β-Catenin destruction complex-independent regulation of Hippo–YAP signaling by APC in intestinal tumorigenesis

Mutations in Adenomatous polyposis coli (APC) underlie familial adenomatous polyposis (FAP), an inherited cancer syndrome characterized by the widespread development of colorectal polyps. APC is best known as a scaffold protein in the β-catenin destruction complex, whose activity is antagonized by canonical Wnt signaling. Whether other effector pathways mediate APC''s tumor suppressor function is less clear. Here we report that activation of YAP, the downstream effector of the Hippo signaling pathway, is a general hallmark of tubular adenomas from FAP patients. We show that APC functions as a scaffold protein that facilitates the Hippo kinase cascade by interacting with Sav1 and Lats1. Consistent with the molecular link between APC and the Hippo signaling pathway, genetic analysis reveals that YAP is absolutely required for the development of APC-deficient adenomas. These findings establish Hippo–YAP signaling as a critical effector pathway downstream from APC, independent from its involvement in the β-catenin destruction complex.     

Noncanonical Activation of β-Catenin by Porphyromonas gingivalis

Porphyromonas gingivalis is an established pathogen in periodontal disease and an emerging pathogen in serious systemic conditions, including some forms of cancer. We investigated the effect of P. gingivalis on β-catenin signaling, a major pathway in the control of cell proliferation and tumorigenesis. Infection of gingival epithelial cells with P. gingivalis did not influence the phosphorylation status of β-catenin but resulted in proteolytic processing. The use of mutants deficient in gingipain production, along with gingipain-specific inhibitors, revealed that gingipain proteolytic activity was required for β-catenin processing. The β-catenin destruction complex components Axin1, adenomatous polyposis coli (APC), and GSK3β were also proteolytically processed by P. gingivalis gingipains. Cell fractionation and Western blotting demonstrated that β-catenin fragments were translocated to the nucleus. The accumulation of β-catenin in the nucleus following P. gingivalis infection was confirmed by immunofluorescence microscopy. A luciferase reporter assay showed that P. gingivalis increased the activity of the β-catenin-dependent TCF/LEF promoter. P. gingivalis did not increase Wnt3a mRNA levels, a finding consistent with P. gingivalis-induced proteolytic processing causing the increase in TCF/LEF promoter activity. Thus, our data indicate that P. gingivalis can induce the noncanonical activation of β-catenin and disassociation of the β-catenin destruction complex by gingipain-dependent proteolytic processing. β-Catenin activation in epithelial cells by P. gingivalis may contribute to a proliferative phenotype.     

Cross-talk between TGF-β/Smad pathway and Wnt/β-catenin pathway in pathological scar formation

TGF-β1 is a key factor in the process of wound healing, which is regulated by TGF-β/Smad pathway. We previously demonstrated that TGF-β1 contributed to pathological scar formation. And previous studies also suggested Wnt/β-catenin pathway might be involved in wound healing. However, their role and relation in pathological scar formation remains not very clear. For evaluating TGF-β1 and β-catenin, key factors of the two signal pathways, immunohistochemistry, western blot analysis and RT-PCR were used. Simultaneously, immunohistochemistry were used to evaluate Smad2, Smad3 and Wnt-1, which were also the important factors. We found that they all significantly accumulated in pathological scars compared with normal skins (P<0.05), that implied the two signal pathways both contributed to pathological scar formation. Meanwhile, β-catenin expression showed a tendency to increase first and then decrease under the influence of different concentrations of TGF-β1 (P<0.01). It is possible that there is a complicated interaction between the two signal pathways in pathological scar formation (both synergy and antagonism).     

A novel AXIN2 germline variant associated with attenuated FAP without signs of oligondontia or ectodermal dysplasia

Truncating mutations in the AXIN2 gene, a key regulator of β-catenin degradation in the Wnt pathway, have been reported in three families with gastrointestinal adenomatous polyposis and features of ectodermal dysplasia. However, the role of AXIN2 in familial adenomatous polyposis (FAP) syndrome is not completely understood. We performed an in-depth study of APC and MUTYH, and ruled out their implication in 23 FAP families. We then investigated the role of other genes involved in the Wnt pathway, including AXIN2, and identified a novel missense variant in AXIN2 in one family with attenuated FAP. Carriers of the variant exhibited a variable number of polyps but none showed any sign of ectodermal dysplasia. We have demonstrated the pathogenicity of this novel variant by establishing its low frequency in controls as well as by LOH analysis, a segregation study, and immunofluorescent staining of AXIN2 and β-catenin proteins. This report expands the phenotype known to be related to AXIN2 alterations and raises the question of whether to screen AXIN2 in FAP cases negative for alterations in APC and MUTYH.     

