ZNRF3 acts as a tumour suppressor by the Wnt signalling pathway in human gastric adenocarcinoma

Abstract

E3 ubiquitin ligases regulate a variety of biological processes through the ubiquitin-proteasome system, together with ubiquitin activating enzyme E1 and ubiquitin-conjugating enzyme E2. Previous studies have demonstrated that zinc and ring finger 3 (ZNRF3), which belongs to the E3 ubiquitin ligases family is involved in the Wnt signalling pathway, which plays an important role in causing cancer. However, the expression and function of ZNRF3 in human gastric adenocarcinoma still remains unclear. Immunohistochemical and western blot analysis showed a significant down-regulation of ZNRF3 protein in gastric adenocarcinoma tissues compared with adjacent normal gastric tissues. In addition, there was a correlation between the down-regulation of ZNRF3 and poor tissue differentiation in gastric adenocarcinoma. To investigate the potential function of ZNRF3 in cell proliferation and apoptosis, a gastric cell line SGC7901 was employed. The over-expression of wild-type ZNRF3, which was accomplished by the transient transfection of recombinant pEGFP-ZNRF3 (or empty plasmids as control) into the cell line SGC7901, was confirmed by western blot analysis. Flow-cytometry-based and Cell Counting Kit-8 assays showed that over-expression of wt ZNRF3 induced apoptosis and suppressed proliferation. ZNRF3-overexpressing gastric cells displayed partly attenuated protein levels of beta-catenin and TCF-4 compared with those transfected with the empty plasmid. Our study demonstrates a novel gastric adenocarcinoma suppressor and reveals that ZNRF3 inhibits gastric cancer cell growth and promotes the cell apoptosis by affecting the Wnt/beta-catenin/TCF signalling pathway.

MiR-146b-5p Promotes Metastasis and Induces Epithelial-Mesenchymal Transition in Thyroid Cancer by Targeting ZNRF3

“…These findings reveal a novel mechanism of miR-146b-5p mediated induction of EMT and suggest that ZNRF3 plays a tumor suppressor role in PTC. A similar role for ZNRF3 was demonstrated in human gastric adenocarcinoma in a recent study that showed that ZNRF3 inhibits gastric cancer cell growth and promotes apoptosis through the modulation of the Wnt/β-catenin signaling pathway [23]. Mutations in ZNRF3 and its homolog RING finger 43 (RNF43) have been linked to pancreatic ductal adenocarcinoma and mucinous ovarian tumors [24,25] confirming the role of these ubiquitin ligases as tumor suppressors.…”

Role of the Wnt/β-catenin pathway in gastric cancer: An in-depth literature review

“…These molecular changes seem to be required to drive early carcinogenesis events in the stomach, a hypothesis that is supported by studies showing that GSK3b phosphorylation and inactivation is associated with cancer progression in gastric cancer [105] . Different studies have shown downregulation-in occasion by unspecified mechanisms-of various negative regulators of the Wnt/b-catenin signaling involved in proliferation and invasion in gastric cancer, including sFRP, Sox7, Sox10, Sox17, HSulf-1, RACK1, ZNRF3 and OSR1 [78,[106][107][108][109][110][111][112][113] . Some Wnt-target genes, such as Dkk-1, Axin, Nemo kinase, etc., have shown to cause inhibition of Wnt signaling itself [114,115] .…”

ZnRF3 Induces Apoptosis of Gastric Cancer Cells by Antagonizing Wnt and Hedgehog Signaling

“…Many studies have indicated that Wnt/b-catenin and Hedgehog signaling pathways are important in the regulation of tissue growth and development. Thus, dysregulated Wnt/b-catenin signaling is involved in many cancers including colorectal, hepatocellular, and gastric cancers and also hereditary diseases [4][5][6]. Wnt proteins bind to receptors of the Frizzled family on the cell surface and regulate the turnover of the b-catenin transcription cofactor and regulate gene expression programs that are relevant for organism development [7,8].…”

“…There are several types of E3-ubiquitin ligases, which control the levels and turnover of different proteins in multiple subcellular locations, and their deregulation can contribute to various diseases including carcinogenesis [21]. ZnRF3 has been shown to inhibit Wnt signaling by enhancing the breakdown of frizzled and LRP6 [18], and overexpression of ZnRF3 was found to induce apoptosis by lowering the protein levels of b-catenin and TCF-4 [5]. Also expression of ZnRF3 was found to be reduced in gastric cancers compared to the normal surrounding tissue [5] and mutated in pancreatic cancer [22].…”

“…ZnRF3 has been shown to inhibit Wnt signaling by enhancing the breakdown of frizzled and LRP6 [18], and overexpression of ZnRF3 was found to induce apoptosis by lowering the protein levels of b-catenin and TCF-4 [5]. Also expression of ZnRF3 was found to be reduced in gastric cancers compared to the normal surrounding tissue [5] and mutated in pancreatic cancer [22]. Crosstalk between the signaling pathways of Wnt and Hedgehog has been described and also that the Hedgehog/Gli1 signaling is reduced by ubiquitinylation of Gli1 by the p300/CBP associated factor (PCAF), which is involved in the regulation of development and tumorigenesis functions as both acetyltransferase and as E3-ubiquitin ligase [23].…”