamel epithelium located at the cervical loop of normal developing human tooth buds. Additionally, when WNT5A was overexpressed in enamel epithelium cells (LS-8), the clones expressing high levels of WNT5A (S) exhibited characteristics of tumorigenic cells, including growth factor independence, loss of anchorage dependence, loss of contact inhibition, and tumor formation in immunocompromised mice. Moreover, overexpression of WNT5A drastically increased LS-8 cell migration and actin reorganization when compared with controls. Suppression of endogenous WNT5A in LS-8 cells (AS) greatly impaired their migration and AS cells failed to form significant actin reorganization and membrane protrusion was rarely seen. Taken together, our data indicate that WNT5A signaling is important in modulating tumorigenic behaviors of enamel epithelium cells in ameloblastomas.

WNT-5A, but not matrix metalloproteinase 3 or beta-catenin protein, expression is related to early stages of lip carcinogenesis

BACKGROUND

Oncogenic Wnt/beta-catenin signaling occurs in numerous types of cancers, but little is known about the role of the Wnt protein family member, WNT-5A, in lip carcinogenesis. The aim of this study was to investigate WNT-5A, beta-catenin, and matrix metalloproteinase (MMP)-3 protein expression in actinic cheilitis (AC), and lip squamous cell carcinoma (LSCC).

METHODS

Twenty-one cases of AC, and fifty-one cases of LSCC were analyzed, with normal lip mucosa used as a control. Qualitative and semi-quantitative analyses of WNT-5A, beta-catenin, and MMP-3 immunostaining pattern and cellular distribution were performed.

RESULTS

WNT-5A was observed in more than 50% of the cells, scattered in all layers of AC, in contrast to the absence of immunostaining in normal lip mucosa. AC presented a higher level of WNT-5A expression than LSCC (P = 0.0289, Fisher test), while MMP-3 immunoexpression was statistically more significant in LSCC than in AC (P = 0.0285, Fisher test). Immunolabeling of beta-catenin protein was differentially distributed between samples; the majority of AC cases (61.90%) demonstrated a membranous-cytoplasmic pattern, while a considerable number of LSCC cases (29.41%) revealed a cytoplasmic pattern, instead of the usual membranous pattern.

CONCLUSIONS

The present results suggest that WNT-5A may be an important marker during initial events of AC malignant transformation, in which non-canonical and canonical Wnt/beta-catenin signaling pathways could be involved. Additionally, WNT-5A might recruit other events in LSCC, such as MMP-3 protein synthesis, as its presence is increased in established malignant processes without beta-catenin dependency.

Transcriptional outcome of Wnt-Frizzled signal transduction in inflammation: evolving concepts

Wnt-Frizzled signaling was first identified as a key event in Drosophila development. Over the years, ample evidence has accumulated regarding the multiple roles of Wnt-Frizzled signaling in mammalian cell differentiation and tissue/organ morphogenesis. It is thus not surprising that variations in the regulatory network of the Wnt signaling scheme would lead to alterations in cellular organization and cell activation and to the development of pathogenic conditions. Several reports have accordingly implied the involvement of Wnt-Frizzled signaling in the activation of proinflammatory mediators in inflammatory disorders. We will discuss how Wnt-Frizzled signaling may initiate/augment inflammation, focusing on its transcriptional outcome.

Adiponectin stimulates Wnt inhibitory factor-1 expression through epigenetic regulations involving the transcription factor specificity protein 1

Adiponectin (ADN) is an adipokine possessing growth inhibitory activities against various types of cancer cells. Our previous results demonstrated that ADN could impede Wnt/beta-catenin-signaling pathways in MDA-MB-231 human breast carcinoma cells [Wang,Y. et al. (2006) Adiponectin modulates the glycogen synthase kinase-3 beta/beta-catenin signaling pathway and attenuates mammary tumorigenesis of MDA-MB-231 cells in nude mice. Cancer Res., 66, 11462-11470]. Here, we extended our studies to elucidate the effects of ADN on regulating the expressions of Wnt inhibitory factor-1 (WIF1), a Wnt antagonist frequently silenced in human breast tumors. Our results showed that ADN time dependently stimulated WIF1 gene and protein expressions in MDA-MB-231 cells. Overexpression of WIF1 exerted similar inhibitory effects to those of ADN on cell proliferations, nuclear beta-catenin activities, cyclin D1 expressions and serum-induced phosphorylations of Akt and glycogen synthase kinase-3 beta. Blockage of WIF1 activities significantly attenuated the suppressive effects of ADN on MDA-MB-231 cell growth. Furthermore, our in vivo studies showed that both supplementation of recombinant ADN and adenovirus-mediated overexpression of this adipokine substantially enhanced WIF1 expressions in MDA-MB-231 tumors implanted in nude mice. More interestingly, we found that ADN could alleviate methylation of CpG islands located within the proximal promoter region of WIF1, possibly involving the specificity protein 1 (Sp1) transcription factor and its downstream target DNA methyltransferase 1 (DNMT1). Upon ADN treatment, the protein levels of both Sp1 and DNMT1 were significantly decreased. Using silencing RNA approaches, we confirmed that downregulation of Sp1 resulted in an increased expression of WIF1 and decreased methylation of WIF1 promoter. Taken together, these data suggest that ADN might elicit its antitumor activities at least partially through promoting WIF1 expressions.

