Cancer Letters

Cancer Letters

Volume 520, 1 November 2021, Pages 409-421
Cancer Letters

Bcl2-associated athanogene 4 promotes the invasion and metastasis of gastric cancer cells by activating the PI3K/AKT/NF-κB/ZEB1 axis

https://doi.org/10.1016/j.canlet.2021.08.020Get rights and content

Highlights

  • Elevated BAG4 expression was positively correlated with T stage, lymph node metastasis and tumor size of GC and associated with unfavorable outcome of the patients.

  • Over-expression of BAG4 increases the migration and invasion of GC cells.

  • BAG4 activated PI3K/AKT/NF-κB/ZEB1 axis to induce epithelial-mesenchymal transition (EMT).

  • Manipulating BAG4 expression resulted in changes of p65 nuclear translocation and ZEB1 expression.

Abstract

Bcl2-associated athanogene 4 (BAG4) has been found to be aberrantly expressed in several types of human cancers. However, little is known about its expression, role, and clinical significance in gastric cancer (GC). In this study, we aimed to address these issues and to explore the underlying mechanisms. The expression level of BAG4, measured by immunohistochemistry, was significantly higher in GC tissues than in paired normal tissues. Elevated BAG4 expression was positively correlated with T stage, lymph node metastasis, and tumor size of GC and was associated with unfavorable outcomes of the patients. The overexpression of BAG4 promoted the in vitro invasion and in vivo metastasis of GC cells, and opposite results were observed after silencing of BAG4. Silencing of BAG4 significantly reduced the phosphorylation of PI3K, AKT, and p65, whereas overexpression of BAG4 markedly enhanced the phosphorylation of these molecules. At the same time, manipulating BAG4 expression resulted in the corresponding changes in p65 nuclear translocation and ZEB1 expression. Luciferase reporter and chromatin immunoprecipitation assays verified that p65 binds to the promoter of ZEB1 to upregulate its transcription. Our results demonstrate that BAG4 plays an oncogenic role in the invasion and metastasis of GC cells by activating the PI3K/AKT/NF-κB/ZEB1 axis to induce epithelial-mesenchymal transition.

Introduction

Gastric cancer (GC) is the fifth most common cancer and the third leading cause of cancer-related deaths worldwide [1]. Despite recent progress in the early detection and treatment of GC, the prognosis of patients with GC remains poor [2]. Invasion and metastasis are important biological characteristics of GC and are major contributors to the poor prognosis of GC patients [3]. Therefore, an insight into the underlying molecular mechanisms is urgently needed.

Bcl2-associated athanogene 4 (BAG4), also known as silencer of death domains (SODD), is a member of the human BAG family of proteins, and plays a role in diverse cell biological processes, such as apoptosis [4], cytoskeleton remodeling [5], autophagy [6], proliferation, migration, and invasion [7]. BAG4 has been found to be aberrantly expressed in several human malignancies and associated with aggressive behaviors, including pancreatic cancer [8], ovarian cancer [9], breast cancer [10], acute lymphoblastic leukemia [11], and colon cancer [12]. Although a recent study has suggested that BAG4 enhances the proliferation, migration, and invasion of GC cell lines [7], the clinical significance and possible molecular mechanisms of BAG4 in GC have not been fully elucidated.

In the present study, we found that BAG4 was overexpressed in tumor tissues and was positively correlated with the clinicopathological parameters of GC and poor prognosis of GC patients. Further mechanistic studies revealed that BAG4 activated the PI3K/AKT/NF-κB/ZEB1 axis to induce the epithelial-mesenchymal transition (EMT) of GC cells, thereby enhancing their invasive and metastatic abilities. Our findings demonstrate that BAG4 is involved in the progression of GC and may serve as a potential prognostic marker and therapeutic target for GC.

Section snippets

Patients and clinical samples

A total of 196 GC specimens with paired cancerous and adjacent normal tissues were obtained from patients who underwent radical resection at the First Hospital of Lanzhou University (Lanzhou, China) between January 2010 and December 2012. None of the patients received radiotherapy, chemotherapy, targeted therapy, or immunotherapy prior to surgery. All patients had at least 5 years of follow-up data. The clinicopathological characteristics of all the subjects were summarized in Supplementary

BAG4 expression is upregulated in GC tissues and associated with poor prognosis of the patients

To investigate the clinical significance of BAG4 expression in GC, we evaluated the level of BAG4 expression in 196 pairs of GC tissues and matched normal tissues by IHC staining. BAG4 staining was observed in the cytoplasm and nucleus of GC cells, mainly in the nucleus (Fig. 1A). BAG4 expression was low or absent in the adjacent normal gastric mucosa (Fig. 1Aa) but high in tumor tissues and metastatic lymph nodes (Fig. 1Ab-f). The intensity of BAG4 staining in tumors increased as the tumor

Discussion

The mechanisms underlying GC invasion and metastasis remain unclear. The present study found that BAG4 is overexpressed in GC and plays an important role in the invasion and metastasis of the disease. Moreover, BAG4 activates the PI3K/AKT/NF-κB/ZEB1 axis to induce EMT, thereby promoting the invasion and metastasis of GC cells. Although Yi et al. have recently reported that BAG4 facilitates the invasion and metastasis of GC cell lines, to our knowledge, this is the first study to report the

Authors' contributions section

Conception and design: L. Jiang, Y. Chen, N. Yao. Development of methodology: L. Jiang, Y. Chen, J. Wang. Acquisition of data (provided animals, acquired and managed patients, provided facilities, etc.): L. Jiang, Y. Chen, G. Min, J. Wang, W. Chen, H. Wang, X. Wang. Analysis and interpretation of data (e.g., statistical analysis, biostatistics, computational analysis): J. Wang, W. Chen, H. Wang, X. Wang. Writing, review, and/or revision of the manuscript: L. Jiang, Y. Chen, N. Yao.

Consent for publication

All authors have agreed to publish this manuscript in this journal.

Declaration of competing interest

The authors declare that they have no competing interest.

Acknowledgments

This work was supported by the National Natural Science Foundation of China (grant no. 82060527), Science Foundation of the First Hospital of Lanzhou University (no. ldyyyn2019-02), and the Science and Technology Development Guiding Plan Project of Lanzhou, China (no. 2020-ZD-66). We would like to thank Editage (www.editage.cn) for English language editing.

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