Original Article
Copyright ©2014 Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. May 21, 2014; 20(19): 5839-5848
Published online May 21, 2014. doi: 10.3748/wjg.v20.i19.5839
Down-regulated γ-catenin expression is associated with tumor aggressiveness in esophageal cancer
Wang-Kai Fang, Lian-Di Liao, Wei Gu, Bo Chen, Zhi-Yong Wu, Jian-Yi Wu, Jian Shen, Li-Yan Xu, En-Min Li
Wang-Kai Fang, Wei Gu, Jian-Yi Wu, En-Min Li, Department of Biochemistry and Molecular Biology, The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College, Shantou 515041, Guangdong Province, China
Lian-Di Liao, Bo Chen, Jian Shen, Li-Yan Xu, Institute of Oncologic Pathology, Shantou University Medical College, Shantou 515041, Guangdong Province, China
Zhi-Yong Wu, Department of Oncology Surgery, Affiliated Shantou Hospital of Sun Yat-sen University, Shantou 515041, Guangdong Province, China
Author contributions: Fang WK performed the majority of the experiments and wrote the paper; Li EM and Xu LY designed the study; Liao LD performed the statistical analysis; Wu ZY and Wu JY coordinated and collected the human material; Gu W, Chen B and Shen J contributed new reagents and analytic tools.
Supported by the National Natural Science Foundation of China, No. 81101613; the Guangdong Provincial Natural Science Foundation of China, No. S2011040004363; the Specialized Research Fund for the Doctoral Program of Higher Education of China, No. 20114402120005; the National Basic Research Program of China, No. 2012CB526600; and the Natural Science Foundation of China-Guangdong Joint Fund, No. U0932001
Correspondence to: En-Min Li, PhD, Department of Biochemistry and Molecular Biology, The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College, Xinling Rd 22, Shantou 515041, Guangdong Province, China. nmli@stu.edu.cn
Telephone: +86-754-88900413 Fax: +86-754-88900847
Received: December 2, 2013
Revised: January 30, 2014
Accepted: March 6, 2014
Published online: May 21, 2014
Processing time: 166 Days and 19.3 Hours
Abstract

AIM: To evaluate the significance of γ-catenin in clinical pathology, cellular function and signaling mechanism in esophageal squamous cell carcinoma (ESCC).

METHODS: The mRNA expression of γ-catenin was detected by real-time quantitative reverse transcription-polymerase chain reaction in 95 tissue specimens and evaluated for association with the clinicopathologic characteristics and survival time of patients with ESCC. siRNAs against human γ-catenin were used to inhibit γ-catenin expression. Hanging drop aggregation assay and dispase-based dissociation assay were performed to detect the effect of γ-catenin on ESCC cell-cell adhesion. Transwell assay was performed to determine cell migration. Luciferase-based transcriptional reporter assay (TOPflash) was used to measure β-catenin-dependent transcription in cells with reduced γ-catenin expression. The expression and subcellular localizations of β-catenin and E-cadherin were examined using Western blot and immunofluorescence analysis.

RESULTS: γ-catenin mRNA expression was significantly associated with tumor histological grade (P = 0.017) in ESCC. Kaplan-Meier survival analysis showed that γ-catenin expression levels had an impact on the survival curve, with low γ-catenin indicating worse survival (P = 0.003). The multivariate Cox regression analysis demonstrated that γ-catenin was an independent prognostic factor for survival. Experimentally, silencing γ-catenin caused defects in cell-cell adhesion and a concomitant increase in cell migration in both KYSE150 and TE3 ESCC cells. Analysis of Wnt signaling revealed no activation event associated with γ-catenin expression. Total β-catenin and Triton X-100-insoluble β-catenin were significantly reduced in the γ-catenin-specific siRNA-transfected KYSE150 and TE3 cells, whereas Triton X-100-soluble β-catenin was not altered. Moreover, knocking down γ-catenin expression resulted in a significant decrease of E-cadherin and Triton X-100-insoluble desmocollin-2, along with reduced β-catenin and E-cadherin membrane localization in ESCC cells.

CONCLUSION: γ-catenin is a tumor suppressor in ESCC and may serve as a prognostic marker. Dysregulated expression of γ-catenin may play important roles in ESCC progression.

Keywords: γ-catenin, Esophageal squamous cell carcinoma, Independent prognostic factor, Cell-cell adhesion, Cell migration

Core tip: We, like others, have shown in previous work that reduced classic and desmosomal cadherin expression correlated with increased metastasis both in laboratory models and in clinical esophageal squamous cell carcinoma (ESCC) samples; however, a direct functional role of γ-catenin in this process has not been shown. In this study, we report that γ-catenin plays a critical role in ESCC progression. Our work demonstrates that γ-catenin is a tumor metastasis suppressor in ESCC and its expression may serve as a prognostic marker. Loss of γ-catenin leads to significant changes in esophageal cancer cell phenotypes.