7474

WNT5A

hWNT5A;wingless-type MMTV integration site family, member 5A;WNT5A;wingless-type MMTV integration site family, member 5A

WNT-5A protein|protein Wnt-5a

3p21-p14

protein-coding

Wnt5a is a member of the Wnt family of secreted glycoproteins that play essential organizing roles in development. Similar to other Wnt members, Wnt5a can upregulate cell proliferation and has been proposed to have oncogenic function. Here we report that Wnt5a signals through the noncanonical Wnt/Ca++ pathway to suppress cyclin D1 expression and negatively regulate B cell proliferation in a cell-autonomous manner. Wnt5a hemizygous mice develop myeloid leukemias and B cell lymphomas that are clonal in origin and display loss of Wnt5a function in tumor tissues. Furthermore, analysis of human primary leukemias reveals deletion of the WNT5A gene and/or loss of WNT5A expression in a majority of the patient samples. These results demonstrate that Wnt5a suppresses hematopoietic malignancies.

Stabilization of beta-catenin by inhibition of its phosphorylation is characteristic of an activation of the canonical Wnt/beta-catenin signaling pathway and is associated with various human carcinomas. It contrasts to an as yet incompletely characterized action of an alternative noncanonical Wnt signaling pathway on neoplastic transformation. The aim of the present study was to test the effects of a member of the noncanonical Wnt signaling pathway, Wnt-5a, in primary thyroid carcinomas and in thyroid carcinoma cell lines. Compared to normal tissue Wnt-5a mRNA expression was clearly increased in thyroid carcinomas. Immunohistochemically, a bell-shaped response was observed with low to undetectable levels in normal tissue and in anaplastic tumors whereas differentiated thyroid carcinomas showed strong positive immunostaining for Wnt-5a. Transfection of Wnt-5a in a thyroid tumor cell line FTC-133 was able to reduce proliferation, migration, invasiveness and clonogenicity in these cells. These effects of Wnt-5a are associated with membranous beta-catenin translocation and c-myc oncogene suppression and are mediated through an increase in intracellular Ca(2+) release, which via CaMKII pathways promotes beta-catenin phosphorylation. Specific inhibition of beta-catenin phosphorylation by W-7, a calmodulin inhibitor, or by KN-93, a CaMKII inhibitor, supports these findings whereas PKC inhibitors were without effect. This interaction occurs downstream of GSK-3 beta as no Wnt-5a effect was seen on the Ser(9) phosphorylation of GSK-3 beta. Our data are compatible with the hypothesis that Wnt-5a serves as an antagonist to the canonical Wnt-signaling pathway with tumor suppressor activity in differentiated thyroid carcinomas.

Wnt5a is a member of the Wnt family of proteins that signals through the non-canonical Wnt/Ca(2+)pathway to suppress cyclin D1. Deregulation of this pathway has been found in animal models suggesting that it acts as tumour suppressor in acute myeloid leukemia (AML). Although DNA methylation is the main mechanism of regulation of the canonical Wnt pathway in AML, the role of WNT5A abnormalities has never been evaluated in this clinical setting. The methylation status of WNT5A promoter-exon 1 was analyzed by methylation-specific PCR and sequencing in eleven AML-derived cell lines and 252 AML patients. We observed WNT5A hypermethylation in seven cell lines and in 43% (107/252) of AML patients. WNT5A methylation was associated with decreased WNT5A expression (P < 0.001) that was restored after exposure to 5-Aza-2-deoxycytidine. Moreover, WNT5A hypermethylation correlated with upregulation of CYCLIN D1 expression (P < 0.001). Relapse (15%vs 37%, P < 0.001) and mortality (61%vs 79%, P = 0.004) rates were lower for patients in the non-methylated group. Disease-free survival and overall survival at 6 and 7 years, respectively, were 60% and 27% for unmethylated patients and 20% and 0% for hypermethylated patients (P = 0.0001 and P = 0.04, respectively). Interestingly, significant differences were also observed when the analysis was carried out according to cytogenetic risk groups. We demonstrate that WNT5A, a putative tumor suppressor gene in AML, is silenced by methylation in this disease and that this epigenetic event is associated with upregulation of CYCLIN D1 expression and confers poor prognosis in patients with AML.