Embryonic stem cell markers Sox-2 and OCT4 expression and their correlation with WNT signal pathway in cervical squamous cell carcinoma

Background: Both the expression of embryonic stem cells (ESCs) markers (Sox2, Oct4) and the Wnt signal pathway (β-catenin) are crucial for progression of various human malignancies. The purpose of this study was to investigate the clinicopathologic significance of Sox2, Oct4 and β-catenin in cervical squamous cell carcinoma (CSCC) and to study their correlation with the occurrence and prognosis. Methods: Sox2, Oct4 and β-catenin were assessed using immunohistochemistry in normal cervix tissues (n = 28) and invasive cervical squamous cell carcinoma (n = 43). Associations of Sox2, Oct4 and β-catenin levels with clinicopathological characteristics and with overall survival were studied using uni- and multivariate analysis. Results: The expression levels of Sox2, Oct4 and β-catenin were highly increased in CSCC compared with the normal cervix tissues. The ESCs markers expression (Sox2 and Oct4) correlated significantly with β-catenin expression. High expression of Sox2, but not that of Oct4 or β-catenin, was correlated with poorer differentiation (P < 0.05). Furthermore, Sox2 expression was significantly correlated with patients’ status of survival in advanced CSCC (P < 0.05), whereas there was no significant finding in Oct4 or β-catenin expression. Conclusions: These findings provide evidence that both ESCs biomarkers (Sox2, Oct4) and Wnt signal pathway (β-catenin) are activated in CSCC. Sox2 can be regarded as a novel predictor of poor prognosis for CSCC patients.     

Effects of hydrogen sulfide on high glucose-induced glomerular podocyte injury in mice

The aim of this study was to assess the effects of hydrogen sulfide on high glucose-induced mouse podocyte (MPC) injury and the underlying mechanisms. Mouse podocytes were randomly divided into 4 groups, including high glucose (HG), normal glucose (NG), normal glucose + DL-propargylglycine (PPG), and high glucose + NaHS (HG + NaHS) groups for treatment. Then, ZO-2, nephrin, β-catenin, and cystathionine γ-lyase (CSE) protein expression levels were determined by western blot. We found that high glucose significantly reduced nephrin, ZO-2, and CSE expression levels (P<0.05), and overtly elevated β-catenin amounts (P<0.05), in a time-dependent manner. Likewise, PPG at different concentrations in normal glucose resulted in significantly lower CSE, ZO-2, and nephrin levels (P<0.05), and increased β-catenin amounts (P<0.05). Interestingly, significantly increased ZO-2 and nephrin levels, and overtly reduced β-catenin amounts were observed in the HG + NaHS group compared with HG treated cells (P<0.01). Compared with NG treated cells, decreased ZO-2 and nephrin levels and higher β-catenin amounts were obtained in the HG + NaHS group. In conclusion,CSE downregulation contributes to hyperglycemia induced podocyte injury, which is alleviated by exogenous H₂S possibly through ZO-2 upregulation and the subsequent suppression of Wnt/β-catenin pathway.     

Overexpression of β-catenin and cyclinD1 predicts a poor prognosis in ovarian serous carcinomas

Ovarian serous cancer is the most common subtype of epithelial ovarian cancer, and is the leading cause of death from gynecologic cancer. There is an important need for exploration of diagnostic and prognostic markers for this disease. β-catenin and cyclinD1 play central roles in the tumorigenesis for certain cancers. The role of β-catenin and cyclinD1 in diagnosis and prognosis of ovarian serous carcinoma is uncertain. In the present study, the expression of β-catenin and cyclinD1 was examined in 60 ovarian serous carcinomas patients with immunohistochemical staining. The relationship between expression of β-catenin and cyclinD1 and FIGO stage, pathological grade was analyzed. Kaplan-Meier survival function was used to analyze the prognosis. Overexpression of β-catenin is more often detected in patients with FIGO stage III and IV than in those with stage I, and II (P=0.003). No significant relationship was found between expression of β-catenin and pathological grade (P=0.817). Positive expression of β-catenin related to lower survival rate (P=0.034). The expression of cyclinD1 had no relationship with FIGO stage (P=0.829). Overexpression of cyclinD1 was positively to pathological grade (P=0.017) and survival rate (P=0.009). There is a significantly positive relationship between expression of β-catenin and cyclinD1 (P=0.014). No statistical significance was found between expression of β-catenin and cyclinD1 and other pathological parameters. Conclusions: Expression of β-catenin and cyclinD1 may be used as predict markers for poor prognosis.     