Platination of the siRNA sense-strand modulates both efficacy and selectivity in vitro

The use of short interfering RNAs (siRNA) for selective suppression of protein production has rapidly become a commonly used technique for transient modulation of protein levels. In the present paper, we investigate whether introduction of platinated bases in the sense strand can be used to modulate the efficacy of siRNAs. Four different siRNAs were studied, all targeting the initial AU-rich 3' UTR of Wnt-5a mRNA. The siRNAs were characterized with respect to melting properties and translational inhibitory effect in vitro using luciferase as a reporter gene. The translation inhibition studies reveal that all platinated siRNA remain efficient. For an siRNA with partial complementarity to the luciferase gene, platination was shown to reduce the off-target effects. All siRNAs were found to be active in cellular in vitro translation systems, reaching suppression levels well above 80% for the majority of siRNAs investigated.

Sex determination and gonadal development in mammals

Arguably the most defining moment in our lives is fertilization, the point at which we inherit either an X or a Y chromosome from our father. The profoundly different journeys of male and female life are thus decided by a genetic coin toss. These differences begin to unfold during fetal development, when the Y-chromosomal Sry ("sex-determining region Y") gene is activated in males and acts as a switch that diverts the fate of the undifferentiated gonadal primordia, the genital ridges, towards testis development. This sex-determining event sets in train a cascade of morphological changes, gene regulation, and molecular interactions that directs the differentiation of male characteristics. If this does not occur, alternative molecular cascades and cellular events drive the genital ridges toward ovary development. Once testis or ovary differentiation has occurred, our sexual fate is further sealed through the action of sex-specific gonadal hormones. We review here the molecular and cellular events (differentiation, migration, proliferation, and communication) that distinguish testis and ovary during fetal development, and the changes in gene regulation that underpin these two alternate pathways. The growing body of knowledge relating to testis development, and the beginnings of a picture of ovary development, together illustrate the complex mechanisms by which these organ systems develop, inform the etiology, diagnosis, and management of disorders of sexual development, and help define what it is to be male or female.

Wnt-5a mRNA translation is suppressed by the Elav-like protein HuR in human breast epithelial cells

Wnt-5a is a non-transforming Wnt protein. Since Wnt-5a mRNA and protein levels differ within and between tumours, the potential of Wnt-5a as a prognostic factor has been debated. We have previously shown that the lack of Wnt-5a protein is a predictor of shorter disease-free survival in human breast cancer. Recently, however, we also showed that the breast tumours lacking Wnt-5a protein had a high or normal level of Wnt-5a mRNA that might explain the discrepancies in previous studies. We here report that Wnt-5a is regulated at the post-transcriptional level. The regulation was mediated by the Embryonic Lethal Abnormal Vision (ELAV)-like protein HuR, which inhibited translation of Wnt-5a when bound to highly conserved AU-rich sequences in the 3′-untranslated region (3′-UTR) of the Wnt-5a mRNA molecule, as shown by both HA-tagged Wnt-5a- and Luciferase-Wnt-5a-3′-UTR reporter assays. The HuR-dependent inhibition of Wnt-5a was supported by the fact that active HuR is located in the cytoplasm in invasive human breast tumours and that hypoxia-induced activation of HuR inhibits translation of both Luciferase-Wnt-5a-3′-UTR and endogenous Wnt-5a protein. We propose that the lack of Wnt-5a protein expression in invasive human breast tumours is caused by a HuR-mediated suppression of Wnt-5a mRNA translation.

