Abstract
BackgroundGastric cancer is one of the most common malignant tumors. Cyclin G2 has been shown to be associated with the development of multiple types of tumors, but its underlying mechanisms in gastric tumors is not well-understood. The aim of this study is to investigate the role and the underlying mechanisms of cyclin G2 on Wnt/β-catenin signaling in gastric cancer.MethodsReal-time PCR, immunohistochemistry and in silico assay were used to determine the expression of cyclin G2 in gastric cancer. TCGA datasets were used to evaluate the association between cyclin G2 expression and the prognostic landscape of gastric cancers. The effects of ectopic and endogenous cyclin G2 on the proliferation and migration of gastric cancer cells were assessed using the MTS assay, colony formation assay, cell cycle assay, wound healing assay and transwell assay. Moreover, a xenograft model and a metastasis model of nude mice was used to determine the influence of cyclin G2 on gastric tumor growth and migration in vivo. The effects of cyclin G2 expression on Wnt/β-catenin signaling were explored using a TOPFlash luciferase reporter assay, and the molecular mechanisms involved were investigated using immunoblots assay, yeast two-hybrid screening, immunoprecipitation and Duolink in situ PLA. Ccng2−/− mice were generated to further confirm the inhibitory effect of cyclin G2 on Wnt/β-catenin signaling in vivo. Furthermore, GSK-3β inhibitors were utilized to explore the role of Wnt/β-catenin signaling in the suppression effect of cyclin G2 on gastric cancer cell proliferation and migration.ResultsWe found that cyclin G2 levels were decreased in gastric cancer tissues and were associated with tumor size, migration and poor differentiation status. Moreover, overexpression of cyclin G2 attenuated tumor growth and metastasis both in vitro and in vivo. Dpr1 was identified as a cyclin G2-interacting protein which was required for the cyclin G2-mediated inhibition of β-catenin expression. Mechanically, cyclin G2 impacted the activity of CKI to phosphorylate Dpr1, which has been proved to be a protein that acts as a suppressor of Wnt/β-catenin signaling when unphosphorylated. Furthermore, GSK-3β inhibitors abolished the cyclin G2-induced suppression of cell proliferation and migration.ConclusionsThis study demonstrates that cyclin G2 suppresses Wnt/β-catenin signaling and inhibits gastric cancer cell growth and migration through Dapper1.
Highlights
Gastric cancer is one of the most common malignant tumors
Expression levels of cyclin G2 mRNA were correlated to the differentiation status of gastric cancer cell lines, with the lowest mRNA cyclin G2 expression occurring in the poorly differentiated AGS cells and the highest cyclin G2 expression occurring in the well-differentiated immortalized human gastric epithelial mucosa cell line GES-1 (Fig. 1d)
The protein level of cyclin G2 was not consistent with its mRNA expression in AGS cells (Fig. 1e). These findings suggested that cyclin G2 was involved in the progression of gastric cancers
Summary
Gastric cancer is one of the most common malignant tumors. Cyclin G2 has been shown to be associated with the development of multiple types of tumors, but its underlying mechanisms in gastric tumors is not wellunderstood. The aim of this study is to investigate the role and the underlying mechanisms of cyclin G2 on Wnt/β-catenin signaling in gastric cancer. The precise mechanisms leading to gastric cancer are not fully understood, abnormal activation of the Wnt/β-catenin signaling has been suggested as the major risk factor contributing to cancer development [3, 4]. The potential relationship between low cyclin G2 expression and tumor progression has been previously reported in oral cancer, esophageal cancer, colorectal cancer, thyroid cancer, epithelial ovarian cancer and prostate cancer [9,10,11,12,13,14,15]. There are few reports on the identity of pathways and the precise mechanisms that mediate the roles of cyclin G2 in gastric tumorigenesis and other cancers
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