Wnt5a has been shown to be involved in cancer progression in a variety of tumor types, and regulates multiple intracellular signaling cascades; it is a representative ligand that activates a noncanonical Wnt signaling pathway. The mechanism governing how Wnt5a determines the specificity of these pathways and the relationship with tumorigenesis is still unknown. In this study, we aimed to clarify the tumor suppressor role of Wnt5a in leukemogenesis. In particular, we focused on Ror2 functioning as a Wnt5a receptor to mediate noncanonical Wnt signaling, which inhibits canonical Wnt signaling in K562 cells. We found that up-regulation of Wnt5a expression increased Ror2 expression in K562 cells and Wnt5a and Ror2 were co-expressed in the cytoplasm. Also, Wnt5a induced the intrnalization of Ror2. Co-immunoprecipitation experiments were performed to determine whether Ror2 binds to Wnt5a, and inhibits Wnt5a binding with Frizzled4 and LRP5 in Wnt5a treated K562 cells. Wnt5a had no effect on total ss-catenin expression levels, but regulated tyrosine phosphorylation of ss-catenin and translocation of ss-catenin from the cytoplasm to the nucleus. Furthermore, expression of Wnt5a was associated with suppression of ss-catenin/TCF-dependent transcriptional activity and down-regulated the expression of cyclin D1, a downstream target gene of the canonical Wnt signaling pathway. We hypothesize that Wnt5a plays the role of a tumor suppressor in leukemogenesis through the Wnt5a/Ror2 noncanonical signaling pathway that inhibits Wnt canonical signaling.

AIM: To investigate the expression and clinical significance of Wnt member 5a (Wnt5a) and receptor tyrosine kinase-like orphan receptor 2 (Ror2) in hepatocellular carcinoma (HCC). METHODS: In HCC tissues obtained from 85 patients, the protein expressions of Wnt5a, Ror2, beta-catenin, and Ki-67 via immunohistochemical staining using the Envision Plus System. The antibody binding was visualized with 3, 3-diaminobenzidine tetrahydrochloride (DAB) before brief counterstaining with Mayers hematoxylin. The degree of immunohistochemical staining was recorded using a semiquantitative and subjective grading system. The mRNA expression of Ror2 was examined by real-time reverse transcription polymerase chain reaction, including nineteen of the 85 HCC and three normal liver tissues. The ratios of Ror2 to the housekeeping gene GAPDH represented the normalized relative levels of Ror2 expression. To determine the prognostic factor, the outcome of the 82 patients was determined by reviewing their medical charts. The overall and disease-free survival rates were estimated using the Kaplan-Meier method and compared with the log-rank test. The prognostic analysis was carried out with univariate and multivariate Cox regressions models. RESULTS: Compared to nontumorous (hepatitis or cirrhotic) tissues, Ror2 mRNA expression was clearly decreased in HCC. Ror2 and Wnt5a protein expressions in the majority of HCC patients (63% and 77%, respectively) was significantly less in tumor tissues, as compared to adjacent nontumorous tissues, and this reduction was correlated with increasing serum alpha-fetoprotein and tumor stage. In 68% (58/85) of the HCC cases, the expression of beta-catenin in tumor tissues was either downregulated in the cellular membrane, upregulated in the cytoplasm, or both. Survival analysis indicated that Wnt5a and Ror2 protein expressions could be regarded as independent prognostic factors for HCC; HCC patients with decreased Wnt5a or Ror2 protein expression had a poorer prognosis than those with elevated Wnt5a and Ror2 expression (P = 0.016, P = 0.007, respectively). CONCLUSION: Wnt5a and Ror2 may serve as tumor suppressor genes in the development of HCC, and may serve as clinicopathologic biomarkers for prognosis in HCC patients.