Dickkopf-related protein 1/cytoskeleton-associated protein 4 signaling activation by Helicobacter pylori-induced activator protein-1 promotes gastric tumorigenesis via the PI3K/AKT/mTOR pathway

Abstract

BACKGROUND Gastric cancer (GC) is a common malignant tumor with high incidence and mortality rates globally, especially in East Asian countries. Helicobacter pylori ( H. pylori ) infection is a significant and independent risk factor for GC. However, its underlying mechanism of action is not fully understood. Dickkopf-related protein (DKK) 1 is a Wnt signaling antagonist, and cytoskeleton-associated protein (CKAP) 4 is a newly identified DKK1 receptor. Recent studies found that the binding of DKK1 to CAKP4 mediated the procancer signaling of DKK1 inde-pendent of Wnt signaling. We hypothesize that H. pylori -induced activation of DKK1/CKAP4 signaling contributes to the initiation and progression of GC. AIM To investigate the interaction of H. pylori infection, DKK1 and CAKP4 in GC, as well as the underlying molecular mechanisms. METHODS RNA sequencing was used to identify differentially expressed genes (DEGs) between H. pylori -infected and uninfected primary GC cells. Gain- and loss-of-function experiments were performed to verify the H. pylori -induced upregulation of activator protein-1 (AP-1) in GC cells. A dual-luciferase reporter assay and co-immunoprecipitation were used to determine the binding of AP-1 to the DKK1 promoter and DKK1 to CKAP4. Western blotting and immunohistochemistry detected the expression of DKK1, CKAP4, and phos-phatidylinositol 3-kinase (PI3K) pathway-related proteins in GC cells and tissues. Functional experiments and tumorigenicity in nude mice detected malignant behavior of GC cells in vitro and in vivo . RESULTS We identified 32 DEGs between primary GC cells with and without H. pylori infection, including JUN, fos-like antigen-1 (FOSL1), and DKK1, and confirmed that the three proteins and CKAP4 were highly expressed in H. pylori -infected GC cells, H. pylori -infected gerbil gastric tissues, and human GC tissues. JUN and FOSL1 form AP-1 to transcriptionally activate DKK1 expression by binding to the DKK1 promoter. Activated DKK1 bound to CKAP4, but not the most common Wnt coreceptor low-density lipoprotein receptor-related protein 5/6, to promote GC cell growth, colony formation, migration, invasion, and xenograft tumor growth in nude mice. All these effects were driven by activation of the PI3K/AKT/mammalian target of rapamycin (mTOR) pathway. Targeting the PI3K signaling pathway by LY294002 inhibited DKK1-mediated CKAP4/PI3K signaling activity and the malignant behavior of GC cells. CONCLUSION H. pylori induces JUN and FOSL1 expression to form AP-1, which transcriptionally activates DKK1. Binding of DKK1 to KAKP4 contributes to gastric tumorige...

Investigating the Molecular Mechanisms Underlying Early Response to Inflammation and Helicobacter pylori Infection in Human Gastric Epithelial Cells

“…Our transcriptomic analysis revealed that in H. pylori-infected GES-1 cells, the expression of AP-1 related genes such as FOS, FOSB, FOSL1, FOSL2, and JUN, was statistically increased with respect to both non-infected and TNF-treated cells. Of note, DKK1, the gene encoding the Dickkopf-related protein, which was recently identified as a target of H. pylori activated AP-1 signaling [38], was upregulated as well in infected GES-1 cells in comparison to either non-infected or TNF-treated cells. Thus, it may be concluded that AP-1 signaling is operating in H. pylori infected GES-1 cells also due to direct increased expression of this set of transcription factors.…”

“…It is known that H. pylori infection leads to activation of the activator protein 1 (AP-1) cascade [37] and to increased expression of members of this family of transcription factors [38]. Our transcriptomic analysis revealed that in H. pylori-infected GES-1 cells, the expression of AP-1 related genes such as FOS, FOSB, FOSL1, FOSL2, and JUN, was statistically increased with respect to both non-infected and TNF-treated cells.…”

DKK1 Promotes Epithelial–Mesenchymal Transition and Cisplatin Resistance in Gastric Cancer via Activation of the PI3K/AKT Pathway

“…H. pylori infection is a well-known factor that contributes to the genesis and development of GC. Recent evidence has shown that DKK1 transcription could be induced by H. pylori infection and further lead to gastric tumorigenesis via activation of the CKAP4/PI3K/AKT/mTOR pathway [49]. Herein, identifying small molecule drugs or antibodies blocking the DKK1/CKAP4 axis could be an important aspect of GC treatment.…”