Beta-catenin transcriptional activity is inhibited downstream of nuclear localisation and is not influenced by IGF signalling in oesophageal cancer cells

The Wnt signaling pathway in tumorigenesis, pharmacological targets, and drug development for cancer therapy

Wnt signaling was initially recognized to be vital for tissue development and homeostasis maintenance. Further studies revealed that this pathway is also important for tumorigenesis and progression. Abnormal expression of signaling components through gene mutation or epigenetic regulation is closely associated with tumor progression and poor prognosis in several tissues. Additionally, Wnt signaling also influences the tumor microenvironment and immune response. Some strategies and drugs have been proposed to target this pathway, such as blocking receptors/ligands, targeting intracellular molecules, beta-catenin/TCF4 complex and its downstream target genes, or tumor microenvironment and immune response. Here we discuss the roles of these components in Wnt signaling pathway in tumorigenesis and cancer progression, the underlying mechanisms that is responsible for the activation of Wnt signaling, and a series of drugs targeting the Wnt pathway provide multiple therapeutic values. Although some of these drugs exhibit exciting anti-cancer effect, clinical trials and systematic evaluation should be strictly performed along with multiple-omics technology.

Wnt5a induces ROR1 and ROR2 to activate RhoA in esophageal squamous cell carcinoma cells

Background: Wnt5a is a nontransforming Wnt family member and identified as an oncogenic role on cell motility of breast cancer and glioblastoma. However, Wnt5a signaling in esophageal squamous cell carcinoma (ESCC) progression remains poorly defined.

Materials and methods: Immunohistochemistry assays were used to measure the Wnt5a expression in ESCC sections. We evaluated the role of receptor tyrosine kinase-like orphan receptor (ROR)1/2 and RhoA on the invasion of ESCC cells by using cell invasion assay, immunoprecipitation, immunofluorescence, and Rho activation assay.

Results: Wnt5a was highly expressed in invasive ESCC tissues compared with that in noninvasive and nonmalignant tissues. In vitro assay showed that sfrp2 (Wnt5a antagonist) largely blocked the invasion but not the colony formation of KYSE410 and KYSE520 ESCC cells. Anti-ROR1 mAb and ROR2-shRNA markedly inhibited the disheveled-associated activator of morphogenesis 1 (DAAM1) activity, RhoA activity, microfilament formation and the invasion of ESCC cells. Fluorescent phalloidin staining experiment showed ROR1/ROR2, receptors of Wnt5a signaling, and regulated the reassembly of actin filaments in ESCC cells. Further experiments showed that ROR1 was strongly associated with ROR2 in KYSE410 cells. The activation of RhoA, not Rac1 or Rac2, was involved in ROR1/ROR2 signaling pathway. By using DAAM1 shRNA, we found that RhoA was downstream of DAAM1, which could be rescued by the overexpression of wild-type DAAM1. This could be further proved by a RhoA inhibitor CCG-1423 which could inhibit the invasion of ESCC cells but not DAAM1 activity.

Conclusions: Wnt5a promotes ESCC cell invasion via ROR1 and ROR2 receptors and DAAM1/RhoA signaling pathway.

Wnt/β-Catenin Signaling Activation beyond Robust Nuclear β-Catenin Accumulation in Nondysplastic Barrett's Esophagus: Regulation via Dickkopf-1

INTRODUCTION: Wnt/β-catenin signaling activation has been reported only during the late steps of Barrett’s esophagus (BE) neoplastic progression, but not in BE metaplasia, based on the absence of nuclear β-catenin. However, β-catenin transcriptional activity has been recorded in absence of robust nuclear accumulation. Thus, we aimed to investigate the Wnt/β-catenin signaling in nondysplastic BE. METHODS: Esophageal tissues from healthy and BE patients without dysplasia were analyzed for Wnt target gene expression by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunohistochemistry. Esophageal squamous (EPC1-& EPC2-hTERT), BE metaplastic (CP-A), and adenocarcinoma (OE33) cell lines were characterized for Wnt activation by qRT-PCR, Western blot, and luciferase assay. Wnt activity regulation was examined by using recombinant Wnt3a and Dickkopf-1 (Dkk1) as well as Dkk1 short interfering RNA. RESULTS: Wnt target genes (AXIN2, c-MYC, Cyclin D1, Dkk1) and Wnt3a were significantly upregulated in nondysplastic BE compared with squamous mucosa. Elevated levels of dephosphorylated β-catenin were detected in nondysplastic BE. Nuclear active β-catenin and TOPflash activity were increased in CP-A and OE33 cells compared with squamous cells. Wnt3a-mediated β-catenin signaling activation was abolished by Dkk1 in CP-A cells. TOPFlash activity was elevated following Dkk1 silencing in CP-A but not in OE33 cells. Dysplastic and esophageal adenocarcinoma tissues demonstrated further Dkk1 and AXIN2 overexpression. CONCLUSIONS: Despite the absence of robust nuclear accumulation, β-catenin is transcriptionally active in nondysplastic BE. Dkk1 overexpression regulates β-catenin signaling in BE metaplastic but not in adenocarcinoma cells, suggesting that early perturbation of Dkk1-mediated signaling suppression may contribute to BE malignant transformation.