Increased expression of Wnt5a in psoriatic plaques

Psoriasis vulgaris is characterized by hyperproliferation and incomplete terminal differentiation of epidermal keratinocytes. Despite the established role of Wnt pathways in the regulation of stem cell proliferation and differentiation, they have not yet been associated with the pathophysiology of psoriasis. Here, we took biopsies from uninvolved and from lesional skin of 20 patients with plaque-type psoriasis. The biopsies were used for microarray RNA expression profiling. Based on paired samples from 13 patients, we defined 179 genes that were more than 2-fold differentially expressed in lesional skin. This list included 16 genes with known or possible association to the canonical Wnt/beta-catenin or the non-canonical Wnt/Ca2+ pathway. The expression of Wnt5a was 4-fold higher in lesional skin. Other Wnt molecules were largely unchanged (Wnt4 and Wnt16), or tended to be expressed at lower levels (Wnt7b). The mRNA expression levels of two inhibitory factors related to Wnt signaling, frizzled-related protein, and dickkopf homolog 2, were reduced in lesional skin, as was mRNA expression of cyclin D1. These findings were confirmed by quantitative reverse transcription-PCR experiments. We conclude that Wnt5a and other Wnt pathway genes are differentially expressed in psoriatic plaques. Their functional contribution to the pathophysiology of psoriasis needs to be elaborated.

Distinct effects of glucose and glucosamine on vascular endothelial and smooth muscle cells: evidence for a protective role for glucosamine in atherosclerosis

Accelerated atherosclerosis is one of the major vascular complications of diabetes. Factors including hyperglycemia and hyperinsulinemia may contribute to accelerated vascular disease. Among the several mechanisms proposed to explain the link between hyperglycemia and vascular dysfunction is the hexosamine pathway, where glucose is converted to glucosamine. Although some animal experiments suggest that glucosamine may mediate insulin resistance, it is not clear whether glucosamine is the mediator of vascular complications associated with hyperglycemia. Several processes may contribute to diabetic atherosclerosis including decreased vascular heparin sulfate proteoglycans (HSPG), increased endothelial permeability and increased smooth muscle cell (SMC) proliferation. In this study, we determined the effects of glucose and glucosamine on endothelial cells and SMCs in vitro and on atherosclerosis in apoE null mice. Incubation of endothelial cells with glucosamine, but not glucose, significantly increased matrix HSPG (perlecan) containing heparin-like sequences. Increased HSPG in endothelial cells was associated with decreased protein transport across endothelial cell monolayers and decreased monocyte binding to subendothelial matrix. Glucose increased SMC proliferation, whereas glucosamine significantly inhibited SMC growth. The antiproliferative effect of glucosamine was mediated via induction of perlecan HSPG. We tested if glucosamine affects atherosclerosis development in apoE-null mice. Glucosamine significantly reduced the atherosclerotic lesion in aortic root. (P < 0.05) These data suggest that macrovascular disease associated with hyperglycemia is unlikely due to glucosamine. In fact, glucosamine by increasing HSPG showed atheroprotective effects.

Gene expression changes in an in vitro model of chondroinduction: a comparison of two methods

There are many useful technologies to describe patterns of gene expression that occur during tissue repair and regeneration. Results from different methods used in one experimental setting are not often compared. In this case study of chondrogenesis, we compare two methods to identify differentially expressed genes, representational difference analysis and targeted macroarray analysis, as a model for investigating genes that may be relevant to tissue repair. We sought to identify genes whose expression was altered when human dermal fibroblasts were cultured in a three-dimensional, porous collagen sponge with the chondroinductive agent, demineralized bone. Both representational difference analysis and macroarray experiments revealed several functional families of genes as up-regulated or down-regulated in chondroinduced fibroblasts. An advantage of representational difference analysis is that altered expression of specific mRNA transcripts can be revealed. In this example, representational difference analysis uncovered the up-regulation of a specific transcript of Wnt5a in fibroblasts cultured with demineralized bone. Representational difference analysis is limited, however, as there can be false negatives for genes not readily amplified by polymerase chain reaction. We conclude that small arrays containing functional classes of genes can be used to ask specific, hypothesis-driven questions at minimal cost. It may be prudent, however, to use more than one method to survey differences in gene expression in order to validate and expand findings.