Clinicopathological significance of wnt/β-catenin signaling pathway in esophageal squamous cell carcinoma

Background/Aim: Esophageal squamous cell carcinoma (ESCC) is one of the most common malignant tumors. It has been reported that Wnt signaling pathway plays an important role in Esophageal Cancer progression, metastasis and invasion. However the clinicopathological significance of Wnt2, GSK3β, and β-catenin in ESCC has been little reported. In the present study, the aim of this study was to investigate the clinicopathologic and prognosis roles of Wnt2, GSK3β, and β-catenin in ESCC tissue. Methods: 265 ESCC samples were analyzed by immunohistochemistry using Wnt2, GSK3β, and β-catenin antibodies. Then, correlation of Wnt2, GSK3β, and β-catenin expression with clinicopathological features and prognosis of ESCC patients was statistically analyzed. Results: Cytoplasmic Wnt2 overexpression was detected in 55.5% (147 of 265) ESCCs, which was significantly correlated with the degree of differentiation (P = 0.031). Cytoplasmic GSK3β overexpression was detected in 7.2% (19 of 265) ESCCs, and aberrant β-catenin expression was identified in 54.3% (144 of 265) of ESCCs. The positive rate of Wnt2 significantly increased with the malignant degree of Kazak ESCC patients. The aberrant β-catenin expression in GSK3β-negative ESCC was significantly associated with the ethnic, tumor size, tumor location, degree of differentiation, AJCC stage, lymph node status. Furthermore, the expression of β-catenin implicated the ethnic difference (P = 0.019). In Kaplan-Meier curve analysis, no significant correlation was observed between the expression of Wnt2, GSK3β, β-catenin and the poor prognosis of ESCCs. Conclusion: The aberrant β-catenin expression could be an adverse underlying factor in carcinogenesis and progression of ESCC. There was a different statistical signification for β-catenin in Kazakhs to compare with Hans.     

MicroRNA-29 mediates TGFβ1-induced extracellular matrix synthesis by targeting wnt/β-catenin pathway in human orbital fibroblasts

Purpose: Transforming growth factor β1 (TGFβ1) is very important in the synthesis and degradation of extracellular matrix (ECM) and also in the mediation of human orbital fibroblasts (OFs) proliferation. MicroRNA-29 (MiR-29) plays an important role in this process. In the present study, the effects of TGFβ1 on the expression of miR-29 and whether miR-29 is involved in pro-survival signaling pathways mediated by TGFβ1 were examined in human OFs. Methods: Detecting the influence of TGFβ1 on the expression of miR-29a/b/c by real-time PCR analysis. Using 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) to detecting the influence of miR-29 on the increased proliferation caused by TGF-β1 on the human orbital fibroblasts. Using soft agar assay to detecting the influence of miR-29 on the increased colony formation caused by TGF-β1 on the human orbital fibroblasts. Western blot was used to detect the specific mechanisin. Results: TGFβ1 treatment decreases the expression of miR-29 in OFs. In the cultured OFs, the value of optical density (OD) in the group treated with miR-29 is lower than that in the group treated without miR-29 (P < 0.05). In the cultured OFs, the ratio of colony formation in the group treated with miR-29 is lower than that in the group treated without miR-29 (P < 0.05). In OFs, miR-29 decreases the secretion of Wnt3a and activation of β-catenin whether the treatment of TGFβ1 was used or not. MiR-29 decreases expression of Collagen, type I, alpha 1 (COL1A1) through down-regulation of wnt/β-catenin pathway. Conclusions: In OFs TGFβ1 treatment decreases expression of miR-29 which can cause the inhibition of normal ability of TGFβ1. MiR-29 inhibits TGFβ1-induced proliferation of OFS cell and decreases colony formation of OFS cell after TGFβ1 treatment. MiR-29 Mediates TGFβ1-induced Extracellular matrix synthesis through activation of Wnt/β-catenin pathway in human OFs.     