Clinical significance of expression of Klotho and β-Catenin in esophageal squamous cell carcinoma

AIM: To investigate the clinical significance of expression of Klotho and β-Catenin in esophageal carcinoma.

METHODS: Tissue microarray technique and immunohistochemistry were used to examine Klotho and β-Catenin expression in 75 esophageal carcinoma tissue specimens and matched tumor-adjacent esophageal tissue. Correlations between Klotho and β-Catenin expression and clinical and pathological features were then analyzed.

RESULTS: The positive rate of Klotho expression was significantly lower in esophageal carcinoma tissue than in tumor-adjacent tissue (14.9% vs 63.4%, P < 0.05). The expression of Klotho was correlated with tumor invasion and clinical stage (both P < 0.05). The positive rate of β-Catenin expression was significantly higher in esophageal carcinoma tissue than in tumor-adjacent tissue (80.0% vs 16.4%, P < 0.05). The expression of Klotho was correlated with lymph node metastasis and tumor clinical stage (r = -0.276, P < 0.05).

CONCLUSION: The positive rates of Klotho and β-Catenin expression differed significantly between esophageal carcinoma and tumor-adjacent tissue. Klotho and β-Catenin may be used as important markers for esophageal carcinoma and are helpful for prognosis prediction in esophageal carcinoma.

Wnt-reporter expression pattern in the mouse intestine during homeostasis

Background

The canonical Wnt signaling pathway is a known regulator of cell proliferation during development and maintenance of the intestinal epithelium. Perturbations in this pathway lead to aberrant epithelial proliferation and intestinal cancer. In the mature intestine, proliferation is confined to the relatively quiescent stem cells and the rapidly cycling transient-amplifying cells in the intestinal crypts. Although the Wnt signal is believed to regulate all proliferating intestinal cells, surprisingly, this has not been thoroughly demonstrated. This important determination has implications on intestinal function, especially during epithelial expansion and regeneration, and warrants an extensive characterization of Wnt-activated cells.

Methods

To identify intestinal epithelial cells that actively receive a Wnt signal, we analyzed intestinal Wnt-reporter expression patterns in two different mouse lines using immunohistochemistry, enzymatic activity, in situ hybridization and qRT-PCR, then corroborated results with reporter-independent analyses. Wnt-receiving cells were further characterized for co-expression of proliferation markers, putative stem cell markers and cellular differentiation markers using an immunohistochemical approach. Finally, to demonstrate that Wnt-reporter mice have utility in detecting perturbations in intestinal Wnt signaling, the reporter response to gamma-irradiation was examined.

Results

Wnt-activated cells were primarily restricted to the base of the small intestinal and colonic crypts, and were highest in numbers in the proximal small intestine, decreasing in frequency in a gradient toward the large intestine. Interestingly, the majority of the Wnt-reporter-expressing cells did not overlap with the transient-amplifying cell population. Further, while Wnt-activated cells expressed the putative stem cell marker Musashi-1, they did not co-express DCAMKL-1 or cell differentiation markers. Finally, gamma-irradiation stimulated an increase in Wnt-activated intestinal crypt cells.

Conclusion

We show, for the first time, detailed characterization of the intestine from Wnt-reporter mice. Further, our data show that the majority of Wnt-receiving cells reside in the stem cell niche of the crypt base and do not extend into the proliferative transient-amplifying cell population. We also show that the Wnt-reporter mice can be used to detect changes in intestinal epithelial Wnt signaling upon physiologic injury. Our findings have an important impact on understanding the regulation of the intestinal stem cell hierarchy during homeostasis and in disease states.