Influence of omega-3 fatty acids on the growth of human colon carcinoma in nude mice

The present study investigated the influence of dietary omega-3 fatty acid supplementation on the growth of human colon carcinoma xenograft in athymic nude mice. Four diets were fed to evaluate the effect of levels and types of fat on colon tumor growth. Animals were maintained on a standard diet modified by addition of fats containing omega-3 and omega-6 fatty acids to represent high and low fat intakes for 53 days. The final mean estimated tumor weight for the high fat corn oil (24%) fed group was 2,302 mg, whereas the low fat (8% corn oil) group was 1,681 mg. The final mean tumor weight of the high fat menhaden oil fed group was 782 mg representing a 66% decrease in growth compared to the high fat corn oil group and a decrease of 54% compared to the low corn oil fed group. The high fat golden algae oil fed group resulted in a mean final tumor weight of 223 mg representing a 90% inhibition of tumor growth relative to the high fat corn oil fed group and 87% inhibition of growth compared to the low fat corn oil fed group. These findings indicate that dietary omega-3 fatty acids possess significant tumor suppressing properties and that the primary tumor suppressing fatty acid is docosahexaenoic acid. Histopathologic examination of control and treated tumors and expression array analyses (human cytokine and apoptosis arrays) support the tumor growth inhibition data and provide evidence for discussion of possible mechanisms for the observed growth inhibition.

Full-length cDNAs: more than just reaching the ends

The development of functional genomic resources is essential to understand and utilize information generated from genome sequencing projects. Central to the development of this technology is the creation of high-quality cDNA resources and improved technologies for analyzing coding and noncoding mRNA sequences. The isolation and mapping of cDNAs is an entrée to characterizing the information that is of significant biological relevance in the genome of an organism. However, a bottleneck is often encountered when attempting to bring to full-length (or at least full-coding) a number of incomplete cDNAs in parallel, since this involves the nonsystematic, time consuming, and labor-intensive iterative screening of a number of cDNA libraries of variable quality and/or directed strategies to process individual clones (e.g., 5' rapid amplification of cDNA ends). Here, we review the current state of the art in cDNA library generation, as well as present an analysis of the different steps involved in cDNA library generation.

Expression of Wnt genes in human colon cancers

A polymerase chain reaction-based approach was used to study the expression of Wnt genes in human colon carcinoma tissue and normal colon mucosa. In a number of cases Wnts 2, 4, 5a, 6 and/or 7a were found to be more highly expressed in colon carcinoma tissue compared to surrounding normal-appearing mucosa from the same patients. Wnts 4, 5a, 6 and 7a, but not 2, were also found to be expressed in colon cancer cell lines. The increased levels of expression of these Wnt genes in tumor tissue may indicate their possible involvement in human colon tumorigenesis.

The battle of the sexes

The sex determining gene, Sry, determines the sex of the organism by initiating development of a testis rather than an ovary from the cells of the bipotential gonad. In the 10 years since the discovery of Sry, new genes and cellular pathways that operate in the establishment of the gonadal primordium and the initiation of testis development have been discovered. Experiments defining mechanisms downstream of Sry are providing clear examples of how a regulatory transcription factor initiates cellular processes including proliferation and cell migration, which in turn influence architectural patterning, fate commitment, and differentiation of cells within an organ.

A conserved 30 base pair element in the Wnt-5a promoter is sufficient both to drive its' early embryonic expression and to mediate its' repression by otx2

We have characterised a short (30 base pair) element from the Xenopus Wnt-5a promoter which is nearly identical to one located in the human Wnt-5a promoter, and has the same position relative to the transcription start site. When placed in front of a LacZ gene, this element can reproduce the same expression pattern observed for Wnt-5a at the late gastrula stage. Further we show that gastrula stage Wnt-5a expression is repressed by otx2, something which is reflected by the mutually exclusive expression patterns of these two genes. The isolated promoter sequence contains an OTX- consensus binding site and its' activity in embryos is repressed by ectopically expressed otx2.

Expression of fetal kidney growth factors in a kidney tumor line: role of FGF2 in kidney development

To identify growth factors which may play a role in kidney organogenesis, we have analyzed culture supernatants from the pediatric kidney tumor cell line G401. G401 cells were found to secrete fibroblast growth factor 2 (FGF2), a potent mitogen for mesenchymal cells, OP-1/BMP7, an epithelial cell growth inhibitor, and midkine (MK). Northern blotting confirmed expression of FGF2, OP-1/BMP7 and MK mRNA, as well as Wnt5A mRNA in G401 cells. In situ hybridization and immunocytochemistry on human fetal kidney demonstrated FGF2 expression in epithelial cells of the branching ureteric bud epithelium, nephron precursors ("S-shaped bodies"), proximal tubule epithelium and the parietal epithelium of the glomerulus. FGF2 protein in condensed "caps" of induced mesenchymal cells was also detected by immunocytochemistry. FGF2 protein was found to be concentrated in nuclei, particularly in proximal tubule epithelial cells. Recombinant FGF2 was found to act as a mitogen on primary mouse fetal kidney cell cultures. The results demonstrate G401 cells secrete a variety of fetal kidney growth factors and that FGF2 may act as a mitogen for fetal kidney cells and thus could play a role in the morphogenesis of the kidney.