Raddeanin A inhibited epithelial-mesenchymal transition (EMT) and angiogenesis in glioblastoma by downregulating β-catenin expression

Raddeanin A (RA), an oleanane-type triterpenoid saponin derived from Anemone raddeana Regel, has been found to suppress the viability and metastasis of several cancers, including GBM, through various signaling pathways. However, the mechanisms underlying the anti-GBM properties of RA have not been fully elucidated. Epithelial to mesenchymal transition (EMT) and angiogenesis are important for the genesis and progression of GBM. These two crucial processes can be regulated by multiple molecular, including β-catenin, which has been demonstrated to act as a pro-tumorigenic molecular. In this study, we aimed to determine whether RA could suppress EMT and angiogenesis by inhibiting the action of β-catenin in GBM. We found that RA inhibited the proliferation, invasion and migratory properties of GBM cells. RA was also found to have downregulated the expressions of β-catenin and EMT-related biomarkers (N-cadherin, vimentin, and snail). In addition, the overexpression of β-catenin reversed the therapeutic effects of RA exerted on the EMT of GBM cells. RA restricted angiogenesis, as shown by the tube formation assay and CAM assay, while it downregulated VEGF levels in HUVECs. Moreover, massive β-catenin could reverse the suppression of angiogenesis induced by RA. Finally, we demonstrated that RA inhibited tumor growth and prolonged survival time in an intracranial U87 xenograft mouse model. Similar to the results in vitro, RA downregulated the expression of β-catenin, EMT makers and VEGF, and decreased vessel density in vivo. In summary, our results demonstrated that RA repressed GBM via downregulating β-catenin-mediated EMT and angiogenesis both in vitro and in vivo.     

WNT5A Inhibits Hepatocyte Proliferation and Concludes β-Catenin Signaling in Liver Regeneration

Activation of Wnt/β-catenin signaling during liver regeneration (LR) after partial hepatectomy (PH) is observed in several species. However, how this pathway is turned off when hepatocyte proliferation is no longer required is unknown. We assessed LR in liver-specific knockouts of Wntless (Wls-LKO), a protein required for Wnt secretion from a cell. When subjected to PH, Wls-LKO showed prolongation of hepatocyte proliferation for up to 4 days compared with littermate controls. This coincided with increased β-catenin–T-cell factor 4 interaction and cyclin-D1 expression. Wls-LKO showed decreased expression and secretion of inhibitory Wnt5a during LR. Wnt5a expression increased between 24 and 48 hours, and Frizzled-2 between 24 and 72 hours, after PH in normal mice. Treatment of primary mouse hepatocytes and liver tumor cells with Wnt5a led to a notable decrease in β-catenin–T-cell factor activity, cyclin-D1 expression, and cell proliferation. Intriguingly, Wnt5a-LKO did not display any prolongation of LR because of compensation by other cells. In addition, Wnt5a-LKO hepatocytes failed to respond to exogenous Wnt5a treatment in culture because of a compensatory decrease in Frizzled-2 expression. In conclusion, we demonstrate Wnt5a to be, by default, a negative regulator of β-catenin signaling and hepatocyte proliferation, both in vitro and in vivo. We also provide evidence that the Wnt5a/Frizzled-2 axis suppresses β-catenin signaling in hepatocytes in an autocrine manner, thereby contributing to timely conclusion of the LR process.Other than its roles in hepatic development, metabolic zonation, and hepatocarcinogenesis, β-catenin signaling plays an important role in liver regeneration (LR).¹ Liver is a unique organ in its ability to respond physiologically through non–stem cell–dependent regeneration after surgical or toxin-induced loss of hepatic mass.² After partial hepatectomy (PH), several signaling pathways get activated in tandem to ensure proper initiation and progression of the regenerative process, which entails orderly proliferation of all resident cells of the liver.² One pathway that is activated early during LR is the Wnt/β-catenin signaling pathway. This pathway has been shown to be highly relevant in ensuring proper G₁ to S phase transition of hepatocytes through regulation of its key target, cyclin-D1.^3,4 In fact, several studies have shown that disruption of Wnt/β-catenin signaling in various genetic mouse models leads to blunted LR, although, as many other signaling molecules, β-catenin too has been deemed redundant because its loss delays, but does not completely prevent, regeneration.An important attribute of LR is the ability of this process to spontaneously terminate when the normal hepatic mass consistent with the prehepatectomy mass is re-established. Because hepatocytes have seemingly unlimited proliferative capacity,^5,6 there must exist some regulatory mechanisms to stop the LR process. It has been suggested that pathways such as transforming growth factor-β signaling may play a role in the termination of LR.⁷ Furthermore, the role of extracellular matrix in regulating hepatocyte proliferation, especially during LR, has also been recently suggested.⁸We took an alternative approach to address termination mechanisms of LR. We hypothesized that because a series of proproliferative signaling pathways are turned on to initiate LR soon after PH, identification of negative regulators of such signaling mechanisms may yield clues to the overall LR termination processes. Because β-catenin is a proproliferative signal in LR, identification of what terminates β-catenin signaling might eventually be contributing to cessation of LR. Interestingly, examination of β-catenin signaling, cyclin-D1 expression, and markers of S phase in albumin-cre–driven Wntless knockout (KO) or liver-specific KOs of Wntless (Wls-LKO) mice revealed temporal prolongation of the hepatocyte proliferative program. This suggested that hepatocytes might be a source of Wnt that negatively regulates β-catenin signaling, because Wntless protein is specific for only Wnt secretion. Further analysis revealed Wnt5a to be differentially regulated during LR and contributed to inhibiting β-catenin activity in primary hepatocytes and liver tumor cells. Intriguingly, liver-specific Wnt5a KO lacked any spontaneous phenotype and displayed normal initiation and termination of LR. This is likely because of adaptive changes such as reduced expression of Frizzled-2 in the Wnt5a-LKO hepatocytes. In conclusion, we demonstrate Wnt5a to be, by default, a negative regulator of β-catenin signaling and hepatocyte proliferation in vitro and in vivo. Furthermore, we provide evidence that Wnt5a may be one of the effectors that is secreted by hepatocytes to suppress β-catenin signaling in hepatocytes in an autocrine manner, which, through Frizzled-2, terminates β-catenin signaling, thereby contributing to timely conclusion of the process of LR.     

