39P - Casein kinase 2 modulates epithelial–mesenchymal transition through helicobacter pylori CagA-dependent pathway in gastric cancer cells

Background

Helicobacter pylori is the most important carcinogen in human gastric cancer. However, the pathogenic molecular mechanism which underlies the carcinogenesis in gastric cancer by H. pylori remains largely unknown. In this study, we understand that molecular biological mechanism related to gastric carcinogenesis by investigating the role of CK2 in EMT. Casein kinase 2 is a serine/threonine protein kinase and consists of two catalytic subunits (α or α’) and regulatory subunits (β). CK2 regulates many substrates and its involved in cell growth, proliferation, invasion. EMT is involved in many signaling pathways, but the key regulatory kinases in this process have not been clearly identified. Although the role of CK2 catalytic subunits has remained largely uncharacterized, several studies have recently focused on regulator subunits in EMT.

Methods

AGS and MKN74 cells as human gastric epithelial cells and H. pylori strains, H. pylori 60190 (CagA+) and H. pylori ΔCagA (CagA-) were used. Protein and mRNA levels of CK2 were tested by Western blot and RT-PCR in AGS cells infected with H. pylori 60190. We also examined in vivo assay through tumor weight and size by xenograft mouse model. Expression levels of CK2 were analyzed in 54 gastric tissues from patients with gastric carcinoma by immunohistochemistry.

Results

Although CK2α protein expression remained unchanged during H. pylori infection, we found that CK2α kinase activity was increased in gastric epithelial cells. We also found that the CK2β protein level decreased in H. pylori-infected gastric cancer cells in CagA-dependent manner and demonstrated that CagA induced CK2β degradation via HDM2. We observed that CagA induced HDM2 protein phosphorylation and that p53 levels were decreased in H. pylori-infected gastric cancer cells. We also found that the downregulation of CK2β triggered the upregulation of Snail levels in gastric cancer cells. Furthermore, our in vivo experiments and functional assays of migration suggest that CK2β downregulation is a major factor responsible for the EMT in gastric cancer.

Conclusions

In summary, we have shown that the downregulation of CK2β in H. pylori-infected gastric cancer cells promotes the EMT in CagA-dependent manner.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Yonsei University College of Medicine.

Funding

National Research Foundation Of Korea.

Disclosure

All authors have declared no conflicts of interest.