The influence of hypoxia-mediated CEACAM6 upregulation on epithelial cell and macrophage response in the context of gastric cancer.

Background: The hypoxic microenvironment is a key component of the gastric tumour niche. Carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) is upregulated in gastric cancer and is considered a novel biomarker for the disease. However, no prior studies have elaborated on the status of CEACAM6 and its role in the hypoxic gastric cancer niche.

Methods: In this short study, we evaluated the effect of hypoxia in modulating CEACAM6 level in gastric cancer cells (GCCs) through western blotting and determined the effect of CEACAM6 upregulation on gastric cancer progression through clonogenicity, cell proliferation and migration assays. The wound-healing ability of GCCs was downregulated by siRNA-mediated CEACAM6 silencing. Human gastric cancer biopsy samples were examined by immunofluorescence microscopy to assess the level of a hypoxia marker HIF1α and CEACAM6. The effect of empty vector or CEACAM6-expression on peripheral blood-derived mononuclear cell (PBMC)-derived macrophage polarization under normoxia or hypoxia was studied by incubating macrophages in conditioned medium collected from GCC cultures. Macrophage polarization status was observed using flow cytometry and fluorescence microscopy. Reactive oxygen species (ROS) generation by macrophages was evaluated using fluorescence microscopy.

Results: We identified that hypoxia promoted CEACAM6 in GCCs, and these cells acquired increased proliferative potential and migration ability. Moreover, the cell culture supernatant from hypoxia-exposed CEACAM6-overexpressing cells promoted an M2-like macrophage population and discouraged the M1 phenotype.

Conclusion: This study established that hypoxia increased CEACAM6 which promoted gastric cancer progression by influencing GCC proliferation and motility as well as macrophage polarization.