Isolation, characterisation and embryonic expression of WNT11, a gene which maps to 11q13.5 and has possible roles in the development of skeleton, kidney and lung

The Wnt gene family encodes a set of signalling molecules, thought to play an important role in key processes of embryonic development. In vertebrates as a whole 20 different Wnt genes have been identified to date, however, a complement of only 16 have been identified in man and for some of these the complete coding sequences are unavailable. We have recently isolated the full-length cDNA sequence of a new human WNT gene, WNT11, investigated its genomic organisation and performed detailed expression studies in early human embryos. These have shown that the expression of human WNT11 is restricted to the perichondrium of the developing skeleton, lung mesenchyme, the tips of the ureteric buds and other areas of the urogenital system and the cortex of the adrenal gland. This, for the first time, provides information for the embryonic expression of human WNT11. We have mapped WNT11 to 11q13.5 and this together with its expression in the perichondrium of the developing skeleton, makes it a plausible candidate gene for HBM, which has been previously linked to markers from this region.

Regulation of Wnt5a expression in human mammary cells by protein kinase C activity and the cytoskeleton

The Wnts can be classified into two classes based on their ability to transform cells. The Wnt5a class can antagonize the effects of transforming Wnts partly through effects on cell migration. To understand the mechanisms of regulation of Wnt5a, we investigated its expression in human normal and breast cancer cell lines. Elevation of Wnt5a in HB2, a normal breast epithelial cell line, was linearly correlated with cell density, but this did not occur in cancer cell lines. We examined intracellular events responsible for the regulation of Wnt5a by cell to cell contacts, using various metabolic agents known to affect signal transduction pathways. Agents that selectively blocked protein kinase C (calphostin C) or protein tyrosine kinases (genistein) reduced the level of Wnt5a expression markedly. Protein kinase C activation by phorbol 12-myristate 13-acetate up-regulated Wnt5a partly through prolongation of Wnt5a mRNA half-life. Cytoskeleton reorganization following cytochalasin D treatment caused an induction of Wnt5a, which was associated with changes in cell morphology. Calphostin C did not block these effects, showing that protein kinase C is acting upstream of cytoskeletal modulation. However, the cancer cell lines treated with cytochalasin D showed no changes in cell morphology or Wnt5a induction, suggesting disruption of this regulatory pathway in cancer.

Isolation of two novel WNT genes, WNT14 and WNT15, one of which (WNT15) is closely linked to WNT3 on human chromosome 17q21

The Wnt gene family consists of at least 15 structurally related genes that encode secreted extracellular signaling factors. Wnt proteins function in a range of critical developmental processes in both vertebrates and invertebrates and are implicated in regulation of cell growth and differentiation in certain adult mammalian tissues, including the mammary gland. We have isolated a number of WNT sequences from human genomic DNA, two of which, designated WNT14 and WNT15, represent novel members of the Wnt gene family. We also isolated WNT sequences from human mammary cDNA and present evidence that WNT13 is expressed in human breast tissue, in addition to those previously described. WNT14 and WNT15 appear to have originated from an ancestral branch of the Wnt gene family that also includes the Wnt9 sequences found in jawless and cartilaginous fishes. A Wnt14 cDNA was also isolated from chicken and a partial Wnt15 sequence from mouse. We show that human WNT14 maps to chromosome 1 and that WNT15 maps distal to BRCA1 on chromosome 17q21, where it lies within 125 kb of another WNT family member, WNT3.

Alternative poly(A) site selection in complex transcription units: means to an end?

