SOX2 interferes with the function of CDX2 in bile acid-induced gastric intestinal metaplasia

Ting Yuan; Zhen Ni; Chuan Han; Yali Min; Nina Sun; Caifang Liu; Miao Shi; Wenquan Lu; Na Wang; Feng Du; Qiong Wu; Ning Xie; Yongquan Shi

doi:10.1186/s12935-019-0739-8

SOX2 interferes with the function of CDX2 in bile acid-induced gastric intestinal metaplasia

Cancer Cell Int. 2019 Jan 31:19:24. doi: 10.1186/s12935-019-0739-8. eCollection 2019.

Authors

Ting Yuan^#^{1

2}, Zhen Ni^#^{1

3}, Chuan Han^#^{1

4}, Yali Min⁵, Nina Sun^{1

6}, Caifang Liu^{1

6}, Miao Shi^{1

6}, Wenquan Lu^{1

7}, Na Wang¹, Feng Du¹, Qiong Wu¹, Ning Xie⁸, Yongquan Shi¹

Affiliations

¹ 1State key Laboratory of Cancer Biology, National Clinical Research Center for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, 710032 China.
² The 150 Hospital of the People's Liberation Army, Luoyang, 471000 China.
³ Department of Gastroenterology, The General Hospital of Western Theater Command, Chengdu, 610083 China.
⁴ Rocket Army Emei Sanatorium, Emei, 614200 China.
⁵ 5Department of Gastroenterology, The Second Affiliated Hospital of Xi'an Medical University, Xi'an, 710032 China.
⁶ 6College of Postgraduates, Xi'an Medical University, Xi'an, 710032 China.
⁷ 7Department of Gastroenterology, First Affiliated Hospital, Zhengzhou University, Zhengzhou, 450000 China.
⁸ 8Department of Gastroenterology, Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710032 China.

^# Contributed equally.

Abstract

Background: Intestinal metaplasia (IM) is a premalignant lesion associated with gastric cancer. Both animal and clinical studies have revealed that bile acid reflux and subsequent chronic inflammation are key causal factors of IM. Previous studies indicated that SOX2, the key transcription factor in gastric differentiation, was downregulated during IM development while CDX2, the pivotal intestine-specific transcription factor was upregulated significantly. However, it remains unclear whether the downregulation of SOX2 promotes gastric IM emergence or is merely a concomitant phenomenon. In addition, the underlying mechanisms of SOX2 downregulation during IM development are unclear.

Methods: Gastric cell lines were treated with deoxycholic acid (DCA) in a dose-dependent manner. The expression of CDX2 and miR-21 in gastric tissue microarray were detected by immunohistochemistry and in situ hybridization. Coimmunoprecipitation and immunofluorescence were performed to ascertain the interaction of SOX2 and CDX2. Luciferase reporter assays were used to detect the transcriptional activity of CDX2, and confirm miR-21 binding to SOX2 3'-UTR. The protein level of SOX2, CDX2 and downstream IM-specific genes were investigated using western blotting. mRNA level of miR-21, SOX2, CDX2 and downstream IM-specific genes were detected by qRT-PCR.

Results: Bile acid treatment could suppress SOX2 expression and simultaneously induce expression of CDX2 in gastric cell lines. Furthermore, we demonstrated that SOX2 overexpression could significantly inhibit bile acid- and exogenous CDX2-induced IM-specific gene expression, including KLF4, cadherin 17 and HNF4α expression. In contrast, SOX2 knockdown had the opposite effect. A dual-luciferase reporter assay demonstrated that SOX2 overexpression could significantly suppress CDX2 transcriptional activity in HEK293T cells. CDX2 and SOX2 could form protein complexes in the nucleus. In addition, bile acid induced the expression of miR-21. The inhibition of SOX2 in bile acid-treated gastric cell lines was rescued by miR-21 knockdown.

Conclusions: These findings suggested that SOX2 can interfere with the transcriptional activity of CDX2 in bile acid-induced IM and that miR-21 might play a key role in this process, which shed new lights in the prevention of gastric cancer.

Keywords: Bile acid; CDX2; Intestinal metaplasia; SOX2; miR-21.