Nuclear localizaiton of β-catenin is associated with poor survival and chemo-/radioresistance in human cervical squamous cell cancer

Nuclear expression of β-catenin has been suggested as an independent prognostic marker in a variety of cancers. The objective of this study was to investigate the clinicopathologic significance of nuclear β-catenin expression in patients with cervical squamous cell carcinoma (CSCC). In this original research article, we detected nuclear β-catenin expression in 29/171 CSCC tissues (17.0%). Patients without nuclear β-catenin expression had a significantly better outcome than patients with nuclear β-catenin expression (93.7% versus 82.7% P = 0.027). Furthermore, nuclear β-catenin expression was predictive of prognosis in CSCC patients with early stage disease (FIGO stage I or tumor size ≤ 4 cm), with well/moderately differentiated tumors, or lymph node metastasis. Interestingly, nuclear β-catenin expression correlated with poor outcome in patients who received postoperative chemotherapy or radiotherapy. Multivariate analysis suggested that nuclear β-catenin expression is an independent prognostic indicator in CSCC. Our findings suggest that nuclear β-catenin expression may be used as a prognostic biomarker in CSCC, especially for patients with early stage disease, well/moderately differentiated tumors, or lymph node metastasis. Moreover, nuclear β-catenin expression has potential as a predictive marker of chemoresistance and radioresistance in CSCC.     

Wnt/β-catenin pathway is required for epithelial to mesenchymal transition in CXCL12 over expressed breast cancer cells

CXCL12 is positively associated with the metastasis and prognosis of various human malignancies. Cancer-associated fibroblasts (CAFs), the main cells secreting CXCL12, are capable of inducing epithelial to mesenchymal transition (EMT) of breast cancer cells. However, it has not been completely understood whether CXCL12 is involved in EMT of breast cancer cells and the underlying mechanisms. The present study aimed to investigate the effects of CXCL12 on the EMT and cancer stem cell (CSC)-like phenotypes formation by transfecting pEGFP-N1-CXCL12 plasmid into MCF-7 cells. Real time-PCR and Western blot analysis demonstrated the successful over expression of CXCL12 in MCF-7 cells. Cell counting kit-8 assay, wound healing assay and Transwell invasion analysis confirmed that over expression of CXCL12 significantly promoted the proliferation, migration and invasion in MCF-7 cells (P<0.05). In addition, ALDH activity was dramatically enhanced compared with parental (P<0.001), accompanied by the notably elevated mRNA and protein levels of OCT-4, Nanog, and SOX2 in CXCL12 overexpressed-MCF-7 cells (P<0.001). Furthermore, we observed the down regulation of E-cadherin and up regulation of vimentin, N-cadherin, and α-SMA in CXCL12 overexpressed-MCF-7 cells (P<0.01). Meanwhile, western blot and immunofluorescence assay showed that over expression of CXCL12 activated Wnt/β-catenin pathway to induce EMT of MCF-7 cells, as evidenced by the increased expression of E-cadherin after silencing β-catenin by siRNA interference (P<0.001). Collectively, our findings suggested that over expression of CXCL12 could trigger EMT by activating Wnt/β-catenin pathway and induce CSC-like phenotypes formation to promote the proliferation and metastasis in MCF-7. Hence, CXCL12 may become a promising candidate for breast cancer therapy.