Many genes have been described and characterized which result in alternative polyadenylation site use at the 3'-end of their mRNAs based on the cellular environment. In this survey and summary article 95 genes are discussed in which alternative polyadenylation is a consequence of tandem arrays of poly(A) signals within a single 3'-untranslated region. An additional 31 genes are described in which polyadenylation at a promoter-proximal site competes with a splicing reaction to influence expression of multiple mRNAs. Some have a composite internal/terminal exon which can be differentially processed. Others contain alternative 3'-terminal exons, the first of which can be skipped in some cells. In some cases the mRNAs formed from these three classes of genes are differentially processed from the primary transcript during the cell cycle or in a tissue-specific or developmentally specific pattern. Immunoglobulin heavy chain genes have composite exons; regulated production of two different Ig mRNAs has been shown to involve B cell stage-specific changes in trans -acting factors involved in formation of the active polyadenylation complex. Changes in the activity of some of these same factors occur during viral infection and take-over of the cellular machinery, suggesting the potential applicability of at least some aspects of the Ig model. The differential expression of a number of genes that undergo alternative poly(A) site choice or polyadenylation/splicing competition could be regulated at the level of amounts and activities of either generic or tissue-specific polyadenylation factors and/or splicing factors.

A Role for the Wnt Gene Family in Hematopoiesis: Expansion of Multilineage Progenitor Cells

The microenvironment is a key regulator of hematopoietic stem cells (HSCs) and is a likely source of extracellular factors that control stem cell fate. A better understanding of these microenvironmental factors may come from investigations of developmental cell fate determination in which the critical roles of cell-cell interactions of multipotential cells have been shown. The Wnt gene family is known to regulate the cell fate and cell-cell interactions of multipotential cells in a variety of tissues. Expression of Wnts and of their putative receptors encoded by murine homologs of the Drosophila frizzled gene in hematopoietic tissues was examined by reverse transcriptase-polymerase chain reaction. Wnt-5a and Wnt-10b were expressed in day-11 murine yolk sac, day-14 fetal liver, and fetal liver AA4+ cells. The expression profiles of four murine frizzled homologs, Mfz3-7, were nearly identical to that of Wnt-5a and Wnt-10b. Notably, Wnt-10b was expressed in the fetal liver AA4+ Sca+ c-kit+ (flASK) HSC population. A role for Wnts in HSC fate determination was studied by treatment of HSC populations in culture with soluble WNT proteins. The addition of conditioned media from cells transfected with Wnt-1, Wnt-5a, or Wnt-10b cDNAs to cultures of flASK cells stimulated a sevenfold, eightfold, and 11-fold expansion in cell number, respectively, relative to control media. Removal of WNT-5a from this media by immunodepletion depleted the stimulatory activity from the media, whereas addition of a partially purified WNT-5a stimulated a fivefold expansion relative to control cells. Transduction of flASK cells with a retrovirus bearing a Wnt-5a cDNA enhanced proliferation. We conclude that WNTs stimulate the survival/proliferation of hematopoietic progenitors, demonstrating that WNTs comprise a novel class of hematopoietic cell regulators.

A Role for the Wnt Gene Family in Hematopoiesis: Expansion of Multilineage Progenitor Cells

The microenvironment is a key regulator of hematopoietic stem cells (HSCs) and is a likely source of extracellular factors that control stem cell fate. A better understanding of these microenvironmental factors may come from investigations of developmental cell fate determination in which the critical roles of cell-cell interactions of multipotential cells have been shown. The Wnt gene family is known to regulate the cell fate and cell-cell interactions of multipotential cells in a variety of tissues. Expression of Wnts and of their putative receptors encoded by murine homologs of the Drosophila frizzled gene in hematopoietic tissues was examined by reverse transcriptase-polymerase chain reaction. Wnt-5a and Wnt-10b were expressed in day-11 murine yolk sac, day-14 fetal liver, and fetal liver AA4+ cells. The expression profiles of four murine frizzled homologs, Mfz3-7, were nearly identical to that of Wnt-5a and Wnt-10b. Notably, Wnt-10b was expressed in the fetal liver AA4+ Sca+ c-kit+ (flASK) HSC population. A role for Wnts in HSC fate determination was studied by treatment of HSC populations in culture with soluble WNT proteins. The addition of conditioned media from cells transfected with Wnt-1, Wnt-5a, or Wnt-10b cDNAs to cultures of flASK cells stimulated a sevenfold, eightfold, and 11-fold expansion in cell number, respectively, relative to control media. Removal of WNT-5a from this media by immunodepletion depleted the stimulatory activity from the media, whereas addition of a partially purified WNT-5a stimulated a fivefold expansion relative to control cells. Transduction of flASK cells with a retrovirus bearing a Wnt-5a cDNA enhanced proliferation. We conclude that WNTs stimulate the survival/proliferation of hematopoietic progenitors, demonstrating that WNTs comprise a novel class of hematopoietic cell regulators.